The Plant Cell, Evolution, & Reproduction

Question 1

angiosperm pollination

Answer 1

pollen grains from another to stigma:
- self-pollinate (dioecious)
- cross-pollinate w aid of pollinators, elements, gravity

Question 2

coevolution: pollinators & flowers

Answer 2

• pollinators - food; flowers - spread genes
• disadvantage: diff sides of partnership struggling
• insect pop in decline (biggest pollinators)

Question 3

pollination ecology

Answer 3

• flowers produce nectar (nectary glands), pollen is NOT eaten
• depending on species/targeted pollinator, nectary glands can be on perianth, stamen, carpel/pistil, or receptacle

Question 4

beetles

Answer 4

• one of 1st pollinators
• most don’t have specialized nectar feeders
• flowers pollinated are bowl-shaped w exposed stigma and anthers, nectary glands near surface
• target methods: strong smell, white/yellow, primitive flowers of ancient species

Question 5

bees

Answer 5

• one of best pollinators
• have nectary glands close to flower surface as a bee proboscis (tongue) is short compared to other pollinators
• target methods: bright colour, markings (UV), sweet smell, electric field

Question 6

flies, mosquitoes

Answer 6

• less efficient than bees, but can be pollinators
• have proboscis for accessing nectary glands
• target methods: pale/dull/dark, rotten/blood/poop smell

Question 7

butterflies, moths

Answer 7

• longer tongues (proboscis) -> nectary glands near receptacle

moth - nocturnal:
- white/yellow, fragrant at night

butterflies - diurnal:
- bright, fragrant in day

Question 8

animals

Answer 8

some birds have long narrow beaks for nectar
- target methods:
bright red/yellow, minimal odour, large/sturdy inflorescence, copious amounts of nectar, nectar in long corolla tubes

bats, primarily tropics
- target methods:
open at night, dull, large enough for bat head or bat-like inflorescence, large amounts of nectar (replenish nightly)

Question 9

pollination ecology: orchid specialization

Answer 9

very specialized to attract pollinators
ex. pretending to be a mate, trapping insects for a while, etc.

Question 10

when do angiosperms’ female gametophyte develop in relation to male gametophyte?

Answer 10

• female gametophyte is developed before pollination, not timed (unlike gymnosperms); usually ready before pollen is

Question 11

pollen anatomy

Answer 11

• exine very sturdy and hard to destroy
• mature male gametophyte - germinated pollen grain w vegetative nucleus and 2 sperms within tube cell

Question 12

angiosperm pollen life cycle

Answer 12

(1) anther produces microsporocytes (2n)
(2) each microsporocyte undergoes meiosis producing a tetrad of microspores (1n)
(3) microspore divides by mitosis to 2 cells (versus 4 in gymnosperms) and matures into pollen grain
(4) tube cell produces pollen tube, generative cell gives rise to 2 sperm cells

Question 13

angiosperm life cycle

Answer 13

(1) megasporocyte (2n) undergoes meiosis to produce 4 megaspores, 1 survives
(2) surviving megaspore (1n) undergoes 3 nuclear divisions -> 8 haploid nuclei; 4 nuclei on either end of embryo sac
(3) pollen deposited on receptive stigma
(4) pollen germinates & grows pollen ube
(5) pollen tube grows toward ovary and into micropyle (hours-days from pollination)
(6) sperm cells released
(7) 2 sperm enter micropyle, released into synergids
(8) one sperm fertilizes the egg, while other unites w central nuclei -> produce a triploid (3n) endosperm (double fertilization)

Question 14

fertilization def

Answer 14

union of sperm (1n) and egg (1n)

Question 15

double fertilization def

Answer 15

sperm (1n) fuses w central nuclei (2n)
-> resulting endosperm (3n) food for embryo
-> in monocots like corn/grass, endosperm large part of seed (human food)
-> in some flowers like lilies, endosperm (5n)

Question 16

seed, integument, ovary

Answer 16

seed = ovule (embryo, endosperm)
integument = seed coat
ovary -matures-> fruit (not food for embryo)

Question 17

Seed

Answer 17

• embryo develops within seed
• triploid endosperm (nutrition for embryo upon germination)
• seeds become dormant & resilient against adverse conditions
• fruit develops from ovary

Question 18

Fruit (basic characteristics)

Answer 18

• fruit = matured ovary & accessory parts, contains seeds
• all fruits develop from flower ovaries
• fleshy or dry at maturity

Question 19

fruit anatomy regions (4)

Answer 19

pericap - all 3 regions
exocarp - skin
endocarp - inner boundary around seed(s)
mesocarp - tissue between exocarp and endocarp

Question 20

What is fleshy mesocarp for?

Answer 20

animal consumption

Question 21

What is dry mesocarp for?

Answer 21

wind dispersal & gravity

Question 22

fleshy fruits

Answer 22

simple fleshy fruits:
- drupe - 1 pit inside
- berry - from compound ovary (>1 seed), fleshy pericarp
- pome - from enlarged hypanthum (floral tube) growing around ovary; papery endocarp

aggregate fruits:
single flower w several to many pistils maturing on a swollen receptacle

multiple fruits:
several to many individual flowers in single inflorescence

Question 23

dry fruits

Answer 23

dehiscent fruits (split at maturity)
- capsules: at least 2 carpels, split in variety of ways

indehiscent fruits
- single seed united w pericap

wind dispersal (hairs, small, light weight, seed wings)
water dispersal (some have inflated covering for buoyancy)
animal dispersal (seeds pass through digestive protected by seed coat, fruits & seeds adhere to fur/feathers)

Question 24

how are dry fruits grouped?

Answer 24

based on the way they split

Question 25

germination favourable conditions

Answer 25

water, oxygen, temperature, light (red spectrum)

Question 26

vivipary

Answer 26

no dormancy, embryo continues to grow while fruit is on parent