Resistance of photosynthesis to high temperature in two bean varieties (Phaseolus vulgaris L.)

The increase in the basal fluorescence (F-0) by increases in temperature has been widely used as a screening technique to assess the temperature at which plant species suffer irreversible damage in their photosynthetic apparatus. This method has been used in this study to assess the resistance to extreme high temperature in two bean varieties, Barbucho (Chilean, non commercially bred) and Blue lake (commercially available in the UK). The results suggested that the two varieties have a similar threshold for high temperature at 42-43 degrees C, however, at 40 degrees C, Barbucho maintains its photosynthetic functions for a longer period of time compared to Blue-Lake as observed by mean of simultaneous measurement of gas exchange and room temperature fluorescence. It seems likely that inhibition at 40 degrees C in Blue-Lake is related to the instability of Photosystem II.