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biology > 2.4 - sexual reproduction in plants > Flashcards

2.4 - sexual reproduction in plants Flashcards

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1
Q

what’s a dicotyledon

A

plant that produces seeds that contain 2 cotyledons; they have 2 primary leaves

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2
Q

what’s an insect pollinated flower

A

type of flower that relies on insects to transfer pollen grains between flowers

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3
Q

what’s the calyx

A
  • first part of flower formed
  • consists of leafy structures that protect flower during development
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4
Q

what’s the corolla

A

all the petals of a flower

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5
Q

what’s the carpel

A

female part of plant consisting of stigma, style, + ovary

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6
Q

what’s the stamen

A

male part of plant consisting of anther + filament that’s involved in production of male gametes in form of pollen grains

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7
Q

describe the adaptations of insect pollinated plants

A
  • internal anthers + small stigma directly touch insects
  • large, bright petals + nectar from glands attract insects
  • may produce chemicals to mimic sent of female insects or to intoxicate insects
  • grow individually
  • large pollen grains, sometimes w/ projections that attach to insect
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8
Q

what’s a wind pollinated plant

A

type of flower relying on wind to transfer pollen grains between flowers

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9
Q

describe the adaptations of wind pollinated plants

A
  • external anthers optimise pollen dispersal
  • excess pollen compensates for wind wastage
  • feathery stigma catches pollen from air
  • small, dull petals (no need to attract insects)
  • grow densely over large area
  • light pollen grains
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10
Q

how does pollen grain form in anther

A
  • large numbers of pollen mother cells produced by mitosis
  • meiosis of diploid mother cells in anther forms 4 haploid microspores
  • haploid microspores mature into pollen grains via mitosis
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11
Q

describe role of tapetum in pollen grain development

A
  • specialised layer of cells in anther
  • provides nutrients to developing pollen grains
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12
Q

describe the structure of mature pollen grains

A

generative cell (haploid nucleus) - produces 2 male gametes via mitosis
pollen tube cell (has own nucleus) - elongates to penetrate ovule
outer protective coating

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13
Q

define dehiscence

A

splitting of anther resulting in release of pollen grains

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14
Q

how does ovule form in ovary

A
  • meiosis of megaspore cell produces 4 haploid megaspores
  • growth + development (involving 3 meiotic divisions) of one of the megaspores
  • embryo sac forms containing 8 haploid nuceli
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15
Q

describe the structure of the embryo sac

A
  • 2 polar nuclei form endosperm
  • ovum forms zygote
  • 2 synergids help generative nucleus of pollen grain to reach ovum
  • 3 antipodal cells
  • outer protective coating
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16
Q

define pollination

A

deposition of pollen onto stigma from anther

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17
Q

name the 2 types of pollination

A
  • cross pollination
  • self pollination
18
Q

what’s cross pollination

A

type of pollination in which pollen is transferred from anther of one plant to stigma of different plant

19
Q

what’s self pollination

A

type of pollination in which pollen is transferred from anther of plant to stigma of same plant

20
Q

compare genetic diversity produced by cross + self pollination

A

cross pollination results in plants w/ greater genetic diversity
self pollination produces plants w/ less diversity

21
Q

compare genetic diversity produced by cross + self pollination

A

cross pollination results in plants w/ greater genetic diversity
self pollination produces plants w/ less diversity

22
Q

outline the adaptations of flowers that promote cross pollination

A
  • maturation of pollen + ovary at different times
  • physical features prevent self pollination, e.g: heterostyly, male + female flowers on different parts of the plant
23
Q

where does double fertilisation occur

A

embryo sac of ovule

24
Q

how do male nuclei reach embryo sac

A
  • pollen grain from one plant lands of stigma of another
  • mitosis of pollen grain to form a pollen tube nucleus + 2 male gametes
  • pollen tube grows from grain down to ovule via digestion of style
  • pollen tube delivers 2 male gametes
25
Q

how does pollen tube enter into embryo sac

A

via micropyle

26
Q

define micropyle

A
  • pore in integument of ovule through which pollen tube enters embryo sac
  • remains as pore in testa (seed coat)
27
Q

what happens in double fertilisation

A

in embryo sac of ovule:
- one sperm fertilises ovum to form diploid zygote
- one sperm cell fuses w/ 2 polar nuclei to form triploid primary endosperm

28
Q

what happens to ovule following double fertilisation

A

develops into seed

29
Q

how is diploid embryo formed following double fertilisation

A

diploid zygote undergoes mitosis to form diploid embryo

30
Q

how is endosperm formed

A

nucleus of triploid endosperm divides by mitosis to form endosperm

31
Q

what’s the function of the endosperm

A

acts as nutrient source for embryo

32
Q

what structure forms the testa

A

integuments develop into testa

33
Q

what happens to ovary following double fertilisation

A

develops into fruit wall surrounding seed

34
Q

what’s the plumule

A

part of plant embryo that develops into primary shoot

35
Q

what’s the radicle

A

part of plant embryo that develops into root

36
Q

what’s the hilum

A

scar of testa as result of separation from its funicle

37
Q

define germination

A

process by which plant grows from seed

38
Q

give an example of non-endospermic seed

A

broad bean (Vicia faba)

39
Q

describe the stages of germination in a non-endospermic seed

A
  • seed absorbs water through micropyle causing swelling of cotyledon, enzyme activation + rupture of seed coat
  • food reserves from cotyledons are hydrolysed
  • provides energy for growth of plumule + radicle, as well as respiration
40
Q

describe the stages of germination in an endospermic seed

A
  1. seed absorbs water, activating embryo to secrete cell-signalling plant growth factor, gibberellin
  2. gibberellins induce synthesis of amylase
    - amylase diffuses to endosperm layer + causes hydrolysis of starch to glucose
41
Q

state the factors affecting seed germination

A
  • water availability (trigger secretions of gibberellin)
  • temperature
  • availability of O2 for respiration
  • use of fertiliser provides extra nutrients for growth

biology (24 decks)

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