chapter 22
Plants take signals from the changing lengths of day and night throughout the year, in a response called photoperiodism.
photoperiodism
stigma
the tip of a carpel, covered with a sticky substance that holds pollen grains when they land there.
Vegetative reproduction
type of asexual reproduction in which stems, leaves, or roots attached to the parent plant produce new individuals.
plant hormones can be released when
- response to normal changes - internal changes like parts of the plant's life cycle -
Flowering plants that produce many seeds within one ovary have larger fruit.
Flowering plants that produce many seeds within one ovary have larger fruit.
Flowers contain reproductive organs protected by specialized leaves.
Flowers contain reproductive organs protected by specialized leaves.
rhizomes
Other plants, such as irises, can reproduce using horizontal underground stems called rhizomes. New plants grow from buds in the rhizome's joints, even if separated from the parent plant.
regeneration
Plants that can grow a new individual from a fragment of a stem, leaf, or root are reproducing by regeneration
stolons
Some plants send out stems that grow horizontally along the ground. These stems are called runners, or stolons. At certain points on a stolon, roots and leaves are produced, and a new plant can grow. Strawberries reproduce almost exclusively in this way.
the filament supports the
anther
Gibberellins
plant hormones that produce dramatic increases in size. grapes
gametophytes of flowering plants are
tiny and enclosed within flowering parts.
style
tube that leads from the stigma to the ovary
in flowering plants, as in all vascular plants, the
sprorophyte is the dominant phase
Life Cycle of Nonvascular Plants: Moss
- Only plants (nonvascular plants) where the gametophyte phase is dominant - Moss = gametophytes - Sometimes, can see the sporophytes that are stalklike structures that are growing from the gametophyte - The moss sporophyte looks like a brown stem with a tiny cup called a capsule - Capsule at the tip of the moss sporophyte contains spore producing sacs called sporangia - When the spores are mature, the capsule opens and releases the spores - The spores allow seedless plants to disperse to new areas - If the spore lands in a favorable spot, it'll grow to become a gametophyte. - A moss gametophyte produces gametes in special reproductive structures. Each male structure- produces hundreds of sperm with whiplike flagella - Each female structure produces a single egg - Water= present; sperm swims toward the egg and the sporophyte phase begins once again
Life of Seedless Vascular Plants: Ferns
- Sporophyte is the dominant phase for all vascular plants, including seedless vascular plants such as ferns - Underside of a fern leaf = frond, might see sori - Sori: clusters of sporangia, which are spore producing sacs - Sori look like brown dots on the fern frond - Spores are released from the sporangia when they are mature. If a spore lands into a suitable spot for growing, it will grow into a gametophyte - Prothallus: fern gametophyte - Prothallus is a plant body the size of fingernail, anchors itself to soil with tiny threadlike structures called rhizoids. Contains reproductive structures that produce sperm and eggs - When free standing water = present, male structures release sperm and swims toward the egg. When the sperm fertilizes the egg, a zygote forms on the prothallus. The zygote grows above the prothallus and will eventually rot away. - Newly forming fronds: fiddleheads, slowly uncurl as they grow - Eventually, the sporophyte will produce spores on the underside of each frond, and the cycle will begin again
tubers
A potato is actually a tuber, an underground stem modified for storage. The "eyes" of a potato are buds that can sprout new plants
A spore marks the beginning of the haploid phase of the plant life cycle. A spore divides by mitosis and grows into a mature gametophyte (guh-MEE-tuh-FYT), or gamete-producing plant. Specialized parts of a mature gametophyte produce gametes—sperm and eggs—through mitosis. When a sperm meets an egg, fertilization takes place, and the cycle continues with a new sporophyte.
A spore marks the beginning of the haploid phase of the plant life cycle. A spore divides by mitosis and grows into a mature gametophyte (guh-MEE-tuh-FYT), or gamete-producing plant. Specialized parts of a mature gametophyte produce gametes—sperm and eggs—through mitosis. When a sperm meets an egg, fertilization takes place, and the cycle continues with a new sporophyte.
