Question

Identify the correct order of events in pollen-pistil interaction from the options given below 

I.Release of male gametes into the embryo sac. 
II.Deposition of pollen grains on stigma 
III.Entry of pollen tube into embryo sac. 
IV.Development of pollen tube 
V.Entry of pollen tube into the ovule,

• A. II-IV-III-V-I
• B. V-IV-III-II-I
• C. IV-III-II-I-V
• D. II-IV-V-III-I

Answer 1

The Correct Option is D

The correct sequence of events during pollen-pistil interaction in angiosperms is as follows:

1. Deposition of pollen grains on stigma (II): The process begins when pollen grains land on the receptive surface of the stigma.

2. Development of pollen tube (IV): Compatible pollen grains germinate and develop a pollen tube that grows through the style.

3. Entry of pollen tube into the ovule (V): The pollen tube enters the ovule through the micropyle (porogamy being the most common method).

4. Entry of pollen tube into embryo sac (III): After entering the ovule, the pollen tube penetrates the embryo sac.

5. Release of male gametes into the embryo sac (I): Finally, the pollen tube discharges its contents, including the two male gametes, into the embryo sac for double fertilization.

The correct chronological order is therefore: II → IV → V → III → I

Thus, the correct option is (D) II → IV → V → III → I.

Answer 2

The process begins with pollen deposition on stigma (II), followed by pollen tube development (IV). The tube then grows through the style to enter the ovule (V), penetrates the embryo sac (III), and finally releases male gametes (I) for fertilization. This ordered sequence ensures successful delivery of sperm cells to the female gametophyte, with each step involving complex biochemical recognition events between pollen and pistil tissues.

The correct sequence is (B) II → IV → V → III → I.