Compound leaves are associated with high hydraulic conductance and photosynthetic capacity: evidence from trees in Northest China
Compound leaves are associated with high hydraulic conductance and photosynthetic capacity: evidence from trees in Northest China
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复叶与高导水率和光合作用能力相关：来自中国东北地区树木的证据
作者：
Da Yang;Yong-Jiang Zhang;Jia Song;Cun-Yang Niu;Guang-You Hao
分析单叶和复叶树种在关键功能性状上的差异，有助于更好地理解复叶形态的适应意义。特别是，这一信息可能为长期提出的CL树种快速生长假说提供机制解释。本文以东北典型温带森林共生长的5种SL和5种CL树种为研究对象，研究了CL树种较高的水力效率是否意味着其具有较高的光合能力。我们发现CL种在全枝水平上的水力导度显著高于SL种（0.52±0.13 vs 0.15±0.04 × 10−4 kg m−2 s−1 Pa−1,P = 0.029）。两者的净光合速率（14.7±2.43 vs 12.5±2.05 μmol m−2 s−1,P = 0.511）无显著差异。但这在很大程度上是由于两个功能群中的每一个都存在一个异常物种。对功能性状的群内变异的仔细研究表明，两种木材类型（环型和扩散多孔型）在各自功能群中的差异可能导致了它们的异常生理表现。潜在的高。CL种的光合能力似乎需要环状多孔木材来实现高水力效率。由于它的局限性。在叶片光合能力上，渗透性较低的扩散多孔木材在很大程度上阻碍了其与土壤的结合。复叶树种的“丢弃”策略（即每年更换茎状茎）本质上需要。高碳同化率以补偿它们额外的碳损失。我们的结果首次显示出明显的分化。同域SL和CL物种之间的水力结构和CO2同化，这有助于探索。复叶树木潜在快速生长的潜在机制。
Characterizing differences in key functional traits between simple-leaved (SL) and compound-leaved (CL) tree species can contribute to a better understanding of the adaptive significance of compound leaf form. In particular, this information may provide a mechanistic explanation to the long-proposed fast-growth hypothesis of CL tree species. Here, using five SL and five CL tree species co-occurring in a typical temperate forest of Northeast China, we tested whether higher hydraulic efficiency underlies potentially high photosynthetic capacity in CL species. We found that the CL species had significantly higher hydraulic conductance at the whole-branch level than the SL species (0.52 ± 0.13 vs 0.15 ± 0.04 × 10−4 kg m−2 s−1 Pa−1, P = 0.029). No significant difference in net photosynthetic rate (14.7 ± 2.43 vs 12.5 ± 2.05 μmol m−2 s−1, P = 0.511) was detected between these two.groups, but this was largely due to the existence of one outlier species in each of the two functional groups. Scrutinization of the.intragroup variations in functional traits revealed that distinctions of the two outlier species in wood type (ring- vs diffuse-porous).from their respective functional groups have likely contributed to their aberrant physiological performances. The potentially high.photosynthetic capacity of CL species seems to require ring-porous wood to achieve high hydraulic efficiency. Due to its limitation.on leaf photosynthetic capacity, diffuse-porous wood with lower hydraulic conductivity largely precludes its combination with the.‘throw-away’ strategy (i.e., annually replacing the stem-like rachises) of compound-leaved tree species, which intrinsically requires.high carbon assimilation rate to compensate for their extra carbon losses. Our results for the first time show clear differentiation.in hydraulic architecture and CO2 assimilation between sympatric SL and CL species, which contributes to the probing of the.underlying mechanism responsible for the potential fast growth of trees with compound leaves.