plant life and physiology (exam 2) Flashcards
ethylene is best known for what doing what to fruit?
ripening fruit
ethylene participates in what processes of leaves?
senescence (deterioration) and abscission (breaking off)
what two chemicals determine when a leaf will fall?
cytokinin and ethelene
cytokinin and ethylene produce an enzyme that what?
separates cells (not breaks them)
how is energy from photosynthesis converted to chemical energy?
absorption of the pigment chlorophyll
what do seeds (of weeds, specifically) require to germinate?
light
blue light trigger what response to light in plants?
phototropism
define phototropism
the growth/movement response of a plant to light
what is phototropin?
a pigment in the plasma membrane
how does phototropin result in a signal transduction cascade?
it absorbs blue light, undergoes conformational change, and this exposes an active site for a protein kinase
phototropin also mediates what?
stomate opening in response to blue light
blue light’s wavelength causes a what?
biological response
red light is needed for what reproductive process?
seed germination (often times)
what is phytochrome?
a red/far-red light photoreceptor
Pr stands for an _____ state and Pfr stands for an _______ state
inactive, active
Active Pfr results in what 3 things?
chlorophyll synthesis
hook unfolding
leaf expansion
Pr best absorbs ______ (red light or far-red light) and Pfr best absorbs _____ (red light or far-red light)
red light, far-red light (the opposite of what results from the type of light)
Pfr undergoes a change in _____ to expose proteins in order to enter a nucleus
conformation
T or F: all plants have both a sporophyte and a gametophyte generation
true, but the dominant phase varies
a sporophyte is = to what?
the plant
where are gametophytes produced?
in the flowers of angiosperms
the male gametophyte (has sperm) is what?
pollen
the female gametophyte (has egg) is what?
an embryo sac
what is the function of sepals?
protect the flower and conduct photosynthesis (if they’re green)
are all sepals green?
no, some are the same color as the petals
what is the function of petals?
attracting pollinators
what is the function of a stamen?
produces pollen (orange tips called anthers contain pollen)
what is the function of a pistil?
bears ovules and those ovules produce embryo sacs
floral organs are arranged in what?
whorls
what two parts of the flower are NOT involved in the life cycle?
the sepals and petals
what is the life-cycle of angiosperms?
meiosis –> gametophyte development –> pollination –> fertilization –> embryo development –> seed formation
microspores (in anthers) develop into what?
pollen
megaspores are located where?
in ovules
what fraction of megaspores are “aborted?”
3/4
the surviving spore from a megaspore develops into what?
the embryo sac
define pollination
the transfer of pollen from an anther to the stigma of a pistil
birds are most attracted to which color of flower?
red
what are the two types of pollination?
targeted and nontargeted
nontargeted pollination requires _____ (large or small) amounts of pollen
large
give two examples of how nontargeted pollination is carried out
wind and water
targeted pollination requires _____ (more or less) amounts of pollen, and what else is necessary for it?
less, needs to attract a pollinator
give examples of how targeted pollination is carried out
animals like birds, insects (beetles and bees), and bats
pollen can grow when it lands on what?
a compatible stigma
what process answers the question “is this the right type of pollen?”
recognition of pollen at the stigma
the 3rd nucleus from a microspore grows into what?
a pollen tube
what is the function of a pollen tube?
it carries nonmotile sperm to the ovule & egg
what directs growth of a pollen tube?
gene expression in the tube’s nucleus
most flowers are hermaphroditic - define hermaphroditic
flowers contain both male and female reproductive organs
what are the two main results/possibilities of hermaphroditic flowers?
self-pollination
inbreeding (accumulation of genetic defects)
define outcrossing
when a plant is fertilized by pollen from a different plant - typically via an animal pollinator
define unisexual flowers
flowers that have male OR female reproductive organs
define monoecy
male and female reproductive organs on one plant
define dioecy
separate plants with male or female reproductive organs
some flowers possess self-_____, which helps prevent self-pollination or inbreeding
self-incompatibility
pollen is only accepted by stigmas of the _____ (same or different) species
same
what occurs if pollen is determined to be not compatible after recognition at the stigma?
pollen does nothing - doesn’t germinate
what are the 4 steps pollen goes through when germinating?
1) forms a pollen tube
2) pollen tube grows through the style
3) pollen reaches the ovary and ovules
4) sperm is released into embryo sac
initially, the pollen tube consists of two _____ (haploid or diploid) cells called the ______ cell and the ______ cell
haploid cells
generative cell and the tube cell
the generative cell divides ______ (mitotically or meiotically) to produce two ______ (haploid or diploid) sperm cells
mitotically
two haploid sperm cells
what are synergid cells?
two cells that lie adjacent to the egg cell in the female gametophyte of an angiosperm
when the pollen tube arrives at the ovary, what happens to the synergid cells?
one of them degenerates
two sperm cells unite with parts of the ovary: what are they?
