BIOL:1412 Midterm 4

Pollen growth

- lands on compatible stigma of pistil - grows: forms pollen tube - carries (nonmotile) sperm to ovule, egg - growth of pollen tube directed by gene expression in tube nucleus

Alternation of generations

2 different body types make up the life cycle of all plants (gametophyte and sporophyte)

Vascular Cambium

3rd kind of meristem, provides secondary growth for plants

You have discovered a new plant species that is a woody tree with a taproot. When it flowers, it is likely that the flower parts will be in multiples of

4 or 5

If you drove a nail into the trunk of a tree that grows 6 inches taller every year, after 5 years how much higher would the nail be?

?? not 30

florigen

A flowering signal, probably a protein, that is made in leaves under certain conditions and that travels to the shoot apical meristems, inducing them to switch from vegetative to reproductive growth. (signal for flowering)

Light

Absorbed by pigments. Blue light triggers phototropism. •Phototropin- pigment in plasma membrane •Absorbs blue light, undergoes conformational change, exposes active site for a kinase •Signal transduction cascade leading to auxin-induced stem elongation •Phototropin also mediates stomate opening in response to blue light

Companion cells

Adjacent to and provides metabolic functions for sieve elements

Plasmodesmata

An open channel in the cell wall of plants through which strands of cytosol connect from adjacent cells (sharing of small molecules)

Macronutrients

C HOPKNS CaFe Mg (important and required for plant growth) C,H,O= for sugars P= DNA, RNA, ATP K= osmoregulation N= DNA, RNA, ATP, proteins S= proteins Ca= cell wall Fe= cell wall, e- transport Mg= chlorophyll

If a molecular biologist were interested in engineering soybeans to be more water efficient, they would transform the plants with the enzymes for

C4 photosynthesis.

HOw do plants take in CO2 and H2O

CO2 from atmosphere H2O from soil

Which two essential elements do plants obtain directly from the atmosphere?

Carbon and oxygen

Plant cell types: Sclerenchyma

Cell walls very hard, thick secondary walls strengthened w/ lignin. Dead (no cytoplasm or nucleus) long, slender: fibers Isodiametric: Sclereids

The vascular system in plants is most analogous to which animal system?

Circulatory system

Jasmonate

Class of plant hormones involved in herbivory and abiotic stress response

Which match of a plant tissue system with one of their functions is incorrect? Dermal system—facilitates photosynthesis in shoots Dermal system—controls water loss Vascular system—allows water and nutrient transport Ground system—facilitates photosynthesis in shoots Ground system—facilitates starch storage in roots

Dermal system—facilitates photosynthesis in shoots

Leaf morphology

Different margins/edges in order to maximize gas uptake and light absorption TYPES: tendril- support fleshy leaves store water spine- protection Bract- associated with flowering

Which statement about plant development is true? a.) Once differentiated, plant cells cannot change their cell fate. b.) Differential gene expression mediated by transcription factors plays an important role in determining cell fate. c.) Throughout development, the range of possible cell fates becomes progressively less restricted. d.) The developmental potential of early embryonic cells is narrower than the potential of cells from more advanced embryos. e.) Cell fate is determined only by informational molecules within a cell and not by signals from surrounding cells.

Differential gene expression mediated by transcription factors plays an important role in determining cell fate.

Sporophyte

Diploid, or spore-producing, phase of a olant. Vascular plants have roots, stem, more prominent phase.

GA (Gibberellic Acid)

Embryo produces gibberellin (a hormone, GA) GA diffuses throughout seed Target tissue: aleurone (outer layer of endosperm) Aleurone cells with GA produce a-amylase (enzyme that digests starch to à sugar) Sugars from digested endosperm diffuse to embryo (a "sink") Food reserves are unlocked to support embryo/ seedling growth

Germination

First trigger- external que (common in all plants) is water. Some plants require additional ques. Imbibition of water "activates" embryo and germination begins

After a very wet spring five years ago, the last four years have been extremely dry. If you cut down a sapling planted six years ago, what pattern would you expect to see in its annual rings?

Five rings, with the ring closest to the bark containing more cells with a large diameter

Path of water through plant

Goes thru epidermis (taken up by root hair) moves thru the cortex, thru plasmodesmata. Water heading toward xylem hits endodermis and either diffuses thru or is blocked.

Gametophyte

Haploid, or gamete-producing, phase of a plant. Very small in vascular plants

Auxin

Indoleacetic acid (IAA), a natural plant hormone that has a variety of effects, including stem elongation, root formation, secondary growth, and fruit growth.

Why are tests to determine essential plant elements done hydroponically rather than in soil?

It is easier to control nutrient concentrations in water.

osmosis

It is the movement of water across a membrane from low solute concentration to high solute concentration

What direct role does turgor pressure play in cell expansion?

