Height-related variations of leaf traits reflect strategies for maintaining photosynthetic and hydraulic homeostasis in mature and old Pinus densiflora trees
Height-related variations of leaf traits reflect strategies for maintaining photosynthetic and hydraulic homeostasis in mature and old Pinus densiflora trees
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叶子性状的高度相关变化反映了成熟和老赤松树维持光合和水力稳态的策略
DOI：
10.1007/s00442-018-4325-x
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发表时间：
2019
期刊：
影响因子：
2.7
通讯作者：
Masaki Takashi
中科院分区：
文献类型：
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作者：
Azuma Wakana;Ishii H. Roaki;Masaki Takashi
由于树木的大小和年龄不同，很难区分它们对生长和生理功能的影响。为了推断与年龄相关的高度生长下降的原因，我们比较了赤松成熟树(约100年)和老树(约300年)的各种叶片性状，这些树的高度相似(约30米)，生长在同一林分。在许多叶片性状上，成熟树和老树表现出相似的高度相关趋势，反映了为了维持光合作用和水力平衡而适应与高度相关的水力限制。两个龄级树冠内的光合作用能力都是恒定的，尽管老树比成熟树低4.9-5.4mmolCO2m−2s−1。只有成熟的树木才能观察到光合作用的生化适应，即将更多的氮素分配到树顶的叶片上。叶片膨胀力损失点在两个龄级的树冠内也是恒定的，树龄对叶片水力性状没有显著影响。在成熟树中，叶电容随树高的增加而增加，而整体组织弹性模数则随树高的增加而减小，而老树随树高的变化趋势相反。两个龄级的单位面积叶质量、输液组织面积和木质部面积都随着高度的增加而增加，但单位面积叶质量在老树比成熟树大约30g/m−2。在老树上，叶肉面积随着高度的增加而减小，这表明解剖上对高度的适应可能会对光合作用产生负面影响。我们推断，老树更多地依赖于形态而不是生化适应，这种资源分配的后成熟转变可能是导致高度生长下降的原因。生殖成熟后的浓密花朵。
Because tree size and age co-vary, it is difficult to separate their effects on growth and physiological function. To infer causes for age-related height-growth decline, we compared various leaf traits between mature (ca. 100 years) and old (ca. 300 years) trees ofPinus densiflora, having similar heights (ca. 30 m) and growing in the same stand. For many leaf traits, mature and old trees showed similar height-related trends reflecting acclimation to height-related hydraulic limitation for maintaining photosynthetic and hydraulic homeostasis. Photosynthetic capacity was constant within crowns of both age-classes, though 4.9–5.4 μmol CO2m−2s−1lower for old than for mature trees. Biochemical acclimation of photosynthesis, allocating more nitrogen to treetop leaves, was observed only for mature trees. Leaf turgor loss point was also constant within crowns of both age-classes with no significant effect of age on leaf hydraulic traits. In mature trees, leaf capacitance increased, while bulk tissue elastic modulus decreased with height, whereas opposite height-related trends were observed for old trees. For both age-classes, leaf mass per area (LMA), transfusion-tissue area, and xylem area all increased with height, but LMA was ca. 30 g m−2greater for old than for mature trees. In old trees, mesophyll area decreased with height, suggesting anatomical acclimation to height may negatively affect photosynthetic capacity. We inferred that old trees rely more on morphological than biochemical acclimation and that such post-maturational shift in resource allocation could underlie height-growth decline ofP. densifloraafter reproductive maturity.