Amelioration of chemical and organic fertilizer on photoinhibition of PSⅡ at photosynthetic noonbreak in mulberry leaves grew in salinesodic soils

Using the chlorophyll fluorescence kinetics, the effects of application of chemical fertilizer and organic fertilizer on photoinhibition of PSⅡ at photosynthetic noonbreak in mulberry leaves grew in salinesodic soils were investigated. The results showed that maximal photochemical efficiency of PSⅡ (Fv/Fm) and photosynthetic performance index (PIABS) based on light absorption were only 0.69 and 0.19, respectively. Meanwhile, photoinhibition was significant in leaves of mulberry in salt and alkali soil at photosynthetic noonbreak. Both chemical fertilizer and organic fertilizer increased the Fv/Fm and PIABS although organic fertilizer were superior than chemical fertilizer. With standardization of OJIP curve, the electronic transmission ability of QA to QB in PSⅡelectronic receptor side increased at photosynthetic noonbreak. The application of chemical fertilizer and organic fertilizer alleviated photo inhibition of PSⅡ photosynthetic noonbreak by increasing electronaccepting ability of QB and PQ electronic library, especially, organic fertilizer application also increased electronaccepting ability of QB and decreased QA- accumulation. The application of chemical fertilizer and organic fertilizer increased the activities of oxygen evolution complex (OEC) in PSⅡelectronic receptor side to maintain the normal water cracking function and supply of photosynthetic electron. In addition, the application of chemical fertilizer and organic fertilizer also decreased the dissociation degree of chloroplast thylakoid and increased its adhesion of PSⅡprotein complex to maintain photochemical activity of PSⅡ. The relieve of photo inhibition of PSⅡphotosynthetic noonbreak of organic fertilizer was better than that of chemical fertilizer because the electronic transmission in PSⅡelectronic receptor, while there was few difference between two fertilizers on the condition of OEC and thylakoid membrane.