Saturday, March 28, 2009
Orchid Has "Active" Sex With Itself -- A Flower First?
Researchers say an extension of the male flower part, or anther, turns an upside-down loop to deliver spermlike pollen spores directly into the female cavity.
The anther bends to enter the female chamber from below and is secured in place by a ring structure on its stalk to ensure fertilization.
The flower is the first known plant in which pollination is entirely self-directed, with no outside agents or forces—such as bees or breezes—playing a role.
Biologists observed the elaborate style of reproduction in the bisexual orchid Holcoglossum amesianum, a tree-dwelling plant found in the dry forests of China's southern Yunnan Province
LaiQiang Huang of Tsinghua University in Shenzhen and colleagues studied the unusual flower. The team's findings will appear in tomorrow's issue of the journal Nature.
In more conventional plant sex, creatures such as insects or birds transport pollen from one plant to another, resulting in a fertilized embryo or seed.
Most orchids reproduce in this way, and many are known for their elaborate floral structures (photo: South African Disa uniflora orchid) designed to attract specialized insect pollinators.
But pollen may also be transferred from male to female flowers on a single plant, or from male to female parts on a single blossom. In such cases, plants can fertilize themselves.
While less common in orchids, many flowering plants are known to self-fertilize either some or all of the time. Most rely on wind or fluid secretions to move pollen around.
But no other species does it quite like H. amesianum.