sexual reproduction in flowering plants

Question 1

What is flower ?

Answer 1

reproductive unit meant for sexual reproduction

Question 2

Prefertilisation events that occur in flowering plants give what change to plant and why ?

Answer 2

Hormonal, structural changes occur lead to differentiation & development
of floral primordium, inflorescence are formed bearing floral buds.

Question 3

What is stamen ? What are its part in a body ?

Answer 3

Stamen is male reproductive part in a flowering plant , and it consist of two part in its body :- 1) a long slender and stalk structure called filament . 2) the terminal generally bilobed structure called the anther .

Question 4

—————– end of filament is attached to the thalamus or petal of flower .

Answer 4

Proximal end
( Distal end of filament is attached to the bilobed anther ) .

Question 5

What can you describe about anther ?

Answer 5

Anther is a part of stamen , a typical angiosperm anther is bilobed , and each lobe have two theca ,so all over 1 anther is tetrathecous. ( one lobe in dithecous ). And this theca is divided by a groove which goes longitudinally to seperate them .

Question 6

The bilobed nature of an anther is very distinct in ——————- section of the anther .

Answer 6

transverse

Question 7

The anther is ——————- structure , consisting of four ——————— loacted at the corners , two in each lobe .

Answer 7

1) tertragonal
2) microsporangia

Question 8

Pollen sacs are developed from ——————.

Answer 8

microspornagia

Question 9

What are the name of the microsporangium walls , and how many of them are present around one microsporangium?

Answer 9

1) Epidermis
2) Endothecium
3) middle layer ( short lived :-ephemeral)
4) Tapetum
first 1,2,3 perform protection and help in dehiscence of anther but 4 one provide nourishment to the anther .

Question 10

Why only tapetum give nourishment to pollen grains ?

Answer 10

Tapetum in only wall with nourishing material and it have dense cytoplasm and generally have more than one nucleus .

Question 11

What are other work of tapetum beside giving nourishment to pollen grains ?

Answer 11

1) secrete pollen kit
2)help in entomophily
3)secrete sporopollenin :— ubisch bodies :—enter microsporangia :—- form exine .
4)tapetum :– 1) polyploidy 2)polyteny

Question 12

What is epidermis thickening called ?

Answer 12

exothecium ( outer coat of the anther )

Question 13

What is the importance of endothecium in an anther ?

Answer 13

Endothecium is a fibrous band / thickening made up of alpha cellulose present only on tangential wall, points where thickening is absent known as stomium { forms line of dehiscence }

Question 14

What is a sporogenous tissue ?

Answer 14

When the anther is young , a group of compactly arranged homogenous cell called the sporogenous tissue occupies the centre of each microsporangium.

Question 15

Which is innermost layer of an anther ?

Answer 15

tapetum

Question 16

What is a Microsporogenesis ?

Answer 16

The process of formation of microspore from pollen mother cell through meoisis is called microsporogenesis.

Question 17

How microspore tetrads are form ?

Answer 17

As the anther develops , the cell of sporogenous tissue undergo meiotic division to form microspore tetrads .

Question 18

What is the process of making pollen grains from sporogenous tissue ?

Answer 18

In each microsporangia of anther there are sporogenous tissue (2n) present which turn into pollen mother cell as it gets nourished . Then this PMC (2n) perform meiotic division to make 4 microspore (n) , callase enzyme to digest callose and make 4 microspore cell free . then these microspore goes through mitotic division to develop pollen grains . A pollen grain have 1generative cell(gc) and 1 vegetative cell (vc), which is covered by exine and intine . To remember pollen grain is not a male gametophyte . Now this pollen grain will go through maturation and its generative cell will go through a mitotic division and make 2 male gametophyte .

Question 19

study of pollen grains

Answer 19

palynology

Question 20

What things are consist in angiosperm male gametophyte ?

Answer 20

2 male gametes and one vegetative cell

Question 21

What is the structure of pollen grains ?

Answer 21

Pollen grains are generally spherical measuring about 25-50 micrometers in diameter. It has prominent two layered wall.

Question 22

What are the two layers of pollen grains that help them to survive for a long time period ?

Answer 22

The hard outer layer called the Exine is made up of sporopollenin which is one of the most resistant organic material known. It can withstand high temperatures