Chlorophyll a fluorescence analysis in response to excitation irradiance in bean plants (Phaseolus vulgaris L. and Vigna unguiculata L. Walp) submitted to high temperature stress

Abstract

Bean plants Phaseolus vulgaris L. (cv. Carioca and Negro Huasteco) and Vigna unguiculata L. Walp (cv. Epace-10) were grown in a growth chamber with a photosynthetic photon flux density of 200 μmol m-2 s-1 at leaf level and air temperature of 25±1°C. Fully expanded, first pair leaves of 12-d-old plants were submitted for 90 min to high temperature (25, 30, 35, 40, 45, and 48°C). Chlorophyll a fluorescence parameters (ETR, qP, qN, and F0) were investigated using a modulated fluorimeter at 25°C during recovery considered here as 48 h after stress induction period. An accentuated decrease in qP and an increase in qN at 48°C in Carioca and Negro Huasteco was not observed in Epace-10. In response to excitation irradiance a great potential for ETR was found in Negro Huasteco at 25°C, also demonstrated by net photosynthetic rate. At 48°C ETR was high for Epaceo-10 while it was equal to zero for Carioca and Negro Huasteco. Tolerance to high temperature observed in Epace-10 provided important information about the adaptative characteristics of Vigna cultivars to warm climates.