Using the diurnal variation characteristics of effective quantum yield of PSII photochemistry for drought stress detection in maize

Abstract

The importance of detecting drought stress in crops to alleviate the pressure of the growing population and food demand is well recognized. Although chlorophyll fluorescence (ChlF) is closely related to photosynthesis, it is always disturbed by the intensity of irradiance during the measurement. To detect drought stress more effectively with ChlF, we studied the diurnal relationship of the effective quantum yield of photosystem II (PSII) photochemistry (ΦPSII) and photosynthetically active radiation (PAR). We measured the diurnal ΦPSII, leaf temperature (Tleaf) and PAR of maize leaves (ZhengDan958) by pulse-amplitude modulated (PAM) fluorometry under different drought stresses. We found that in the absence of drought stress, the linearity (indicated by R2) between diurnal ΦPSII and PAR was strong. When drought stress was gradually aggravated, the difference between the ΦPSII values in the morning and those in the afternoon under similar PAR values gradually became significant. Therefore, the R2 values of the linear correlation of the diurnal ΦPSII-PAR regression gradually decreased under increased drought stress. The simulation results of a photosynthesis model showed that the diurnal variation in the response of ΦPSII-PAR during drought may be the result of the fluctuation of the substrate saturated Rubisco capacity (Vcmax) , which was dominated by the dynamics of Tleaf. The results indicated that the linearity of diurnal ΦPSII-PAR regression can be used as an effective and convenient field indicator to monitor drought stress.