CBSE Class 12-science Answered

Pollen-Pistil Interaction

• Pollen-pistil interaction is a sequence of events that occur from the time of pollen deposition over the stigma till the time of entry of pollen tube inside the ovule. 
• The process has checks at several places for the promotion or inhibition of pollen growth.

 Advantages

• It is helpful to the plant breeders in manipulating pollen growth even in incompatible cases.
• It is a safety measure to ensure that illegitimate crossings do not take place.
• Compatibility and incompatibility of the pollen-pistil is determined by special proteins.
• Compatible pollens absorb water and nutrients from the surface of stigma, germinate and produce pollen tube.
• Pollen tube grows into the style whose growth and path is determined by specific chemicals.

Entry of Pollen tube into the Embryo sac

• The fully developed embryo sac consists of 3 antipodal cells, 2 synergids, 1 egg cell and 1 secondary nucleus.
• The pollen tube pierces through the nucellus and ultimately, penetrates the wall of the embryo sac.
• The tip of the pollen tube disintegrates and the 2 male gametes are liberated in the embryo sac.
• One or both the synergids which help in directing the pollen tube towards the egg disintegrates