The effects of disease stress on spectra reflectance and chlorophyll fluorescence characteristics of cotton leaves

In order to provide a new technology and method to monitor cotton infected Verticillium wilt by spectra and chlorophyll fluorescence, the effects of spectra reflectance and chlorophyll fluorescence characteristics of cotton leaves under disease stress were studied. Through treatments of Verticillium wilt by inoculation in experiment field, the physical-chemical parameters, spectrum and chlorophyll fluorescence parameters of cotton leaves were measured and analyzed under disease stress. The results showed that with increasing severity level (SL) of disease, the Ch1.a、Ch1.b、Chl.a+b、LWC and LTNC, were decreased, and Car was gone up and then down in disease cotton leaves. The spectral reflectance of cotton leaves was little by little climbed from visible light region to short wave infrared region (400-2 500 nm) with increasing SL of disease. The spectral characteristic parameters of REP、OSAVI、PRI、G_NDVI、Lo、Depth672 and Area672 on leaves of disease were little by little dropped, whereas R550、R680、TCARI、R1200、R1685、Lwidth and ND672 were little by little climbed with increasing SL. The chlorophyll fluorescence parameters of Fv、Fm、Fv/Fm、Fv/Fo、Fm/Fo、ΦPSII were all decreased, but Fo increased with increasing SL of disease. After analyzing of correlation, it was discovered that besides Car, others agronomy, spectrum and chlorophyll fluorescence parameters were all significant relationship with SL. And the correlation of was best between spectral parameters and SL, the second correlation between agronomy parameters and SL, and the better correlation between chlorophyll fluorescence parameters and SL. The spectral reflectance and chlorophyll fluorescence characteristics of cotton leaves were influenced in some degree by disease of cotton, so it is variable to monitoring of cotton disease by the spectrum and chlorophyll fluorescence.