Drought Stress Detection Using Hyperspectral Reflectance And Chlorophyll Fluorescence Techniques In Cotton Field

Continuous drought stress and different drought stress experments were conducted sincethe bud stage. Two treatments were conducted as CD (continuous drought) and CK (nodrought stress, relative soil water content was between55%and70%) during continuousdrought stress experment; There treatments were conducted as SD (severe drought, relativesoil water content was between35%and45%), MD (moderate drought relative soil watercontent was between45%and55%), CK (no drought stress, relative soil water content wasbetween55%and70%) during different drought stress experment. Using transgenic cottoncultivar Yinrui361as material, leaf spectral reflectance, photosynthesis, chlorophyllfluorescence characteristics, SPAD, leaf water potential and LAI were studied by potexperiment. The results as follows:1. RWC, Pn, Gs, Tr, Fv/Fm, φPSII, qP and PRI showed a downward trend along with theprolonging of the drought stress. Ls increased at the early time, and then decreased later.While NPQ showed an increasing trend. After rewatering, most parameters could not recoverto the initial state except leaf relative water content (RWC). Compared with the initial state ontwo-year average, net photosynthesis (Pn), stomatal conductance (Gs), transpiration rate (Tr),maximal photochemical efficiency of PSⅡin the dark (Fv/Fm), actual photochemicalefficiency of PSⅡin the ligh (φPSII), photochemical quenching coefficient (qP) andphotochemical reflectance index (PRI) in the4th day of stress decreased by53.1%,79.9%,66%,3.8%,11%,5.7%and18.4%, respectively. While stomatal limitation value (Ls) andnon-photochemical quenchin coefficient (NPQ) increased by98.1%and28.6%, respectively.Among them, only Pn, Gs, Tr, Ls, Fv/Fm and PRI have significant differences between valuesin the4th day and the initial state, and And all of this indexs have highly significantcorrelation relationship with leaf relative water content, so they can accurately reflect thewater status of cotton.2. With the increase of water stress, leaf water potential, plant height, leaf area index(LAI), net photosynthesis (Pn), stomatal conductance (Gs), transpiration rate (Tr), maximalphotochemical efficiency of PSⅡin the dark (Fv/Fm), actual photochemical efficiency ofPSⅡin the ligh (φPSII), photochemical quenching coefficient (qP), photochemical reflectanceindex (PRI), normalized difference vegetation index(NDVI), fluorescence of761nm showedan decreasing tendency; soil and plant analyzer development(SPAD), specific leaf weight, intercellular CO2concentration(Ci), non-photochemical quenchin coefficient (NPQ) andfluorescence of687nm showed an increasing tendency. Pn、Gs、PRI、F687have highlysignificant correlation relationship with RWC, while Tr、Fv/Fm、NPQ、NDVI、WI/NDVI havesignificant correlation relationship with RWC. The correlation coefficient of F761、MSI withRWC are0.3496and0.3675, other indexs have low correlation relationship with RWC. SoPn、Gs、PRI、F687can more sensitively and accurately reflect the water status of cotton andF687is the best.The diurnal variation of Pn in cotton stalk leaf under different drought stress is a singlepeak. There were no difference when sunlight was weak, but SD was significantly lower thanCK with increasing illumination intensity. While the Pn of MD begain to decrease at9:00, andthe peak was earlier one hour then SD and CK; The value of Fv/Fm is SD＞MD＞CK,except the sunlight was weak when there were no difference among the three treatments; Thediurnal variation of PRI was similar with Pn; F687of SD was significantly higher than CKand MD in diurnal variation which were also single peaks and difference was extremelysignificant of F761from11:00to15:00during diurnal variation in cotton stalk leaf underdifferent drought stress.