RELATIONSHIP BETWEEN SOME PHYSIOLOGICAL CHARACTERS AND YIELD OF HEAT-TOLERANT, NONTOLERANT, AND TROPICAL TOMATO CULTIVARS GROWN AT HIGH-TEMPERATURE

The relationships between physiological characters; photosynthesis (P(r)), transpiration (E), stomatal conductance (G(s)), and yield of three heat-tolerant tomato (Lycopersicon esculentum Mill.) cvs. Shikiaka, Shuki and Ohio 7663, non heat-tolerant cv. Sataan; and two tropical cvs. Owusu-Bioh and Wosowoso, grown at 40-degrees/23-degrees-C day/night temperatures were examined. Physiological characters were measured at air temperatures of 20-degrees, 30-degrees, and 40-degrees-C. P(r) for heat-tolerant cultivars pooled at the seedling stage (5 - 7 leaves) was significantly greater than non heat-tolerant cultivars at 20-degrees and 40-degrees-C. P(r), E, and G(s) at the flowering and early fruit development stage (13 - 15 leaves) were significantly higher in the heat-tolerant cultivars compared to the other cultivars at all temperatures. P(r) at the seedling stage did not significantly correlate with yield but P(r), E and G(s) were significantly correlated with fruit yield at the flowering and early fruit development stage. A linear relationship between P(r) and G(s) and between E and G(s) revealed a close and significant consequential relationship between E and P(r). Regressions among physiological variables were not homogenous among/between cultivars. Regressions between P(r), E, G(s), and yield were heterogenous among/between cultivars. Heat-tolerant cultivars had greater yields than the other cultivars. The results indicate that yield significantly and positively correlated with P(r), E, and G(s).