4.2. Sexual reproduction in plants 5

Question 1

dicotyledon??

Answer 1

a plant that prods seeds that contain 2 cotyledons; they have 2 primary leaves

Question 2

insect-pollinated flower??

Answer 2

a type of flower that relies on insects to transfer pollen grans bet flowers

Question 3

insect-pollinated flower labels

Answer 3

anther
filament
stamen
stigma
style
ovary
petal
sepal
receptacle
pedicel

Question 4

calyx??

Answer 4

-the first part of the flower that is formed
-consists of leafy structures that protect the flower during development

Question 5

corolla??

Answer 5

all the petals of a flower

Question 6

carpel??

Answer 6

the female part of the plant consisting of a stigma, a style and an ovary

Question 7

stamen??

Answer 7

male part of plant consisting of an anther & a filament involved in prod of male gametes in form of pollen grains

Question 8

adaptations of insect pollinated plants??

Answer 8

-internal anthers & small stigma directly touch insects
-large, bright petals & nectar from glands attract insects
-may prod chemicals to mimic scent of female insects or to intoxicate insects
-grow individually
-large pollen grains, sometimes w projections that attach to insect

Question 9

wind pollinated plant??

Answer 9

type of flower that relies on wind to transfer pollen grains bet flowers

Question 10

adaptations of wind pollinated plants:

Answer 10

-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 areas
-light pollen grains

Question 11

how does a pollen grain form in an anther??

Answer 11

-large numbers of pollen mother cells prod by mitosis
-meiosis of diploid mother cells in anther forms 4 haploid microspores
-haploid microspores mature into pollen grains via mitosis`

Question 12

the role of tapetum in pollen grain development??

Answer 12

-specialised layer of cells in the anther
-provides nutrients to developing pollen grains

Question 13

structure w/ of mature pollen grains??

Answer 13

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

Question 14

dehiscence??

Answer 14

the splitting of the anther resulting in release of pollen grains

Question 15

how does the ovule form in the ovary??

Answer 15

-meiosis of megaspore cell prods 4 haploid megaspores
-growth and development (involving 3 mitotic divisions) of one of the megaspores
-embryo sac forms containing 8 haploid nuclei

Question 16

structure of embryo sac??

Answer 16

-2 polar nuclei form endosperm
-ovum forms zygote
-2 synergids help generative nucleus of pollen grain to reach the ovum
-3 antipodal cells
-outer protective coating

Question 17

pollination??

Answer 17

the deposition of pollen onto a stigma from an anther

Question 18

2 types of pollination??

Answer 18

cross-pollination
self-pollination

Question 19

cross- pollination??

Answer 19

type of pollination in which pollen is transferred from an anther of one plant to a stigma of a diff plant

Question 20

self-pollination??

Answer 20

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

Question 21

compare genetic diversity prod by cross- & self-pollination??

Answer 21

cross-pollination results in plants w/ greater genetic diversity whereas self-pollination prod plants w/ less diversity

Question 22

adaptations of flowers that promote cross-pollination??

Answer 22

-maturation of pollen & ovary at diff times
-physical features prevent self-pollination e.g heterostyly, male & female flowers on diff parts of the plant

Question 23

where does double fertilisation occur??

Answer 23

embryo sac of ovule

Question 24

how do the male nuclei reach the embryo sac??

Answer 24

-pollen grain from 1 plant lands on stigma of another
-mitosis of pollen grain to form a pollen tube nucleus & 2 male gametes
-pollen tube grows from the grain down to the ovule via the digestion of the style
-pollen tube delivers 2 male gametes

Question 25

hoe does pollen tube enter embryo sac??

Answer 25

via the micropyle

Question 26

define micropyle??

Answer 26

pore in the integument of an ovule thru which the pollen tube enters the embryo sac
remains as a pore in the testa(seed coat)

Question 27

what happens during double fertilisation??

Answer 27

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

Question 28

what happens to the ovule following double fertilisation??

Answer 28

develops into seed

Question 29

how is the diploid embryo formed following double fertilisation??

Answer 29

diploid zygote undergoes mitosis to form diploid embryo

Question 30

how is the endosperm formed??

Answer 30

nucleus of triploid endosperm divides by mitosis to form endosperm

Question 31

function of endosperm??

Answer 31

acts as a nutrient source for the embryo

Question 32

what structure forms the testa??

Answer 32

integuments develop into the testa

Question 33

what happens to ovary following double fertilisation??

Answer 33

it develops into a fruit wall surrounding the seed

Question 34

what is the plumule??

Answer 34

the part of a plant embryo that develops into the primary shoot

Question 35

what is the radicle??

Answer 35

part of a plant embryo that develops into the root

Question 36

what is the hilum??

Answer 36

a scar on the testa as a result of seperation from its funicle

Question 37

germination??

Answer 37

process by which a plant grows from a seed

Question 38

example of a non-endospermic seed??

Answer 38

Broad bean

Question 39

stages of germination in a non-endospermic seed??

Answer 39

-seed absorbs water thru micropyle causing swelling of the cotyledon, enzyme activation & rupture of seed coat
-food reserves from cotyledons are hydrolysed
-provides energy for growth of the plumule & radicle as well as respiration

Question 40

stages of germination in an endospermic seed??

Answer 40

1. seed absorbs water, activating the embryo to secrete the cell-signalling plant growth factor gibberellin
2. gibberellins induce the synthesis of amylase
3. amylase diffuses to the endosperm layer causing the hydrolysis of starch to glucose

Question 41

factors affection seed germination??

Answer 41

-water availability (triggers secretions of gibberellin)
-temp
-availability of O2 for respiration
-use of fertiliser provides extra nutrients for growth