Electrical Conductivity Indices and MDH Isozyme Patterns in Plumule Under Heat Shock in Wheat (Triticum Aestivum L. Em. Thell)

Twenty one-day-old seedlings of six wheat varieties grown under controlled conditions (growth chamber at 25 ºC) and heat shocked leaves (heat shock of 45 ºC for 2 and 4 h, 50 ºC for 1 and 2 h) were used for membrane stability test as well as for Malate Dehydrogenase (MDH) isozyme pattern. Membrane injury varied from 18 to 35% in control, 26 to 45%, 29 to 55% in heat shock treatment of 45 ºC for 2 and 4 h respectively, and from 32 to 49.8% and 38 to 59% in heat shock treatment of 50 ºC for 1 and 2 h respectively. For extraction of MDH isozyme from plumule, seven-day-old seedlings of wheat genotypes, viz., WH 147, Raj 3765, DI 9, DI 105, SG 182 and HT 90, were kept in an incubator at a temperature of 50 ºC for 1 and 2 h, while control seedlings were maintained at room temperature. There was a clear-cut polymorphism as revealed by the banding pattern of MDH isozymes. There were some new bands present with Rm value 0.458 at higher heat treatment in HT 90, which were supposed to be the heat shock proteins furnishing heat to HT 90 plants. Relative membrane injury, as inferred from increase in electrical conductivity as well as MDH isozyme banding pattern indicated that genotypes DI 105, HT 90 and DI 9 are relatively heat tolerant