Study on the Evaluation of the Abilities for Protection Against the Ultraviolet B Radiation in the Forest Tree Species.

太阳UV-B（紫外- b辐射，这里取290-315 nm）的增加预计是由于平流层臭氧耗竭造成的。本文研究了UV-B对森林树种生理反应的影响。我们构建了一种新型的UV-B辐射系统，该系统可以控制补充UV-B的剂量与环境UV-B的比例。紫外线增强的程度是环境紫外线的1.3倍。对其光合能力、气体交换和PSⅱ光化学效率、光合色素和UV-B吸收化合物的组成、活性氧清除系统中酶的活性进行了研究。由于森林树木长期暴露在UV-B辐射下，UV-B的增加可能会影响人工林的生产力和天然林的物种组成。杉木（Cryptomeria japonica）是日本最重要的针叶树种之一。杉木人工林面积约占全国人工林面积的45%以上。为了评价UV-B增加对人工林生产力的影响，我们设计了苗圃UV-B辐射的三个水平。它们是，使用不同的UV-B辐射系统增强UV-B处理，使用uv切割膜降低UV-B水平，以及环境中UV-B水平。研究了杉木幼苗的生理反应。在低UV-B环境下生长的杉木幼苗光合速率和PSⅱ光化学效率（Fv/Fm）略有增加，而在高UV-B环境下生长的杉木幼苗的光合速率和PSⅱ光化学效率（Fv/Fm）无显著变化。为了解UV-B增加对天然山毛榉（Fagus crenata）林中种组成的影响，研究了内霸山天然山毛榉（Fagus crenata）林中5种树种的生理反应。采用UV-B切割膜对5种植物进行不同UV-B水平的处理。此外，还研究了在自然环境中生长的幼苗所发生的不同UV-B水平。在较低UV-B水平下生长的山毛榉幼苗，其吸收UV-B的化合物含量明显低于环境条件下生长的山毛榉幼苗，而暴露于强光条件下的山毛榉幼苗，其吸收UV-B的色素含量则有所增加。叶绿素含量、叶绿素a/b比和叶黄素循环色素池大小发生了变化。由于在配备UV-B辐射系统的生长室内进行的初步实验表明，山毛榉幼苗吸收UV-B色素的积累速度很快，因此山毛榉幼苗吸收UV-B色素的差异可归因于幼苗生长环境对UV-B水平的适应。因此，在田间生长的山毛榉幼苗似乎有能力积累吸收紫外线的色素，以响应UV-B水平。然而，不同UV-B水平处理的幼苗叶片衰老时间存在差异。高UV-B处理的幼苗叶片衰老时间提前。虽然5种植物的最大PS II光化学效率变化不显著，但其吸收UV-B色素的量最大。不同UV-B水平的种内PS II光化学效率差异不显著，但不同UV-B水平的种内吸收色素量的变化幅度存在差异。这些结果表明，森林树种有足够的能力抵御太阳瞬时UV-B辐射的增加。而在落叶乔木中，如山毛榉，在太阳UV-B增加的情况下，生育期的缩短可能会降低年生产力。少

Increases in solar UV-B (ultraviolet-B radiation, here taken as 290-315 nm) are expected to result from stratospheric ozone depletion. In this study, the effects of UV-B on physiological responses in forest tree species were examined. We constructed novel UV-B radiation system, which can control the dose of supplemental UV-B in proportion to ambient UV-B. The level of UV-B enhancement was up to 1.3 times that in ambient UV-B. The photosynthetic capacities, such gas exchanges and PS II photochemical efficiency, the composition of photosynthetic pigments and UV-B absorbing compound, the activities of the enzymes in the active oxygen-scavenging system were also examined.Because forest trees are exposed to UV-B radiation on long term basis, the increase of UV-B are likely affected to the productivity in artificial forests and species composition in natural forests.Sugi (Cryptomeria japonica)is one of the most important coniferous species in Japan. The area of sugi plantations occupies appr … More oximately 45% of all the artificial forest. In order to assess the affect of the increased UV-B in the productivity of artificial forest, we designed three levels in UV-B radiation in the nursery. Those were, enhanced UV-B treatments using an UV-B radiation system different, decreased level of UV-B using the UV-cutting films, and ambient level of UV-B. The physiological responses of sugi saplings were examined. While the sugi saplings grown in the decreased UV-B level showed slightly increasing in the photosynthetic rate and PS II photochemical efficiency (Fv/Fm), no significant changes were observed between the saplings in the enhanced UV-B and that in the ambient UV-B.In order to understand the influence of the increased UV-B on the species composition in natural forest, we investigate the physiological responses of the five tree species grown in the natural beech (Fagus crenata) forest Mt. Naeba-san. The five species were treated with different UV-B levels using UV-B cutting films. In addition, the seedlings grown in the naturally occurred different UV-B levels were also examined. While the beech seedlings grown in the decreased UV-B level showed significant decrease in the UV-B absorbing compounds compared with that in the ambient level, the seedlings exposed the strong light, which may include high level of UV-B, showed the increase in the UV-B absorbing pigments. Some changes were observed in the chlorophyll contents, chlorophyll a/b ratio, and the pool size of xanthophyll cycle pigments. Since the preliminary experiment using the growth chambers equipped with UV-B radiation system showed the rapid accumulation of the UV-B absorbing pigments in the beech seedlings, the difference observed in the UV-B absorbing pigments was attributed to be adaptation to the UV-B levels where the seedlings were growing. Therefore, beech seedlings growing in the field seemed to have the abilities to accumulate the UV-absorbing pigments in response to the UV-B levels. However, the differences in the timing of the leaf senescence were observed in the seedlings treated with different UV-B levels. Timing of the leaf senescence was earlier in the seedlings treated with high UV-B level. Although the maximum PS II photochemical efficiency were not significantly changed among the five species, the maximum amount of UV-B absorbing pigments were observed. While the differences in the PS II photochemical efficiency between the different UV-B levels within species were not significantly changed among the five species, differences in the range, of the amounts of UV-absorbing pigments between the different UV-B levels within species were observed.These results suggest that the forest tree species have enough abilities to protect against the increase In instant solar UV-B radiation. In the deciduous tree species, such as beech, however, the shortening of the productive period may decrease the annual productivity when the solar UV-B will be increased. Less