Preliminary study on the effects of water stress on maize leaf physiological status through passive chlorophyll fluorescence detection

The authors studied the effects of water stress on leaf physiological status of maize(Zea mays L.) detected by passive chlorophyll fluorescence(CF) measurements. By putting the detached maize leaves in a desiccator with different durations to obtain five kinds of water stress conditions. The leaf apparent spectra were measured under illuminations with and without a specially designed long wave pass edge filter, using a Li-Cor 1800 integrating sphere coupled with an ASD spectrometer. The CF spectra were derived from the reflectance difference spectra acquired under illuminations with and without the filter. The wavelength of fluorescence spectral peak shifted a little when leaf water content decreased. The CF peak values at 686 nm showed an increasing tendency followed by a decrease, while the CF peak values at 740 nm decreased gradually. The fluorescence intensity ratio of chlorophyll bands (Dif₆₈₆/Dif₇₄₀) was negatively correlated with leaf water content (R²=0.3850，n=21). The CF parameters, Fv/Fm, measured by modulated chlorophyll fluorometer, were positively correlated with the degree of water stress severity while negatively correlated with Dif₆₈₆/Dif₇₄₀. The results indicated that the CF passively detecting technique could be employed to evaluate leaf photosystem status impaired by water stress, which provide a basis for probing the physiological status of crops.