University of São Paulo, "Luiz de Queiroz" College of Agriculture, Soil Science Department, Pádua Dias 11, ZIP Code 13418-900 Piracicaba, São Paulo, Brazil.
University of São Paulo, "Luiz de Queiroz" College of Agriculture, Crop Science Department, Pádua Dias 11, ZIP Code 13418-900 Piracicaba, São Paulo, Brazil.
Ecotoxicol Environ Saf. 2019 Apr 30;171:823-832. doi: 10.1016/j.ecoenv.2019.01.013. Epub 2019 Jan 17.
Various nitrate and ammonium proportions (NO/NH) in the growth media can increase metal phytoextraction compared to supplying solely NO. However, there are no studies showing these effects in plants under copper (Cu) contamination as well as their consequences in plant stress tolerance. The objective was to evaluate the effect of NO/NH proportions in Cu phytoextraction by Panicum maximum cv. Tanzania and its consequence in the oxidative stress, photosynthesis, and antioxidant system under Cu stress. The experiment was carried out in a randomized complete block design, by using a 3 × 4 factorial with six replications. Three NO/NH proportions (100/0, 70/30, and 50/50) were combined with four Cu rates (0.3, 250, 500, and 1000 µmol L) in the nutrient solution. It was found that the largest Cu accumulation in the shoots occurred at the first harvest of the plants supplied with 70/30 NO/NH and Cu 1000 µmol L. Such plants also displayed high concentrations of proline in the shoots as well as high superoxide dismutase activity in the roots. Malondialdehyde concentration was high in the plant parts at the Cu rate of 1000 µmol L. Hence, transpiration rates, stomatal conductance, quantum efficiency of photosystem II, electron transport rate, and net photosynthesis were all low at the Cu rate of 1000 µmol L. Catalase, guaiacol peroxidase, ascorbate peroxidase, and glutathione reductase activities in the roots were high when plants were exposed to Cu 1000 µmol L. In conclusion, the combination of NO with NH increases copper phytoextraction that causes oxidative stress, but also favors the antioxidant system of Tanzania guinea grass in attempt to tolerate such stress.
在生长介质中提供不同比例的硝酸盐和铵盐（NO/NH）可以增加金属的植物提取量，与仅供应 NO 相比。然而，还没有研究表明在铜（Cu）污染下这些比例对植物的影响以及它们对植物胁迫耐受性的影响。本研究的目的是评估不同 NO/NH 比例对潘那尼草最大 cv 的 Cu 植物提取的影响。坦桑尼亚及其在 Cu 胁迫下对氧化应激、光合作用和抗氧化系统的影响。试验采用完全随机区组设计，采用 3×4 因子设计，重复 6 次。三种 NO/NH 比例（100/0、70/30 和 50/50）与四种 Cu 浓度（0.3、250、500 和 1000µmol/L）在营养液中组合。结果表明，在第一次收获时，用 70/30 NO/NH 和 1000µmol/L Cu 供应的植物， shoots 中 Cu 积累量最大。这些植物的 shoots 中脯氨酸浓度也很高，根系中超氧化物歧化酶活性也很高。在 Cu 浓度为 1000µmol/L 时，植物各部位丙二醛浓度较高。因此，在 Cu 浓度为 1000µmol/L 时，蒸腾速率、气孔导度、光系统 II 量子效率、电子传递速率和净光合速率均较低。当植物暴露在 Cu 1000µmol/L 时，根系中的过氧化氢酶、愈创木酚过氧化物酶、抗坏血酸过氧化物酶和谷胱甘肽还原酶活性较高。总之，NO 与 NH 的结合增加了铜的植物提取量，导致氧化应激，但也有利于坦桑尼亚 Guinea 草的抗氧化系统，试图耐受这种胁迫。
