Thigmomorphogenesis: The induction of callose formation and ethylene evolution by mechanical perturbation in bean stems.

Mechanical perturbation by rubbing of the first internode of 11-12 day old plants of Phaseolus vulgaris L. cv. Cherokee wax induces the rapid deposition of callose in the cells of phloem and other tissues. Callose deposition begins immediately after mechanical perturbation, and shows a minor transient peak 1.5 h, and a major peak 6 h later. The callose gradually disappears and is gone after 3 days. If the stems are perturbed every day, the amount of callose decreases by day 2 but then gradually increases again through day 12. Both the top and bottom of the internode produce callose in response to mechanical perturbation. The evolution of ethylene in response to mechanical perturbation begins after 1 h, peaks at 2-3 h and is gone by 5-6 h. A spray of 10-2 M 2-deoxy-D-glucose (DDG) completely blocks stem thickening, callose deposition and ethylene evolution due to mechanical perturbation. DDG at 10-5 to 10-4 M blocks callose production in mechanically perturbed stem segments and increases ethylene evolution from unperturbed stem segments to greater levels than those obtained by mechanically perturbed segments. It is concluded that mechanical perturbation of bean stems tissue induces deposition of callose more rapidly than it induces evolution of ethylene and that DDG can block both processes. [ABSTRACT FROM AUTHOR]