After pollination, one cell in the pollen grain grows into a pollen tube. This tube extends down the style toward the ovule. The other cell in the pollen grain divides by mitosis, producing two sperm. Both sperm travel down the pollen tube. One sperm fertilizes the egg. The other sperm combines with the polar nuclei in the embryo sac. This cell now has a triploid (3n) nucleus. It will become the endosperm, a food supply for the developing plant embryo. The process in which one sperm fertilizes an egg and the other forms a triploid cell is called double fertilization. Double fertilization only happens in flowering plants and gives them an advantage over cone-bearing plants. Cone-bearing plants produce a food supply for each egg before fertilization. However, if the egg of a flowering plant is not fertilized, the plant does not waste energy making an unneeded food supply.
After pollination, one cell in the pollen grain grows into a pollen tube. This tube extends down the style toward the ovule. The other cell in the pollen grain divides by mitosis, producing two sperm. Both sperm travel down the pollen tube. One sperm fertilizes the egg. The other sperm combines with the polar nuclei in the embryo sac. This cell now has a triploid (3n) nucleus. It will become the endosperm, a food supply for the developing plant embryo. The process in which one sperm fertilizes an egg and the other forms a triploid cell is called double fertilization. Double fertilization only happens in flowering plants and gives them an advantage over cone-bearing plants. Cone-bearing plants produce a food supply for each egg before fertilization. However, if the egg of a flowering plant is not fertilized, the plant does not waste energy making an unneeded food supply.
At fertilization, the next sporophyte generation begins. The ovule becomes a seed, which contains an embryo and a nutritious endosperm enclosed by a protective seed coat. Using the nutrients provided by the endosperm, the embryo develops one or two cotyledons, or seed leaves. Recall that monocots have one cotyledon and dicots have two cotyledons. Cotyledons sometimes provide nourishment for the new plant before it can begin producing its own food through photosynthesis.
At fertilization, the next sporophyte generation begins. The ovule becomes a seed, which contains an embryo and a nutritious endosperm enclosed by a protective seed coat. Using the nutrients provided by the endosperm, the embryo develops one or two cotyledons, or seed leaves. Recall that monocots have one cotyledon and dicots have two cotyledons. Cotyledons sometimes provide nourishment for the new plant before it can begin producing its own food through photosynthesis.
Production of Male Gametophytes
Cells within the anthers divide by meiosis to produce four male spores. Each spore divides again, by mitosis, producing two haploid cells. These two cells, together with a thick wall that protects them, form a single pollen grain. Wind-pollinated plants have light, fine pollen grains that can be carried far by the wind. Pollen from wind-pollinated plants, such as ragweed, is the source of some outdoor allergies.
thigmotropism
Many plants also have a response to touch, called thigmotropism. This quality is apparent in climbing plants and vines. Tendrils emerge from the leaf base of these plants and grow in coils around anything they touch. In these curling "fingers," contact with an object triggers the same sort of cell growth that is found with other tropisms. Plants are sensitive to many kinds of touchlike stimuli. For example, a plant regularly exposed to winds on a hillside will grow as if it is being pushed in the direction of the wind. Repeatedly touching a young plant can even stunt its growth.
Most flower species have both male and female structures. However, some can have only one.
Most flower species have both male and female structures. However, some can have only one.
production of female gametophytes
One female gametophyte can form in each ovule of a flower's ovary. One cell in the ovule divides by meiosis to produce four female spores. In most flowering plants, three of these spores die. The nucleus of the last spore grows, dividing by mitosis three times, resulting in one spore with eight nuclei. Membranes grow between the nuclei to form seven cells. Together, these seven cells make up the female gametophyte, which is sometimes called an embryo sac. One large, central cell has two haploid nuclei, called polar nuclei. One of the other cells develops into an egg
Other plant species have seeds that stay dormant even during good growing conditions. For example, strawberry seeds remain dormant until their seed coats are weakened in the digestive tract of an animal. This way, the seeds are not only carried far from the parent plant but they are also deposited with their own batch of fertilizer. Other seeds have waterproof seed coats that can only be cracked by winter ice. Then, in the spring, the embryo can begin to grow with less chance of freezing than if it had begun to grow in the fall.
