Bio exam 2 (ch 16,21,22)
Gymnosperms Are
"Naked Seed" Plants. The sporophytes of most gymnosperms are woody trees or shrubs. Reproductive structures and leaf types are diverse.
Gymnosperm
"Naked seed plants" because the seeds are not enclosed in fruits. They were the 1st seed plants. Use pollen grains for gamete transfer. 4 phyla.
Life cycle of moss
(1) In the sporophyte, cells in sporangia undergo meiosis, which yields haploid spores (2) that develop into male and female gametophytes. (3) Male gametophytes produce sperm that swim in a film of water to (4) the female gametophytes, which produce egg cells. (5) Gametes join and form a zygote, which (6) develops into a new sporophyte.
Double Fertilization
(1) Pollen sticks to a stigma on a flower. (2) A pollen tube grows toward the ovule and transports two sperm nuclei. (3) One sperm nucleus fertilizes the egg cell to form a zygote, and the other fertilizes the central cell's two nuclei to yield the endosperm.
Life Cycle of an Angiosperm
(1) The mature sporophyte produces flowers. (2) Cells in a flower's pollen sac and ovary undergo meiosis, producing spores that develop into haploid male and female gametophytes. (3) Inside each ovule, the female gametophyte includes one egg cell and two nuclei in a central cell. (4) The pollen sac produces pollen, the male gametophytes. (5) A pollen grain delivers two sperm nuclei. One fertilizes the egg and the other fertilizes the nuclei in the central cell, forming a triploid cell that develops into the endosperm. (6) Each ovule develops into a seed; the fruit develops from the ovary wall. (7) Seed germination reveals the young sporophyte.
Life Cycle of a Pine
(1) The mature sporophyte produces male and female cones. (2) Cells in the male and female cone scales undergo meiosis, producing spores that develop into haploid gametophytes consisting of just a few cells each. (3) On the female cones, each scale has two ovules (only one is shown), each of which yields an egg-producing gametophyte. (4) The male cones produce pollen, the male gametophytes. (5) A pollen grain delivers a sperm nucleus to an egg cell via a pollen tube. The fertilized egg (zygote) will become the embryo. (6) The embryo is packaged inside a seed, which will eventually germinate and yield a pine seedling. The resulting zygote is the first cell of the sporophyte generation. The whole process is so slow that fertilization occurs about 15 months after pollination.
Why vascular tissue is considered important in evolution
1. Accommodate the division of labor between roots and shoots. Roots absorb water and minerals; shoots produce food. Xylem and phloem shuttle these materials throughout the plant's body. 2. Support: Lignin strengthens the walls of xylem cells and sclerenchyma fibers. This physical support enables vascular plants to tower over their nonvascular counter-parts, an important adaptation in the intense competition for sunlight.
420 MYA what plants arose? 350 MYA?
420 = vascular plants, 350 = gymnosperms
Plants arose about _____ million years ago from ancestors resembling ____________?
475 million years ago, green algae.
Hormone
A biochemical produced in one part of an organism and transported to another location, where it triggers a response from target cells. A plant's hormones may either diffuse from cell to cell or move larger distances by entering xylem or phloem. Either way, when a hormone reaches a target cell, it binds to a receptor protein. This interaction begins a cascade of chemical reactions that ultimately change the expression of genes in target cells. Regulate many aspects of plant growth, flower and fruit development, and responses to environmental change.
Example of how a given organ may act as either a sink or a source
A developing potato tuber is a sink, storing the plant's sugars in the form of starch. Later, when the plant uses those stored reserves to fuel the growth of new tissues, that same tuber becomes a source. The starch in the tuber breaks down into simple sugars, which are loaded into phloem sap for transport to other plant parts. A similar mobilization occurs each spring when a deciduous tree produces new stems and leaves, using carbohydrates stored in roots. Later in the growing season, leaves approach their mature size and produce sugar of their own. The leaves are then sources, and the roots are again sinks.
Xylem sap
A dilute solution consisting of water and dissolved minerals absorbed from soil.
abscisic acid (abbreviated ABA)
A fifth plant hormone that counters the growth stimulating effects of many other hormones. For example, ABA helps induce bud dormancy during winter. Stresses such as drought also stimulate the production of ABA. One immediate effect is to trigger stomata to close, which helps plants conserve water. ABA also inhibits seed germination, opposing the effects of gibberellins.
Coevolution
A genetic change in one species selects for subsequent change in the genome of another species. Likely to happen when a plant has an exclusive relationship with only one pollinator species.
A herbaceous plant has what stem? A woody plant is made of what?
A herbaceous plant has a green, soft stem. A woody plant is made of tough, bark-covered wood.
How simple, aggregate, and multiple fruits develop
A simple fruit develops from a flower with one carpel. The carpel may have one seed, as in a cherry, or many seeds, as in a tomato. An aggregate fruit develops from one flower with many carpels. Strawberries and raspberries are examples of aggregate fruits. A multiple fruit develops from clusters of flowers that fuse into a single fruit as they mature. Pineapples and figs are multiple fruits.
Simple vs compound leaves
A simple leaf has an undivided blade, whereas compound leaves are divided into leaflets
phloem sap
A solution that also includes water and minerals from the xylem. The organic compounds carried in phloem are dissolved in the phloem sap. The carbohydrates in phloem sap are mostly dissolved sugars such as sucrose. Phloem sap also contains amino acids, hormones, enzymes, and messenger RNA molecules
Companion cell
A specialized parenchyma cell that retains all of its organelles. These cells transfer Carbohydrates into and out of the sieve tube elements and provide energy and proteins to the conducting cells.
vascular bundle
A strand of tissue containing xylem and phloem, often together with collenchyma tissue or sclerenchyma fibers. Occurs in stems and leaves.
Cuticle
A waxy coating that minimizes water loss from the aerial parts of a plant. (water conserving adaptation for plants on land)
alternation of generations part 1
A zygote develops by mitotic cell division into a multicellular, diploid sporophyte.
Apical and lateral meristems
Apical - small patches of actively dividing cells near the tips of roots and shoots. When the cells divide, they give rise to new cells that differentiate into different tissue types. Lateral - produce cells that thicken a stem or root, occur in woody plants. A lateral meristem is usually an internal cylinder of cells extending along most of the length of the plant. When the cells divide, they typically produce tissues to both the inside and the outside of the meristem.
Dormancy
At some point in seed development, hormonal signals "tell" cells in the embryo and endosperm to stop dividing, and the seed gradually loses moisture and enters dormancy. The ripe, mature seeds are firm, dry, and ready for dispersal. Depending on the species, the dormant period can last for days, weeks, months, years, decades, or even centuries. Seed dormancy is a crucial adaptation because it ensures that seeds have time to disperse away from the parent plant before germinating. Moreover, dormancy enables seeds to postpone development if the environment is unfavorable, such as during a drought or frost. Favorable conditions trigger embryo growth to resume when young plants are more likely to survive.
What kind of -trophs are plants?
Autotrophs (use sunlight as an energy source to convert CO2 and H2O into sugars)
Why pollen and seeds are important
Before, the spores of mosses and ferns (seedless plants) could only travel short distances in water and were short lived. Gymnosperms and angiosperms can disperse their seeds (gametes) long distances in dry weather. Can live long too.
Plant roots
Below ground, depend on shoots to provide energy for its metabolism. Anchor plant, absorb water and minerals that move from the stem to the leaves.
