Some questions about pollen and ovule!?

Question

1. What is the function of the tapetum layer?

2. Some pollen grains will not germinate in vitro. They will germinate only on compatible stigma. Can you explain why?

3. in the flowering plants, the megagametophyte and the microgametophyte are totally dependent on the sporophyte. What advantages do this arrangement provide?

Answer 1

Question 1 )What is the function of the tapetum layer?

Answer 1 ) It is a nourishing tissue

Click on the link below to see tapetum around the pollen grains -

http://www.biology.iastate.edu/Courses/2...

Meaning on the link below --

http://www.answers.com/topic/tapetum

Question 2). Some pollen grains will not germinate in vitro. They will germinate only on compatible stigma. Can you explain why?

Answer 2 ) Yes. This is because they require specific stimulant chemical / s for growth / germination  , that are available on the surface of that particular compatible  stigma .

question 3.) In the flowering plants, the megagametophyte and the microgametophyte are totally dependent on the sporophyte. What advantages do this arrangement provide?

Answer 3 ) The sporophytic generation of these plants in question is hardy , self sufficient and adapted to lead harsh terrestrial life .

The gametophytes are not so .

Therefore it is well protected within the sporophyte .

It is the sporophytic generation with its characters mentioned above that has made the land  flora as the dominant flora to day .

Other wise the plant evolution would not have gone beyond the Bryophytes !!!!!!!!!!!