Stress could be defined as an external factor that may have some disadvantageous influence on the plant. In tropical regions, crops suffer abiotic stress especially due to water deficit and high temperature. Cross tolerance allows the plants to be acclimated after a short exposure to a specific stress. The objective of this study was water stress tolerance during bean seed germination influenced by heat shock induced cross tolerance. Seed of the common bean cv 'IAPAR 81' were submitted to imbibition in substrate paper with pure water at 20ºC for 24h. One third of the seeds were maintained at that temperature. One third were submitted to cold shock for 24h at 7ºC in the first assay and 13ºC in the second and the final part were submitted to heat shock for 24h at 38ºC and 33ºC as used for the cold shocks; in all experiments there was no change of substrate. Seeds submitted or not to shock were transferred to paper substrate simulating water potential of 0; -0.6; -0.9 and -1.2MPa, in the first experiment and 0;-0.3; -0.6; -0.9 and -1.2MPa in the second experiment using mannitol at: 0; 22.29; 44.58; 66.87 and 89.17 g.L-1. Treatments were evaluated by germination percentage, abnormal plants, dead seeds and seedling evaluation (shoot, root and total dry matter and by relation of root/shoot). The best development, in water restriction in early germination, was of that seeds that passed through 7ºC or 33ºC for 24h, that allowed the affirmation that induced cross tolerance occurred and that it could be induced at the beginning of the imbibition in bean seeds.
cold shock; heat shock; water deficit; Phaseolus vulgaris L
