A broad-leaf evergreen tree has many flowers in spring but bears no fruit in fall; closer inspection reveals only stamens and no pistils. What is the probable reason for fruit failure?

A broad-leaf evergreen tree has many flowers in spring but bears no fruit in fall; closer inspection reveals only stamens and no pistils. What is the probable reason for fruit failure?

• A. The tree lacked pollinators
• B. The tree was female
• C. The tree was male
• D. The tree had sterile flowers

Answer: (C)

When a plant’s flowers have stamens but no pistils, you’re looking at male flowers. Fruits form only after pollen from the stamens fertilizes ovules inside a pistil. If the flowers on the tree lack pistils entirely, there’s nothing for pollen to fertilize, so fruit cannot develop. In many species, trees can be dioecious (separate male and female trees) or produce male flowers on some branches or seasons; a tree bearing only male flowers will never set fruit. It isn’t mainly a pollinator issue, because even with pollinators, there would still need female parts to receive the pollen. It also isn’t that the flowers are merely sterile in a different way—the evidence here shows the presence of stamens and absence of pistils, pointing to male flowers as the reason for the fruit failure.

When a plant’s flowers have stamens but no pistils, you’re looking at male flowers. Fruits form only after pollen from the stamens fertilizes ovules inside a pistil. If the flowers on the tree lack pistils entirely, there’s nothing for pollen to fertilize, so fruit cannot develop. In many species, trees can be dioecious (separate male and female trees) or produce male flowers on some branches or seasons; a tree bearing only male flowers will never set fruit. It isn’t mainly a pollinator issue, because even with pollinators, there would still need female parts to receive the pollen. It also isn’t that the flowers are merely sterile in a different way—the evidence here shows the presence of stamens and absence of pistils, pointing to male flowers as the reason for the fruit failure.