Plant Reproduction

2N (diploid)

N (haploid)

1. Microsporocytes (2N) divide by meiosis resulting in 4 microspores (N)2. Each microspore divides once by mitosis forming a tube cell and a generative cell3. The cells mature into a single pollen grain--- generative cell will divide to form 2 spermPOLLEN---mobileonly contributes nuclei

1. Megasporcyte (2N) undergoes meiosis resulting in four megaspores (N)2. Three of the megaspores degenerate3. Surviving megaspore divides by mitosis (3 times NO CYTOKINESIS) to form 8 haploid nuclei4. 8 nuclei rearrange5. cell walls form to yield 7 cells (large central cell has 2 nuclei)EMBRYO SAC--- non-mobile-contributes cytoplasm/organelles to the zygotes

Carpel-- stigma, style,ovaryStamen-- anther, filamentPetalSepalReceptacle

Microsporocytes reside in the antherMegasporocytes reside in the ovule

-easier (sure thing)-less genetic diversity-it is going to happen

-creates more genetic diversity (desired traits continue)-may not happen

Because one sperm nucleus unites with egg nucleus to form the zygote (2N)The other sperm nucleus moves through the female gametophyte and fuses with the polar nuclei in the central cells to create the endosperm (3N)

Bean-- -has 2 cotyledons-nutrients in the endosperm are absorbed by the cotyledons and stored-no endosperm is left by the time the seed matures (cotyledon functions as the nutrient storage organ)-no endosperm-- lacking 3N
Corn--- one cotyledon-endosperm is intact

- embryo-food supply-- originating with endosperm-seed coat

they allow offspring to be much more successful in colonizing dry habitats
Mature seed is only 5 to 20% water where a normal plant is 90% water

Dormancy-- seeds may not germinate fora period of time once they are dispersed from the parent plant-- usually a feature of seeds from species that inhabit seasonal environments WATERHEATACID LIGHT
ABSOLUTE REQUIREMENT IS WATER
Abrasion( in addition to water and oxygen)-Revolving drums along pieces of sandpaper (scarified) abrasion from sandpaper scarifies the seeds -- in nature: seed coat can be disrupted by fire, by passage through an animal's digestive tract (exposed to acid and then pooped out) or by abrasion against wind-or water driven soil particles.
Environmental Conditions: (in addition to exposure to water)- Seeds that live northern or alpine areasseeds must undergo a period of cool, wet conditions before they will germinate --seeds native to wildfire habitatsmust be exposed to fire or smoke before they will germinate
Small-seeded Species--need to germinate near the soil surface where individuals are exposed to light and can feed themselves via photosynthesis.

SAM - either be1. vegetative-- leaves (more photosynthesis, sugars)2. reproductive-- flowers (enough energy to support)

-day length (season-- short or long)-temperature (season)-internal cues

An inhibitor of flowering-- it has a major effect of timing of flowering
flc/flc= early flower (low vegetation)
FLC/flc or FLC/FLC= late flowering (high vegetation)