What word connects brain,flower and man?

Pollen.

Pollen is a fine powder produced by flowers as a means of reproduction. The pollen is transferred from the male flower (stamen) to the female flower (pistil) by various means such as wind, insects or birds. The pollen then fertilizes the ovules of the female flower and produces seeds.

Brain is the control center of the nervous system and is responsible for various bodily functions such as thinking, memory and emotions.

Man is a human being, and humans are known to have a highly developed brain and cognitive abilities.