What are the most abundant macronutrients that account for about 96% of the dry weight of a plant? (The other macronutrients account for 3.5%)
Carbon (C), hydrogen (H), oxygen (O),
Describe the angiosperm life cycle which includes an alternation of generations (similar to all other plants) with multicellular diploid and haploid stages
Cells in the sporophyte, or diploid generation, undergo meiosis to produce haploid spore, the sporophyte is the tree at top center. Inside the tree's flowers, each spore divides mitotically to produce a multicellular haploid gametophyte, which undergoes mitosis to generate haploid gametes (egg cells or sperm). In fertilization, gametes fuse to form a diploid zygote. The zygote develops into an embryo, which is packaged inside a seed (which is itself within a fruit). With additional growth, the embryo becomes a mature sporophyte, and the cycle begins anew.
Vascular tissue
Collection of tubes that transfer sugar, water, and minerals throughout the plant. (Not needed in bryophates, the simplest plants) Connects roots, stems, leaves, fruits, and flowers. Consists of xylem and phloem.
How does the embryo continue developing into a mature sporophyte?
Continued development requires seed germination, the resumption of growth and development after a period of seed dormancy. Germination requires water, O2, and a favorable temperature. The seed absorbs water and swells, rupturing the seed coat and exposing the embryo to O2. Meanwhile, enzymes break down the endosperm's starch into sugars. The availability of O2 and sugars means cellular respiration can resume in the embryo. Cell division at apical meristems rapidly lengthens the young roots and shoot. At first, the only energy source is fuel stored in the endosperm. After the shoot emerges from the ground and the first leaves unfold, photosynthesis begins.
Dermal tissue
Covers the plant. In a herbaceous plant, this tissue consists of the epidermis: a single layer of tightly packed, flat, transparent parenchyma cells. In land plants, epidermal cells secrete a cuticle, a waxy layer that coats the epidermis of the leaves and stem. The cuticle conserves water and protects the plant from predators and fungi.
Gymnosperms are divided into four groups:
Cycads, Ginkgo, Conifers, Gnetophytes
Fruit
Developed from parts of a flower, protect and disperse seeds.
Parenchyma cells
Divide to produce the roots that emerge from a houseplant placed in water. Photosynthesis, respiration, gas exchange, and the storage of starch and other materials.
Axillary bud
Each node has this: undeveloped shoot that forms in the angle between the stem and leaf stalk.
Collenchyma cells
Elongated living cells with unevenly thickened primary walls that can stretch as the cells grow. These cells provide elastic support without interfering with the growth of young stems or expanding leaves. Collections of collenchyma cells make up the tough, flexible "strings" in celery stalks.
Two innermost whorls of a flower
Essential for sexual reproduction. The male flower parts consist of stamens, which are filaments that bear pollen-producing bodies called anthers at their tips. The female part at the center of a flower is composed of one or more carpels, the structures enclosing the egg-bearing ovules. The bases of carpels and their enclosed ovules make up the ovary. The upper part of each carpel is a stalklike style that bears a structure called a stigma at its tip. Stigmas receive pollen.
Other angiosperm adaptations
FLOWERS - reproductive structures that produce pollen and egg cells. After fertilization, parts of the flower become a FRUIT that contains seeds. These help angiosperms protect and disperse their pollen and offspring. These came about 160 MYA.
Transpiration rate
Fast transpiration rate - The bigger the concentration gradient between the leaf interior and the surrounding air, low humidity, wind, and high temperatures. If the air is too hot or too dry, however, the plant's stomata close. Transpiration slows when the stomata close, but so does photosynthesis
Roots might form a fibrous root system or a taproot system
Fibrous roots are slender, shallow, and arise from the stem base. typical of monocots Taproots are thick, deep, and have fewer branches. typical of eudicots
pressure flow theory explained
First, sugars are actively transported from photosynthetic cells to companion cells and then into the sieve tube. Then, water moves by osmosis from xylem into the sieve tube, increasing sieve tube pressure. This pressure pushes the sugars toward the sink. At the sink, transport proteins move sugars out of the sieve tube. Since the solute concentration in the phloem decreased, water leaves the sieve tube by osmosis. Transport of sugars from sources to sinks explains how nonphotosynthetic cells obtain sugars (and why fruits are often sweet).
Angiosperms owe their success to which three adaptations?
First, they produce pollen, which enables sperm to fertilize an egg in the absence of free water. In contrast, the sperm cells of mosses and ferns must swim to the egg, so these plants can reproduce sexually only in moist habitats. Second, the seed protects the embryo during dormancy and nourishes the developing seed-ling. Third, flowers not only promote pollination but also develop into fruits that help disperse the seeds far from the parent plant.
Angiosperms
Flowering plants (phylum Magnoliophyta) makes up 95% of all plant species (Apple trees, corn, roses, etc.) 2 largest groups are eudicots and monocots, account for 97% of flowering plants. The first leaf structures to arise in an angiosperm plant embryo are called cotyledons.
How fruit forms underground (peanut plant)
Flowers never form on roots. The yellow flowers of peanut plants, for example, form on the shoot. After fertilization, the petals wither, and the young fruit produces a peg that turns downward and buries itself in the soil. Three to five months later, farmers dig up the plants to harvest the mature fruits. Each fruit consists of a fibrous shell enclosing one to three peanuts—the seeds.
How do plants get nitrogen? (They cant use the nitrogen found in 78% of the atmosphere)
From bacteria that use nitrogen-fixing enzymes to convert N2 to NH4+. Some bacteria are free living, others live in nodules; small swellings on the roots of some types of plants. The bacteria consume sugars that the host plant produced by photosynthesis. The plant incorporates the nitrogen atoms from NH4+ into its own tissues. When the plant dies, decomposers make the nitrogen available to other organisms. Nitrogen fixation is the key to the entire nitrogen cycle, bringing otherwise inaccessible nitrogen to plants, microbes, and all other life.
How does wind and animals play a role in angiosperm production?
Grasses and maples are common examples of wind-pollinated plants, but many other species rely on animal "couriers" that unwittingly carry pollen from flower to flower. Animals usually visit flowers in search of food.
Plants have three main tissue types: Ground tissue, Vascular tissues, Dermal tissue
Ground tissue makes up most of the plant body. Vascular tissues (xylem and phloem) transport materials within the plant. Dermal tissue covers the plant.
Tissues Build Stems, Leaves, and Roots
Ground tissue occupies most of the stem of a herbaceous plant. Vascular bundles are embedded in the ground tissue. Dermal tissue covers the stem.
Plant growth after germination
Growth and development continue after the seed coat ruptures. The root emerges first from the germinating seed, and then the shoot begins to elongate. Rapidly dividing cells in apical meristems continually add length to both roots and shoots. The new cells differentiate into the ground tissue, vascular tissue, and dermal tissue that make up the plant body. The seedling soon begins to take on its mature form. Young roots grow downward in response to gravity, anchoring the plant in the soil and absorbing water and minerals.
alternation of generations part 3
Haploid spores divide by mitosis into a multicellular, haploid gametophyte.
The angiosperm life cycle is an alternation of generations.
Haploid spores form by meiosis in flowers. Each mother cell in a pollen sac divides into four microspores. Each mother cell in an ovule divides into four megaspores. Only one persists. Spores divide mitotically into microscopic gametophytes. During pollination, a pollen grain lands on a stigma. The pollen grain germinates, producing a pollen tube. Sperm nuclei travel through the pollen tube and fertilize the egg and polar nuclei. The zygote develops into an embryo, and the endosperm provides its food. Seeds contain the embryo and endosperm; part of the flower develops into an enclosing fruit. Seeds germinate into young sporophytes, and the cycle begins again.
The seedless vascular plant life cycle is an alternation of generations.