It puts stress on the cell wall.

nitrogen adaptations

Often the most limiting mineral element. Atmospheric nitrogen (N2) not usable to plants. Adaptations to ensure sufficient N= some plants involve carnivory (venus fly trap), symbiosis with nitrogen fixing bacteria (Rhizobium, plant gives carbohydrates)

What are the functions of the cells resulting from a double fertilization event?

One cell goes on to form an embryo; the other cell goes on to form a food source for the embryo.

How many megaspores and how many sperm cells are involved in a double fertilization event?

One megaspore and two sperm cells

Parasitism

Parasite robs/extracts sugars and mineral elements from host plant. Roots of parasitic plant grow into host plant

phytochrome action

Pfr able to enter the nucleus and activate carious transcription factors w/ protein kinase. Without phytochrome there is no synthesis of GA slide 20 L33

Interrupting a long period of darkness with red light shifts the phytochrome ratio in favor of _______, which _______ blooming of short-day plants and _______ blooming of long-day plants

Pfr; inhibits; stimulates

Photoperiodic floral induction

Plant responds to night length

elicitors trigger plant response (may be from the pathogen)

Plants with resistance have receptor specific for elicitor. Susceptible plants do not trigger response and pathogen continues attack

How does primary growth differ from secondary growth in plants?

Primary growth results in height changes; secondary growth results in width changes.

Guard Cells

Proton pump pushes H+ ions out of guard cells, favoring K+ ions (Cl- is also cotransported) which decreases water potential and drives the uptake of water from surrounding tissue. Proton pump activated by blue light, circadian rhythm. Can be overridden (turned off) by ABA (abscisic acid) hormone.

The first mitotic division of the zygote establishes what feature or features of the developing plant?

Root-shoot axis and polarity

Scientists grew several generations of barley plants in hydroponic solutions containing different concentrations of Ni2+ and determined that Ni2+ was an essential micronutrient. They then germinated seeds from those plants in a nickel-free solution. What is the most likely reason that germination was successful in the nickel-free solution?

Seeds took up sufficient Ni2+ from their parent plants for germination.

Phloem loading

Sugars made in the mesophyll are transferred to phloem by simple diffusion

Mineral deficiency symptoms

Symptoms used to ID what mineral is missing. (i.e. Chlorophyll doesn't form without Mg so yellow leaves are Mg deficient.)

What did the experiments conducted by Charles and Francis Darwin demonstrate?

That the top of a plant transmits a signal to the growing region in response to light.

For a short-day plant, which event triggers flowering?

The occurrence of a long night

Both gymnosperms and eudicots are capable of forming wood, but monocots cannot. Why?

The patches of procambium in each monocot bundle couldn't all get lined up to make a smooth cylinder, since they are scattered throughout the stem

You notice that newly emerging daffodil petals are pale yellow. Once expanded, new pigment is rapidly synthesized converting the entire flower to a bright, vibrant yellow. When you extract the pigment and apply it to flowers that are still small and pale, you notice a rapid burst in new pigment production. Which mechanism could explain this?

The pigment is part of a positive-feedback loop

What evolutionary advantage might be gained by a plant carrying out double fertilization instead of single fertilization?

The plant conserves energy by producing a food source for zygotes only when zygotes are successfully formed.

Embryogenesis

The process by which a single-celled zygote becomes a multicellular embryo.

What is the best indicator of cellular identity?

The proteins contained within the cell

Prior to floral induction, what differentiates a vegetative meristem from a reproductive meristem?

There is no difference; all floral reproductive meristems begin as vegetative meristems.

C4 and CAM

These plants have a modified type of photosynthesis that enables the plant to conserve water in dry climates. •C4 photosynthesis- two photosynthetic cell types (mesophyll and bundle sheath; BS contains RUBISCO) •CAM plants open stomata at night, close during day •In both, initial carbon fixation by PEP carboxylase, an enzyme that binds CO2 and not O2

What is a major difference between tracheids and vessel elements?

Tracheids are spindle-shaped; vessel elements are larger in diameter.

apoplast vs symplast

Two paths water can take when it enters the plant. -apoplast: outside plasma membrane, ends at endodermis, blocked by Casparian strip (Membranes select certain ions, increasing their concentration or blocking others) -symplast: inside cells, continuous(uses plasmodesmata)

turgor pressure

Uptake of water by a plant cell is limited. Cell is pushing back w/ an equal amount of force, causing the plant to stand up on its own and this is called turgor pressure

Axillary buds

a bud that grows from the axil of a leaf and may develop into a branch or if in reproductive state, flower cluster.

