lesson 06: angiosperm rep

what are floral organs thought to have evolved from?

leaves

complete flower

has a ll four whorls—calyx, corolla, androecium, and gynoecium

incomplete flower

lacks one or more whorls

calyx

outermost whorl, protexts the flower bud

corolla

functions to attract pollinators—petals

androecium

collective term for all stamens

stamen

male structure of the flower—have a filament(stalk) and an anther

anther

houses microspore mother cells

gynoecium

female part of the flower—one or more carpels

carpel

contains ovary which contains the ovules

style (slender neck of carpel) had a stigma (pollen receptor) at the tip

trends in floral specialization

fusion of separate flower parts

reduction in numbers of flower parts

bilateral symmetry over radial symmetry

angiosperm sporophyte tissue

the plant body and the flower

angiosperm gametophyte

very small, contained within the sporophyte

two kinds—microgametophytes and megagametophytes

microgametophytes

male gametophyte—pollen grain

macrogametophyte

embryo sac—female gametophyte

pollen formation

pollen saces within the anther house microspore mother cells

microspore mother cells undergo meiosis to become microspores

through mitosis, microspores become pollen

pollen structure

consists of two cells—tube cell and generative cell

tube cell

grows pollen tube

generative cell

divides to become two sperm

embryo sac formation

within the ovule, the megaspore mother cell undergoes meiosis to become four megaspores

3 of 4 megaspore disintegrate

mega spore

undergoes mitosis to become a seven-celled, eight-nucleate embryo sac

nuclei distribution in the embryo sac

3 nuclei in the three antipodal cells

two nuclei in the two synergid cells

one nucleus in the egg cell

two nuclei (polar nuclei) are a single cell in the middle

pollen grains develop a ___________ wall

weather resistant; species-specific

pollination

pollen transfer to the stigma

self-pollintation

when pollen comes from the same flower or a different flower on the same plant

advantages of self-pollination

allows for reproduction in environments where pollinators are not reliably available

offspring that are genetically similar to the parents—good in stable environments where the parent plant is well adapted to the area

cross-pollination/out-crossing

transfer of pollen between different individuals, promotes genetic variation

monoecious

species with separate male and female flowers on the same plant

out-crossing in monoecious plants

promoted if the flowers mature at different times

dioecious

species where male and female flowers are produced on different plants—out-crossing is required

dichogamous

flowers where the stamens and carpels reach maturity at different times, promoting out-crossing

self-incompatibaility

where pollen tube growth is blocked because pollen and stigma recognize they are genetically related—promotes out-crossing

co-evolution of pollinators and flowers

mutualistic relationship—results in specialized flowers and pollinators

adaptations that benefit pollinators

timing of opening, color patterns, flower size, odor, and shape

wind pollination

plants do not require a showy corolla or calyx

double fertilization

fertilization of egg to form a zygote and union of sperm with polar nuclei to form triploid endosperm

pollen tube

grown by tube cell down the style to the ovary—passageway for sperm to reach embryo sac

three critical events during embryo development

food supply develops, outer coverings of the ovule form a seed coat, and the ovary develops into a fruit

fruits

mature ovaries or carpels

pericarp

ovary wall—has three layers

true berries

entire pericarp is fleshy

peaches/stone fruits

outer layer becomes hte skin, middle layer is the flesh, and inner layer is the pit around the seed

dry fruit

entire pericarp is dry

aggregate fruits

formed from many ovaries from one flower

fruit development

coordinated with seed maturation by auxin—ethylene triggers ripening of fleshy fruits

apomixes

asexual seed production

vegetative reproduction

new individuals are produced from vegetative tissues

adventitious plantlets

form on leaves from maternity plants, fall off, and take root

somatic embryogenesis

growth of an embryonic plant from any somatic tissue