DISTRIBUTION OF CALCIUM IN TOMATO PLANTS IN RESPONSE TO HEAT-STRESS AND PLANT-GROWTH REGULATORS

Two cultivars of tomato with contrasting response to elevated temperature were compared: sensitive - Roma and tolerant - Robin. Experiments were done on fruit explants and on rooted cuttings with small fruits. In both cases Ca-45 was poorly transported to the fruits. Nevertheless in fruit explants elevated temperature (40 degrees C) increased Ca-45 import into the fruits in both cultivars. In the compared cuttings, treated or not treated with growth regulators and at various temperatures, the greatest differences were observed in the amount of Ca-45 transported to the fruits. Sensitive Roma cuttings scantily supplied their fruits with Ca-45 both under optimal temperature and heat stress. In plants previously treated with NOA + GA(3) high temperature increased Ca-45 transport to the fruits. Robin cuttings inversely responded to heat stress by transporting a much higher portion of Ca-45 to the fruits, both in control and NOA + GA(3) cuttings. The diversity of Ca-45 distribution during elevated temperature in cuttings, but not in fruit explants of both cultivars seems to be connected with an ability to control calcium supply to fruit or at least to prevent its decrease; this mechanism is perhaps located outside the cluster.