'Seeds, who needs 'em?' foresters say.

Researchers have refined a new technique, which doesn't require seeds, for producing commercial stands of genetically similar hardwood trees, Scott A. Merkle of the University of Georgia in Athens and his colleagues report.

The International Paper Co., which funded Merkle's work, began producing sweetgum trees this year using the new cloning technique. It plans to apply for a patent, Merkle says.

Sweetgum trees are one of the few hardwood species that southern paper companies want to add to their tree plantations, which now consist primarily of pine and Douglas fir, Merkle says. Sweetgums grow in the eastern United States and Mexico.

The cloning procedure involves exposing cells from a group of tightly clustered, male flowers to a commercially available, synthetic hormone that acts as a plant growth regulator. The chemical forces the cells to form embryos instead of flowers, Merkle's team reports. Tree embryos normally grow inside seeds.

When exposed to the regulator, the embryos produced by the flower cells clone themselves, making more embryos. "They get caught in a cycle of continuous embryo production," he says. When removed from the regulator, the embryos grow into normal trees.

Other scientists have used a similar cloning technique to produce a few oak and buckeye trees, which have less commercial value than sweetgum, Merkle says.

International Paper scientists plan to test their sweetgum trees' DNA to see how closely the trees resemble each other. If the offspring prove to be almost identical to their parents, the technique of growing trees from flower tissue should help researchers to preserve rare trees and should aid foresters to produce large numbers of trees with the same desired traits, Merkle says.

Also, cloning trees from tissue should eventually prove quicker and less expensive than previous methods, he contends.