Departmento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, Minas Gerais 36570-900, Brazil.
Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC 27695, USA.
Tree Physiol. 2022 Sep 8;42(9):1750-1761. doi: 10.1093/treephys/tpac040.
Ongoing changes in climate, and the consequent mortality of natural and cultivated forests across the globe, highlight the urgent need to understand the plant traits associated with greater tolerance to drought. Here, we aimed at assessing key foliar traits, with a focus on the hydraulic component, that could confer a differential ability to tolerate drought in three commercial hybrids of the most important Eucalyptus species utilized in tropical silviculture: E. urophyla, E. grandis and E. camaldulensis. All genotypes exhibited similar water potential when the 90% stomatal closure (Ψgs90) occurs with Ψgs90 always preceding the start of embolism events. The drought-tolerant hybrid showed a higher leaf resistance to embolism, but the leaf hydraulic efficiency was similar among all genotypes. Other traits presented by the drought-tolerant hybrid were a higher cell wall reinforcement, lower value of osmotic potential at full turgor and greater bulk modulus of elasticity. We also identified that the leaf capacitance after the turgor loss, the ratio between cell wall thickness (t) and lumen breadth (b) ratio (t/b)3, and the minimal conductance might be good proxies for screening drought-tolerant Eucalyptus genotypes. Our findings suggest that xylem resistance to embolism can be an important component of drought tolerance in Eucalyptus in addition to other traits aimed at delaying the development of high tensions in the xylem. Highlight Drought tolerance in tropical Eucalyptus hybrids encompasses a high leaf resistance to embolism and a suite of traits aimed at delaying the development of high tensions in the xylem.
不断变化的气候，以及由此导致的全球天然林和人工林的大量死亡，突出表明迫切需要了解与耐旱性更强相关的植物特征。在这里，我们旨在评估关键叶片特征，重点是水力成分，这些特征可以使三种在热带造林中最重要的桉树商业杂种(Eucalyptus urophyla、Eucalyptus grandis 和 Eucalyptus camaldulensis)具有不同的耐旱能力。当 90%的气孔关闭(Ψgs90)发生时，所有基因型的水势都相似，而 Ψgs90 总是先于栓塞事件的开始。耐旱杂种表现出更高的叶片对栓塞的抵抗力，但所有基因型的叶片水力效率相似。耐旱杂种还具有细胞壁加固程度较高、渗透压在完全膨压下的值较低以及体弹性模量较大等其他特征。我们还发现，在膨压丧失后叶片电容、细胞壁厚度(t)与腔宽(b)比值(t/b)3 和最小电导率可能是筛选耐旱桉树基因型的良好指标。我们的研究结果表明，除了旨在延迟木质部高压发展的其他特征外，木质部对栓塞的抵抗力也可能是桉树耐旱性的一个重要组成部分。
