Physiological effects of nitrogen and potassium nutrition on senescence of cotton functional leaves.

Physiological effects of nitrogen and potassium nutrition on cotton functional leaves were studied by using the material of SCRC 28.Four treatments were conducted with N2K2,N2K1,N1K2 and N0K0.The results indicated that fluorescence parameters Fv/Fm,ФPSⅡ and qP of the functional leaves showed "V"-shaped changing trend of high-low-high in a day at boll forming stage,typically the ФPSⅡ.The value of each fluorescence parameter under N2K1 treatment was generally the highest,while the lowest under N0K0 treatment.Chlorophyll content under N2K2,N1K2 and N2K1 treatments increased by 38.0%,24.0% and 20.7% than of N0K0 at the boll forming stage.In addition,the soluble protein content and SOD activity of functional leaves were lowest under N0K0 treatment at middle and later stages,while the MDA and ABA contents were the highest.It can be concluded that maintaining a certain level of nitrogen and potassium nutrition is helpful to improve physiological performance of functional leaves and delay in senescence.