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biology > sexual reproduction in flowering plants > Flashcards

sexual reproduction in flowering plants Flashcards

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AP® Biology flashcards
1
Q

ornithophily

A

pollination by birds

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2
Q

entomophily

A

pollination by insects

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3
Q

chiropterophily

A

pollination by bats

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4
Q

Stamen

A

The pollen-producing part of a flower, usually with a slender filament supporting the anther.

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5
Q

Anther

A

The part of the stamen where pollen is produced

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6
Q

Pistil

A

The ovule producing part of a flower.

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7
Q

ovary

A

The ovary often supports a long style, topped by a stigma.

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8
Q

anther wall

A

exothecium/epidermis , endothecium & tapetum

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9
Q

carpel

A

the female reproductive organ of a flower, consisting of an ovary, a stigma, and usually a style. It may occur singly or as one of a group

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10
Q

corolla

A

corolla or petals merely refers to the second whorl of a flower, which is interior to the calyx.

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11
Q

calyx

A

the whorl of sepals of a flower collectively forming the outer floral envelope or layer of the perianth enclosing and supporting the developing bud; usually green.

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12
Q

perianth

A

The perianth is the non-reproductive part of the flower, and structure that forms an envelope surrounding the sexual organs, consisting of the calyx (sepals) and the corolla (petals)

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13
Q

In what type of plants are the petals small or absent and green?

A

In wind-pollinated plants

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14
Q

Why are the petals in wind-pollinated plants, small or absent and green?

A

Because they don’t rely on animals for pollination and therefore don’t need to attract them

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15
Q

structure of anther

A

bilobed, four-sided (tetragonal) , containing 4 microsporangia, 2 in each lobe

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16
Q

microsporangia

A

they develop into pollen sacs that are packed with pollen grains

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17
Q

structure of microsporangium (4) and their functions

A

the first 3 layers help in the protection and dehiscence of anther to release pollen.
*tapetum nourishes the developing pollen grains

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18
Q

tapetal cells have dense cytoplasm and generally more than 1 nucleus, why?

A

tapetal cells undergo endomitosis in which the nucleus divides within the nuclear membrane but cytokinesis doesnt occur. This results in …. bi nucleate.

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19
Q

what is the ploidy of microspore tetrads? or what is microsporogenesis?

A

Microspore tetrad cells are microspores arranged in a group of four. Microspores are formed from microspore mother cell (MMC). MMC is a diploid cell which undergoes meiosis to form four haploid microspores which are arranged in a tetrad. This process is known as microsporogenesis. Each of these four microspores develops into a pollen grain. Hence, ploidy of microspore tetrad cells is haploid.

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20
Q

production of pollen grains?

A

microsporogenesis: MMC-meiotic divns -microspore tetrad. -as the anthers mature and dehydrate,the microspores dissociate from each other and develop into pollen grains

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21
Q

layers of pollen grain? what are they made up of?

A

the hard outer layer,exine- sporopollenin thin and continuous layer,intine - cellulose and pectin

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22
Q

what is the function of germ pores?

A

germ pore helps in the formation of the pollen tube and the release of the male gametes during fertilisation.

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23
Q

when the pollen grain is mature,it contains 2 cells __ and ___? describe

A 
VEGETATIVE CELL
bigger 
-has abundant food reserve 
-large irregularly shaped nucleus 
GENERATIVE CELL
-small -floats in cytoplasm of veg.cell 
-spindle shaped with dense cytoplasm and a nucleus. 
In over 60% of angiosperms,pollen grain is shed during this 2 celled stage.but in rest,gen. cell divides mitotically- 2 male gametes before pollen is shed (3celled)
24
Q

What causes pollen allergy?

A

parthenium or carrot grass that came into India as a contaminant with imported wheat,has become ubiquitous in occurence and cause pollen allergy.

25
Q

describe pollen viability ?

