The Study On Estimating Leaf Water Potential Of Cotton Based On Infrared Thermal Images

[Research object]:using infrared thermal imaging technology to extract cotton canopytemperature of the light leaves and wet artificial reference surface (WARS) to thetemperature of Jones’ empirical formula.we calculated CWSI. In order to monitorwater status of cotton canopy accurately、timely and non-contactly,we established amodel of CWSI and leaf water potential to use remote sensing to forecast leaf waterpotential.[Research methods]:This study collected five period of cotton’s infrared thermalimage,such as bud period, flowering period, flowering and boll period and bollperiod,analysis and calculating CWSI;At the same time we used Li-6400photosynthesis system to obtain stomatal conductance(Gs)and transpiration rate(Tr) atdifferent growth stages of cotton under different water and different varieties.And wemeasured leaf water potential with SPKM1400and cotton production and fiberquality; It was analysed that the relationship between these indicators.Finally, weestablished a model of remoting sensing drought monitoring of cotton.[Results]:(1)Varieties was the main influencing factors of cotton yield and quality.Water moisture of the boll stage and boll forming stage and yield was most closelyconnected. Different quality closely contacted with cotton growth period. Elongationby smaller varieties genetic factors significantly associated with moisture and fertilityperiod. The cotton plant uniformity index greatest impact by the irrigation of theflowering stage.Micronaire blooming period Moisture was significant correlation withflowering and boll stage, and the half of the average length with flowering and bollstage and boll opening stage.(2) When the soil moisture content was reduced, leaf water potential decreased,andstomatal closure, transpiration slowed down or even stopped. When drought stressincreased,the soil moisture content was very low,the leaf stomatal conductancedecreases and transpiration water loss weakened, stomatal closure, water leavingreducing to adapt to the arid environment.In a word,leaf water potential could reflectthe plant soil water content, photosynthesis and transpiration,It was an importantphysiological indicators to reflect crop water status.(3) The cotton flowering period roots activities were still distributed in20-40cmdepth soil.In an irrigation cycle,It was tested significant correlation of CWSI and soilmoisture in20cm,40cm and60cm depth soil, correlation coefficients in20cm arehigher than40cm and60cm.CWSI was an accurate reflection of cotton droughtindicators.(4) It was showed a certain regularity of cotton plants of CWSI day change under different irrigation treatments and changes in irrigation cycle and changes in thecotton growing period. in conclusion, in a day the most suitable period to reflect cropwater status CWSI is14:00-16:00.In an irrigation cycle the best time was the3rd-5thday after irrigation. During the whole growth of the cotton, CWSI in boll openingstage and full boll stage was higher than in flowering stage and full floweringstage.When CWSI value was around0.4, cotton lint yield and quality were at thehighest quality.(5) With CWSI increasing, leaf water potential decreased.It was established CWSI-Ψmodels.The models showed that the maximum absolute error of remote sensingmonitoring model predicted and measured values of leaf water potential was0.17Mpa,average absolute error was0.08Mpa. The maximum relative error was17.8%, themean relative error was9.1%, the correlation coefficient was0.9169.Within thetolerance range, the model of CWSI and leaf water potential can realize thequantitative analysis of cotton leaf water potential.[Conclusion]: Remote sensing technology can be used for monitoring and researchingleaf water potential. Remote sensing technology can be both quantitative andqualitative monitoring of a large area of cotton degree of drought.