A drought stress-sensing technique based on wavelet entropy of chlorophyll fluorescence excited with pseudo-random binary sequence

Abstract

Drought stress is one of the most important environmental factors limiting photosynthesis and agriculture yield, but photosynthesis-based drought stress measures are still not well developed. Chlorophyll a fluorescence (ChlF) from photosynthesis II (PSII) tightly couples with photosynthesis and may potentially serve as a measure of drought stress. Traditional ChlF measurement is usually based on a step or pulse excitation, and may not perturb the complex photochemical reactions to show strong ChlF difference under drought stress conditions and limit the sensitivity and robustness of using ChlF to sense drought stress. In this work, a drought stress-sensing technique based on ChlF excited by pseudo-random binary sequence (PRBS) and analyzed by wavelet entropy was established. Four different rice (Oryza sativa L.) varieties with 120 samples for each variety and thirty spinach (Spinacia oleracea L.) samples were measured under different drought stress durations to validate the proposed method. Results show that the proposed wavelet-entropy-based ChlF measure could differentiate all the different drought stress durations for all rice varieties and spinach but the commonly used OJIP-based ChlF induction analysis could not. This work provides a new plant-physiology-based drought stress measurement method and ChlF analysis technique.