Haploid spores form by meiosis in sporangia on sporophyte leaves. Spores are released from the sporangia. Each spore might develop by mitosis into a gametophyte. Gametophytes produce gametes by mitosis. Gametes travel from male to female gametophytes in water. When sperm meets egg, a zygote forms within the gametophyte tissue. The zygote develops by mitosis into a sporophyte, and the cycle begins again.
Gymnosperm life cycle is an alternation of generations.
Haploid spores form by meiosis in sporophyte cones. Male cones produce microspores by meiosis on cone scales. Ovules on female cone scales produce megaspores by meiosis. Spores develop by mitosis into microscopic gametophytes. Gametophytes unite at pollination. A pollen grain germinates, producing a pollen tube. Sperm nuclei travel through the pollen tube to the egg cells. Fertilization occurs. The resulting zygote grows mitotically into an embryo, inside a seed, on a female cone scale.
The bryophyte life cycle is an alternation of generations
Haploid spores form by meiosis in the sporophyte tip. Spores are released from the sporophyte. Each spore might develop by mitosis into a gametophyte. A mature gametophyte is either male or female. Gametophytes produce gametes by mitosis. Gametes travel from male to female gametophytes in water. When sperm meets egg, a zygote forms within the female gametophyte. The zygote develops by mitosis into a sporophyte, and the cycle begins again.
Herbaceous plant
Has a soft, green stem at maturity. (Example: grasses, dandelions, daisies)
Heartwood and sapwood
Heartwood - innermost wood, darker color, older, as the years pass the oldest secondary xylem at the center of the trunk—the heartwood—gradually becomes unable to conduct water. As its function declines, dark-colored chemicals accumulate in the heartwood. Sapwood - outermost wood, lighter color, younger, located near the vascular cambium, transports water and dissolved minerals.
Ground tissue
Important for respiration, photosynthesis, and storage. For example, the pulp of an apple, the photosynthetic area inside a leaf, and the starch-containing cells of a potato.
root cap
In both fibrous and taproot systems, countless root tips explore the soil for water and nutrients. The root cap protects the growing tip from abrasion. Root cap cells, which slough off and are continually replaced, secrete a slimy sub-stance that lubricates the root as it pushes through the soil. Also senses gravity.
vascular bundles in monocots and eudicots
In monocots, vascular bundles are scattered throughout the stem. In eudicots, vascular bundles are arranged in a ring near the epidermis.
How are vascular bundles, which typically have phloem to the outside and xylem toward the inside, arranged differently in monocots and eudicots?
In most monocot stems, vascular bundles are scattered throughout the ground tissue. Most eudicot stems have a single ring of vascular bundles. Ground tissue occupies most of the rest of the eudicot stem: The cortex fills the area between the epidermis and vascular tissue, and pith occupies the center.
Secondary growth
Increases the girth of stems and roots in woody plants. This happens because of natural selection due to the competition for light.
producing the microscopic male and female gametophytes after the flowers have formed
Inside the anther's pollen sacs, diploid cells divide by meiosis to produce four haploid microspores. Each microspore then divides mitotically and produces a two-celled, thick-walled structure called a pollen grain, which is the young male gametophyte. One of the haploid cells inside the pollen grain divides by mitosis to form two sperm nuclei. Meanwhile, meiosis also occurs in the female flower parts. The ovary may contain one or more ovules, each containing a diploid cell that divides by meiosis to produce four haploid megaspores. The megaspore undergoes three mitotic divisions to form the embryo sac, which is a mature female gametophyte. At first, the embryo sac contains eight haploid nuclei. Cell walls soon form, dividing the female gametophyte into seven cells. One of these cells is the egg. In addition, a large, central cell contains a pair of nuclei; as we shall see, both the egg and the central cell's two nuclei participate in fertilization.
When is a flower "complete?" When is it not?
It includes all four whorls, including both male and female parts. In some species, however, the sexes are separate. That is, each flower has either male or female parts but not both. An individual plant may have both types of single-sex flowers, or the plant may produce just one flower type.
All Plants Have Similar
Life Cycles Substituting images in the alternation of generations produces diagrams of other plant life cycles
Alternation of generations
Life cycle in plants and green algae. Multicellular diploid (sporophyte) stage alternates with a multicellular haploid (gametophyte) stage.
3 phyla of Bryophytes
Liverworts (phylum Marchantiophyta) flattened leaflike gametophytes. Closely related to ancestral land plants. Hornworts (phylum Anthocerotophyta) named for their sporophytes which look like tapered horns. Mosses (phylum Bryophyta) closest relatives to vascular plants. Gametophytes resemble short "stems" with many "leaves." The brown or green sporophyte looks nothing like the gametophyte.
Sieve tube elements
Main conducting cells in Phloem. Align end to end to make a single functional unit called a sieve tube. The sieve tube elements are alive, but they lack a nucleus and have little cytoplasm.
How seeds are dispersed
Many animals disperse fruits and seeds. Colored berries attract birds and other animals that carry the ingested seeds to new locations, only to release them in their droppings. Birds and mammals spread seeds when spiny fruits attach to their feathers or fur. Squirrels and other nut-hoarding animals also disperse seeds. Although they later eat many of the seeds they hide, they also forget some of their cache locations. The uneaten seeds may germinate. Wind and water can also distribute seeds. Wind-dispersed fruits, such as those of dandelions and maples, have wings or other structures that catch air currents. Water-dispersed fruits include gourds and coconuts, which may drift across the ocean before colonizing distant lands.
Plants have flexible growth patterns, thanks to
Meristems
Monocot and eudicot flower parts
Monocots - petals, stamens, and other flower parts in multiples of 3. (ex: lilies and tulips) Eudicots - flower parts in multiples of 4 or 5. (ex: buttercups and geraniums have 5 prominent petals on each flower)
Angiosperms reproduce
Mostly sexually and some asexually
monocots
Named for their single cotyledon; their pollen grains have just one pore. Examples of the 70,000 species of monocots are orchids, lilies, grasses, bananas, corn, rice, wheat, and ginger. The grasses include not only lawn plants but also sugar-cane and grains such as rice, wheat, barley, and corn.
Sugars Are Pushed to
Nonphotosynthetic Cells in Phloem. With sufficient light, water, and nutrients, a photosynthetic cell will produce sugars that can be transported in phloem to the plant's nonphotosynthetic cells, which cannot produce food on their own.
Ground tissue cells: what are the 3 main cell types?
Parenchyma, collenchyma, and sclerenchyma.
Meristems
Patches of "immortality" that allow a plant to grow, replace damaged parts, and respond to environmental change. Undergo active mitotic cell division.
2 main parts of leaves
Petiole : stalklike, attaches to the stem and supports the broad, flat blade. Leaf blade: maximizes the surface area available to capture light.
Indeterminate growth
Plants keep growing by adding module after module, as long as the environment allows it.
Determinate growth
Plants that stop growing after their mature size.
Stomata
Pores in the epidermis of stems and leaves (plants exchange gases through the atmosphere with this, close during dry weather to minimize water loss)
2 main functions of fruit
Protect seeds by containing chemicals that animals find distasteful (unripe fruit while the seeds are maturing) Promote seed dispersal by animals, wind, and water; the goal is to get the seeds far away from the parent.
Sclerenchyma cells
Provides inelastic support to parts of a plant that are no longer growing. Cells are dead at maturity. Have thick, rigid secondary cell walls that occupy most of the cell's volume and typically contain lignin that strengthens the cell walls. Some cells are elongated fibers; linen, for example, comes from the soft fibers of the stems of the flax plant. Other cells form hard layers or clusters, such as the small groups of cells that create a pear's gritty texture.
How does algae sexually reproduce?
Releases gametes into the water
How do plants get help from soil organisms in obtaining water and nutrients?
