Hilal Mirna, Parrado María Francisca, Rosa Mariana, Gallardo Miriam, Orce Luis, Massa Eddy Marta, González Juan Antonio, Prado Fernando Eduardo
Facultad de Ciencias Naturales e IML, Universidad Nacional de Tucumán, Tucumán, Argentina.
Photochem Photobiol. 2004 Feb;79(2):205-10. doi: 10.1562/0031-8655(2004)079<0205:eldiqc>2.0.co;2.
UV-B radiation (280-320 nm) is harmful to living organisms and has detrimental effects on plant growth, development and physiology. In this work we examined some mechanisms involved in plant responses to UV-B radiation. Seedlings of quinoa (Chenopodium quinoa Willd.) were exposed to variable numbers of UV-B radiation doses, and the effect on cotyledons was studied. We analyzed (1) cotyledons anatomy and chloroplasts ultrastructure; (2) peroxidase activity involved in the lignification processes; and (3) content of photosynthetic pigments, phenolic compounds and carbohydrates. Exposure to two UV-B doses induced an increase in the wall thickness of epidermal cells, which was associated with lignin deposition and higher activity of the peroxidase. The chloroplast ultrastructure showed an appearance typical of plants under shade conditions, likely in response to reduced light penetration into the mesophyll cells due to the screening effect of epidermal lignin deposition. Exposure to UV-B radiation also led to (1) enhancement in the level of phenolics, which may serve a protective function; (2) strong increase in the fructose content, a fact that might be related to higher requirement of erythrose-4P as a substrate for the synthesis of lignin and phenolics; and (3) reduction in the chlorophyll concentration, evidencing alteration in the photosynthetic system. We propose that the observed lignin deposition in epidermal tissues of quinoa is a resistance mechanism against UV-B radiation, which allows growing of this species in Andean highlands.
紫外线B辐射（280 - 320纳米）对生物有害，对植物的生长、发育和生理机能具有不利影响。在本研究中，我们探究了植物对紫外线B辐射响应的一些机制。将藜麦（Chenopodium quinoa Willd.）幼苗暴露于不同数量的紫外线B辐射剂量下，并研究其对子叶的影响。我们分析了：（1）子叶解剖结构和叶绿体超微结构；（2）木质化过程中涉及的过氧化物酶活性；以及（3）光合色素、酚类化合物和碳水化合物的含量。暴露于两个紫外线B剂量下会导致表皮细胞壁厚度增加，这与木质素沉积和过氧化物酶的较高活性有关。叶绿体超微结构呈现出典型的阴生植物外观，这可能是由于表皮木质素沉积的屏蔽作用导致进入叶肉细胞的光线减少所致。暴露于紫外线B辐射还导致：（1）酚类物质水平提高，这可能具有保护作用；（2）果糖含量大幅增加，这一事实可能与作为木质素和酚类合成底物的赤藓糖-4-磷酸的更高需求有关；以及（3）叶绿素浓度降低，表明光合系统发生了改变。我们认为，在藜麦表皮组织中观察到的木质素沉积是一种抵御紫外线B辐射的抗性机制，这使得该物种能够在安第斯高地生长。
