Laboratory of Plant Conservation Science, Faculty of Agriculture, Meijo University, Nagoya, 468-8502, Japan.
Tomakomai Research Station, Field Science Center for Northern Biosphere, Hokkaido University, Tomakomai, 053-0035, Japan.
Oecologia. 2021 Jun;196(2):331-340. doi: 10.1007/s00442-021-04929-4. Epub 2021 May 8.
Between-branch nitrogen competition is expected to be important during spring in temperate deciduous trees as nitrogen allocation would be higher in branches from earlier budburst than in those from later budburst. Such phenology-induced branch interaction would influence plant photosynthesis, but this has not been evaluated. Warming experiments were conducted on whole crowns (warmed trees; trunks and all branches of the same tree were warmed) or parts of the crowns (warmed branches with unwarmed control branches in the same tree), with unwarmed control trees, in saplings of the deciduous species Fraxinus lanuginosa. Spring leaf phenology and leaf photosynthetic traits were investigated to determine how the difference in temperature affects leaf phenology and photosynthetic traits. The timing of budburst was influenced by temperature-budburst was earlier in warmed trees and warmed branches than in control trees and control branches, but budburst timing did not differ between control trees and control branches or between warmed trees and warmed branches. In contrast, leaf traits were affected by the variation in phenology within crowns-nitrogen content and photosynthetic capacity were greater in the leaves of the warmed branches than in the control branches, but they did not differ between the leaves of warmed trees and control trees. Thus, branch warming altered the distribution of nitrogen between warmed and unwarmed branches as warmed branches developed faster, resulting in intracrown variation in leaf photosynthetic traits.
在温带落叶树的春季，枝间氮竞争预计是很重要的，因为与晚展叶的枝条相比，早展叶枝条的氮分配会更高。这种由物候引起的枝条相互作用会影响植物光合作用，但这一点尚未得到评估。本研究在幼树上进行了全树冠（加温树；同一棵树的树干和所有枝条都被加温）或树冠部分（加温枝条和同一棵树上未加温的对照枝条）的加温实验，同时设置了未加温对照树，研究对象为落叶树种白蜡树。研究了春季叶片物候和叶片光合特性，以确定温度差异如何影响叶片物候和光合特性。萌芽时间受温度影响——加温树和加温枝条的萌芽时间早于对照树和对照枝条，但对照树和对照枝条之间、加温树和加温枝条之间的萌芽时间没有差异。相比之下，叶片特性受树冠内物候变化的影响——在加温枝条的叶片中，氮含量和光合能力大于对照枝条的叶片，但加温树和对照树的叶片之间没有差异。因此，枝条加温改变了加温和未加温枝条之间的氮分配，因为加温枝条生长更快，导致叶片光合特性在树冠内发生变化。