Roots of most land plants are colonized with mycorrhizal fungi. In exchange for sugars produced in photosynthesis, the fungal filaments explore the soil and absorb water and minerals that the roots could not otherwise reach. Phosphorus is poorly soluble in water, doesn't move easily to roots. Mycorrhizae help phosphorus absorption.
Secondary growth thickens and occurs
Secondary growth thickens roots and stems; this growth occurs at lateral meristems. happens in woody plants
Angiosperms Produce
Seeds in Fruits
Fruits come in three forms
Simple: Derived from one flower with one carpel (ex: Olive, cherry, peach, plum, coconut, grape, tomato, pepper, eggplant, apple, pear) Aggregate: Derived from one flower with many separate carpels (ex: Blackberry, strawberry, raspberry, magnolia) Multiple: Derived from tightly clustered flowers whose ovaries fuse as fruit develops (ex: pineapple, fig)
Types of fruit (simple, aggregate, multiple)
Simple: Derived from one flower with one carpel (ex: Olive, cherry, peach, plum, coconut, grape, tomato, pepper, eggplant, apple, pear) Aggregate: Derived from one flower with many separate carpels (ex: Blackberry, strawberry, raspberry, magnolia) Multiple: Derived from tightly clustered flowers whose ovaries fuse as fruit develops (ex: pineapple, fig)
Bryophytes Are the
Simplest Plants, Bryophytes are seedless plants that lack vascular tissue. They also lack true leaves and roots. Materials move from cell to cell within the plant by diffusion and osmosis. ex: liverworts, hornworts, mosses
Plants Have Flexible Growth Patterns: indeterminate growth vs determinate growth
Some plants never stop growing. These plants have indeterminate growth. Plants that stop growing when they reach their mature size have determinate growth.
Woody plants
Stems and roots are made of tough wood covered with bark. (Example: elm and cedar trees)
Vegetative plant parts include
Stems, leaves, and roots
Guard cells
Surrounds the stomata in the epidermis of leaves and stems and function in the opening and closing of the stomata
Auxins vs Cytokinins
The actions of cytokinins and auxins compete with each other. Cytokinins are more concentrated in the roots, whereas auxins are more concentrated in shoot tips. Cytokinins move upward within the xylem and stimulate lateral bud sprouting. In a counteracting effect called apical dominance, the terminal bud of a plant secretes auxins that move downward and suppress the growth of lateral buds. If the shoot tip is removed, the concentration of auxins in lateral buds decreases. Meristem cells in the buds then begin dividing, thanks to the ever-present cytokinins. Apical dominance explains why gardeners can promote bushier growth by pinching off a plant's shoot tip.
pressure flow theory
The explanation of phloem transport. phloem sap moves under positive pressure from "sources" to "sinks." Inside a leaf or other sugar source, companion cells load sucrose into sieve tube elements by active transport (step 1). Because sucrose becomes so much more concentrated in the sieve tubes than in the adjacent xylem, water moves by osmosis out of the xylem and into the phloem sap (step 2). The resulting increased pressure drives phloem sap through the sieve tubes (step 3).
The angiosperm life cycle is an alternation of generations with multicellular diploid and haploid stages.
The first step in angiosperm reproduction is the formation of flowers on the mature sporophyte. A typical flower has four whorls of structures, all of which are modified leaves. The outer whorl consists of sepals, which enclose and protect the inner floral parts. The second whorl is made of petals. The third whorl is the male reproductive parts. Stamens are filaments with pollen-producing anthers on top. The fourth whorl is the female reproductive parts. A carpel includes: the ovary, which encloses one or more ovules. a stalklike style. The top of the style, called the stigma, receives pollen. Inside the flower, meiosis produces haploid spores that develop into gametophytes.
mesophyll
The ground tissue inside a leaf, consists of cells with abundant chloroplasts that produce sugars by photosynthesis.
Mesophyll
The ground tissue inside a leaf. composed mostly of parenchyma cells. Most have abundant chloroplasts and produce sugars by photosynthesis. When the stomata are open, these cells exchange CO2 and O2 directly with the atmosphere. Also exchange materials with vascular tissue. Xylem in the tiniest leaf veins delivers water and minerals to nearby mesophyll cells. Sugars produced in photosynthesis move from the mesophyll cells to the phloem's companion cells and then to the sieve tube elements. The sugars, along with other organic compounds, travel within the phloem to the roots and other nonphotosynthetic plant parts.
alternation of generations part 4
The haploid gametophyte produces gametes by mitotic cell division.
gymnosperm life cycle
The mature sporophyte produces cones, the organs that bear the reproductive structures in gymnosperms. Ovules produce the female reproductive cells, and each female cone scale bears two ovules on its upper surface. Through meiosis, each ovule produces four haploid structures called megaspores, only one of which develops into a female gametophyte. Over many months, the female gametophyte undergoes mitosis and gives rise to two to six egg cells. At the same time, male cones bear sporangia on thin, delicate scales. Through meiosis, these sporangia produce microspores, which eventually become windblown pollen grains (immature male gametophytes). Pollination occurs when pollen grains settle between the scales of female cones and adhere to drops of a sticky secretion. The pollen grain germinates, giving rise to a pollen tube that grows through the ovule toward the egg cell. Two haploid sperm nuclei develop inside the pollen tube; one sperm nucleus fertilizes the haploid egg cell, and the other disintegrates.
How plants respond to other environmental cues besides light
The more CO2 in the atmosphere, the lower the density of stomata on leaves. Likewise, a plant in soil with abundant nitrogen produces fewer lateral roots than it would in nutrient-poor soil. Plants can also sense temperature; many require a prolonged cold spell before producing buds or flowers. A warm period in December, before temperatures have really plummeted, does not stimulate apple and cherry trees' buds to "break," but a similar warm-up in late February does induce growth. Gravity is another important environmental cue.
Outermost whorl of flowers
The outermost whorl (ring of parts) consists of sepals, which are leaflike structures that enclose and protect the inner floral parts. Next is a whorl of petals, which sometimes have bright colors that attract pollinators The sepals and petals do not play a direct role in sexual reproduction.,
Large vs small seeds
The size of a plant's seeds therefore reflects an evolutionary trade-off. Large, heavy seeds contain ample nutrient reserves to fuel seedling growth but may not travel far. Small seeds, on the other hand, store limited nutrients but tend to disperse far and wide. Interestingly, the crops that humans cultivate typically have larger seeds than do their wild ancestors.
life cycle of a fern
The sporophyte produces haploid spores by meiosis in collections of sporangia on the underside of each frond. Once shed, the spores germinate and develop into tiny, heart-shaped gametophytes that produce gametes by mitotic cell division. The swimming sperm require a film of water to reach the egg cell. The gametes fuse, forming a zygote. This diploid cell divides mitotically and forms the sporophyte, which quickly dwarfs the gametophyte.
alternation of generations part 2
The sporophyte produces haploid spores by meiosis.
Specialized functions of stems examples
The stems of climbing plants may form tendrils that coil around objects, maximizing exposure of the leaves to the sun The succulent, fleshy stems of cacti stockpile water. Rhizomes are thickened underground stems that produce both shoots and roots; tubers, such as potatoes, are swollen regions of rhizomes that store starch. Still other stems are protective; the thorns on hawthorn plants, for example, are modified branches.
Photoperiod
The timing of light exposure also influences many aspects of a plant's life. For example, plants respond in several ways to the photoperiod, or day length. Consider the changes that occur in a deciduous forest throughout the year. The short days that accompany the approach of winter are associated with the formation of buds, the loss of leaves, and dormancy. In the spring, as days grow longer, buds resume growth and rapidly transform a barren deciduous forest into a leafy canopy. These seasonal changes illustrate the interactions among photoreceptors, environmental signals, hormones, and the plant's genes.
