COMPUTER-SIMULATION OF THE RAPID ADAPTATION OF ELONGATION GROWTH TO OSMOTIC-STRESS IN SEGMENTS OF COWPEA STEM BY APPLICATION OF THE APOPLAST CANAL MODEL

The transport of water during the adaptive rapid recovery of elongation growth upon additional osmotic stress was examined in the model stem segments of cowpea (Vigna unguiculata L.) by numerical solution of the extended canal equation, which consists of a set of time-dependent non-linear partial differential equations. The calculated dynamic behaviour of the depletion of solute within the apoplast canal effectively explained the reported transient changes in water flow and, therefore, in growth during the adaptation to stress if the stress-induced enhancement of net uptake of solute from the apoplast canal was assumed. The extended canal model was also adequate for simulation of the elastic shrinkage of hypocotyl segments upon exposure to osmotic stress which took place when the supply of energy was limited. It appeared that the function of the canal system in absorbing water is intrinsically stable against perturbations of the water environment.