Abstract
A single episode of thigmic (contact rubbing) stress applied to the apical hook of a dark-grown soybean hypocotyl results in a two-phase response: an initial rapid (s) cessation of elongation followed by a long (h) recovery. Increased Ca2+ in the growth matrix from 1 to 5 mM increased the average pre-stress elongation rate from 22 μm min-1 to 40 μm min-1 further increases in Ca2+ did not further enhance elongation rate, There was no effect of nutritional status on the initial rapid response to a single episode of thigmic stress; all seedlings stopped elongating within seconds regardless of nutrient status. However, seedlings cultured with higher levels of Ca2+ recovered their pre-stress rate more quickly. Correlation of enhanced recovery with enhanced root development was observed for seedlings grown in 5 mM Ca2+. Inclusion of 1.5, or 10 mM K+ in the growth matrix further reduced recovery time from ≥6 h to ≤3h. K+ effects may be due to the ability of seedlings to adjust osmotically. It previously has been shown that seedlings have significantly less K+ in their elongation zone following stress, and the osmotic potential of the expressed sap is lower than that of controls. Physiological and biophysical changes that occur in response to mechanical perturbations have potential for modification by nutritional status.This project was supported in part by NASA grant NAG10-0093.
Published Version
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