Embryo development
The zygote divides to form the embryo. Among the first features of the developing embryo are the cotyledons. Soon, the shoot and root apical meristems form at opposite ends of the embryo. What about the embryo's food supply? Inside the developing seed, the endosperm cells divide more rapidly than the zygote and thus form a large multicellular mass. This endosperm supplies nutrients to the developing embryo, although the timing depends on the type of plant. In many eudicots, the paired cotyledons absorb the endosperm during seed development. In monocots, the mature seed retains the endosperm, and the cotyledon transfers nutrients from the endosperm to the rest of the embryo during germination.
alternation of generations part 5
These sex cells fuse at fertilization, forming a diploid zygote and starting the cycle anew. The sporophyte and gametophyte shown in this generalized plant life cycle are those of a seedless vascular plant.
Xylem
Tissue that transports water and dissolved minerals from the roots to all parts of the plant. The water-conducting cells of xylem are elongated and have thick, lignin-rich secondary walls. They are dead at maturity, which means that no cytoplasm blocks water flow. The two kinds of water-conducting cells in xylem are tracheids and vessel elements.
How does Photoperiod regulates flowering in some species?
Traditionally, biologists used the term "long-day plants" for plants that flower when days are longer than a critical length, usually 9 to 16 hours. These plants typically bloom in the spring or early summer and include lettuce, spinach, beets, clover, and irises. Likewise, "short-day plants" produce flowers when days are shorter than some critical length, usually in late summer or fall. Asters, strawberries, poinsettias, potatoes, soybeans, ragweed, and goldenrods are short-day plants. "Day-neutral plants" such as tomatoes flower at maturity, regardless of day length. However, experiments eventually confirmed that flowering actually requires a defined period of uninterrupted darkness, rather than a certain day length. Thus, short-day plants are really long-night plants, because they flower only if their uninterrupted dark period exceeds a critical length. Similarly, long-day plants are really short-night plants.
Vascular tissues
Transport water, minerals, carbohydrates, and other dissolved compounds throughout the plant.
Where and how do plants obtain their three most abundant elements (C, H, and O)?
Water and the atmosphere. Water enters the plant through the roots. Carbon and oxygen atoms come from the atmosphere in the form of CO2 gas, which diffuses into the leaf or stem through pores called stomata.
Why are bryophytes important?
When their tissue dies they contribute organic matter to soil that larger plants colonize. Can use peat moss for potted plants, it releases water to plant roots. Peat can also be used for cooking fuel or generating electricity.
Pollination
Wind and animals deliver pollen directly to female plant parts, eliminating the need for free water in sexual reproduction.
Pollination adaptation example
Wind-pollination is wasteful because the pollen can land on the ground or in the wrong species so wind-pollinated plants adapt by producing a lot of pollen (ex: oaks, cottonwoods, ragweed, grasses)
Water and minerals are pulled up to leaves in
Xylem (the vascular tissue that transports xylem sap.)
2 types of vascular tissue
Xylem - conducts water and dissolved minerals from the roots to the leaves, rich in lignin Phloem - transports sugars produced in photosynthesis to the roots and other nongreen parts of the plants.
Double Fertilization Yields
Zygote and Endosperm
In a root, ground tissue surrounds
a central core of vascular tissue
A stem or root's bark
a collective term for all tissues to the outside of the vascular cambium. Made up of secondary phloem.
thigmotropism
a directional response to touch. Specialized epidermal cells detect contact with an object, which stimulates the tendril to bend. In only 5 to 10 minutes, the ten-dril completely encircles the object. Auxins and ethylene apparently control thigmotropism. Besides ever-present gravity, a plant also encounters a changing variety of mechanical stimuli, including contact with wind, rain, animals, and other plants. The coiling tendrils of twining plants exhibit thigmotropism.
Ethylene
a gaseous hormone that ripens fruit in many species. Released from one overripe apple can hasten the ripening, and eventual spoiling, of others nearby, leading to the expression "one bad apple spoils the bushel:" Exposure to ethylene also ripens immature fruits after harvest.
angiosperm life cycle is similar to that of
a gymnosperm. The sporophyte is the only conspicuous generation, and both types of plants produce pollen and seeds. They differ too: the reproductive organs in angiosperms are flowers, not cones. Angiosperm's ovules develop into seeds inside the flower's ovary. The ovary develops into the fruit, which helps to protect and disperse the seeds. A gymnosperm's seeds are produced "naked" on the female cone's scales. Pollination in the angiosperm life cycle triggers double fertilization; two sperm nuclei enter the female gametophyte. One sperm nucleus fertilizes the egg, producing the zygote that will develop into the embryo. The other sperm nucleus fertilizes a pair of nuclei in the female gametophyte's central cell. The resulting triploid nucleus develops into the endosperm, a tissue that supplies nutrients to the germinating seedling. The embryo and endosperm, together with a seed coat, make up the seed; one or more seeds develop inside each fruit.
cork cambium
a lateral meristem that gives rise to parenchyma to the inside and cork to the outside. Cork consists of layers of densely packed, waxy cells on the surfaces of mature stems and roots. The cells are dead at maturity and form waterproof, insulating layers that protect the plant.
Seed
a plant embryo together with its stored food, surrounded by a seed coat. Immediately after fertilization, the ovule contains an embryo sac with a diploid zygote and a triploid endosperm. The ovule eventually develops into a seed.
phototropism
a plant grows toward or away from light. This response is adaptive because it bends stems toward light and roots toward darkness. Phototropism occurs in stems when cells on the shaded side elongate more than cells on the opposite side. Photoreceptors and auxins participate in the response. Photoreceptors absorb light, which somehow causes auxins to migrate to the shaded side of the stem. Water follows the auxins into the cells, and the resulting increase in turgor pressure causes the cells to elongate. The stein therefore bends toward the light.
When does a plant open and close its stomata?
a plant that closes its stomata cuts off its supply of CO2. But because plants store extra food as starch, a temporary drop in sugar production causes far less harm than does a rapid loss of water. Most plants conserve water by closing their stomata after dark, when photosynthesis cannot occur anyway. Many plants in dry habitats also use water-saving variations on the photosynthetic pathway.
endosperm
a tissue that supplies nutrients to the germinating seedling. Often contains energy rich starch or oils, like wheat.
The seed coat is
a tough outer layer that protects the embryo from damage, dehydration, and predators.
Plant shoot
aboveground part of the plant
The shoot is the
aboveground part of the plant. The shoot's stem supports the leaves, which produce carbohydrates by photosynthesis.
Near each root's tip, root hairs are extensions of the epidermis that
absorb water and minerals
As opposed to self-sufficient plants, parasitic plants do what?
acquire water, minerals, and food by tapping into the vascular tissues of their hosts.
Plants grow by
adding new modules
Because of cohesion, when water evaporates from the leaves, it pulls
adjacent molecules closer to the stomata.
The similarity among plant life cycles is evidence that
all plants share a common ancestor.
The plant life cycle is called
alternation of generations, in which a multicellular diploid stage alternates with a multicellular haploid stage.
The zygote develops from a single cell into
an embryo
After fertilization, the seed starts to develop. A seed consists of
an embryo, endosperm, and seed coat.
Each node also features an axillary bud, which is..
an undeveloped shoot that could form a new branch or flower.
Roots
anchor the plant and absorb water and minerals that move via the stem to the leaves.
Flowers are the sex organs of
angiosperms
What kind of plant outnumbers the rest of them in numbers and diversity?
angiosperms
Other flowers attract
animal pollinators, which unwittingly carry pollen between plants. the pollinator benefits from its association with plants—animals use plants for food, shelter, or a mating ground.
