REGROWTH KINETICS OF DACTYLIS-GLOMERATA FOLLOWING DEFOLIATION

This study describes and analyses the regrowth kinetics of vegetative plants of Dactylis glomerata L. following defoliation. Plants were grown hydroponically in growth chambers at two constant temperatures, 17 and 25 °C. The variations with time of shoot and root f. wts after the cutting were measured using a non-destructive method. During regrowth, the shoots were found to grow almost exponentially with time, whereas the growth rate of roots slowed markedly. A decrease in root f. wt was observed under the severest level of cutting.The regrowth kinetics were analyzed on an energetical basis. Shoot and root growth were calculated as the difference between the input of the carbon substrates supplied by photosynthesis and the loss of carbon associated with respiratory processes. A satisfactory description of the experimental kinetics was obtained under the main assumption that during regrowth the net photosynthetic production is partitioned between shoots and roots according to a constant ratio. From this analysis, the effect of defoliation can be interpreted in terms of a perturbation of the internal energetical equilibrium which, in roots, modifies the proportion of carbon substrates utilized for growth and maintenance requirements. © 1990 Annals of Botany Company.