David Teresa S, David Jorge S, Pinto Clara A, Cermak Jan, Nadezhdin Valery, Nadezhdina Nadezhda
Instituto Nacional de Recursos Biológicos I.P., Quinta do Marquês, Av. da República, 2780-159 Oeiras, Portugal.
Instituto Superior de Agronomia, Technical University of Lisbon, Tapada da Ajuda, 1349-017 Lisboa, Portugal.
Funct Plant Biol. 2012 Mar;39(2):103-115. doi: 10.1071/FP11185.
The topology of the xylem network is likely to affect the transport of water, propagation of embolism and plant survival and growth. Few studies have been conducted on the hydraulics of the entire water pathway in trees. We evaluated the hydraulic connections from roots to branches in a mature Quercus suber L. tree, through sap flow responses upon branch severing. Sap flow was recorded in branches, stem and roots by the heat field deformation (HFD) method. Results showed that roots, except for the taproot, were hydraulically connected to all branches, but the rest of the tree (stem, branches and taproot) was highly sectored. In the large roots that showed an integrated response to branch severing, the outer xylem was preferentially connected to the same side branch and the inner xylem to the opposite branch. The hydraulic sectoriality in branches, stem and taproot may be regarded as an adaptive trait to water stress. The integrated hydraulic structure of roots is advantageous under patchy soil conditions, but may allow the spread of root diseases. The HFD sap flow method proved extremely useful to calculate xylem flux connectivity between different organs of a large tree, providing a comprehensive picture of its hydraulic architecture.
木质部网络的拓扑结构可能会影响水分运输、栓塞传播以及植物的存活和生长。针对树木整个水分运输路径的水力特性，开展的研究较少。我们通过切断树枝后液流的响应，评估了一棵成熟的栓皮栎树从根部到树枝的水力连接情况。采用热场变形（HFD）法记录树枝、树干和根部的液流。结果表明，除主根外，其他根系在水力上与所有树枝相连，但树的其他部分（树干、树枝和主根）水力分区明显。在对树枝切断表现出综合响应的大根中，外侧木质部优先与同侧树枝相连，内侧木质部则与对侧树枝相连。树枝、树干和主根中的水力分区可视为对水分胁迫的一种适应性特征。根系的整体水力结构在斑驳土壤条件下具有优势，但可能会使根部病害蔓延。HFD液流法被证明对于计算大树不同器官之间的木质部通量连通性非常有用，能全面呈现其水力结构。
