Functional responses of baobab (Adansonia digitata L.) seedlings to drought conditions: Differences between western and south-eastern Africa
Functional responses of baobab (Adansonia digitata L.) seedlings to drought conditions: Differences between western and south-eastern Africa
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DOI：
10.1016/j.envexpbot.2011.09.011
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发表时间：
2012
影响因子：
5.7
通讯作者：
S. Smedt;A. Sanchez;N. V. D. Bilcke;D. Simbo;G. Potters;R. Samson
中科院分区：
文献类型：
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作者：
S. Smedt;A. Sanchez;N. V. D. Bilcke;D. Simbo;G. Potters;R. Samson
猴面包树（Adansonia digitalata L.）是非洲旱地的重要多用途树种，常见于萨凡纳最干燥的地区。尽管季节性干旱是这些地区植物生长和生存的主要限制因素之一，但有关猴面包树幼苗应对干旱的机制的报道却很少。因此，本研究的目的是研究猴面包树幼苗在短期土壤干旱胁迫下的功能反应。由于非洲西部和东南部的猴面包树之间存在遗传差异，因此在马里和马拉维（分别是非洲西部和东南部）收集了种子。人们发现猴面包树幼苗利用多种机制来应对干旱。首先，由于叶子脱落，叶面积减少，但并非所有叶子都脱落，甚至形成了一些形态改变的叶子。其次，在干旱条件下，相对更多的生物量被分配给根系。第三，由于猴面包树幼苗的气孔控制严格，在干旱条件下，光合作用和蒸腾作用显着降低，而叶片水势几乎没有变化。随着干旱的持续，光合作用的非气孔限制变得重要。主根中储存的部分水被用于拯救部分老叶、形成新叶、形成新根以及维持代谢过程。主根含水量与气孔闭合程度之间存在显着相关性。前者的机制主要与节水有关，使猴面包树幼苗在干旱期间保持高水分状态，这有助于防止木质部空化并使其能够在干旱时期生存。观察到不同来源的猴面包树幼苗对干旱反应的差异：马拉维幼苗能够保留更多的叶子并形成更多的新叶子，而马里幼苗则倾向于将更多的生物量分配给根系。因此，来自西非的猴面包树幼苗表现出更多的抗旱特性。马拉维和马里之间的这些不同策略与猴面包树分支之间的遗传差异一致，并表明可以选择耐旱性优越的种植材料。
The baobab tree (Adansonia digitata L.) is an important multi-purpose tree species of dryland Africa, commonly found in the driest parts of the Savannah. Although seasonal drought is one of the major constraints for plant growth and survival in these regions, little has been reported about the mechanisms baobab seedlings use to deal with drought. Therefore, the aim of this study was to investigate the functional responses of baobab seedlings under a short-term soil drought stress. As genetic differences between baobab trees from western and south-eastern Africa have been reported, seeds were collected in both Mali and Malawi (western and south-eastern Africa, respectively). Baobab seedlings were found to use a number of mechanisms to cope with drought. First, leaf area was reduced due to leaf shedding, though not all leaves were shed and even some leaves with altered morphology were formed. Second, under drought, relatively more biomass was allocated to the root system. Third, as baobab seedlings had a tight stomatal control, under drought conditions photosynthesis and transpiration were significantly reduced while leaf water potential barely changed. Non-stomatal limitations on photosynthesis became important as drought persevered. Part of the water stored in the taproot was being used for the salvation of part of the old leaves, for the formation of new ones, for the formation of new roots, and for the maintenance of metabolic processes. There was a significant correlation between water content of the taproot and stomatal closure. The former mechanisms, mainly related to water conservation, allow baobab seedlings to keep a high water status during drought events which helps to prevent xylem cavitation and allow them to survive dry periods. Differences between the drought responses of baobab seedlings from different origins were observed: Malawian seedlings were able to retain more leaves and to form more new ones, while Malian seedlings tended to allocate more biomass to their root system. Therefore, baobab seedlings from western Africa showed more drought-avoidance characteristics. These different strategies between Malawi and Mali agree with genetic differences between baobab clades, and suggest that superior planting material in terms of drought tolerance can be selected.