Department of Biological Sciences, Faculty of Sciences, UNESP - São Paulo State University, Bauru, Brazil.
PLoS One. 2022 Jul 6;17(7):e0270849. doi: 10.1371/journal.pone.0270849. eCollection 2022.
Water and nitrogen availability are two major environmental factors that can impair plant growth, and when combined, their effects on plant performance can be either intensified or reduced. The objective of this study was to analyze the influence of nitrogen availability on the responses of Amaranthus cruentus's metabolism to water stress. The plants were cultivated in plastic pots filled with vermiculite, kept under greenhouse conditions, and were watered three times a week with 70% of a full strength nitrogen-free Long Ashton solution, containing 1.97 or 9.88 kg N ha-1 as ammonium nitrate. Photosynthetic parameters were evaluated in planta, and leaves were harvested for chemical analysis of photosynthetic pigments, proline, and phenolic contents. Higher nitrogen supply increased the shoot dry matter, photosynthetic pigments, photosynthesis, stomatal conductance, transpiration, total leaf nitrogen, proline, nitrate, and ammonium but reduced the concentration of flavonoids and total phenols. Six days of water stress did not affect dry matter, photosynthetic pigments, leaf nitrogen, ammonium, or specialized metabolites but increased the proline under high nitrogen and negatively affected stomatal conductance, transpiration, photosynthesis, relative water content, instantaneous water use efficiency, and leaf nitrate. The negative effect was more pronounced under high nitrogen supply. The results show that the addition of a high amount of nitrogen made the physiological processes of plants more sensitive to water stress, indicating that the plant response to water restriction depends on the interaction between the different environmental stressors to which the plants are subjected.
水和氮素供应是影响植物生长的两个主要环境因素，当它们共同作用时，其对植物性能的影响可能会加剧或减弱。本研究旨在分析氮素供应对千日红代谢对水分胁迫响应的影响。植物在装满珍珠岩的塑料盆中种植，在温室条件下养护，每周浇水三次，用 70%的全强度无氮朗氏液（含硝酸铵 1.97 或 9.88 千克氮/公顷）。在植株上评估光合作用参数，并收获叶片进行光合色素、脯氨酸和酚类含量的化学分析。较高的氮供应增加了地上部分的干物质、光合色素、光合作用、气孔导度、蒸腾作用、总叶氮、脯氨酸、硝酸盐和铵，但降低了类黄酮和总酚的浓度。6 天的水分胁迫不影响干物质、光合色素、叶片氮、铵或特殊代谢物，但在高氮条件下增加脯氨酸，并对气孔导度、蒸腾作用、光合作用、相对含水量、瞬时水分利用效率和叶片硝酸盐产生负面影响。在高氮供应下，负面影响更为明显。结果表明，高氮的添加使植物的生理过程对水分胁迫更加敏感，这表明植物对水分限制的响应取决于植物所承受的不同环境胁迫因子之间的相互作用。
