Proline accumulation: A parameter for evaluation of sensitivity of tomato varieties to drought stress?

Abstract

The pattern of proline accumulation and the growth response were followed in several tomato (Lycopersicon esculentum Mill.) varieties which were exposed to 7 days of drought stress followed by a 15‐day period of rewatering. During dehydration, water potential and leaf elongation rates decreased more in var. ‘Hosen’ and ‘S‐5’ than in ‘LX‐11’, ‘1970’, ‘Pakmor’, ‘Faculty‐16’, ‘Alcobaca’ and ‘475’. Proline accumulation during stress was greatest in the first two varieties. In ‘Hosen’ and ‘S‐5’ rewatering resulted in a decrease of proline to control levels, whereas in the other varieties accumulation of proline continued long after turgor had been regained. The extent of this continued accumulation was not correlated with the degree to which each variety was dehydrated. Upon rewatering of the plants the rate of leaf elongation was increased, but the final leaf size as well as whole shoot and root fresh weight of the recovered plants were not colated with the degree of “suffering” that each variety experienced during the drought period. Incubation of detached young tomato leaves in polyethylene glycol solution for 48 h resulted in a substantial accumulation of proline. The varietal differences observed under these conditions were reminiscent of the differential responses in proline accumulation obtained in the intact plants. It is concluded that proline accumulation at the time of dehydration signals drought stress in tomato plants but does not correlate with the overall varietal sensitivity to transient dehydration in recovered plants.