Resumen
Screening test was conducted on 54genotypes of tomato to analyze the effect of heat stress and categorize them as heat tolerant or heat susceptible ones. Seedlings were grown at temperatures of 28/22oC day/night. Four weeks after sowing, plants were exposed to high temperatures of 40/32oC day/night for one week. Data for various morphological (root and shoot length, root and shoot fresh and dry weight, number of leaves) and physiological parameters (chlorophyll contents, sub-stomatal CO2, transpiration rate, stomatal conductance, photosynthetic rate, water use efficiency and leaf temperature) were recorded. Heat stress had a negative effect on all physiological and morphological processes of the genotypes. However, ?Parter Improved?, ?Legend? and ?Roma? were the most tolerant genotypes whereas ?Grus Chovka?, ?Nepoli?, ?Tima France?, ?Kaldera? and ?Cold Set? were susceptible to heat stress.