State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A & F University, Yangling, Shaanxi 712100, China.
Plant Physiol Biochem. 2018 Jun;127:185-193. doi: 10.1016/j.plaphy.2018.03.031. Epub 2018 Mar 28.
Using a hydroponics culture system, we monitored morphological, physiological, and molecular changes in Malus prunifolia seedlings when drought conditions induced by 5% polyethylene glycol (PEG) were combined with a low or normal supply of N (0.05 mM or 1 mM NHNO, respectively). Under either nutrient level, drought stress negatively inhibited seedling performance, as manifested by reduced photosynthesis and biomass production, decreased accumulations of total N, and inhibited root growth. Concentrations of NO and NH and the activities of enzymes involved in N metabolism (nitrate reductase, glutamine synthetase, and glutamate synthase) were also significantly decreased under drought stress. The net influx of NO at the surface of the fine roots declined while that of NH rose markedly, suggesting that the latter may play a more important role in improving drought tolerance in M. prunifolia. Consistently, two ammonium transporters (AMT1;2 and AMT4;2) were notably up-regulated in response to drought stress, whereas most genes related to nitrate uptake, reduction, and N metabolism were down-regulated. At the normal N level, PEG-treated plants showed higher values for biomass production, root growth, and N uptake/reduction when compared with plants exposed to the lower N supply. These results suggest that the negative effect of drought stress on M. prunifolia may be alleviated when more nitrogen is available.
我们采用水培培养系统，监测了在 5%聚乙二醇（PEG）诱导干旱条件下，与低或正常氮供应（分别为 0.05 mM 或 1 mM NHNO）相结合时，平榛幼苗的形态、生理和分子变化。在任一养分水平下，干旱胁迫均显著抑制了幼苗的生长，表现为光合作用和生物量生产减少、总氮积累减少、根系生长受抑制。氮代谢相关酶（硝酸还原酶、谷氨酰胺合成酶和谷氨酸合酶）的活性和 NO、NH 的浓度也在干旱胁迫下显著降低。细根表面的硝酸盐净流入减少，而 NH 的流入明显增加，这表明后者可能在提高平榛的耐旱性方面发挥更重要的作用。一致地，两个铵转运蛋白（AMT1;2 和 AMT4;2）对干旱胁迫显著上调，而大多数与硝酸盐吸收、还原和氮代谢相关的基因则下调。在正常氮水平下，与低氮供应相比，PEG 处理的植物在生物量生产、根系生长和氮吸收/还原方面表现出更高的数值，这表明当氮供应增加时，干旱胁迫对平榛的负面影响可能会减轻。