Gibberellins
another class of plant hormone that causes shoot elongation. Young shoots produce gibberellins, which stimulate both cell division and cell elongation. Also trigger seed germination by inducing the production of enzymes that digest starch in the seed.
What is a sink?
any plant part that does not photosynthesize. Examples of sinks include flowers, fruits, shoot apical meristems, roots, and storage organs. If these cells do not receive enough sugar to generate the ATP they require, the plant may die or fail to reproduce.
What is a source?
any plant part that produces or releases sugars
Some species of angiosperms also reproduce
asexually, forming new individuals by mitotic division. Offspring produced asexually are genetically identical to each other and to their parents. Asexual reproduction is advantageous when conditions are stable and plants are well-adapted to their surroundings.
Primary growth occurs
at the apical meristems. New cells can differentiate into any tissue type.
Leaves are flattened
blades supported with a stalk-like petiole
Essential nutrients
chemicals that are vital for metabolism, growth, and reproduction.
Xylem transport relies on
cohesion
cohesion-tension theory
cohesive properties of water—the tendency for water molecules to form hydrogen bonds and "cling" together. As water molecules evaporate through the stomata, additional water diffuses out of leaf veins and into the mesophyll. Water molecules leaving the vein attract molecules adjacent to them in the xylem, pulling them toward the vein ending. Each water molecule tugs on the one behind it (step 2). As evaporation from leaf surfaces pulls water up the stem, additional water enters roots from the soil (step 3). Just behind each growing root tip, the epidermis is fringed with root hairs. The plant's millions of root hairs, coupled with filaments of mycorrhizal fungi, add up to an enormous surface area for water and mineral absorption. The solution flows among and within the cells that make up the outer portion of the root until it reaches the endodermis. At that point, a waxy barrier forces the materials that had gone around cells to now enter the cells of the endodermis. Water enters by osmosis, because the concentration of solutes in cells is generally higher than in the soil. Materials that cross the endodermis continue into the xylem, enter the transpiration stream, and move up the plant. As we have already seen, the water eventually returns to the atmosphere through the open stomata in the leaves and stem; the dissolved nutrients are incorporated into the plant's tissues. As long as sufficient moisture is available in the soil, the cohesion between water molecules is enough to move continuous, narrow columns of xylem sap upward against the force of gravity. This mechanism exploits the physical properties of water and requires no energy input from the plant.
The cuticle
conserves water and protects the plant. Pores in the cuticle, called stomata (singular stoma), allow leaves to exchange gases with the atmosphere.
A stem or root's wood
consists of secondary xylem, and it can accumulate to massive proportions. For example, a giant sequoia tree in California is 100 meters tall and more than 7 meters in diameter. Secondary phloem occupies much less volume. This tissue forms the live, innermost layer of bark. Durable and useful.
Pollen
consists of the male gametophytes of seed plants; each pollen grain produces sperm. Allows gymnosperms and angiosperms to reproduce over great distances.
Plant terminal bud
contains undeveloped tissue at the shoot tip.
Dermal tissue
covers the plant; it consists of the epidermis, which is coated with a waxy cuticle.
As the concentration of water within the mesophyll decreases, water molecules
diffuse out of nearby veins. Those molecules, in turn, pull neighboring water molecules up the xylem. This movement of water molecules is repeated all the way down the xylem. Along the way, water molecules diffuse into "thirsty" tissues.
Gravitropism
directional growth in response to gravity. As a seed germinates, its shoot points upward toward light, and its roots grow downward into the soil. Turn the plant sideways, and the stem and roots bend according to the new direction of gravity. No one knows exactly how gravitropism works, although it is clear that the root cap must be present for roots to respond to gravity. One hypothesis centers on starch-rich plastids inside the root cap cells. These organelles function as gravity detectors, sinking to the bottoms of the cells (see figure 22.16). Some-how the position of the plastids tells the cells which direction is down. Turning a root sideways causes the plastids to move, redistributing calcium ions and auxins in a way that bends the root downward.
Phloem tissue transports
dissolved organic compounds like sugars. Sieve tube elements are the conducting cells; companion cells transfer materials in and out of sieve tubes.
Compound leaves are
divided into leaflets attached to one petiole.
Seeds
dormant plant embryo packaged with a food supply; tough outer coat that keeps the interior from drying out. The food supply sustains the young plant between the time the plant germinates until it can do photosynthesis. Is considered a reproductive adaptation for gymnosperms and angiosperms.
The origin of seeds
dormant, protected plant embryos with a nutrient supply—was also adaptive. Seeds might travel far from the parent and only germinate when conditions are favorable
Cytokinins
earned their name because they stimulate cytokinesis, or cell division. In flowering plants, most cytokinins affect roots and developing organs such as seeds, fruits, and young leaves. Cytokinins also slow the aging of mature leaves, so these hormones are used to extend the shelf lives of leafy vegetables.
Transpiration
evaporation of water from a leaf, this is how plants lose water. (ex: heat from the sun)
When stomata are open, mesophyll cells
exchange gases with the atmosphere.
Ovules produce
female gametophytes (embryo sacs)
Angiosperms are
flowering plants, recently the origin of flowers and fruits introduced new reproductive adaptations
2 angiosperms unique to angiosperms
flowers and fruits
Angiosperm life cycle includes
flowers, fruits, and seeds
Today, most plant species have reproductive structures called
flowers, which develop into seed-toting fruits. Flowers produce pollen and eggs; wind or animals usually carry pollen from plant to plant. Fruits protect the seeds and disperse them to new habitats. Variation in flowers and fruits is the result of millions of years of evolution.
Asexual reproduction
forming new individuals by mitotic cell division. A parent organism produces offspring that are genetically identical to it and to each other—they are clones. Also called vegetative reproduction, is advantageous when conditions are stable and plants are well-adapted to their surroundings, because the clones will be equally suited to the same environment.
The pollen grain and embryo sac are
gametophyes
Sexual reproduction yields
genetically variable offspring with a mix of traits derived from two parents. Scrambling genes in this way is adaptive in a changing environment. After all, a gene combination that is successful today might not work in the future if selective pressures change. Producing variable offspring improves reproductive success in an uncertain world.
The most famous nitrogen-fixing bacteria
genus Rhizobium, stimulates nodule formation on the roots of legumes (clover, beans, peas, peanuts, soybeans, and alfalfa).
Common ancestor to plants
green algae (their chloroplasts have the same pigment, similar DNA, similar cell wall, starch nutrient reserve)
Plant cells form these 3 main tissue systems
ground tissue, dermal tissue, and vascular tissue
Plant tissues
group of cells that interact to provide a specific function
When the pollen grain germinates, a pollen tube begins to
grow toward the ovule.
eudicots
have two cotyledons (the first leaf structures to arise in the embryo), and their pollen grains feature three or more pores. 175,000 species exist, representing about 2/3 of all angiosperms. Eudicots include roses, chili peppers, elm trees, daisies, sunflowers, oaks, tomatoes, beans, and many others.
Seedless vascular plants
have xylem and phloem but don't produce seeds. Have true roots, stems, and leaves. The leaves and roots arise from underground stems called rhizomes that store carbohydrates that provide energy for the growth of new leaves and roots. Have sperm that requires a film of water to reach the egg, live in moist habitats. Includes 2 phyla with 4 lineages.
Secondary xylem eventually becomes unable to conduct water, forming
heartwood
According to pressure flow theory, phloem sap moves from
high pressure at sources to low pressure at sinks. Water movement causes the pressure changes in the phloem tissue.
