Sep. 20, 2005 The way in which a problematic weed overruns and secures itself to crops and man-made structures--and how it clings to the surfaces it climbs--has been revealed by Agricultural Research Service scientists.
Redvine (Brunnichia ovata), a perennial woody vine that regenerates new growth from woody rootstocks and climbs by its tendrils, is a big problem for Mississippi Delta crops, especially soybeans.
Tendrils are organs used by some vines to assist their climbing, but little has been known about how they develop or support the vine. At the ARS Southern Weed Science Research Unit in Stoneville, Miss., plant physiologist 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 of the shoot. Vaughn and Meloche discovered that epidermal cells along the length of the vine's tendril expand in response to touch by elongating toward a stimulus. The tendrils themselves, as a whole, respond by coiling around the object for support. Cells enriched with phenols break apart as the tendrils rub against the object. Then the phenols react with an enzyme, polyphenol oxidase (PPO), to produce a sticky, phenolic polymer cement used by the tendrils to stick to the vine's climbing surface.
This is the first time the PPO enzyme has been implicated in generating an adhesive in a climbing plant. In another first, the researchers also discovered that the weed's tendrils produce gelatinous fiber cells, the same structures found in leaning trees trying to right themselves. These fiber cells are also enriched in lignin to radically increase their strength. Then the cells automatically die, which leads to a dry, rigid coil structure securely anchoring the vine to the support.
The researchers found a unique cell wall composition with this process and are looking at steps in the metabolic pathways that might be inhibited to control redvine.
ARS is the U.S. Department of Agriculture's chief in-house scientific research agency.
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