Effect of Fluoride-stress on Photosynthesis of Tea Leaves

Effect of Fluoride(F)-stress on photosynthetic gas exchange parameters was studied using 10-month-old clonal plants of the tea,Camellia sinensis(L.)O.Kuntze cv.Ruixiang.The plants were grown in pots and fertilized with a nutrient solution containing 0,100,200,600or 1 800mg·L-1 F on a three times a week,24-week application.The photosynthesis characteristics of the tea leaves were determined using aportable photosynthesis system(Li-6400).The result showed that the tea leaves had increased CO2assimilation,stomatal conductance, transpiraition rate,intercellular CO2 concentration,and chlorophyll content when the F level was below 100 mg·L-1.With the F concentration increased up to 600mg·L-1,the CO2assimilation,stomatal conductance and transpiration rate decreased,but no differences in the intercellular CO2 concentration,water use efficiency or biomass.Symptoms of F-stress were apparent when the F concention was beyond 600mg·L-1(F content in the tea leaves was(2880±220)mg·kg-1.