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KMID : 0368419910340040303
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Journal of Plant Biology
1991 Volume.34 No. 4 p.303 ~ p.309
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Sequestration of Orthophosphate by D(+)-Mannose Feeding Increases Nonphotochemical Quenchings in Chinese Cabbage Leaves
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Park, Youn Il/朴淵一
Suh, Kye Hong/Hong, Young Nam/徐桂弘/洪英男
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Abstract
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Limitation of photosynthesis in detached Chinese cabbage (Brassica campestris L.) leaves was induced by feeding of mannose (25 mM) for 12 h in the light, and changes in the basic thylakoid functions under this condition were investigated. The acid soluble phosphate content and CO_2 uptake rate was decreased by 66% and 67%, respectively. However, the starch content was increased by 24% compared to those of controls. From the fast induction curves of chlorophyll fluorescence, dark level fluorescence (F_O) slightly increased while intermediate plateau fluorescence level (F_I) to peak level fluorescence (F_P) transient was significantly decreased with a slight decrease in the F_O-to-F_I transient. This data means that reduction of secondary electron acceptor of PSⅡ (Q_B) might be more severely inhibited than that of primary electron acceptor of PSⅡ (Q_A) by decrease in phosphate level. The strong decline of (F_V)_m//F_m ratio suggests that efficiency of excitation energy capture by PSⅡ was decreased markedly. The quenching of F_O (qO), an indicator of state transition, was also occurred over the slow induction kinetics of chlorophyll fluorescence. From quenching analysis, fluorescence was dominantly quenched by nonphotochemical quenchings (qE+qT). These results showed that the capture and transfer efficiency of excitation energy to PSⅡ reaction center in thylakoid was decreased with the decline of leaf phosphate level, and that the state transition was occurred during the induction of photosynthesis under these conditions.
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