大規模ガラス温室内のトマト群落におけるクロロフィル蛍光パラメータ(F_v/F_m), SPAD値およびクロロフィル濃度の垂直分布の解析

概要

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In our previous study, it has been proved that photosynthetic abilities in leaves, e.g. maximum net photosynthetic rate, decreases with depth from the top of the year-round cultured tomato plant canopy in a large-scale greenhouse. In this study, we assessed the distribution of photosynthetic abilities within tomato plant canopy by measuring chlorophyll fluorescence parameter (Fv/Fm), SPAD value and chlorophyll concentrations and then investigated the relationships among these parameters. Maximum net photosynthetic rates in leaves within middle and lower layers decreased to half and seventh parts of that within upper layer, respectively. Fv/Fm significantly increased with depth in the canopy, however, SPAD value and chlorophyll a/b ratio significantly decreased with depth in the canopy. Low chlorophyll a/b ratio and high Fv/Fm in leaves within the lower layer suggested that these leaves acclimated to the low light condition and had high light-utilization efficiency for photosynthesis. These results indicated that the decreases in the photosynthetic abilities in leaves with depth in the tomato plant canopy are caused by the low-light acclimation. Furthermore, the correlations between chlorophyll a/b ratio and Fv/Fm, and SPAD value were observed. This result suggested that the measurements of Fv/Fm and SPAD value can be used as a rapid and concise tool to assess the photosynthetic abilities in leaves within tomato plant canopies.
2006-12-01