The first hormone produced by a plant as part of an induced response to drought stress is

abscisic acid.

root function

anchorage, absorption of water and minerals, storage

Primary growth occurs

at the apex of the shoot.

Redwood trees can grow to be 300 feet tall because they have rigid bundles of cells that support the tree the way rebar supports a tall building. What type of cell in the redwood performs this function? a. Parenchyma b. Sclerenchyma fibers c. Collenchyma d. Sclerenchyma sclereids e. Epidermal cuticle

b. Sclerenchyma fibers

Which of the following plant cell types have functional chloroplasts? a. parenchyma in root cortex b. Fibers in leaf phloem c. Parenchyma in leaf mesophyll d. sclereids in the shell of a nut

c. Parenchyma in leaf mesophyll

In a newly discovered organism, which characteristic would point to its being a plant rather than an animal? a. The presence of different cell types. b. The ability to respond to the environment. c. The ability to add new organs. d. The ability to form embryos. e. The presence of different tissues.

c. The ability to add new organs

ground tissue

carries out photosynthesis, stores photosynthetic products, and helps support the plant

The three tissue systems in the plant body are in a(n) _______ arrangement.

concentric

Phloem (vascular tissue)

conducts food. Conducting cell: sieve element (alive but highly modified, lacks many major organs)

Xylem (vascular tissue)

conducts water. Conducting cells - Tracheids, vessel elements (hollow tubes, Dead). Vessel elements have elaborate secondary walls and only in angiosperms. Tracheids found in all vascular plants

The plasma membrane of plant cells

contains an ATP-dependent proton pump.

Which of the following is not a nutritional adaptation? a. ability to establish Rhizobium residency in roots b. modification of leaf development to ensnare an insect c. evolution of capacity to detect and grow roots into the tissues of another plant d. evolution of ability to form thick secondary walls on long, hollow cells that transport water

d. evolution of ability to form thick secondary walls on long, hollow cells that transport water

The association of plant roots with mycorrhizal fungi a. is deleterious to the plant. b. retards root function. c. decreases root surface area. d. provides an energy source for the plant. e. increases nutrient uptake—especially phosphate.

e. increases nutrient uptake—especially phosphate.

Seeds contain

embryo with root and shoot apical meristems, 1 or 2 cotyledons, food storage in cotyledons or endosperm

Researchers discover that a species of maple tree cannot survive and complete its life cycle without tiny amounts of cadmium. For this tree, cadmium is a(n)

essential micronutrient

You place a tank of an unknown gas next to a tree full of green lemons and open the valve. The fruit ripens, and the tree's leaves fall off. That tank must contain

ethylene

A student views a cross section of a plant stem under a microscope. She decides that the plant must be a monocot because its vascular tissue

has vascular bundles scattered throughout.

Caterpillars feeding on the leaves of a plant may

ingest growth-stunting protease inhibitor produced in response to production of jasmonate.

Self-incompatibility

is a mechanism in some plants to prevent self-fertilization.

Many plants have evolved over time to use animal pollinators rather than wind or water. This adaptation probably occurred because animal pollination

is more efficient.

Pollination

is the transfer of pollen from the anther to the stigma of pistil.

Which of the following is not involved in a plant bending toward light (phototropism)? a. Blue light activation of phototropin b. Asymmetric stem elongation mediated by higher auxin levels on the shaded side of the shoot c. Polar auxin transport d. Antagonism with cytokinin coming from the root

its not c

Which of the following is not true of photoperiodic induction of flowering? a. It allows plants to optimize seed production by flowering when pollinators are available and in time to complete seed development before a killing freeze b. It relies on a Pfr-setting of an internal clock c. Florigen is synthesized in the shoot apical meristem, where it regulates flowering genes d. The length of night is the environmental cue that induces photoperiodic flowering

its not d

Modular organization

leaf, bud, stem

•What organ perceives photoperiod?

leaves

Grafting experiments involved in the characterization of florigen

led to the proposal of a flowering hormone.

Phototropins are

light receptors for phototropism

If a corn plant lacks the micronutrient _______, it will not be able to complete synthesis of its chlorophyll.

magnesium

Bud scale

modified leaf that protects meristem (SAM). Present thru winter, fall off when ready to grow leaving scar

Lettuce seeds are exposed to this sequence of light: red, far-red, red, red, far-red. They will

not germinate

monocot characteristics

one cotyledon embyro leaf veins usually parallel vascular bundles usually complexly arranged fibrous root system floral parts usually in multiples of 3

Apical dominance

phenomenon in which the closer a bud is to the stem's tip, the more its growth is inhibited. Auxin blocks cytokinin from growing the branches

Leaf function

photosynthesis (each leaf has 1 axillary bud)

You are working with a plant that you have infected with a fungus. Chemical analysis shows that one chemical is produced in large amounts, and in culture, this chemical inhibits fungal growth. You have found a plant that makes a(n)

phytoalexin.

