Abstract

The objective of this study was to quantify the effect of potassium (K) supply on osmotic adjustment and drought avoidance mechanisms of Eucalyptus seedlings growing under short-term water stress. The effects of K supply on plant growth, nutritional status, leaf gas exchange parameters, leaf water potential (Ψ_w), leaf area (LA), stomatal density (SD), leaf carbon (C) and nitrogen (N) isotopic compositions (δ¹³C and δ¹⁵N ‰) and leaf C/N ratio under polyethylene glycol (PEG)-induced water deficit were measured. Under both control (non-PEG) and osmotic stress (+PEG) conditions, K supply increased plant growth, boosting dry matter yield with decreased C/N leaf ratio and δ¹⁵N ‰ values. The +PEG significantly reduced LA, plant growth, dry matter yield, Ψ_w, number of stomata per plant and leaf gas exchange, relative to non-PEG condition. Potassium supply alleviated osmotic-induced alterations in Eucalyptus seedlings by better regulating leaf development as well as SD, thus improving the rate of leaf gas exchange parameters, mesophyll conductance to CO₂ (lower δ¹³C ‰ values) and water use efficiency (WUE). Consequently, K-supplied plants under drought better acclimated to osmotic stress than K-deficient plants, which in turn induced lower CO₂ assimilation and dry matter yield, as well as higher leaf δ¹³C ‰ and δ¹⁵N ‰ values. In conclusion, management practices should seek to optimize K-nutrition to improve WUE, photosynthesis-related parameters and plant growth under water deficit conditions.

中文翻译：

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钾供应在 PEG 诱导的渗透胁迫下调节桉树叶水分状态：整合叶片气体交换、碳氮同位素组成和植物生长

摘要

本研究的目的是量化钾 (K) 供应对短期水分胁迫下生长的桉树幼苗渗透调节和干旱避免机制的影响。钾供应对植物生长、营养状况、叶片气体交换参数、叶片水势（Ψ _w）、叶面积（LA）、气孔密度（SD）、叶片碳（C）和氮（N）同位素组成的影响（测量了聚乙二醇（PEG）诱导的水分亏缺下的δ ¹³ C和δ ^{15 N ‰）和叶片C / N比。}在对照（非 PEG）和渗透胁迫（+PEG）条件下，钾供应增加了植物生长，提高了干物质产量，同时降低了 C/N 叶比和 δ ¹⁵N‰ 值。相对于非PEG条件，+PEG显着降低了LA、植物生长、干物质产量、Ψ _{w 、每株植物的气孔数量和叶片气体交换。}钾供应通过更好地调节叶片发育和 SD 来缓解桉树幼苗中渗透引起的变化，从而提高叶片气体交换参数的速率、叶肉对 CO ₂的电导率（较低的 δ ¹³ C ‰ 值）和水分利用效率（WUE） . 因此，在干旱条件下，供钾植物比缺钾植物更好地适应渗透胁迫，进而导致较低的 CO ₂同化和干物质产量，以及较高的叶片 δ ¹³ C ‰ 和 δ ¹⁵N‰ 值。总之，管理实践应寻求优化钾营养，以改善水分不足条件下的 WUE、光合作用相关参数和植物生长。