Sexual Reproduction in Flowering Plants

Question 1

Androecium

Answer 1

The male reproductive organ

Stamen – made up of anther and filament

Question 2

Microsporangium

Answer 2

Present in the anther and develops into a pollen sac

Question 3

Tapetum

Answer 3

The innermost layer of microsporangia having multinucleate cells

Provides nourishment to pollen grains

Question 4

Sporogenous tissue

Answer 4

Microspore mother cell

Homogenous tissue present in the microsporangia of a young anther

Each cell is capable of developing into microspore mother cell

Question 5

Microsporogenesis

Answer 5

Formation of microspores tetrad by meiosis in the microspore mother cells or pollen mother cells (PMC)

Microspores develop into pollen grains

Question 6

Exine

Answer 6

The outer layer of pollen grains

Made up of sporopollenin, the most resistant organic compound known

Germpore- does not contain sporopollenin

Question 7

Intine

Answer 7

The inner layer of pollen grains

Made up of cellulose and pectin

Question 8

Vegetative cell

Answer 8

The large cell of pollen grains with ample food reserve

Has irregular nucleus

Question 9

Generative cell

Answer 9

The smaller spindle-shaped cell of pollen grains

Divides mitotically forming two male gametes

Question 10

Gynoecium

Answer 10

The female reproductive organ

Pistil – made up of stigma, style and ovary

Syncarpous- pistils fused, e.g. Papaver

Apocarpous- pistils free, e.g. Michelia

Question 11

Megasporangium

Answer 11

Ovule

Present in the ovary, attached to placenta

One ovule – wheat, mango, paddy

Many ovules – watermelon, papaya, orchids

Question 12

Funicle

Answer 12

The stalk by which an ovule is attached to the placenta

Question 13

Hilum

Answer 13

The junction between funicle and ovule

Question 14

Integuments

Answer 14

The double protective envelope of the ovule

Encloses nucellus except at micropyle

Question 15

Micropyle

Answer 15

A small opening in the integuments

Pollen tube enters through this pore

Question 16

Chalaza

Answer 16

The basal part of the ovule opposite to the micropylar end

Antipodal cells are present at the chalazal end

Question 17

Megasporogenesis

Answer 17

Formation of megaspores by meiosis in the megaspore mother cell (MMC)

Only one cell at the micropylar end differentiates into the megaspore mother cell

Question 18

Female gametophyte

Answer 18

Embryo sac

Only one of the four megaspores develop into female gametophyte, rest three degenerate

Question 19

Embryo sac

Answer 19

8 nucleate and 7 celled

Egg apparatus – 3 cells at the micropylar end, 2 synergids and 1 egg cell.

Antipodals – 3 cells at the chalazal end

Central cell- 2 polar nuclei

Question 20

Autogamy

Answer 20

Self-pollination within the same flower

Cleistogamous – flowers which do not open

E.g. Oxalis, Viola, Commelina

Question 21

Geitonogamy

Answer 21

Transfer of pollen to the different flower of the same plant

Question 22

Xenogamy

Answer 22

Transfer of pollen to the stigma of different plant

Question 23

Pollinating agents

Answer 23

Insects or wind – Water hyacinth, water lily

Water – Vallisneria, Hydrilla, Zostera (seagrasses)

Wind – grasses

Moth – Yucca, moth lays eggs in the ovary

Question 24

Emasculation

Answer 24

Removal of anthers from the bisexual flower to facilitate cross-fertilization

Question 25

Bagging

Answer 25

Covering of emasculated flower with a bag to prevent contamination of stigma by unwanted pollen

Question 26

Double fertilization

Answer 26

Syngamy – fusion of egg nucleus and male gamete to form a zygote Triple fusion – formation of a triploid primary endosperm nucleus by fusion of the second male gamete and two polar nuclei

Question 27

Endosperm

Answer 27

Develops from primary endosperm cell (PEC) Triploid Coconut water and tender coconut – free-nuclear endosperm

Question 28

Perisperm

Answer 28

Residual nucellus in the seed E.g. black pepper, beet

Question 29

False fruit

Answer 29

Example – Apple and strawberry, thalamus is a part of the fruit

Question 30

Parthenocarpy

Answer 30

Development of fruit without fertilisation Can be induced by growth hormone application Seedless fruits E.g. banana

Question 31

Apomixis

Answer 31

Asexual reproduction Production of seed without fertilisation Embryo is formed without fertilisation from diploid egg cell E.g. Asteraceae, grasses

Question 32

Polyembryony

Answer 32

Nucellar cells develop into embryos Formation of multiple embryos in a seed. All the plants are genetically identical E.g. Mango, Citrus