Stable Isotopes Reveal the Contribution of Corticular Photosynthesis to Growth in Branches of Eucalyptus miniata
Stable Isotopes Reveal the Contribution of Corticular Photosynthesis to Growth in Branches of Eucalyptus miniata
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DOI：
10.1104/pp.110.163337
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发表时间：
2011-01-01
期刊：
影响因子：
7.4
通讯作者：
Hutley, Lindsay B.
中科院分区：
文献类型：
--
作者：
Cernusak, Lucas A.;Hutley, Lindsay B.
落叶树皮习性在木本植物桉属中广泛存在。具有落叶树皮的物种会季节性地脱落一层死皮，从而随着年龄和直径的增加，在树枝和茎上保持光滑的树皮表面。这在防火方面造成了巨大的成本，因为光滑树皮的物种的树皮比粗糙树皮的物种更薄，后者会积累连续的死皮层。桉树与火密切相关，这表明光滑树皮的习性也一定能带来显着的好处。我们认为这种好处是皮质光合作用。为了测试这一点，我们量化了生长在澳大利亚北部热带稀树草原的光滑树皮的迷你桉树枝皮层光合作用对木材生产的贡献。我们用铝箔覆盖树枝部分四年，以阻止皮质光合作用，然后比较铝箔覆盖和未覆盖的树枝部分的氧和碳稳定同位素组成。我们开发了理论来计算由皮质光合作用构建的木材的比例以及根据观察到的同位素差异在皮质光合作用期间的平均比例再固定率。铝箔覆盖 4 年，木材 Delta C-13 增加了 0.5%（P = 0.002，n = 6），木材 Delta O-18 增加了 0.5%（P = 0.02，n = 6）。根据这些数据，我们估计未覆盖的树枝部分中的 11% +/- 3% 的木材是由皮层光合产物构成的，平均 delta C-13 为 -34.8%，皮层光合作用期间的平均比例再固定率为 0.71 +/- 0.15。这表明皮层光合作用对光滑树皮桉树的碳经济做出了重大贡献。
The deciduous bark habit is widespread in the woody plant genus Eucalyptus. Species with deciduous bark seasonally shed a layer of dead bark, thereby maintaining smooth-bark surfaces on branches and stems as they age and increase in diameter. This has a significant cost in terms of fire protection, because smooth-barked species have thinner bark than rough-barked species that accumulate successive layers of dead bark. Eucalypts are closely associated with fire, suggesting that the smooth-bark habit must also provide a significant benefit. We suggest that this benefit is corticular photosynthesis. To test this, we quantified the contribution of corticular photosynthesis to wood production in smooth-barked branches of Eucalyptus miniata growing in tropical savanna in northern Australia. We covered branch sections with aluminum foil for 4 years to block corticular photosynthesis and then compared the oxygen and carbon stable isotope composition of foil-covered and uncovered branch sections. We developed theory to calculate the proportion of wood constructed from corticular photosynthate and the mean proportional refixation rate during corticular photosynthesis from the observed isotopic differences. Coverage with aluminum foil for 4 years increased wood delta C-13 by 0.5%(P = 0.002, n = 6) and wood delta O-18 by 0.5% (P = 0.02, n = 6). Based on these data, we estimated that 11% +/- 3% of wood in the uncovered branch sections was constructed from corticular photosynthate, with a mean delta C-13 of -34.8%, and that the mean proportional refixation rate during corticular photosynthesis was 0.71 +/- 0.15. This demonstrates that corticular photosynthesis makes a significant contribution to the carbon economy of smooth-barked eucalypts.