1) one sperm nucleus fertilizes the egg to form a 2n zygote (1st cell of 2n sporophyte generation)
2) the other sperm nucleus unites with the two polar nuclei in the center of the ovary to form a triploid (3n) nucleus
what is the purpose of the second sperm uniting with the polar nuclei?
to produce nutritive tissue for the developing embryo (is a food source)
in what types of plants does double fertilization occur?
in angiosperms only
what is an endosperm?
the triploid cell (1 sperm + 2 1N nuclei from polar nuclei) created for nutrition for the embryo
endosperms can persist until when?
the seed germinates (or earlier)
when a zygote develops into an embryo, this is the beginning of a new what?
sporophyte
how does plant embryogenesis differ from that of animals?
animal’s embryogenesis is early on when the organs are formed
plants are always producing new organs, so their embryogenesis stage is considered to be when the plant is contained within and nutritionally dependent on maternal tissues
what two cells are produced after step 1 of embryogenesis (the first mitotic division of the zygote)? what are their purposes?
terminal cell = the embryo itself
basal cell = the suspensor (a channel for providing nutrients)
what is the second step of embryogenesis?
what is the second step of embryogenesis?
the globular stage - the embryo continues to divide into a globular embryo
what happens during morphogenesis of embryogenesis (steps 3 and 4 of embryogenesis)?
layers form
cotyledons form during the heart stage of the embryo
shoot and root apical meristems are organized in the torpedo-stage of the embryo
any growth that occurs to the embryo after morphogenesis is to what? (3)
increase in size, accumulate storage molecules (proteins, lipids, and carbs), and prepare for physiological independence
only what two parts of the flower stay attached after a fruit is developed? why?
only the sepals and pistils stay attached because everything else (anthers, stigma, etc.) aren’t needed anymore
what reproductive parts of the flower turn into the seed and fruit?
ovule = seed
ovary = fruit
seeds are inside the fruit as the ovule is inside the ovary
the ovule (seed) contains what two things from reproduction?
the embryo and endosperm
what is the covering of an ovule (a seed)?
the seed coat
what is a fruit biologically described as?
a ripened, mature ovary
what is the purpose of plants producing fleshy fruits?
to “pay” an animal to spread its seeds in the fruit around (similar to how pollen is spread by bugs/birds)
as ovules develop into seeds, changes occur in the ________ wall
ovary
dry fruits use what kind of dispersal of their seeds?
mechanical dispersal - no animal dispersal required
what is dormancy?
an embryo waits for good growing conditions to develop (i.e. can tolerate bad growing seasons)
how does dormancy take effect?
an embryo loses water as it matures, so the hormone abscisic acid (ABA) is deployed (b/c plant is under water stress)
the embryo can reduce down to 10% water & use very slow metabolism, which leaves it in the dormant stage
how long can dormancy last?
days - years
how is flowering controlled in angiosperms?
the SAM first forms the vegetative organs (leaves, stem, buds) and then when ready produces floral organs (sepals, petals, stamens, carpals)
define a perennial
a plant that flowers year after year
define an annual plant
a plant that completes it’s flowering life cycle in one year
define a biennial plant
life cycle is completed in two years - they require a “chilling period” before they can flower
of the types of flowering life cycles, which are ancestral and which are more advanced?
perennial is ancestral and annuals/biennials are more advanced
what are the 2 main ways the SAM switches from vegetative to reproductive growth?
1) internal cues in all plants - indicates maturation or a “phase change”
2) some plants use external cues like daylength or chilling
what is photoperiodism?
when plants use daylength as an external cue for reproductive growth
what is vernalization?
when plants use chilling/temperature as an external cue for reproductive growth
what is the difference between a juvenile and adult plant?
in a juvenile, flowering is prevented
in an adult, flowering is possible after a certain period of growth
what are the advantages of the juvenile stage of plants?
gives plants time to build up resources because flowering requires a lot of energy
allows for more success when completing flowering, seed, and fruit production
what is actually being measured when plants are dependent on temperature for flowering?
water availability - more available during certain seasons
define short day plants, long day plants, and day neutral plants
short day: flower when the days are short (long nights)
long day: flower when the days are long (short nights)
day neutral: daylength doesn’t affect flowering time
what did the 1920 Maryland Mammoth experiment show?
that some plants flower depending on temp & others on day length
does the length of day or night actually determine whether flowering occurs? how is this known?
length of night - dark treatment during the day has no effect on flowering but light treatment during the night does
which organ of the plant perceives the photoperiod?
the leaves (can cover as little as 1/8th of a leaf and flowering would still be effected by light treatment at night)
what is the chemical that travels through the phloem and causes photoperiodism?
florigen
white light works well for photoperiodism - what other wavelength of light works?
red light has same success as white light
why doesn’t far-red light work for photoperiodism?
because it inactivates phytochrome
florigen (FT) is a transcription factor and an accumulation of what?
CONSTANS (CO) - a gene encoding a transcription factor required for flowering
where is florigen produced?
in the companion cells to sieve tube elements in leaves
what is the first step of florigen’s transcription pathway?
a photoperiodic stimulus (light) stabilizes CO (which acts as a transcription factor)
what is the second step of florigen’s transcription pathway?
FT (florigen) is made via transcription and enters a sieve tube element through pleasmodesmata
what is the third step of florigen’s transcription pathway?
FT is transported through the phloem and up to the apical bud
what is the fourth step of florigen’s transcription pathway?
FT combines with FD (another flowering protein) and this complex acts as a transcription factor for AP1 protein
what is the final step of florigen’s transcription pathway?
AP1 (a protein) is made and acts to initiate flowering
CO accumulation in long day plants turns ______ (on or off) FT in long days
on
CO accumulation in short day plants turns _____ (on or off) FT in long days
off
