Department of Plant Biology and Ecology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Apdo. 644, E-48080, Bilbao, Spain.
Plant Physiol Biochem. 2020 Oct;155:725-734. doi: 10.1016/j.plaphy.2020.08.007. Epub 2020 Aug 13.
Currently it is estimated that the 20% of total cultivated land is affected by salt. Besides, drought events will increase worldwide. These factors are affecting plant growth and crop production compromising food security. Within this context, quinoa (Chenopodium quinoa) is becoming an alternative pseudocereal for food supply due to its capacity to grow under harsh environmental conditions. Besides, it is being proposed as key model species to study the physiological processes that permit this tolerance, although how N metabolism responds has been barely studied. This paper addresses, on one hand, the response of quinoa's N metabolism (N uptake, translocation, reduction and assimilation) under the forthcoming climatic conditions and, on the other hand, the comparison of the effects of both stresses when plants have similar relative water content and photosynthetic rates. Under mild salt stress (120 and 240 mM NaCl) N assimilation is not affected, while the N uptake is favored. Under severe salt stress (500 mM NaCl), N uptake is reduced, decreasing leaf nitrate and protein concentration; nevertheless, leaf free amino acids are maintained -to perform osmotic adjustment-. N uptake rate is more affected under drought than under severe salt; furthermore, under severe salt stress, quinoa allocates more nitrogen to roots to finely regulate NO and Cl uptake, while under drought it allocates more to leaves to ensure photosynthesis. These results indicate that quinoa's N metabolism is tolerant to drought and salt stress, although the strategies of this species for coping with the aforementioned stresses are different.
目前，据估计，全球有 20%的耕地受到盐的影响。此外，干旱事件将在全球范围内增加。这些因素影响着植物的生长和作物的产量，危及粮食安全。在这种情况下，藜麦（Chenopodium quinoa）因其在恶劣环境条件下生长的能力而成为一种替代粮食的伪谷物。此外，它被提议作为研究允许这种耐受性的生理过程的关键模式物种，尽管人们对氮代谢的反应知之甚少。本文一方面探讨了藜麦氮代谢（氮吸收、转运、还原和同化）对未来气候条件的反应，另一方面比较了当植物具有相似的相对含水量和光合速率时，两种胁迫的影响。在轻度盐胁迫（120 和 240 mM NaCl）下，氮同化不受影响，而氮吸收则受到促进。在严重盐胁迫（500 mM NaCl）下，氮吸收减少，叶片硝酸盐和蛋白质浓度降低；然而，叶片游离氨基酸得以维持——以进行渗透调节。干旱对氮吸收的影响大于严重盐胁迫；此外，在严重盐胁迫下，藜麦将更多的氮分配到根部，以精细调节氮和氯的吸收，而在干旱条件下，将更多的氮分配到叶片以确保光合作用。这些结果表明，藜麦的氮代谢对干旱和盐胁迫具有耐受性，尽管该物种应对上述胁迫的策略不同。