A

period for which pollen grains remain viable -highly variable
-to an extent,depends on prevailing temp&humidity
+some cereals rice,wheat..-lose via. within 30mins of their release
+some members of Solanaceae,rosaceae..- remain via.for month

26
Q

cryopreservation-

A

crop breeding programs-pollen banks -pollen grains of large no.of species are stored in liquid nitrogen (-196 C)

27
Q

define: monocarpellary,multicarpellary syncarpous, apocarpous

A

monocarpellary : single pistil

multi. .: more than 1
syncarpous: pistils are fused together eg; papaver
apocarpous: pistils are free eg:michellia

28
Q

Structure of ovule

A

+The ovule -small structure attached to the placenta by means of a stalk- funicle.
+The body of the ovule fuses with funicle in the region called hilum - the junction between ovule and funicle.
+Each ovule has one or two protective envelopes called integuments.
+Integuments encircle the ovule except at the tip where a small opening called the micropyle is present.
+ Opposite the micropylar end is the chalaza. The chalaza represents the basal part of the ovule.
+A mass of cells; called nucellus; is enclosed within the integuments. The cells of nucellus have abundant reserve food material.
+Embryo sac or female gametophyte is located in the nucellus.

29
Q

explain megasporogenesis.

A

process of formation of megaspores from the megaspore mother cell
-ovules generally differentiate a single megaspore mother cell in the micropylar region of the nucellus. MMC undergoes meiotic division - resulting in the production of 4 megaspores. -3 of the megaspores degenerate and only one is functional- develops into a female gametophyte, embryo sac. [monosporic development]

30
Q

describe monosporic development ?

A

Nucleus undergo mitotic division2-nucleate embryo-sac is formed
Nuclei undergo mitotic division again4-nucleate embryo-sac is formed
Nuclei undergo yet another mitotic division8-nucleate embryo-sac is formed
Cell wall formation takes place leading to the organisation of embryo.
The nuclei formed inside get rearranged to form the final structure of Embryo sac as follows:Egg apparatus2 synergids, 1 egg cell located at micropylar end Antipodals3 cells at basal end of ovuleLocated at chalazal end Central cell2 polar nuclei fused together

31
Q

embryo-sac is 7-celled, but 8-nucleate. why

A

in the central cell, 2 polar nuclei fuse to form a single cell.

32
Q

Even though each pollen grain has two male gametes. Why are at least 10 pollen grains and not 5 pollen grains required to fertilise 10 ovules present in a particular carpel?

A

Double fertilisation -One of the male gametes fuse with the egg cell to form zygote while other male gamete fuses with polar nuclei and form primary endosperm nucleus.

33
Q

define pollination

A

transfer of pollen grains from the anther to stigma

34
Q

kinds of pollination

A

autogamy- same flower
geitonogamy- another flower of same plant common pansy(viola),oxalis,commelina.
-chasmogamous(exposed anthers and stigma)
-cleistogamous(doesn’t open at all)
xenogamy-diff plant of same species

35
Q

What are the agents of pollination? their names?

A

abiotic- wind,water biotic-animals

wind: anemophily
water: hydrophily
insect: entamophily
bird: ormitophily

36
Q

adaptations for wind polln:

A
  • pollen grains : light and non sticky -often possess well exposed stamens(so pollen is easily dispersed in wind)
  • large often feathery stigma (to easliy trap air borne pollen)
  • flowers often have single ovule in each ovary
  • numerous flowers packed into an inflorescence
  • quite common in grasses.
37
Q

adaptations of water polln

A
  • limited to abt 30 genera,mostly monocotyledons.
  • water is a regular mode of transport
  • pollen grains in most species are long,ribbon-like and carried passively in water.
  • pollen grain-protected from wetting by mucilagenous covering
38
Q

examples of water polln (fresh $ marine)

A

freshwater- Vallisneria,hydrilla

marine-zostera

39
Q

in vallisneria, flowers?

A

reach the water surface by a long stalk and pollen is released onto the water surface and it reaches the stigma by being carried by water currents

40
Q

in some plants like sea-grasses, flowers?

A

remain submerged in water and pollen- released inside the water.

41
Q

adaptations of animal/insect polln.

A
  • flowers are large,colorful,fragrant and rich in nectar (floral rewards)
  • pollen grains are gen.sticky
  • if flower is small,theyre packed into inflorenscense
  • flowers pollinated by flies and beetles secrete foul odours to attract these animals
  • in some species,floral reward is to provide a safe space to lay eggs,eg:amorphophallus(tallest flower),moth and plant yucca (cant complete life cylces w/ one another) _moth-deposits egg in locule ,flower-gets pollinated _larvae of moth come out of eggs as seeds start developing.
42
Q

why outbreeding devices? mention them

A

continued self polln. results in inbreeding depression.
4 devices:
-pollen and stigma receptivity- not synchronised.
-anther and stigma are placed at diff positions(so no contact b/w them)
-self incompatibility (genetic mechanism)
-production of unisexual flowers

43
Q

the function of filiform apparatus?

