Enhancing thermotolerance of tomato plants (Lycopersieon esculentum Mill.) by heat hardening of seeds

Abstract

Best results represented by germination parameters were obtained by soaking the seeds for 5 min before exposure to 50 °C, 60 °C and 70 °C for 0.5 h, 1 h and 2 h. According to the germination data, these treatments were chosen to study their effect on vegetative growth as well as some biochemical parameters (experiment II). The study showed that seed hardening increased growth criteria expressed by stem length, number of branches, number and area of leaves and fresh and dry weight of shoots. The same treatments increased photosynthetic pigments, i.e. (chlorophylls “a” and “b”) and carotenoids of tomato leaves as well as the studied chemical constituents of shoots (reducing sugars, sucrose, amino acids, proline and proteins as well as nucleic acids and saturated fatty acids. Maximum response was attained by treatment with 60 °C for 1 h and 2 h.