Detection of the photosynthesis protective mechanisms of C3 and C4Crops from hyper spectral data
C3、C4作物的光保护机制差异的光谱探测研究

The classif ication of C3 and C4 plant functional types has become an important issue in global change research, butthe mechanism of using remote sensing data remains unclear. In this paper, a diurnal variation experiment was designed for soybean(C3 plant functional type)and maize(C4 plant functional type)to acquire canopy spectra under different illumination andtemperature conditions, and chlorophyll fl uorescence(ChlF)signals and photochemical refl ectance index(PRI)were extractedfrom the canopy spectra. The results showed that:(1)the amplitudes of the diurnal variation in ChlF between soybean and maizewere signif icantly different, as the relative ChlF of soybean increased rapidly under heat and high irradiance stresses in theafternoon, but the increasing trend was not found in maize;(2)there was also an apparent increase in the ratio f688/f760 of ChlFintensities of soybean in the afternoon, but this did not appear in maize;(3)the midday photosynthetic depression occurred in C3crops owing to the stressed light and temperature, with a rapid increase in PRI. However, there was no apparent noon depressionin C4 crops. Based on the different characteristics between the responses of C3 and C4 crops to high irradiance and temperaturestressws, we proposed a potential method to discriminate C3 and C4 plants by multitemporal and hyper spectral remote sensingdata.