New Insight Into How Burdensome Weed Climbs Surfaces

Redvine (Brunnichia ovata), a perennial woody vine that regeneratesnew growth from woody rootstocks and climbs by its tendrils, is a bigproblem for Mississippi Delta crops, especially soybeans.

Tendrils are organs used by some vines to assist their climbing, butlittle has been known about how they develop or support the vine. Atthe ARS Southern Weed Science Research Unit in Stoneville, Miss., plantphysiologist Kevin C. Vaughn and post-doctoral scientist Christopher G.Meloche discovered two unique aspects of redvine tendrils.

Redvine tendrils begin as straight, thin and flexible appendages ofthe shoot. Vaughn and Meloche discovered that epidermal cells along thelength of the vine's tendril expand in response to touch by elongatingtoward a stimulus. The tendrils themselves, as a whole, respond bycoiling around the object for support. Cells enriched with phenolsbreak apart as the tendrils rub against the object. Then the phenolsreact with an enzyme, polyphenol oxidase (PPO), to produce a sticky,phenolic polymer cement used by the tendrils to stick to the vine'sclimbing surface.

This is the first time the PPO enzyme has been implicated ingenerating an adhesive in a climbing plant. In another first, theresearchers also discovered that the weed's tendrils produce gelatinousfiber cells, the same structures found in leaning trees trying to rightthemselves. These fiber cells are also enriched in lignin to radicallyincrease their strength. Then the cells automatically die, which leadsto a dry, rigid coil structure securely anchoring the vine to thesupport.

The researchers found a unique cell wall composition with thisprocess and are looking at steps in the metabolic pathways that mightbe inhibited to control redvine.

ARS is the U.S. Department of Agriculture's chief in-house scientific research agency.