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Chinese Journal of Applied Ecology ›› 2003, Vol. ›› Issue (6): 867-870.

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Effects of high temperature stress on net photosynthetic rate and photosystem Ⅱ activity in Citrus

GUO Yanping, ZHOU Huifen, ZENG Guanghui, ZHANG Liangcheng   

  1. Department of Horticulture, Zhejiang University, Hangzhou 310029, China
  • Received:2002-03-29 Revised:2002-09-23 Online:2003-06-15

Abstract: Table ADC-225-MK3 CO2 gas analyzer and PAM 2000 portable fluorescence measurement system were used to measure the net photosynthetic rate (Pn), initial fluorescence (Fo), maximal photochemical efficiency of PSⅡ (Fv/Fm) and electron transport rate (ETR) of satsuma mandarin (Citrus unshiu Marc.) and navel orange (C. sinensis Osbeck) leaves. The results showed that exposure of citrus plants to high temperature (38~40 ℃) led to a lowering of Pn, Fv/Fm, and ETR, whereas Fo increased. After exposure to high temperature for 25 days, compared with normal temperature (25 ℃),the Pn of satsuma mandarin and navel orange leaves decreased by 55.6% and 39.8%, Fv/Fm decreased by 22.0% and 6.7% and ETR reduced by 55.0% and 41.5 %, respectively. On the other hand, Fo increased 113.8% and 14.9%,respectively. With subsequent transfer to the 25 ℃ culture room for 10 days, Pn, Fv/Fm, Fo and ETR recovered significantly. These results demonstrated that the reduction of Pn in Citrus was related to the inactivation of PSⅡ reaction center.

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