In greenhouses, growth of plants is affected by accumulation of nitrate in the soil due to extended durations of nitrogen fertilizer application. Dopamine has been shown to play an important role in plant growth and stress resistance. We studied effects of dopamine on antioxidation, mineral nutrients, and fruit quality in cucumber (Cucumis sativus L. “Jin You No. 1”) under nitrate stress. Excessive nitrate inhibited root growth, resulting in reduced root length, volume, and activity. The content of malondialdehyde and superoxide anion increased significantly, and the activities of antioxidant enzymes such as superoxide dismutase, catalase, and ascorbate peroxidase increased, whereas peroxidase decreased under high-nitrate conditions. We also found that the length, cross-sectional diameter, and total yield of fruits were significantly decreased under nitrate stress. Moreover, fruit quality, such as reducing sugar, soluble sugar, soluble protein, and vitamin C, was significantly reduced under high-nitrate conditions. Excessive nitrate caused accumulation of nitrogen and potassium in the roots, stems, and leaves of plants, but reduced accumulation of phosphorus. Conversely, dopamine promoted root growth and root activity, reduced malondialdehyde and superoxide anion content, increased activities of antioxidant enzymes, improved yield and quality, and balanced ion absorption. Our results show that dopamine plays an overall positive role for cucumbers under nitrate stress.

在温室中，由于氮肥施用时间延长，植物的生长受到土壤中硝酸盐积累的影响。多巴胺已被证明在植物生长和抗逆性方面发挥重要作用。我们研究了多巴胺对黄瓜 ( Cucumis sativusL. “金油 1 号”）在硝酸盐胁迫下。过量的硝酸盐抑制根系生长，导致根系长度、体积和活性降低。丙二醛和超氧阴离子含量显着增加，超氧化物歧化酶、过氧化氢酶、抗坏血酸过氧化物酶等抗氧化酶活性增加，而高硝酸盐条件下过氧化物酶活性降低。我们还发现硝酸盐胁迫下果实的长度、横截面直径和总产量显着降低。此外，在高硝酸盐条件下，果实品质，如还原糖、可溶性糖、可溶性蛋白质和维生素C，显着降低。过量的硝酸盐导致植物根、茎和叶中氮和钾的积累，但减少了磷的积累。反过来，多巴胺促进根系生长和根系活性，降低丙二醛和超氧阴离子含量，增加抗氧化酶活性，提高产量和质量，平衡离子吸收。我们的研究结果表明，多巴胺对硝酸盐胁迫下的黄瓜起着积极的作用。