Water sources and water-use efficiency in mediterranean coastal dune vegetation.
Water sources and water-use efficiency in mediterranean coastal dune vegetation.
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DOI：
10.1055/s-2004-820882
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发表时间：
2004-05
期刊：
影响因子：
3.9
通讯作者：
G. Alessio;M. De Lillis;E. Brugnoli;M. Lauteri
中科院分区：
文献类型：
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作者：
G. Alessio;M. De Lillis;E. Brugnoli;M. Lauteri
在沿海环境中，植物必须科普各种水源：雨水，地下水位，海水和混合物。它们通常具有不同的同位素特征（（18）O/（16）O和D/H比值）。木质部水反映了水源的同位素组成。此外，水利用效率（WUE）可以用碳同位素区分（Delta）分析来评估。2001年6 ~ 8月，对移动的沙丘多年生草本植物（海沙草（Ammophila littoralis）、Ephalus farctus）和固定沙丘硬叶灌木和攀缘植物（杨梅（Arbutus unedo）、阿月浑子（Pistacia lentiscus）、沙田柚（Phillyrea angustifolia）、冬青（Qercus Ilex）、尖柏（Juniperus oxycedrus）、糙叶菝葜（Smilax aspera））的气体交换、叶片干物质δ（18 O）和木质部水的同位素组成进行了测定。同化率相当低，并没有表现出明确的季节模式，可能是由于有限的降水和气孔导度普遍较低的值。最低值显示在S中。阿斯佩拉。根据δ（18）O和δ分析，发现了不同的生理模式。高位芽植物木质部水的δ（18）O值非常稳定，与地下水位一致，表明其依赖于可靠的水源; δ值相对较高，表明其内在WUE较低，但尖杉除外。令人惊讶的是，非常高的δ（18）O值被发现的木质部水从S。八月的Aspera这表明，由于露水或雾的发生，叶水逆扩散到茎中的木质部汁液或叶或茎直接吸收水。δ值低表明S.阿斯佩拉。不同的移动的沙丘物种表现出不同的策略：E. farctus依赖表层水分，WUE较低，这与其一年生植物式的营养循环有关; littoralis使用较深的水源，表现出较高的水分利用效率与其持久的营养习性。
In coastal environments plants have to cope with various water sources: rainwater, water table, seawater, and mixtures. These are usually characterized by different isotopic signatures ( (18)O/ (16)O and D/H ratios). Xylem water reflects the isotopic compositions of the water sources. Additionally, water-use efficiency (WUE) can be assessed with carbon isotope discrimination (Delta) analyses. Gas exchange, Delta of leaf dry matter, and isotopic composition (delta (18)O) of xylem water were measured from June to August 2001 in herbaceous perennials of mobile dunes (Ammophila littoralis, Elymus farctus) and sclerophyllous shrubs and climbers (Arbutus unedo, Pistacia lentiscus, Phillyrea angustifolia, Qercus ilex, Juniperus oxycedrus, Smilax aspera) of consolidated dunes. Assimilation rates were rather low and did not show clear seasonal patterns, possibly due to limited precipitation and generally low values of stomatal conductance. The lowest values were shown in S. aspera. Different physiological patterns were found, on the basis of delta (18)O and Delta analyses. Values of delta (18)O of xylem water of phanerophytes were remarkably constant and matched those of the water table, indicating dependence on a reliable water source; values of Delta were relatively high, indicating low intrinsic WUE, with the exception of J. oxycedrus. Surprisingly, very high delta (18)O values were found for the xylem water from S. aspera in August. This suggests retrodiffusion of leaf water to xylem sap in the stem or direct uptake of water by leaves or stems, owing to dew or fog occurrence. Low Delta values indicated high WUE in S. aspera. Contrasting strategies were shown by the species of mobile dunes: E. farctus relied on superficial water and exhibited low WUE, accordingly to its therophyte-like vegetative cycle; on the contrary, A. littoralis used deeper water sources, showing higher WUE in relation to its long-lasting vegetative habit.