Study On Photosynthesis Of Strawberry Under Water Stress

Strawberry (Fragaria chiloensis Duch),a herbaceos perennial rose family strawberry belongs to (Fragaria L.) , gets its popularity for its soft succulence, mineral substance , rich Vitamin C and iron of fruit. Water is one of the main factor affecting strawberry growth. But high temperature and drought affected strawberry's growth ,and restricted strawberry directly getting over summer in south of China. With the aim of offering scientific basis for drought resistant variety choice,and BR application in cultivation to strawberry, Fragaria chiloensis 'zhangji' was used as materials under the different water stress, the photosynthetic characteristic, gas exchanges , chlorophyll contents change, and the effect of BR on photosynthesis and antioxidase activties to strawberry were studied.Test results as follows:1. Photosynthetic index and photosynthetic pigments contents change were determined under different soil relative water content(30%,40% and 50%). The results indicated that: water stress decreeased net photosynthetic rate(Pn) and light saturation point, limited stomatal conductance(Gs), intercellular CO₂ concentration(Ci) and transpiration rate(Tr). and the photosynthetic efficiency of strawberry declined with the aggravating of stress degree. The content of photosynthetic pigments was also reduced with the aggravating of stress degree. The photosynthesis and chlorophyll contents are different in strawberry leaves of different position, Mid-position leaves of strawberry was the highest , secondly in lower-position leaves, and lowest in upper-position, newly-spreaded leaves.2. With the prolonging of water stress, the net photosynthetic rate , transpiration rate, stomatal conductance and intercellular CO2 concentration declined without exception, and the photosynthetic efficiency of stawberry declined with the prolonging of stress time. The content of photosynthetic pigments and water use efficiency (WUE) was also reduced with the prolonging of stress time 3 The activities of super oxide dismutase (SOD) , Catalase (CAT) and peroxidase (POD) and malondialdehyde (MDA) contents in strawberry leaves were influenced by brassinolide BR under water stress. The activities of SOD, CAT and POD were increasing in the first and then declining, and MDA contents were always increasing with the prolonging of stress time in the strawberry leaves. The activities of SOD, POD and CATin the strawberry leaves treated with BR were higher than that in the strawberry leaves which were not treated with BR. The amount of MDA in the strawberry leave treated with BR was less than that in the strawberry leaves which were not treated with BR.