Plant Test (cap 8, 28-21) Flashcards
how does a sperm fertilize an egg in a plant
pollen lands on stigma-pollen tube forms and two sperm go down the tube opening (micropyle) of the ovary in the carpel. one sperm fertilizes the forming the zygote, the other sperm combines with two polar nuclei of the embryo sac forming a triploid cell that develops into endosperm-food for growing embryo
what is “alternation of generation” of a flowering plant
alternating between the sporophyte (diploid) stage and the gametophyte (haploid) stage in plants
double fertilization
two sperm used for fertilization
what is self-incompatibility in plants
ability of a seed plant to reject its own pollen and sometimes the pollen of closely related individuals
explain how a seed germinates. what is the order of events
- seed takes in water (ambition) due to a low water potential; seeds expands and ruptures coat
- gibberillins (hormone) break dormancy
- enzymes begin digesting the endosperm or cotyledons and nutrients go to growing regions of embryo
- radicle (embryonic root emerges)
- shoot tip breaks through the soil: eudicot: (get hook first) light causes hypocotyl to straighten, cotyledons separate and epicotyl spreads leaves. monocot: coleoptile pushes up through the soil-grows straight up, shoot then grows up through coleoptile
ethylene
fruit ripening, helps leaf abscission, senescence (programmed cell death in plants)
auxin
stimulates stem elongation, promotes lateral and adventitious root growth, regalates fruit development, retards leaf abscission
gibberellins
stimulate stem elongation, pollen development, pollen tube growth and seed development and germination
abscisic acid
inhibits growth; closes stomata during drought, promotes seed dormancy, inhibits germination
brassenosteroids
promote cell expansion and cell division in shoots, promotes root growth (low conc.), inhibits root growth (high conc.) promotes seed germination
know what phytochrome are
photoreceptors that absorb mostly red light
what are concerns people have with genetically modified crops
allergens; transgene escape (ex: creating supersedes); effect on non-target organisms
what causes short-day and long-day plants to flower
- response to light based on phytochromes
- red wavelength of 660nm increased germination; far-red light (730)nm inhibited germination
- last light determines the seed response
- reversible-phytochrome switches Pr in dark switches to Pfr in light
what causes a plant to grow towards the light
auxin-elongates the cells by creating proton pumps that lower pH of cell wall which activates enzymes (expansins) to break the cell wall so more water comes in and expands cell
effect of light on plants
etiolation: adaptations for growing in darkness de0etiolation: in which shoots and roots grow normally
mesophyll cells:
can be spongy or palisades. the main cells that conduct photosynthesis
guard cells
regulate the opening and closing of the stomata. if they are turgid=stomata is open (a lot of water) if they are flaccid=stomata is closed (not a low of water)
tracheids
xylem cells that conduct water. they are dead cells