Takshak S, Agrawal S B
Laboratory of Air Pollution and Global Climate Change, Department of Botany, Banaras Hindu University, Varanasi, India.
Plant Biol (Stuttg). 2017 Nov;19(6):904-916. doi: 10.1111/plb.12601. Epub 2017 Aug 2.
Supplemental (s)-UV-B radiation has adverse effects on the majority of plants. The present study was conducted to evaluate the effects of exogenous application of the growth hormone indole acetic acid (IAA) on various morphological, physiological and biochemical characteristics of Withania somnifera, an indigenous medicinal plant, subjected to s-UV-B. The s-UV-B-treated plants received ambient + 3.6 kJm ·day biologically effective UV-B, and IAA was applied at two doses (200 and 400 ppm) to s-UV-B-exposed plants. The plant was forced to compromise its growth, development and photosynthetic patterns to survive under s-UV-B by increasing concentrations of secondary metabolites and antioxidants (thiol, proline, ascorbic acid, α-tocopherol, ascorbate peroxidase, catalase, glutathione reductase, peroxidase, polyphenol oxidase, superoxide dismutase) to counteract oxidative stress. Increases in secondary metabolites were evidenced as increased activity of phenylpropanoid pathway enzymes: phenylalanine ammonia lyase, cinnamyl alcohol dehydrogenase, 4-coumarate CoA ligase, chalcone isomerase and dihydroflavonol reductase. Application of different IAA doses reversed the detrimental effects of s-UV-B on W. somnifera by improving growth and photosynthesis and reducing concentrations of secondary metabolites and non-enzymatic antioxidants. Antioxidant enzymes, however, had a synergistic effect on s-UV-B treatment and IAA application. The effects of s-UV-B on W. somnifera are ameliorated to varying degrees upon exogenous IAA application, and synergistic enhancement of antioxidant enzymes under s-UV-B+IAA treatment might be responsible for the partial recuperation of growth and plant protein content, as a UV-B-exposed plant is forced to allocate most of its photosynthate towards production of enzymes related to antioxidant defence.
补充（s）-UV-B辐射对大多数植物有不利影响。本研究旨在评估外源施用生长激素吲哚乙酸（IAA）对本土药用植物睡茄在经受s-UV-B辐射时的各种形态、生理和生化特性的影响。经s-UV-B处理的植物接受环境+3.6 kJm·天的生物有效UV-B，并且以两种剂量（200和400 ppm）将IAA施用于经s-UV-B处理的植物。该植物被迫通过增加次生代谢物和抗氧化剂（硫醇、脯氨酸、抗坏血酸、α-生育酚、抗坏血酸过氧化物酶、过氧化氢酶、谷胱甘肽还原酶、过氧化物酶、多酚氧化酶、超氧化物歧化酶）的浓度来对抗氧化应激，从而在s-UV-B条件下生存，其生长、发育和光合模式因此受到影响。次生代谢物的增加表现为苯丙烷途径酶（苯丙氨酸解氨酶、肉桂醇脱氢酶、4-香豆酸辅酶A连接酶、查尔酮异构酶和二氢黄酮醇还原酶）活性的增加。施用不同剂量的IAA通过改善生长和光合作用以及降低次生代谢物和非酶抗氧化剂的浓度，逆转了s-UV-B对睡茄的有害影响。然而，抗氧化酶对s-UV-B处理和IAA施用具有协同作用。外源施用IAA后，s-UV-B对睡茄的影响在不同程度上得到改善，并且在s-UV-B+IAA处理下抗氧化酶的协同增强可能是生长和植物蛋白质含量部分恢复的原因，因为暴露于UV-B的植物被迫将其大部分光合产物用于生产与抗氧化防御相关的酶。
