Mateus Nikolas de Souza, Leite Antônio Florentino, Santos Elcio Ferreira, Ferraz Alexandre de Vicente, Goncalves José Leonardo de Moraes, Lavres José
Stable Isotope Laboratory, Center for Nuclear Energy in Agriculture, University of São Paulo, Piracicaba, Brazil.
Applied Ecology Laboratory, Department of Forest Sciences, Luiz de Queiroz College of Agriculture, University of São Paulo, Piracicaba, Brazil.
Front Plant Sci. 2021 Mar 15;12:632342. doi: 10.3389/fpls.2021.632342. eCollection 2021.
, the most widely planted tree genus worldwide, is frequently cultivated in soils with low water and nutrient availability. Sodium (Na) can substitute some physiological functions of potassium (K), directly influencing plants' water status. However, the extent to which K can be replaced by Na in drought conditions remains poorly understood. A greenhouse experiment was conducted with three genotypes under two water conditions (well-watered and water-stressed) and five combination rates of K and Na, representing substitutions of 0/100, 25/75, 50/50, 75/25, and 100/0 (percentage of Na/percentage of K), to investigate growth and photosynthesis-related parameters. This study focused on the positive effects of Na supply since, depending on the levels applied, the Na supply may induce plants to salinity stress (>100 mM of NaCl). Plants supplied with low to intermediate K replacement by Na reduced the critical level of K without showing symptoms of K deficiency and provided higher total dry matter (TDM) than those seedlings supplied only with K in both water conditions. Those plants supplied with low to intermediate K replacement by Na had improved CO assimilation (), stomatal density (Std), K use efficiency (UE ), and water use efficiency (WUE), in addition to reduced leaf water potential (w) and maintenance of leaf turgidity, with the stomata partially closed, indicated by the higher values of leaf carbon isotope composition (δC‰). Meanwhile, combination rates higher than 50% of K replacement by Na led to K-deficient plants, characterized by the lower values of TDM, δC‰, WUE, and leaf K concentration and higher leaf Na concentration. There was positive evidence of partial replacement of K by Na in seedlings; meanwhile, the ideal percentage of substitution increased according to the drought tolerance of the species ( < < ).
作为全球种植最广泛的树种属，[具体树种名称未给出]常种植于水分和养分供应不足的土壤中。钠（Na）可替代钾（K）的一些生理功能，直接影响植物的水分状况。然而，在干旱条件下Na替代K的程度仍知之甚少。进行了一项温室试验，选用三种基因型植株，设置两种水分条件（充分浇水和水分胁迫）以及五种K和Na的组合比例，分别代表0/100、25/75、50/50、75/25和100/0（Na的百分比/K的百分比），以研究生长和光合作用相关参数。本研究聚焦于Na供应的积极影响，因为根据施用水平，Na供应可能会使植物遭受盐胁迫（>100 mM的NaCl）。在两种水分条件下，用Na替代低至中等水平K的植株降低了K的临界水平且未表现出缺K症状，并且比仅供应K的幼苗具有更高的总干物质（TDM）。那些用Na替代低至中等水平K的植株除了降低叶片水势（ψw）并维持叶片膨压（气孔部分关闭，表现为叶片碳同位素组成（δ13C‰）值较高）外，还改善了CO2同化（[具体指标未给出]）、气孔密度（Std）、K利用效率（KUE）和水分利用效率（WUE）。同时，K被Na替代率高于50%的组合比例导致植株缺K，其特征是TDM、δ13C‰、WUE和叶片K浓度较低，叶片Na浓度较高。有确凿证据表明在[具体树种名称未给出]幼苗中K可被Na部分替代；同时，理想的替代百分比根据物种的耐旱性增加（[具体耐旱性比较未完整给出]）。
