Abstract
In this experiment, primary leaves of two varieties of Adzuki beans, Buchishouryukei-1 which is cold sensitive in the budding stage and Akanedainagon which is cold resistant in the budding stage were used. The primary leaves were exposed to chilling in the shade (10-13°C, 72% shading) for either 28 days(28-day group) or 18 days(18-day group). In Akanedainagon, chlorophyll was synthesized under subsequent greening conditions (20-25°C, sunlight), even in the 28-day group though more slowly than in the 18-day group, and no plants in the 28-day group died. In contrast, in Buchishouryukei-1, the greening treatment did not lead to chlorophyll synthesis in the primary leaves in the 28-day group; moreover, the death rate was about 20% before the greening treatment and it further increased thereafter. In primary leaves of Buchishouryukei-1, H2O2 content and superoxide dismutase (SOD) activity were markedly higher in the 28-day group than in the 18-day group, and SOD, ascorbate peroxidase and catalase activities in the 28-day group were markedly decreased by greening treatment. On the other hand, in the primary leaves of Akanedainagon, only a slight increase in H2O2 content and SOD activity, and no change in the oxidation-inhibiting enzymes were observed in the 28-day group. Long-term (28-days) chilling and shading were found to cause H2O2 accumulation in the primary leaves of Buchishouryukei-1. The difference between the two varieties in the cold resistance of primary leaves could be attributed to the difference in the O2- formation brought about by the chilling and shading treatment.
