Question

Which wall of microsporangium which produce iaa for the developing pollen grain is?

Answer 1

Cuticle................

Answer 2

The correct answer is tapetum.  

It is the innermost layer of the microsporangium. It offers nourishment to the growing pollen grains. At the time of microsporogenesis, the cells of the tapetum generate different hormones, enzymes, amino acids, and other nutritive components needed for the growth of pollen grains. It also generates the exine layer of the pollen grains that comprise the sporopollenin.