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

为了阐明红黄素的光保护作用，我们进行了以下五个实验。在第一个实验中，比较了缺乏红黄素积累能力的野生型和突变体。与野生型相比，突变体的最大光合速率、Fv/Fm值、叶绿素含量和光合作用相关蛋白水平的下降幅度更大。(2)在试验二中，比较了四种不同光强下生长的幼树。在冬季观察到Fv/Fm降低、红黄素升高和DEPS升高之间的关系。高光强下的幼树积累了大量的红黄素。(3)对生长在4个不同海拔高度的成熟树的日照针叶进行了比较。虽然Fv/Fm值在高海拔地区下降较多，但红黄素水平在不同海拔之间没有差异。但不同海拔的红黄素积累和消失的时间不同。(4)在第四个实验中，考察了红黄素的消失过程。即使玉米黄质完全再转化为紫黄质，Fv/Fm也低于最大值。Fv/Fm的最大值与玉米黄质消失时的值在较高海拔地区的差异较大，说明生长在较高海拔地区的树木受到的光损害较严重。(5)在第五个试验中，比较了不同地区选择的优树。红黄素含量在优树间差异显著，遗传差异的差异小于环境差异的差异。

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.