Auxins
hormones with many effects on plant growth and development. For example, by promoting cell elongation, auxins control plant responses to light and gravity. In addition, the embryos inside seeds secrete auxins that stimulate fruit development. Auxins have commercial uses. These hormones stimulate the growth of roots from cuttings, which is important in the asexual production of plants. A synthetic auxin called 2,4-D (2,4-dichlorophenoxyacetic acid) is a widely used herbicide, although the mechanism by which this compound kills plants is unclear.
vascular cambium
internal cylinder of meristem tissue that produces most of the diameter of a woody root or stem. This lateral meristem forms a thin layer between the primary xylem and phloem. When a cell in the vascular cambium divides, it produces two daughter cells. One of the two cells remains a meristem cell. If the other cell matures to the inside of the cambium, it becomes secondary xylem; if it matures to the outside, it becomes secondary phloem.
How can you tell the difference between a simple leaf and one leaflet of a compound leaf?
leaf has an axillary bud at its base, whereas an individual leaflet does not
Ground tissue occupies most of a
leaf. Vascular bundles are embedded in the ground tissue. Dermal tissue covers the leaf
Primary organs of photosynthesis
leaves
Stems support
leaves
Primary growth
lengthens the shoot or root tip by adding cells produced by the apical meristems
Tracheids
long, narrow cells that overlap at their tapered ends. Water moves from tracheid to tracheid through pits, which are thin areas in the cell wall.
These photos show how the fruit forms. After pollination, the flower
loses its petals. A developing seed releases hormones that trigger fruit formation. The ovary swells.
How photosynthesis affected the atmosphere
lowered CO2 levels, increased O2 levels, increased ozone layer
Plants need 16 essential elements/nutrients (9 macronutrients, 7 micronutrients)
macronutrients (needed in large amounts) Carbon (C), oxygen (O), hydrogen (H), nitrogen (N), potassium (K), calcium (Ca), magnesium (Mg), phosphorus (P), and sulfur (S). micronutrients - needed in small amounts
Plants need 16 essential elements/nutrients (9 macronutrients, 7 micronutrients) How is it absorbed?
macronutrients (needed in large amounts) Carbon (C), oxygen (O), hydrogen (H), nitrogen (N), potassium (K), calcium (Ca), magnesium (Mg), phosphorus (P), and sulfur (S). micronutrients - needed in small amounts Leaves and roots absorb nutrients from air and soil.
Plant organs
made up of multiple interacting tissues
Anthers produce
male gametophytes (pollen grains)
Plant growth occurs at
meristems, regions of active cell division
Tree rings arise from alternating
moist and dry seasons. Wood that forms in the spring has larger cells than wood that forms in the summer.
vascular cylinders of monocot and eudicot roots
monocot roots, a ring of vascular tissue surrounds a central core (pith) of parenchyma cells. In most eudicots, the vascular cylinder consists of a solid core of xylem, with ridges that project toward the root's exterior. Phloem strands are generally located between the "arms" of the xylem core.
All plants are
multicellular organisms with eukaryotic cells
What are the most common ingredients in commercial fertilizers?
nitrogen (N), phosphorus (P), potassium (K),
Leaves attach to stems at
nodes. Spaces between nodes are internodes.
vegetative plant parts are
non reproductive
Ground tissue consists of three main cell types
parenchyma, collenchyma, and sclerenchyma. The cells that compose ground tissue are important sites of photosynthesis, respiration, storage, and support.
sugars are pushed to nonphotosynthetic cells in
phloem
Node
point at which one or more leaves attaches to the stem, also has an axillary bud
Some flowers release
pollen grains in the wind
What happens after a pollen grain lands on a stigma of the correct species
pollen tube emerges (step 1). The pollen grain's two haploid sperm nuclei enter the pollen tube as it grows through the tissue of the style toward the ovary (step 2). When the pollen tube reaches an ovule, it discharges its two sperm nuclei into the embryo sac. Then, in double fertilization, the sperm nuclei fertilize the egg and the central cell's two nuclei (step 3 & 5). That is, one sperm nucleus fuses with the haploid egg nucleus and forms a diploid zygote, which will develop into the embryo. The second sperm nucleus fuses with the haploid nuclei in the central cell. The resulting triploid nucleus divides to form a tissue called endosperm, which is composed of parenchyma cells that store food for the embryo.
If a pollen grain lands on a receptive stigma, what occurs?
pollination
What is the next step after the pollen sac opens and releases millions of pollen grains?
pollination
Lignin
polymer that strengthens cell walls. Allows vascular plants to grow tall and form branches. This is an adaptation because tall plants can reach sunlight better.
Plant leaves
produce carbohydrates such as sucrose by photosynthesis, made up of flattened blade supported by a stalklike petiole
haploid (gametophyte) stage
produces gametes by mitosis cell division; these sex cells fuse at fertilization. The sporophyte develops from the zygote, starting the cycle again.
cork cambium
produces parenchyma cells toward the inside and dense, waxy cells called cork toward the outside. Cork is the outer protective layer of bark.
vascular cambium
produces secondary xylem toward the inside of the stem and secondary phloem toward the outside.
Fruits do what to seeds?
protect and disperse seeds. Seeds carried away from parent plants decrease the chance of competition among parents, offspring, and siblings. Unripe fruits, which contain immature seeds, are usually distasteful. Ripe fruits are tasty; mature seeds are deposited in droppings.
Flowers are what type of organ?
reproductive
Reproductive and vegetative parts of a plant
reproductive - flowers vegetative - stems, leaves, and roots
Flowers
reproductive organs that bring together eggs and sperm
Some of the sugar produced in the shoot system travels through the stem to the
roots, which are usually belowground.
Plant growth begins with
seed germination
cotyledons
seed leaves. (The cotyledons are called "seed leaves" because in many species they emerge from the soil with the seedling and carry out photosynthesis for a short time. But they are not true leaves.)
Bryophytes
seedless plants that lack vascular tissue (and lignin). Small, compact, simplest plants. Each cell can absorb water and minerals directly from surroundings. Use osmosis and diffusion to transport materials between cells. Don't have true leaves or roots. Photosynthesis in flattened leaflike areas. Rhizoids that anchor it to the ground. Rhizoids cannot tap distant sources of water so the plant is restricted to moist, shady environments. Can enter dormancy during droughts.
Flowers and seeds are produced by angiosperms that
sexually reproduce, yielding genetically unique offspring with traits derived from two parents. Sexual reproduction produces variable offspring, increasing reproductive success in a changing world.
Many seedless vascular plants live in
shady, moist habitats. these plants cannot reproduce sexually in the absence of free water. Most live on land, where their roots and rhizomes help stabilize soil and prevent erosion. But not all species are terrestrial.
Vessel elements
short, wide, barrel-shaped conducting cells that stack end to end, forming long, continuous tubes. Their side walls have pits, but their end walls are either perforated or absent. Water moves much faster in vessels than in tracheids, both because of their greater diameter and because water can pass easily through each vessel element's end wall. Narrower tracheids are less vulnerable to air bubble formation.
Roots and fruits, which require sugar but do not carry out photosynthesis, are
sinks
diploid (sporophyte) stage
some cells undergo meiosis and produce haploid spores, these spores divide by mitosis to form the gametophyte.
Internodes
stem area between nodes
Tissues build
stems, leaves, and roots
Vegetative plant parts include
stems, leaves, and roots
Pollination brings pollen to the
stigma
functions other than absorption in roots
storage and gas exchange. Beet and carrot roots stockpile starch, for example, and desert plant roots may store water. In oxygen-poor habitats such as swamps, specialized roots grow up into the air, allowing oxygen to diffuse in.
