Binks Oliver, Meir Patrick, Rowland Lucy, da Costa Antonio Carlos Lola, Vasconcelos Steel Silva, de Oliveira Alex Antonio Ribeiro, Ferreira Leandro, Mencuccini Maurizio
School of Geosciences, The Crew Building, The King's Buildings, University of Edinburgh, Edinburgh, EH9 3JN, UK
School of Geosciences, The Crew Building, The King's Buildings, University of Edinburgh, Edinburgh, EH9 3JN, UK.
Tree Physiol. 2016 Dec;36(12):1550-1561. doi: 10.1093/treephys/tpw078. Epub 2016 Sep 10.
Dry periods are predicted to become more frequent and severe in the future in some parts of the tropics, including Amazonia, potentially causing reduced productivity, higher tree mortality and increased emissions of stored carbon. Using a long-term (12 year) through-fall exclusion (TFE) experiment in the tropics, we test the hypothesis that trees produce leaves adapted to cope with higher levels of water stress, by examining the following leaf characteristics: area, thickness, leaf mass per area, vein density, stomatal density, the thickness of palisade mesophyll, spongy mesophyll and both of the epidermal layers, internal cavity volume and the average cell sizes of the palisade and spongy mesophyll. We also test whether differences in leaf anatomy are consistent with observed differential drought-induced mortality responses among taxa, and look for relationships between leaf anatomy, and leaf water relations and gas exchange parameters. Our data show that trees do not produce leaves that are more xeromorphic in response to 12 years of soil moisture deficit. However, the drought treatment did result in increases in the thickness of the adaxial epidermis (TFE: 20.5 ± 1.5 µm, control: 16.7 ± 1.0 µm) and the internal cavity volume (TFE: 2.43 ± 0.50 mm cm, control: 1.77 ± 0.30 mm cm). No consistent differences were detected between drought-resistant and drought-sensitive taxa, although interactions occurred between drought-sensitivity status and drought treatment for the palisade mesophyll thickness (P = 0.034) and the cavity volume of the leaves (P = 0.025). The limited response to water deficit probably reflects a tight co-ordination between leaf morphology, water relations and photosynthetic properties. This suggests that there is little plasticity in these aspects of plant anatomy in these taxa, and that phenotypic plasticity in leaf traits may not facilitate the acclimation of Amazonian trees to the predicted future reductions in dry season water availability.
预计在包括亚马逊地区在内的热带地区的一些地方，未来干旱期将变得更加频繁和严重，这可能导致生产力下降、树木死亡率升高以及储存碳排放量增加。我们在热带地区进行了一项为期12年的穿透降雨排除（TFE）长期实验，通过研究以下叶片特征来检验树木是否会产生适应更高水平水分胁迫的叶片这一假设：面积、厚度、单位面积叶质量、叶脉密度、气孔密度、栅栏叶肉、海绵叶肉以及两个表皮层的厚度、内部腔室体积以及栅栏叶肉和海绵叶肉的平均细胞大小。我们还测试了叶片解剖结构的差异是否与观察到的不同分类群之间干旱诱导的死亡率差异一致，并寻找叶片解剖结构与叶片水分关系和气体交换参数之间的关系。我们的数据表明，树木不会因12年的土壤水分亏缺而产生更具旱生形态的叶片。然而，干旱处理确实导致了近轴表皮厚度增加（TFE：20.5±1.5微米，对照：16.7±1.0微米）和内部腔室体积增加（TFE：2.43±0.50立方毫米/平方厘米，对照：1.77±0.30立方毫米/平方厘米）。尽管在栅栏叶肉厚度（P = 0.034）和叶片腔室体积（P = 0.025）方面，干旱敏感性状态与干旱处理之间存在相互作用，但在抗旱和干旱敏感分类群之间未检测到一致的差异。对水分亏缺的有限响应可能反映了叶片形态、水分关系和光合特性之间的紧密协调。这表明这些分类群在植物解剖学的这些方面几乎没有可塑性，并且叶片性状的表型可塑性可能无法促进亚马逊树木适应未来预计的旱季水分可利用性的降低。
