Das Susmita, Majumder Barsha, Biswas Asok K
Plant Physiology and Biochemistry Laboratory, Centre of Advanced Studies, Department of Botany, University of Calcutta, Kolkata, West Bengal, 700019, India.
Ecotoxicology. 2018 Dec;27(10):1387-1403. doi: 10.1007/s10646-018-1994-5. Epub 2018 Nov 8.
Arsenic is a carcinogenic metalloid, exists in two important oxidation states-arsenate (As-V) and arsenite (As-III). The influence of arsenate with or without silicate on the growth and thiol metabolism in rice (Oryza sativa L. cv. MTU-1010) seedlings were investigated. Arsenate was more toxic for root growth than shoot growth where the root lengths were short, characteristically fragile and root tips turned brown. The multiple comparison analysis using Tukey's HSD (honest significant difference) tests indicated that the rate of arsenate accumulation and its conversion to arsenite by arsenate reductase were significantly increased in all arsenate treated seedlings while in seedlings treated jointly with arsenate and silicate, arsenate accumulation and its conversion to arsenite decreased. Silicate content was detected in the seedlings treated with silicate alone and under co-application of arsenate with silicate. In the test seedlings arsenic toxicity increased ascorbate and glutathione contents along with the activities of their regulatory enzymes, viz., ascorbate peroxidase, glutathione reductase, glutathione peroxidase and glutathione-s-transferase to reduce the toxicity level induced by arsenic whereas ascorbate oxidase activity was decreased to maintain sufficient ascorbate pool under arsenate treatment. Phytochelatins production were increased in both root and shoot of the test seedlings under arsenate exposure to alter the detrimental effects of arsenic by chelation with arsenite and their subsequent sequestration into vacuole. Thus, joint application of silicate along with arsenate showed significant alterations on all the parameters tested compared to arsenate treatment alone due to less availability of arsenic in the tissue leading to better growth and metabolism in rice seedlings. Thus use of silicon in arsenic contaminated medium may help to grow rice with improved vigour.
砷是一种致癌类金属，存在两种重要的氧化态——砷酸盐（As-V）和亚砷酸盐（As-III）。研究了有无硅酸盐存在时砷酸盐对水稻（Oryza sativa L. cv. MTU-1010）幼苗生长及硫醇代谢的影响。砷酸盐对根系生长的毒性比对地上部分生长的毒性更大，根系长度变短，特征性地脆弱，根尖变褐。使用Tukey's HSD（真实显著差异）检验的多重比较分析表明，在所有经砷酸盐处理的幼苗中，砷酸盐的积累速率及其被砷酸盐还原酶转化为亚砷酸盐的速率显著增加，而在砷酸盐和硅酸盐共同处理的幼苗中，砷酸盐的积累及其向亚砷酸盐的转化减少。在单独用硅酸盐处理以及砷酸盐与硅酸盐共同施用的幼苗中检测到了硅酸盐含量。在受试幼苗中，砷毒性增加了抗坏血酸和谷胱甘肽的含量以及它们的调节酶即抗坏血酸过氧化物酶、谷胱甘肽还原酶、谷胱甘肽过氧化物酶和谷胱甘肽-S-转移酶的活性，以降低砷诱导的毒性水平，而抗坏血酸氧化酶活性降低，以在砷酸盐处理下维持足够的抗坏血酸库。在砷酸盐暴露下，受试幼苗的根和地上部分中植物螯合肽的产生均增加，通过与亚砷酸盐螯合并随后将其隔离到液泡中来改变砷的有害影响。因此，与单独的砷酸盐处理相比，硅酸盐与砷酸盐联合施用对所有测试参数均显示出显著变化，这是由于组织中砷的有效性降低，导致水稻幼苗生长和代谢更好。因此，在受砷污染的培养基中使用硅可能有助于培育活力更强的水稻。