The male gametophyte of angiosperms

pollen grain

Plant Cell Types: Parenchyma

primary wall only present, living cell wall (nuclei in cells)

Out-crossing

production of seeds using pollen from a different flower. Used to combat inbreeding and subsequent accumulation of genetic defects from self-fertilization

The root cap

protects the root apical meristem.

phytochrome

red light receptor. Seed germination. Control of flowering. 2 interconvertible states (Pfr: active; Pr: inactive)

Micronutrients

required in much smaller amounts (still relevant for healthy plant growth)

Stomatal compromise seeks to balance a plant's need to enable _______ of water and _______ of CO2

retention; uptake

sequestering

separating 2 different components of a potential poison

Sugar moves from a sugar beet's root to its new leaves. The sugar travels through a system composed of cells attached end to end and connected by a set of pores. The sugar is traveling through _______, which are _______.

sieve tube elements; alive

Bryophytes

simplest land plants, non vascular

Dermal tissue

single layer of cells on outside of the plant known as epidermis (for protection)

Fertilization of a flower is complete when the

sperm in the pollen tube reaches the egg cell.

Pollen germination depends on recognition by cells in the

stigma of the pistil

stem function

support, transport, storage

3 root forms

tap fibrous adventitious (root comes from stem, not seed)

when water is taken up by a root, once it gets through the epidermis, it next enters

the cortex

Stomata

the small openings on the undersides of most leaves through which oxygen and carbon dioxide can move. Accompanied by guard cells which Opens and closes stomata by changing water potential (fill GC with water, get longer and open pore)

All the following are characteristics of the xerophytes

thick cuticles. stomata in crypts. succulence. leaf hairs (trichomes) to diffract light

Vascular tissue

transports fluids and products of photosynthesis

Endosperm

triploid (3n) nutritive tissue in an angiosperm seed. Product of second fertilization event

dicot characteristics

two cotyledons (embryo) leaf veins usually net like vascular bundles usually arranged in a ring taproot usually present floral parts usually in multiples of 4 or 5

other external cues for flowering

vernalization (chilling) biennials (life cycle in 2 years; dies after flowering)

Double fertilization

•2 sperm in each pollen •1 fuses with egg--->zygote •Beginning of new sporophyte generation •1 fuses with central cell---> endosperm •Nutritive tissue for developing embryo, seedling •Triploid (1N from sperm, 1N + 1N from 2 polar nuclei in central cell)

cytokinin

•Adenine-like molecule •Shoot induction •Axillary bud outgrowth •Prevention of leaf senescence

What makes the SAM switch from vegetative to reproductive growth?

•All plants: internal cues (Maturation or "phase change") •Many plants: external cues also (Daylength- "photoperiodism" and Chilling- "vernalization")

Critical daylength

•Days must be shorter than some critical daylength for SDP's to flower •Days must be longer than some critical daylength for LDP's to flower

Plant hormones

•Effective at very low concentrations •No endocrine glands in plants •Plant hormones can work where they are formed as well as in other tissues and organs •Small molecules- diffuse through plant •Regulate growth •Coordinate physiological processes •Mediate responses to the environment •"to excite"

Flower organization

•Floral organs arranged in whorls Sepal: protects flower before it emerges Petals: attract pollinators Female reproductive parts: pistil •Bears ovules •Ovules produce embryo sac (Stigma, Style, Ovary) Male reproductive parts: Stamen- produces pollen (Anther, Filament)

Polar transport of auxin

•IAA is a weak acid •Uncharged form crosses plasma membrane •In cell, higher pH-> IAA becomes charged, trapped •Can exit cell only through efflux carriers on "root end" of each cell •ATP required to maintain pH difference •5 in apoplast •7 in symplast

Effect of a hormone depends on...

•Its concentration •Its location The presence and concentration of other hormones

Angiosperm life cycle

•Meiosis •Gametophyte development •Pollination •Fertilization •Embryo development •Seed formation

Hypersensitive response to infection

•Phytoalexins (antibiotics) •Pathogenesis-related proteins •Physical isolation- necrotic lesion

Photoperiodic plants

•Short day plants (SDP): flower when days are short •Long day plants(LDP): flower under long days •Day neutral (DNP): daylength does not affect flowering time

How does GA cause endosperm cells to make a-amylase?

•Transcription, translation of a-amylase gene •Transcription factor binds to promoter •Kept in check by repressor •GA binds receptor, enters nucleus •Complex removes repressor •a-amylase is produced (slide 4 L33)

abscisic acid (ABA)

•Water stress response •Stomate closing •Dormancy •Seeds •Winter buds