Other plant species have seeds that stay dormant even during good growing conditions. For example, strawberry seeds remain dormant until their seed coats are weakened in the digestive tract of an animal. This way, the seeds are not only carried far from the parent plant but they are also deposited with their own batch of fertilizer. Other seeds have waterproof seed coats that can only be cracked by winter ice. Then, in the spring, the embryo can begin to grow with less chance of freezing than if it had begun to grow in the fall.
Life Cycle of Seed Plants: Conifers
Sporophyte is the familiar form for all seed plants. Produces two types of spores that develop into male and female gametophytes. Gametes of seed plants are microscopic. Pine tree: typical conifer sporophyte. Two different types of cones: cone-bearing plants have male and female cones. Female cones are usually larger and more scaly than male cones. They live and grow for several years. Each scale of a female pine cone has two ovules that produce spores. One spore in each ovule can develop into a microscopic female gametophyte, and the rest will die. Male spores are produced inside of male cones, which only live for a few weeks. Male spores develop into pollen grains, which are the very tiny male gametophytes of seed plants. When a pollen grain lands on a female cone, it sticks. Pollination occurs in a cone-bearing plant when a pollen grain reaches the small opening of an ovule. After pollination, eggs are produced inside the ovule and a pollen tube begins to grow from the pollen grain toward an egg. In pine species, it takes a year for the pollen tube to reach the egg, which is only several millimeters away.
Sporophyte is the familiar form for all seed plants. Produces two types of spores that develop into male and female gametophytes. Gametes of seed plants are microscopic. Pine tree: typical conifer sporophyte. Two different types of cones: cone-bearing plants have male and female cones. Female cones are usually larger and more scaly than male cones. They live and grow for several years. Each scale of a female pine cone has two ovules that produce spores. One spore in each ovule can develop into a microscopic female gametophyte, and the rest will die. Male spores are produced inside of male cones, which only live for a few weeks. Male spores develop into pollen grains, which are the very tiny male gametophytes of seed plants. When a pollen grain lands on a female cone, it sticks. Pollination occurs in a cone-bearing plant when a pollen grain reaches the small opening of an ovule. After pollination, eggs are produced inside the ovule and a pollen tube begins to grow from the pollen grain toward an egg. In pine species, it takes a year for the pollen tube to reach the egg, which is only several millimeters away.
Sporophyte is the familiar form for all seed plants. Produces two types of spores that develop into male and female gametophytes. Gametes of seed plants are microscopic. Pine tree: typical conifer sporophyte. Two different types of cones: cone-bearing plants have male and female cones. Female cones are usually larger and more scaly than male cones. They live and grow for several years. Each scale of a female pine cone has two ovules that produce spores. One spore in each ovule can develop into a microscopic female gametophyte, and the rest will die. Male spores are produced inside of male cones, which only live for a few weeks. Male spores develop into pollen grains, which are the very tiny male gametophytes of seed plants. When a pollen grain lands on a female cone, it sticks. Pollination occurs in a cone-bearing plant when a pollen grain reaches the small opening of an ovule. After pollination, eggs are produced inside the ovule and a pollen tube begins to grow from the pollen grain toward an egg. In pine species, it takes a year for the pollen tube to reach the egg, which is only several millimeters away.
The diploid phase of a plant life cycle begins with a fertilized egg, called a zygote. A zygote divides by mitosis and grows into a mature sporophyte (SPAWR-uh-FYT), or spore-producing plant. A mature sporophyte has specialized cells that divide by meiosis to produce haploid spores.
