Plant Reproduction Flashcards
Alternation of Generations
both haploid and diploid multicellular stages
gametophyte
HAPLOID and makes gametes through mitosis
sporophytes
DIPLOID and makes spores through meiosis
Gametes vs Spore
gametes: maature haploid germ cell that can unite with opposite sex to form a zygote = always haploid
spore: a minute, one-celled reproductive unit that can make a new individual without sexual fusion = usually haploid
byrophytes
seedless non-vascular plants
- haploid gametophyte is larger than the sporophyte - gametophyte dominated!
seedless vascular plants
sporophyte is larger than the gametophyte BUT the gametophyte is independent of the diploid sprophyte
angiosperms and gymnosperms
sporophyte-dominant
angiosperms have flowers, fruit-covered seeds, double fertilization
gymnosperms - no flowers, “naked” seeds, no double fertilization
flowers, fruits, double fertilization
flowers attract pollinators
fruits facilitate seed dispersal
double fertilization - invest resources for nourishment of developing embryo
sepals
outermost layer; green, leafy structure, protect flower bud before it opens
petals
next outer layer, brightly colored to attract pollinators
stamens
male reproductive structures
- anthers, filaments, microsporangia, microspores
carpel
innermost layer of the female reproductive structures
- stigma, style, ovary, megasporangia, megaspores
anthers
hold the microsporangia
filaments
support the anthers
microsporangia and microspores
microsporangia are structures that produce microspores which develop into male gametophytes; microsporangium are pollen sacs where microspores develop into pollen grains
stigma
location where pollen (male gametophyte) is deposited
style
connects the stigma to the ovary
ovary
holds the megasporangia
megasporangia and megaspores
structures that produce megaspores which develop into female gametophytes
male gametophyte in angiosperms and gymnosperms
pollen - multiceullar, haploid stage that PRODUCES the sperm; protects against dessication of sperm = reproduce away from water!
microspores
haploid from a diploid cell. mother diploid microspore devides by meiosis and makes 4 microspores - each one will form a pollen grain through mitosis?
with maturity - microsporangia burst and releases pollen grains to be transported to stigmas by environmental factors
embryo sac
female gametophyte
development of embryo sac
polar nuclei
triploid endosperm
micropyle
antipodal cells
egg cell
synergid cells
- single ccell in the diploid megasporangium undergoes meiosis to make 4 megaspores: only one haploid megaspore survives
- megaspore undergoes mitosis without complete cell division (8 nuclei 7 cells)
two nuclei (polar nuclei) in the center form a single diploid central cell -> fuses with a sperm to make triploid endosperm which will provide nourishment to developing embryo (like animal yolk)
micropyle: site where sperm enter the embryo sac
antipodal cells: 3 nuceli developed into this which will degeerate for nutriets to the embryosac
egg cell: nucleus closest to micropyle
synergid cells: two other adjacent nuclei that help guid pollen tube for successful fertilization
integument
structure that protects the megasporangium and later embryo sac; develops into the seed coat after fertilization and protects the entire seed
why are seeds important
reproduction away from water!
micropyle
opening that allows the pollen tube to enter the female gametophyte for fertilization
fruit
ovule wall will become part of the fruit
double fertilization
unique to angiosperms out of all plants and organisms!
-when pollen is deposited in stigma it will ferminate and grow through the style to reach ovule and are guided to micropyle - the generative cell divdes mitosis to get 2 sperm cells: one fertilizes and makes the diploid zygote the other fusues with the polar 2 nuclei and forms the triploid endosperm for nutrition for the embryo
after fertilization
ovule and ovary?
no other sperm can enter
fertilized ovule - seed
ovary - fruit!
apical cell and basal cell
after fertilization, zygote enters temporary development - divides into upper and lower cell
basal cell - suspensor: makes connection with maternal tissue and will provide a route for nutrition to be transported from th mother plant to the growing embryo (similar to placental umbilical cord)
apical cell - proembryo that will actyally develop into a plant
endosperm - accumulates starches, lipids,proteins and nourishes the developing cotyledons
THEN the seed loses up to 95% if uts water and development is suspended
cotyledons
embryonic leaves, energy storage for later embryo development
dormancy
seed enters this period of suspended development for dispersal and ideal conditions to grow - growth resumes when the seed germinates: developing seedling rely on food reserves of cotyledons until first leaves start photosynthesizing;
period of stasis or inactivity, 95% loss in water - low metabolism and concentration of sugars - can last months, years, centuries
self-pollinate vs cross-polinating
pollen from the anther is deposited on the stigma of the same flower or another flower of the same plant – self-pollination is less energy consuming but less genetic diversity
cross-polinnation: whole different individual
evolution of avoiding self-pollination
pollen and ovary maturing at different times
-physical features like different lengths in stigma and anther
-male and female flowers on different parts of the plant
-each plant only having male only or female only gametophytes so different plants have different flowers
-“incompatible genes” prevent pollen from germinating into the stigma
pollination syndromes - the ways diffrent plant species are pollinated
animals, wind, water
plants pollinated by animals usually have nectar to attract animals or extra pollen; plants with wind or water must have massive amounts of pollen
birds
active during the day, visual stimuli - brightly colored, odorless flowers; usually curved/tubular shape for beak
bees butterflies wasps and flies
active during the day, visual and olfactory stimuli - strong sense of smell
flies like rotting smells; even additional colors of in UV range outside of humans
sweet smells for bees and butterflies
moths and bats
active at night; visual and olfactory stimuli - white or pale,colored, highly scented; bats like larger flowers
germination
reinitiating development; signals indicate favorable conditions for growth
germination factors: water, specific wavelengths of light, sustained period of cold, fire, scarification
water - start of rainy season and rehydration of seed
light - favorable sunlight conditions and seed is not too far under the soil
cold - seed does not germinate until the cold season is over
fire - reduced competition from taller trees
scarification - chemical treatment with acids, seed has passed through digestive tract of an animal?
fruit develops from and its purpose
the ovary; for seed dispersal - can find favorable and less compeititve conditions
fruit dispersal methods (4)
propulsion: explode out of the plant (violets
wind: lightweight, wing or parachute like appendages (dandelions)
water: coconuts, light buoyant to float
animal: tiny “hooks” to attach to passing animals OR very sweet and fatty so that it will be eaten and deposited in new location (sandburs, blackberries); birds disperse brightly colored fruits and mammals disperse highly scented fruits because better sense of smell
