Eucalyptus are widely planted in regions with low rainfall, occasioning frequent drought stresses. To alleviate the stress-induced effects on plants growing in these environments, soil fertilization with potassium (K) may affect drought-adaptive plant mechanisms, notably on tropical soils with low K availability. This work aimed to evaluate the K dynamic nutrition in eucalyptus in response to soil-K and -water availabilities, correlating the K nutritional status with the physiological responses of contrasting eucalyptus clones to drought tolerance. A complete randomized design was used to investigate the effects of three water regimes (well-watered, moderate water deficit, and severe water deficit) and two K soil supplies (sufficient and low K) on growth and physiological responses of two elite eucalyptus clones: "VM01" (E. urophylla X camaldulensis) and "AEC 0144" (E. urophylla). Results depicted that the K-well-nourished E. urophylla X camaldulensis clone under severe water deficit maintained shoot biomass accumulation by upregulating the K-content in leaves and stems, gas exchange, water use efficiency (WUEI ), leaf water potential (Ψw), and chlorophyll a fluorescence parameters, compared to E. urophylla clone. Meanwhile, E. urophylla with a severe water deficit showed a decreased of K content in leaves and stem, as well as a reduction in the accumulation of dry mass. Therefore, the K-use efficiency and the apparent electron transport rate through photosystem II were positively correlated in plants grown in low K, indicating the importance of K in maintaining leaf photochemical processes. In conclusion, management strategy should seek to enhance K-nutrition to optimize water-use efficiencies and photosynthesis.

中文翻译：

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提高叶和茎中的钾含量提高桉树无性系的耐旱性

桉树广泛种植在降雨量低的地区，造成频繁的干旱胁迫。为了减轻胁迫对在这些环境中生长的植物的影响，钾 (K) 土壤施肥可能会影响植物适应干旱的机制，特别是在钾含量低的热带土壤上。这项工作旨在评估桉树中响应土壤钾和水分可用性的钾动态营养，将钾营养状况与对比桉树无性系对干旱耐受性的生理反应相关联。使用完整的随机设计来研究三种水分状况（充分浇水、中度缺水和严重缺水）和两种钾肥土壤供应（充足和低钾）对两种优良桉树无性系的生长和生理反应的影响： “VM01”（E. urophylla X camaldulensis）和“AEC 0144”（E. urophylla）。结果表明，在严重缺水条件下，K 营养良好的 E. urophylla X camaldulensis 克隆通过上调叶和茎中的 K 含量、气体交换、水分利用效率 (WUEI)、叶水势 (Ψw) 来维持地上部生物量积累和叶绿素 a 荧光参数，与 E. urophylla 克隆相比。同时，严重缺水的尾叶桉叶片和茎中钾含量降低，干物质积累减少。因此，在低钾条件下生长的植物中，钾的利用效率和通过光系统 II 的表观电子传输速率呈正相关，表明钾在维持叶片光化学过程中的重要性。综上所述，