The diploid phase of a plant life cycle begins with a fertilized egg, called a zygote. A zygote divides by mitosis and grows into a mature sporophyte (SPAWR-uh-FYT), or spore-producing plant. A mature sporophyte has specialized cells that divide by meiosis to produce haploid spores.
each carpel is made up of three parts:
The tip, called the stigma, is often covered with a sticky substance that holds pollen grains when they land there. The style is a tube that leads from the stigma to the ovary. Female gametophytes are produced inside the ovary, which is found at the base of a flower.
bulbs
Tulips, daffodils, and onion plants can all reproduce asexually with bulbs. Bulbs are underground stems surrounded by modified leaves adapted for storage, covered with a protective, papery skin. In favorable conditions, bulbs can divide to produce new plants.
Two sperm also develop inside the pollen grain during this time. Eventually, these sperm travel down the pollen tube toward the egg. The sperm of seed plants do not have flagella, since they do not need to swim through water to reach an egg. One sperm may fertilize an egg, forming a zygote, which will develop into an embryo. Meanwhile, the ovule develops into a protective pine seed. Each scale of a female pine cone can be home to two developing pine seeds. Once the seeds are mature, the scales open up and release them. The life cycle then begins again with a new sporophyte—a pine tree seedling.
Two sperm also develop inside the pollen grain during this time. Eventually, these sperm travel down the pollen tube toward the egg. The sperm of seed plants do not have flagella, since they do not need to swim through water to reach an egg. One sperm may fertilize an egg, forming a zygote, which will develop into an embryo. Meanwhile, the ovule develops into a protective pine seed. Each scale of a female pine cone can be home to two developing pine seeds. Once the seeds are mature, the scales open up and release them. The life cycle then begins again with a new sporophyte—a pine tree seedling.
vegetative propagation
Vegetative propagation takes advantage of a plant's ability to grow new individuals from fragments of a parent plant.
this tube extends
down the style toward the ovule
gravitropism
When a seed germinates underground, the root grows downward into the soil, and the shoot grows upward toward the soil surface. This up-and-down growth of a plant is called gravitropism, because the plant is responding to Earth's gravitational pull. Downward growth is positive gravitropism because the growth is in the direction that gravity pulls. Upward growth is negative gravitropism because it is growth against the force of gravity. Auxins play a part in gravitropism, which is more complex than phototropism. Root growth is stimulated by low levels of auxin, but is slowed down by high levels of auxin. Auxins build up on the lower side of horizontally growing roots so that the upper side grows faster and the root grows downward. At the same time, high levels of auxin, which stimulate shoot growth, build up in the lower side of the stem. This buildup causes the stem to grow upward.
phototropism
When light hits a plant stem, it causes auxins to build up on the shaded side. Remember that in a stem, auxins cause cell elongation. As described earlier, cell lengthening on the shaded side of a stem causes the stem to bend toward the light. This tendency of a plant to grow toward light is called phototropism. If you grow a plant in a space with only one small light source, that plant will lean toward the light through the process of phototropism, as shown in FIGURE 22.16. Let's say you turn that plant around so that it's pointing away from the light. If you come back in a few days, you will likely find the plant growing in the direction of the light again.
