The quantum yield of photosynthetic electron transport evaluated by chlorophyll fluorescence as an indicator of drought tolerance in durum wheat

The chlorophyll fluorescence parameters Delta F/Fm' and Fv'/Fm', related respectively to the quantum yield of photosynthetic electron transport and to the efficiency of excitation capture by the open centres of photosystem II, have been evaluated as possible indicators of drought tolerance in durum wheat. Delta F/Fm' and Fv'/Fm' measurements were carried out on excised leaves, both control and dehydrated, of 25 cultivars. Delta F/Fm' and Fv'/Fm' values were obtained at two times after the start of fluorescence measurement: at 14 s, i.e. during the induction curve (Delta F/Fm'(14s) and Fv'/Fm'(14s)) and at 200 s, i.e. at steady state fluorescence (Delta F/Fm'(200s) and Fv'/Fm'(200s)). In dehydrated leaves a mean significant decrease of 20 % (P < 0.001) was observed in Delta F/Fm'(14s) values. In contrast, no great differences were observed between control and dehydrated leaves with regard to Delta F/Fm'(200s), Fv'/Fm'(14s) and Fv'/Fm'(200s). The percentage decrease of Delta F/Fm'(14s) after dehydration was correlated with the drought susceptibility index (DSI) of the cultivars, evaluated on a yield basis and a significant correlation (r = 0.72, P < 0.001) was found.