A

plays an imp. role in guiding the pollen tubes into the synergid.

44
Q

how do plants ensure that polln. only takes place between compatible species?

A

pollination doesnt guarantee the right transfer of the right type of pollen. -pistil has the ability to recognise the pollen,whether it is of the right type or not (i.e,compatible or not). -if it is compatible,the pistil accepts the pollen and promotes post-polln. events for fertilisation. -if it is not compatible,the pistil rejects the pollen by preventing pollen germination on stigma or the pollen tube growth in the style. +The ability of the pistil to recognise pollen followed by its accceptance or rejection is the result of a continuous dialogue b/w pollen grain and the pistil. These dialogue-mediated-chemical components of the pollen interacting with those of the pistil.

45
Q

explain pollen-pistil interaction?

A
  • following compatible polln.,the pollen grain germinates on stigma- produce- a pollen tube through one of the germ pores.
  • Contents of pollen grain move into the pollen tube.
  • pollen tube grows and reaches ovary.
  • after it reaches ovary,it enters the ovule through the micropyle- enters one of the synergids through the filiform apparatus. +All these events from pollen deposition on stigma until pollen tube enters ovule are together referred to as pollen-pistil interaction
46
Q

why artificial hybridisation?

A

breeders are interested in crossing diff species and often genera to combine desirable characters to produce commercially ‘superior’ varieties.

47
Q

if the female parent bears bisexual flowers, […] is called emasculation.

A

if the female parent bears bisexual flowers, removal of anthers from flower buds before the anther dehisces using a pair of forceps is called emasculation

48
Q

covering emasculated flowers with a bag of suitable size, generally made up of butter paper,to prevent contamination of its stigma with unwanted pollen is called […]

A

bagging.

49
Q

how is artificial hybridisation done?

A

2 imp things to take care of :
*to ensure that only the desired pollen grains are used for polln
*stigma has to be protected from being contaminated by unwanted pollen.
bisexual female parent:
-emasculation: anther removed from flower bud using forceps
-bagging: flower is then bagged- butter paper
-when the stigma of bagged flower attains receptivity,mature pollen grains collected from anther of male parent are dusted on stigma
-flowers are rebagged-fruits allowed to develop.
unisexual female parent:
no emasculation
-bagged before flower opens
-[rest same as above]

50
Q

Why does endosperm development precede embryo development?

A

-primnary endosperm cell - divides repeatedly - triploid endosperm tissue.
Cells of this tissue - filled with reserve food materials - used for the developing embryo

51
Q

stages of endosperm developement

A

1) PEN undergoes successive nucleur divisions - free nuclei. ——–> Free nucleur endosperm eg: water from tender coconut
2) Subsequently,cell wall formation takes place, endosperm becomes cellular ——-> Cellular endosperm eg:White kernel surrounding the coconut water

52
Q

Endosperm may either be […] eg: pea,groundnut,beans… before seed maturation or […] eg:castor,coconut

A

Endosperm may either be completely consumed by developing embryo eg: pea,groundnut,beans… before seed maturation or it may persist in the mature seed and be used up during seed germination eg:castor,coconut

53
Q

the early stages of embryo development […] is similar in both monocotyledons and dicotyledons the early stages of embryo

A

embryogeny is similar in both monocotyledons and dicotyledons

54
Q

zygote divides to form […] and subsequently to the […].

A

zygote divides to form pro-embryo (2-celled)) and subsequently to the globular,heart-shaped and mature embryo

55
Q

escribe the structure of a typical dicotyledonous embryo

A

A typical dicotyledonous embryo consists of an embryonal axis and 2 cotyledons.
The portion of the embryonal axis - above the level of cotyledon - epicotyl - terminates with the plumule or stem tip.
The cylindrical portion - below the level of cotyledons - hypocotyl - terminates at its lower end in the radicle or root tip –>covered with a root cap.

56
Q

Describe the structure of the embryo of monocotyledons

A

only 1 cotyledon In the grass family,cotyledon - Scutellum - situated towards one side (lateral side)of the embryonal axis.
At its lower end,the embryonal axis has radical and root cap - enclosed in an undifferentiated sheath - coleorrhiza.
Portion of embryonal axis above the level of scutellum - epicotyl.
Epicotyl has - a shoot apex & a few leaf primordia enclosed in a hollow foliar structure - coleoptile.

biology (5 decks)

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