Question

Which chemical is released on the stigma by pollen grains?

Answer 1

it's not chemical but a sugary substance what which help pollen grains to develop his pollen tube
HOPE THIS HELPS YOU

Answer 2

Answer:

HEY MATE HOPE MY KNOWLEDGE REJUVENATES YOUR CONSCIENCE.

The stigma, which is the topmost part of the flask-like looking Pistil (female reproductive part of plant) releases a sugary substance when pollen grains fall on their surface. This breaks the pollen sac and the male gamete stats moving towards the ovary for some fun! yeh for fertilization.

Explanation: