竹类植物是热带生态系统的重要组成部分,然而他们对极端气候的脆弱性,比如干旱,由于对其水力特性的了解有限,因此了解甚少。刺槐,一种常用的热带竹种,在2019年的严重干旱事件中,其死亡率明显高于其他同时发生的竹子,但其潜在机制仍不清楚。本研究调查了与干旱响应相关的叶和茎水力性状,包括使用光学和X射线显微层析成像方法估计的叶茎栓塞抗性(P50leaf;P50stem),叶片压力-体积和水分释放曲线。此外,我们调查了季节性水势,使用稳定同位素的天然栓塞水平(PLC)和木质部水源。我们发现C.pergracile对栓塞表现出很强的抵抗力,显示低P50leaf,P50stem,和膨胀损失点,尽管它的叶片水分迅速流失。有趣的是,它的叶子比它的茎表现出更大的抗栓塞能力,表明缺乏有效的水力脆弱性分割(HVS)来保护茎免受过度的木质部张力。在旱季,大约49%的水是从20厘米深的土壤层吸收的。因此,观察到叶片水势的显着日变化和中午PLC从雨季的5.87±2.33%增加到旱季的12.87±4.09%。总之,这项研究表明,快速的叶片失水,高度依赖地表水,即使在典型的旱季,C.pergracile中缺乏有效的HVS也会加速水分消耗并增加木质部栓塞,这可以解释其在2019年极端干旱事件期间的高死亡率。
Bamboo plants are an essential component of tropical ecosystems, yet their vulnerability to climate extremes, such as drought, is poorly understood due to limited knowledge of their hydraulic properties. Cephalostachyum pergracile, a commonly used tropical bamboo species, exhibited a substantially higher mortality rate than other co-occurring bamboos during a severe drought event in 2019, but the underlying mechanisms remain unclear. This study investigated the leaf and stem hydraulic traits related to drought responses, including leaf-stem embolism resistance (P50leaf; P50stem) estimated using optical and X-ray microtomography methods, leaf pressure-volume and water-releasing curves. Additionally, we investigated the seasonal water potentials, native embolism level (PLC) and xylem water source using stable isotope. We found that C. pergracile exhibited strong resistance to embolism, showing low P50leaf, P50stem, and turgor loss point, despite its rapid leaf water loss. Interestingly, its leaves displayed greater resistance to embolism than its stem, suggesting a lack of effective hydraulic vulnerability segmentation (HVS) to protect the stem from excessive xylem tension. During the dry season, approximately 49% of the water was absorbed from the upper 20-cm-deep soil layer. Consequently, significant diurnal variation in leaf water potentials and an increase in midday PLC from 5.87 ± 2.33% in the wet season to 12.87 ± 4.09% in the dry season were observed. In summary, this study demonstrated that the rapid leaf water loss, high reliance on surface water, and a lack of effective HVS in C. pergracile accelerated water depletion and increased xylem embolism even in the typical dry season, which may explain its high mortality rate during extreme drought events in 2019.