While the seed develops, the surrounding ovary grows into a fruit. The development of a pumpkin fruit is shown in FIGURE 22.8. Remember, a fruit is the mature ovary of a flowering plant. You have probably eaten many fruits, such as apples, watermelons, and cherries. Many foods that you think of as vegetables, grains, nuts, or beans are also technically fruits. Sweet peppers, tomatoes, and cucumbers are fruits that contain many seeds. The shells of peanuts are also fruit, while the two peanut "halves" inside the shell are cotyledons
While the seed develops, the surrounding ovary grows into a fruit. The development of a pumpkin fruit is shown in FIGURE 22.8. Remember, a fruit is the mature ovary of a flowering plant. You have probably eaten many fruits, such as apples, watermelons, and cherries. Many foods that you think of as vegetables, grains, nuts, or beans are also technically fruits. Sweet peppers, tomatoes, and cucumbers are fruits that contain many seeds. The shells of peanuts are also fruit, while the two peanut "halves" inside the shell are cotyledons
Alternation of Generations
alternates between diploid and haploid phases
ethylene
causes ripening and is naturally produced by fruits apples and tomatoes
Hormone
chemical messenger produced in one part of an organism that stimulates or suppresses the activity of cells in another part.
function of fruit in flowering plants
disperse seeds
Germination
embryo breaks out of seed coat and begins growing a seedling. begins when the embryo starts to take up water. As the embryo grows, the embryonic root, called a radicle, breaks through the cracks. Water also activates enzymes inside the seed. Recall that enzymes are proteins that need specific conditions to speed up chemical reactions. These enzymes help to break down material in the endosperm into sugars, which are moved to the growing embryo.
Dormancy
embryo stops growing
ovary
female gametophytes are produced inside the ovary, which is found at the base of a flower
each stamen has a stalk called
filament
Endosperm
food supply for the developing plant embryo
after pollination, one cell in a pollen grain
grows into a pollen tube
carpel
innermost layer of a flower is made up of a female structure
Petals:
layer just inside of the sepals, which are also modified leaves. Bright colors attract animals/pollinators. Monocot flowers- have sepals and petals that look the same. EX) lilies. These structures are often called tepals. Flowering plants that are not pollinated by animals usually have small sepals and petals, or have none at all.
stamen
male structure of the flower
Sepals:
modified leaves that protect the developing flower. Often green, but can be brightly colored as well.
auxins
plant hormones involved in the lengthening of plant cells produced in the apical meristem, or growing tip. Auxins stimulate growth of the primary stem, preventing growth of new branches. Gardeners can use this property of auxins to control branching patterns by cutting off the tip of a growing stem. With no growing tip, there is less auxin in the stem, and side branches are encouraged to grow. Conversely, high concentrations of auxins can prevent plant growth altogether, particularly in the roots. For this reason, auxins are a common ingredient in herbicides, chemicals used to kill unwanted plants.
Hormones have an influence when they move from the cells that secrete them to the cells for which they are targeted. Target cells have receptors that recognize the hormone. Most plant cells have receptors for many different hormones. When a hormone meets the right receptor, it triggers a response. Plant hormones are divided into several different groups based on their functions and chemical properties.
please just read it and do well on teh test
anthers produce
pollen grains, the male gametophytes
a lot of energy is required to
produce so much pollen
Plant life cycles alternate between producing spores and gametes.
read it *******
As the embryo continues to grow, a young shoot called the plumule eventually breaks through the surface of the soil. In most monocots, the cotyledon stays underground while the shoot grows upwards. Some species of dicots have cotyledons that stay below ground, but the cotyledons of other dicots emerge above ground with the growing shoot. When leaves emerge from the shoot, they begin to make food through photosynthesis. Once photosynthesis begins, the young plant is called a seedling.
read this
wind-pollinated species have
small or inconspicuous flowers and produce large amounts of pollen
cytokinins
stimulate cytokinesis, final stage of cell division They are produced in growing roots and developing seeds and fruits. They are also involved in the growth of side branches. This sideways growth is called lateral growth. Commercial florists make use of another property of cytokinins—they slow the aging process of some plant organs. For example, leaves dipped in a cytokinin solution stay green much longer than normal.
animal pollination is a lot more successful
than wind pollination
when a pollen grain reaches the stigma of the same plant species,
the flower has been pollinated
tropism
the movement of a plant in response to an environmental stimulus.
double fertilization
the process in which one sperm fertilizes an egg and the other forms a triploid cell