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Leaf photosynthesis and chlorophy11 fluorescence in a chlorophy11-deficient mutant of barley

Tan Xinxing, Xu Daquan, Tang Zesheng

Shanghai Institute of Plant Physiology,The Chinese Academy of Sciences.Shanghai 200032；China

Abstract

A comparative study of barley leaf photosynthesis and chlorophy11 fluorescence was made between a Chl-deficient mutant (with light green leaf,LG) and its wild-type (dark green leaf,DG) in order to further explore the regulatory mechanism of photosynthesis.As compared with DG,LG had a lower net photosynthesis rate (Pn) and apparent quantum yield (AQY), but a higher stomatal conductance, indicating that the lower Pn of LG may result from lower Chl (Chl a and Chl b) content, but not from lower stomatal conductance.PSⅡ photochemical efficiency (Fv/Fm) was about 10% higher in LG than in DG, which is different from the chlorophy11 b-less mutant of barley reported by Leverenz et al. (1992). Furthermore, LG had higher Chl a/Chl b ratio, a relative larger PQ pool, as indicated by fluorescence parameter T_(1/2), and a higher PSⅡ electron transport (H_(2)O_(2)→DMBQ) rate as well as whole chain electron transport (H_(2)O_(2)→MV) rate, but a lower PSⅠ electron transport (DCPIP→MV) rate when expressed in unit Chl(Table 4). From these results, it is deduced that the higher PSⅡ photochemical efficiency in LG results from the less excittation energy transfer from PSⅡ to PSⅠ, which may compensate the lower light harvest capacity due to Chl deficiency.High light (about 1 700#mu#mol photons m~(-1)s~(_1)) treatment resulted in a smaller decrease of Fv/Fm in LG than in DG, indicating that the mutant is less sensitive to photoinhibition conditions, Which is contrary to that of chlorophy11-deficient mutant of soybean reported by Xu et al.(1993).

Key words: Photosynthesis;Chlorophyll fluorescence;PS Ⅱ photochemical efficiency;Chlorophyll-deficient mutant;Barley

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Citing This Article：

Tan Xinxing, Xu Daquan, Tang Zesheng. Leaf photosynthesis and chlorophy11 fluorescence in a chlorophy11-deficient mutant of barley. Acta Physiol Sin 1996; 48 (1): (in Chinese with English abstract).