Sexual Reproduction in flowering plants

Question 1

Parts of a stamen

Answer 1

A long slender stalk called filament and a bilobed structure called anther

Question 2

Structure of anther

Answer 2

It is bilobed and dithecous. It consists of four microsporangia —> which develop into pollen sacs.

Question 3

Structure of microsporangia

Answer 3

It is surrounded by four wall layers – epidermis, endothecium, middle layers and tapetum. Outer three layers are for protection while the tapetum nourishes the developing pollen grains

Question 4

Tapetum

Answer 4

Cells of tapetum possess dense cytoplasm and the cells are binucleate

Question 5

Microsporogenisis

Answer 5

The cells of the sporogenous tissue undergoes meiotic division to form microspore tetrads (haploid).

Question 6

Layers of pollen grains

Answer 6

Exine made up of sporopollenin. It has prominent apertures called germ pores. The inner wall intine is made up of cellulose and pectin

Question 7

Mature stage of pollen grains

Answer 7

Pollen grains have two cells the the vegetative and generative cell. The vegetative cell is bigger has abundant food reserve and has a large irregularly shaped nucleus while the generative cell is much smaller has a nucleus and floats in the cytoplasm of vegetative cell

Question 8

Viability of different pollens

Answer 8

Wheat and cereal – 30 minutes of it’s release
Rosacea leguminouseae and solanacea – months

Question 9

Pollen banks

Answer 9

We can store a large number of pollen grains for a long period of time in liquid nitrogen at -196°C

Question 10

Kinda of pollination

Answer 10

Autogamy, geitnogamy and xenogamy

Question 11

Features of wind pollinated flowers

Answer 11

Produced in large amounts, non-sticky and light feathery stigma well exposed stamens and not colourful and does not produce nectar

Question 12

Examples of wind pollinated flowers

Answer 12

Maize and grass

Question 13

Features of water pollinated flowers

Answer 13

Long ribbon like pollen grains which are protected from wetting by mucilaginous covering

Question 14

How are water hyacinth and water Lily pollinated?

Answer 14

The flowers emerge above the level of water and are pollinated by insects and wind

Question 15

Features of insect pollinated flowers

Answer 15

They are large colourful and produce nectar. They sometimes secrete foul odour in order to attract flies and beetles. The pollen grains are generally sticky

Question 16

What are used as floral rewards

Answer 16

Nectar and pollen grains are usual floral rewards. In some species floral rewards are in providing a safe space to lay eggs
Eg species of moth and yucca and amorphophallus.

Question 17

What is self incompatibility

Answer 17

Genetic mechanism that prevents self pollen from fertilizing the ovules by inhibiting pollen germination

Question 18

What is emasculation

Answer 18

Removal of anther from a bisexual flower with use of forceps

Question 19

What is bagging

Answer 19

Emasculated flowers are cover with perforated paper bag to prevent getting fertilized by undesirable pollen grains