Research on biosynthesis of UV absorbing substances in epidermis of plant leaves and their function to protect the plants from injury by UV radiation.

紫外线B(UV-B)辐射(280-320 nm)会导致植物生长迟缓和叶表面黄化等可见伤害。这些危害似乎受控于植物生长过程中的环境条件。伤害的程度被认为取决于植物叶片表皮吸收紫外线(UV)物质含量的差异。本研究比较了豌豆突变体和蚕豆叶表皮中紫外线吸收物质的含量与这些植物对紫外线-C(UV-C)的抗性。在接下来的实验中，研究了UV-B辐射对黄瓜植株第一片叶片的影响以及环境条件对植株对UV-B辐射敏感性的影响。研究了UV-B辐射对过氧化氢解毒代谢途径中限速酶谷胱甘肽还原酶(GR)酶性质的影响。主要研究结果如下：(1)豌豆叶片表皮含有黄酮酸…类id物质较多，在260 ns和320 ns处有吸收峰，在可见光区几乎没有吸收。这些物质的含量与UV-B辐射的抗性呈平行关系。(2)在20ﾟC下，UV-B辐射引起黄瓜幼苗子叶和第一片叶的生长迟缓和第一片叶的黄化，但在25ﾟC时没有发现生长抑制，但观察到了黄瓜第一片叶的黄化现象。但UV-A辐射不能恢复UV-B引起的黄化。(4)UV-B辐射降低了子叶GR与底物的亲和力。阐明了黄瓜植株对UV-B辐射的敏感性取决于UV-B辐射时的温度和光照条件。UV-B辐射对植物的伤害机制、对UV-B的防御机制以及环境条件对UV吸收物质生物合成的影响还有待于进一步研究。较少

Radiation of ultraviolet-B (UV-B) region (280-320nm) causes growth retardation of plants and visible injury such as chlorosis on leaf surface. These damages seem to be under the control of the environmental conditions during plant growth. The extent of damage is thought to depend on the differences of content of ultraviolet (UV) absorbing substances in the epidermis of plant leaves. In the present studies, the content of UV absorbing substances in leaf epidermis of pea mutant and broad bean was compared with resistance of these plants to ultraviolet-C (UV-C). In the next experiments, effects of UV-B radiation on first leaves of cucumber plants and effects of environmental conditions on the sensitivity of plant to UV-B were examined. Effects of UV-B radiation on enzymic properties of glutathione reductase (GR), rate-limiting enzyme in metabolic pathway to detoxify hydrogen peroxide, were also examined. Outline of the results obtained are as follows.(1)Epidermis of pea leaves has flavono … More id-like substances, which have absorbance peaks at 260 and 320 ns and little absorbance in visible region. The content of these substances showed a parallelism with resistance to UV-B radiation.(2)UV-B irradiation caused the growth retardation of cotyledons and first leaves of cucumber seedlings and chlorosis on first leaves at 20ﾟC. But, the growth retardation could not be found on the irradiation at 25ﾟC, though chlorosis was observed.(3)high intensity of ultraviolet-A (UV-A) restored the retardation of growth of first leaves when it was given together with UV-B. But, chlorosis caused by UV-B was not restored by UV-A radiation.(4)UV-B radiation lowered the affinity of GR in cotyledons to substrates. It was clarified in the present work that the sensitivity of cucumber plants to UV-B was dependent on temperature and light condition at the time of UV-B radiation. Mechanism of plant damage caused by UV-B radiation, defense mechanism to UV-B and, in addition, effects of environmental conditions on biosynthesis of UV absorbing substances must be more investigated. Less