Question

(a) State 2 reasons why pollen grain is well preserved as a fossil?

(b) What is the significance of cleistogamous flowers? (2M)

Answer 1

(a) The outer layer of pollen grain called exine is made up of a highly resistant fatty substance sporopollenin. Sporopollenin is not degraded by any enzyme and is not affected by high temperature, strong acid or strong alkali. Because of the sporopollenin, pollen grains are well preserved as fossils.
(b) Cleistogamous flowers are intersexual. They remain closed causing self pollination. The significance of cleistogamous flowers is that pollination and seed set are assured in them even in the absence of pollinators.