Application of the growth regulator salicylic acid (SA) and the polyamine spermidine (Spd) can be used to manage various plant abiotic stresses. We aimed to evaluate the sole and combined effects of SA and Spd on maize (Zea mays) under individual and combined drought and chromium (Cr) stress. Drought, Cr, and drought + Cr treatments caused oxidative stress by inducing higher production of reactive oxygen species (H₂O₂, O₂⁻), enhanced malondialdehyde content and increased relative membrane permeability. Increased oxidative stress and higher Cr uptake in the host plant reduced the content of carotenoids, other photosynthetic pigments and protein, and changed carbohydrate metabolism. Combined drought + Cr stress was more damaging for the growth of maize plants than the individual stresses. Exogenous treatments of SA and Spd alleviated the adverse effects of drought and Cr toxicity, reflected by accumulations of osmolytes, antioxidants and endogenous polyamines. Single applications of Spd (0.1 mM) increased plant height, shoot fresh weight, leaf area, above-ground dry matter accumulation and polyamine content under drought, Cr, and drought + Cr stress conditions. However, the combined treatment SA + Spd (0.25 mM + 0.05 mM) was more effective in increasing protein and water contents, photosynthetic pigments, and carotenoids. The same treatment increased Cr tolerance in the maize plants by decreasing uptake of this heavy metal from root to shoot. The SA + Spd treatment also decreased oxidative stress by promoting antioxidant enzyme activities, and enhanced levels of proline, soluble sugars, and carbohydrate contents under individual and combined stress conditions. Results indicate that the combined half-dose application of SA + Spd may be utilized to boost the tolerance in maize under individual as well as combined drought and Cr stress conditions.

生长调节剂水杨酸（SA）和多胺亚精胺（Spd）的应用可用于处理各种植物非生物胁迫。我们的目的是评估干旱和铬（Cr）单独和联合胁迫下，SA和Spd对玉米（Zea mays）的唯一和综合影响。干旱，Cr和干旱+ CR通过诱导更高的生产活性氧物种（H引起的氧化应激的治疗₂ ö ₂，O- ₂ ^-），提高丙二醛含量并增加相对膜通透性。寄主植物中增加的氧化应激和更高的Cr吸收量减少了类胡萝卜素，其他光合色素和蛋白质的含量，并改变了碳水化合物的代谢。干旱+铬联合胁迫比单独胁迫对玉米植物的生长损害更大。SA和Spd的外源处理减轻了干旱和Cr毒性的不利影响，这反映在渗透压，抗氧化剂和内源多胺的积累上。Spd（0.1 mM）的单次施用在干旱，Cr和干旱+ Cr胁迫条件下增加了株高，枝条鲜重，叶面积，地上干物质积累和多胺含量。但是，联合处理SA + Spd（0.25 mM + 0。05 mM）在增加蛋白质和水含量，光合色素和类胡萝卜素方面更有效。相同的处理方法通过减少从根到芽对重金属的吸收，提高了玉米植物对Cr的耐受性。SA + Spd处理还可以通过促进抗氧化酶的活性来降低氧化应激，并在单独和复合应激条件下提高脯氨酸，可溶性糖和碳水化合物的含量。结果表明，SA + Spd的半剂量组合施用可用于提高玉米在单独以及干旱和Cr胁迫条件下的耐性。SA + Spd处理还可以通过促进抗氧化酶的活性来降低氧化应激，并在单独和复合应激条件下提高脯氨酸，可溶性糖和碳水化合物的含量。结果表明，SA + Spd的半剂量组合施用可用于提高玉米在单独以及干旱和Cr胁迫条件下的耐性。SA + Spd处理还可以通过促进抗氧化酶的活性来降低氧化应激，并在单独和复合应激条件下提高脯氨酸，可溶性糖和碳水化合物的含量。结果表明，SA + Spd的半剂量组合施用可用于提高玉米在单独以及干旱和Cr胁迫条件下的耐性。