Diverse response of tomato fruit explants to high temperature

Abstract

Tomato explains (fruit with a pedicel and a piece of peduncle), with fruit growth stimulated by treating the flowers with NOA + (i A3 (NG-series) were used as a model system for studying the effect of high temperature on C-.sue rose uptake, its distribution and C a rctranslocation. Twocultivars with contrasting responses to high temperature were compared. I11 sensitive cv. Roma heat stress during 22h (40°C for I Oh and 30°C for I2h), drastically depressed the uptake of1 'C-sucrose coinciding with diminished fruit 'c-supply. It also decreased the specific activity c! soluble acid invertase and the calcium content. All these strong negative responses to high temperature were markedly reduced 111 the NG-treated series involving remobili/ation of Ca to the fruits and a higher stability of the invertase activity. This indicates the indirect role of flower treatment with NG in addaptation to heat stress. In tolerant ev. Robin even higher temperatures (42°C for I Oh and 34°C for I2h) were not stressful. They did not affect the C-sucrosc uptake and stimulated IJC-supply to the fruit. Increased specific activity of acid invertase and a higher calcium content were also recorded but only in the control explains. In contrast to ev. Roma elevated temperature was slightly stressful forcv. Robin explains of NG-series. The differences in response of both cullivar explains to elevated temperature, based on unequal fruit supply with 14C-sucrosc, seem to be eausaly connected with two factors: the invertase activity being more or less sensitive to the heal stress, the ability to translocate Ca to the heated fruits.