Variation in some physiological parameters in relation to high temperature stress in common bean (Phaseolus vulgaris L.)

The present study aimed at assessment of variation for various physiological parameters in relation to heat stress. Invariably the parameters like canopy temperature, thylakoid damage higher in HT (high temperature) as compared to OT (optimum temperature) whereas the parameters like PS-II quantum efficiency (Fv/Fm), leaf chlorophyll index (SPAD), membrane stability index and shoot dry weight were higher in OT as compared to HT. Canopy temperature under OT was lowest in Matterhorn (24.115) and highest in Buster (26.873). PS-II quantum efficiency ranged from 0.735 (Stampede) to 0.789 (Buster) under HT. Under both OT and HT conditions cell membrane stability was highest for Lariat (0.813 and 0.787 respectively) and lowest for Topaz under OT (0.727) and Stampede under HT (0.657) respectively. The leaf chlorophyll index (SPAD) values had almost similar range of variation under both OT and HT with ranges of 49.725 (Matterhorn) to 55.900 (Topaz) and 48.200 (Lariat) to 53.725 (Roza) under OT and HT respectively Lariat had the highest shoot dry weight (7.940 and 3.032) whereas, Buster had lowest shoot biomass under both OT and HT conditions (3.510 and 2.040) respectively. High temperature caused highest decrease in shoot dry weight (53.754%) followed by MSI (10.625%) while as, parameters like canopy temperature witnessed an increase under HT (37.577%) followed by thylakoid damage (24.064%). Canopy temperature was negatively correlated with PS-II quantum efficiency as well as membrane stability index, and positively correlated with thylakoid damage under both OT and HT conditions. Similarly, PS-II quantum efficiency was positively correlated with MSI and negatively correlated with thylakoid damage.