Study on the photoprotective functions of rhodoxanthin accumulated in the needles of Cryptomeria japonica and Chamaecyparis obtusa

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In order to elucidate the photoprotective role of rhodoxanthin, following five experiments were conducted. In the first experiment the wild type and the mutant lacking the ability of rhodoxanthin accumulation were compared. The maximum photosynthetic rates and the Fv/Fm values, chlorophyll contents, and the levels of photosynthesis related proteins decreased more significantly in the mutant than in the wild type. (2) In the second experiment, the saplings grown in four different light intensities were compared. The relationships among the decrease in Fv/Fm, the increase in rhodoxanthin and the increase in DEPS were observed during the winter. The saplings under the higher light intensities accumulated large amount of rhodoxanthin. (3) In the Third experiment the sun exposed needles of the mature trees grown in four different altitudes were compared. Although the values of Fv/Fm were more decreased in the higher altitudes, the levels of rhodoxanthin were not differed among the altitudes. However, the timing of the accumulation and disappearance of rhodoxanthin were differed among the altitudes. (4) In the fourth experiment, the process of rhodoxanthin disappearance were examined. The values of Fv/Fm were lower than maximum level, even when the zeaxanthin had perfectly re-converted to violaxanthin. The differences in the Fv/Fm values between the maximum value and the value when zeaxanthin had disappeared were greater in the higher altitude, indicated that the trees grown in higher altitude were more severely photo-damaged. (5) In the fifth experiment, the plus-trees selected from different regions were compared. The level of rhodoxanthin were significantly differed among the plus trees, the difference attributed to the genetic difference were smaller than that attributed to environmental differences.