Numerous advances have been made to mitigate the repercussion of toxic metals on photosynthetic prokaryotes, i.e. cyanobacteria. One strategy is exogenous supplementation of plant growth regulators (PGRs). This perhaps intensifies the resistance ability of cyanobacteria to encounter the environmental stresses by augmenting their physiological functioning and decontaminant efficiency. Thus, the aim of the present study was to determine if the PGRs auxin (indole-3 acetic acid, IAA; 300 nM) and cytokinin (kinetin, KN; 10 nM) are able to mitigate the toxic environmentally relevant doses of chromium (Cr^VI; 100 and 150 µM) in cyanobacteria (Nostoc muscorum ATCC 27,683 and Anabaena sp. PCC 7120). The response was assessed by estimating oxidative stress [in vitro and in vivo (superoxide radical; O₂^·−, hydrogen peroxide H₂O₂ and malondialdehyde equivalents contents; MDA)], feasible alteration in whole cell oxygen evolution, ascorbate–glutathione cycle and their metabolites. Intracellular Cr accumulation raised the production of ROS by down-regulating the photosynthetic rate due to decreased pigment contents (Chl a; chlorophyll a, Car; carotenoids and PC; phycocyanin) and reduced growth despite the accelerated activity of the ascorbate–glutathione (AsA-GSH) cycle enzymes (viz. APX; ascorbate peroxidase, GR; glutathione reductase and DHAR; dehydroascorbate reductase). Concurrently, exogenous PGRs (auxin and cytokinin) moderated the negative effects of Cr on the growth, by lowering the cellular Cr accumulation and ROS level and by modulating the pigment system, photosynthesis and a further rise in the efficiency of AsA-GSH cycle, thereby acting as positive regulators of the metal detoxification machinery. Thus, exogenous application of PGRs (auxin and cytokinin) could improve the growth in cyanobacteria in Cr-polluted environments, hence maintaining productivity in paddy cultivation as well as having potential to be used as bio-remediator in metal-contaminated aquatic systems.

在减轻有毒金属对光合原核生物（即蓝藻）的影响方面已经取得了许多进展。一种策略是外源性补充植物生长调节剂 (PGR)。这可能通过增强蓝藻的生理功能和净化效率来增强蓝藻抵抗环境压力的能力。因此，本研究的目的是确定 PGRs 生长素（indole-3 乙酸，IAA；300 nM）和细胞分裂素（激动素，KN；10 nM）是否能够减轻铬（Cr ^VI ; 100和150μM）在蓝藻（发菜muscorum ATCC 27683和鱼腥。藻PCC 7120）。通过估计氧化应激来评估反应[体外和体内（超氧自由基；O ₂ ^·-，过氧化氢 H ₂ O ₂和丙二醛当量含量；MDA）]，全细胞氧气释放、抗坏血酸-谷胱甘肽循环及其代谢物的可行改变。由于色素含量降低（Chl a；叶绿素a, 汽车; 类胡萝卜素和 PC；尽管抗坏血酸 - 谷胱甘肽 (AsA-GSH) 循环酶（即 APX；抗坏血酸过氧化物酶，GR；谷胱甘肽还原酶和 DHAR；脱氢抗坏血酸还原酶）的活性加快，但藻蓝蛋白仍会减少生长。同时，外源性 PGRs（生长素和细胞分裂素）通过降低细胞 Cr 积累和 ROS 水平以及通过调节色素系统、光合作用和 AsA-GSH 循环效率的进一步提高来缓和 Cr 对生长的负面影响，从而充当金属解毒机制的正调节器。因此，外源应用 PGRs（生长素和细胞分裂素）可以改善 Cr 污染环境中蓝藻的生长，