In addition to carrying out photosynthesis, leaves can
store nutrients, provide protection, and even trap animals. Onion bulbs, for example, are collections of the fleshy bases of leaves that store nutrients. Cactus spines are modified leaves that deter predators. Some flower parts, such as petals, are modified leaves. And in carnivorous plants, leaves attract, capture, and digest prey, as shown in the chapter-opening photo.
Plant stem
supports leaves, sugar moves down to support the roots. Has nodes and internodes.
Guard cells
surround each stoma and control its opening and closing.
Endosperm cells divide rapidly and nourish
the embryo
Cotyledons are
the embryo's "seed leaves." Embryonic shoots and roots also form.
Modifications in vascular tissue led to
the evolution of seedless vascular plants, like ferns.
In many angiosperms, the ovary grows rapidly to form
the fruit, which contains one or more seeds
endodermis
the innermost cell layer of the cortex. The walls of its tightly packed cells contain a ribbon of waxy, waterproof material. These deposits form a barrier that blocks the passive diffusion of water and dissolved substances into the xylem. The endodermis therefore acts as a filter, enabling the plant to exclude toxins and control the concentrations of some minerals
tropism
the orientation of a plant part toward or away from a stimulus such as light, gravity, or touch. All tropisms result from differential growth, in which one side of the responding organ grows faster than the other
Major evolutionary events in plants include
the origins of vascular tissue, pollen and seeds, and flowers.
At the same time, a fruit develops from
the ovary enclosing the developing seed(s).
Two sperm nuclei travel through
the pollen tube to the ovule.
Germination
the resumption of growth and development after a period of seed dormancy. It usually requires water, oxygen, and a favorable temperature. First, the seed absorbs water. The incoming water swells the seed, rupturing the seed coat and exposing the plant embryo to oxygen. Water also may cause the embryo to release hormones that stimulate the production of starch-digesting enzymes
Dermal tissue forms
the root epidermis.
Xylem transport is explained by cohesion-tension theory, Cohesion is
the tendency for water molecules to form hydrogen bonds with one another.
Pollination
the transfer of pollen from an anther to a receptive stigma. Usually, either animals or wind carry the pollen. Flower color, shape, and odor attract animal pollinators. For example, hummingbirds are attracted to red, tubular ',flowers. Beetles visit dull-colored flowers with spicy scents, whereas blue or yellow sweet-smelling blooms attract bees. Bee-pollinated flowers often have markings that are visible only at ultraviolet wavelengths of light, which bees can perceive. Butterflies prefer red or purple flowers with wide landing pads. Moths and bats pollinate white or yellow, heavily scented flowers, which are easy to locate at night.
Vascular tissue forms
the transportation system that connects plant parts.Xylem and phloem function in different ways.
Parasitic plants tap into
the vascular tissue of other plants. Mistletoe roots push through the epidermis of this tree, connecting to its xylem and phloem.
In double fertilization
these sperm nuclei fertilize the egg and the two polar nuclei. Double fertilization results in a diploid zygote and triploid endosperm nucleus.
The green leaves of this strawberry plant are sugar "sources" because
they carry out photosynthesis.
gametophyte and sporophyte trend in plants
they tend to vary in size and independence in different plants
taproot system
thick main root from which lateral branches emerge. Taproots grow fast and deep, maximizing support and enabling a plant to use minerals and water deep in the soil. Most eudicots develop taproot systems.
Plant cells build
tissue
Phloem
tissue transports dissolved organic compounds, primarily sugars produced in photosynthesis. The main conducting cells are sieve tube elements and adjacent to each sieve tube element is at least one companion cell.
Apical meristems produce
tissues that lengthen the tips of shoots and roots.
Double fertilization
two sperm nuclei enter the female gametophyte. One sperm nucleus fertilizes the egg, producing the zygote that will develop into the embryo. The other sperm nucleus fertilizes a pair of nuclei in the female gametophyte's central cell. The resulting triploid nucleus develops into the endosperm
Simple leaves have
undivided blades
Plants grow by adding
units, or modules, consisting of repeated nodes and internodes
Veins
vascular bundles inside leaves, and they are often a leaf's most prominent external feature. Many monocots have parallel veins, with several major longitudinal veins connected by smaller minor veins. Most eudicots have netted veins, with minor veins branching in all directions from large, prominent midveins.
Veins , monocot vs eudicots
vascular bundles inside leaves. Many monocots have parallel veins; most eudicots have netted veins.
Gymnosperms are plants with
vascular tissue and seeds, such as pine trees.
The presence or absence of these characters defines each plant group
vascular tissue, pollen and seeds, and flowers.
Mesophyll cells also exchange materials with
vascular tissues
sapwood transports
water and dissolved minerals
Xylem tissue transports
water and minerals from the roots to other plant parts. It consists of long, narrow cells called tracheids and wide, barrel-shaped cells called vessel elements.
Soil and air provide
water and nutrients
Vascular tissues transport
water, minerals, carbohydrates, and other dissolved compounds.
fibrous root system
widespread network of slender roots arising from the plant's stem. Grasses and other monocots usually have fibrous root systems. Because they are relatively shallow, these roots rapidly absorb minerals and water near the soil surface and prevent erosion.
water and minerals are pulled up to leaves in
xylem
Seedless vascular plants have
xylem and phloem but not seeds. These plants typically have true roots, stems, and leaves. ex: club mosses spike mosses whisk ferns horsetails true ferns
Seedless vascular plant lineages and phyla
• Club mosses (phylum Lycopodiophyta) small plants, simple leaves, looks like needles. club-like reproductive structures. Club and spike mosses also called lycopods. • Whisk ferns (phylum Pteridophyta) simple plants, rhizomes, no roots. Most species have no obvious leaves. Branched stems that resemble whisk brooms. • Horsetails (phylum Pteridophyta) grow along streams or at the borders of forests. Branched rhizomes. Green aerial stems bearing spores at tips. Also called scouring rushes because their stems and leaves contain abrasive silica particles. Native Americans used these to polish bows and arrows, and early colonists and pioneers used them to scrub pots and pans. • True ferns (phylum Pteridophyta) largest group of seedless vascular plants. The fronds, or leaves, of ferns are their most obvious feature. Ferns were especially widespread and abundant during the Carboniferous period, when their huge fronds dominated warm, moist forests. Their remains form most coal deposits.
4 phyla of gymnosperms
• Cycads (phylum Cycadophyta) live in tropical and subtropical regions. palmlike leaves, produce large cones. Dominated Mesozoic era. Today, they are popular ornamental plants, but many species are near extinction in the wild because of slow growth, low reproductive rates, and shrinking habitats. • The ginkgo (phylum Ginkgophyta), also called the maidenhair tree, fan-shaped leaves. one species exists. It no longer grows wild in nature, but it is a popular cultivated tree. Ginkgos have male and female organs on separate plants; female ginkgo trees have fleshy seeds that produce a foul odor. Some people believe that extracts of ginkgo leaves may improve memory and concentration. • Conifers (phylum Pinophyta) such as pine trees are by far the most familiar gymnosperms. Have needlelike or scalelike leaves, and they produce egg cells and pollen in cones. Called "evergreens" because most retain their leaves all year. This term is somewhat misleading, however, because conifers do shed their needles. They just do it a few needles at a time, turning over their entire needle supply every few years. • Gnetophytes (phylum Gnetophyta) Some details of their life history suggest a close relationship with the flowering plants, but molecular evidence places these puzzling plants with the conifers. One example is Welwitschia, a slow-growing African plant with a single pair of large, strap-shaped leaves that persist throughout the life of the plant. Ephedra is also a gnetophyte. This plant was once used in weight-loss remedies, but its use in dietary supplements was banned after a series of ephedra-related deaths.
