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Male and female plants have differences too (Released: 10/10/96)

by Renu Sehgal, Office of University Communications.

STORRS, Conn. -- Females are shrewd investors and save for expenditures, while males spend what they have, according to research conducted by a University of Connecticut doctoral student. But she's not talking about humans.

''Female plants assess risk and save energy over time, while male plants live from paycheck to paycheck,'' said Adrienne Nicotra of Willington, a graduate student in the Department of Ecology & Evolutionary Biology writing her doctoral dissertation on the ecological differences between male and female plants.

Most plants have both male and female parts, but a small group of plant species such as holly and willows have separate male and female plants. These plants are called dioecious and they provide an excellent opportunity to study reproduction and the differences between plant sexes, Nicotra said.

''People are aware of differences in animals -- females are larger or males are more colorful in some species for example. In dioecious plants, the females produce the fruits and -- much like female animals -- they incur a cost for reproducing that males do not. Unlike animals, they cannot get up and go in search of food. Therefore, female plants have to be more efficient using the resources they have available to them,'' she said.

Nicotra conducted her dissertation research at La Selva Biological Station in Cosa Rica. In tropical forests like the one in Costa Rica, plants with separate sexes make up about 20 percent of the woody species. She studied Siparuna tonduziana plants, which are distantly related to Laurels.

She found that the males can spend all their energy producing flowers. The male flowers contain pollen, which is needed to fertilize the eggs in the female flowers for fruit production.

''Most people don't equate bushes or trees producing fruit with reproduction, but it's the same thing,'' Nicotra said. ''Pregnant women undergo many changes in food consumption and metabolism.''

Female plants go through similar changes when reproducing, so they must conserve the energy they receive, she said. To do this, the plants are more efficient with their resources. When they are not reproducing they grow at a faster rate then males. Some of these plants flower only once a year or every two to three years depending on how much energy they can save up.

Because of these differences in males and females, the size of the male gives away how much it will flower while female plants are unpredictable bloomers, Nicotra said.

Nicotra, originally from New Haven and Woodstock, N.Y., will be defending her dissertation next summer.