Carbohydrate uptake from xylem vessels and its distribution among stem tissues and buds in walnut (Juglans regia L.)
Carbohydrate uptake from xylem vessels and its distribution among stem tissues and buds in walnut (Juglans regia L.)
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DOI：
10.1093/treephys/tpp103
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发表时间：
2010-01-01
期刊：
影响因子：
4
通讯作者：
Lacointe, Andre
中科院分区：
文献类型：
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作者：
Bonhomme, Marc;Peuch, Mederic;Lacointe, Andre
萌芽模式是树木构型的关键决定因素。导致某些芽优先于其他芽的机制尚未完全解释，但可溶性糖的可用性可能起着重要作用，特别是在生长期开始时木质部汁液中的可溶性糖。在这里，我们测量了不同组织（芽，木质部和树皮）中的碳可用性。为了评估芽利用木质部汁液碳水化合物的能力，在休眠期间直到芽断裂，测定了核桃（Juglans regia cv“Franquette”）木质部导管与薄壁细胞、树皮和芽之间的通量。这种吸收能力根据温度、糖和所研究片段的分支上的位置而变化。12月至3月，在木质部组织中，蔗糖吸收的活性成分是主要的扩散相比（90%的总吸收），而活性成分占更温和的数额在芽（50%的吸收）。木质部对己糖的主动吸收发生得较晚（4月）。芽萌发前1个月，木质部导管和芽之间的流速增加，达到2000 μ g蔗糖h（-1）gDW（-1）。流量似乎取决于芽的位置在分支。然而，这项研究强烈表明，它们主要取决于芽的库强度和芽，木质部薄壁组织和树皮之间的库竞争。
Bud break pattern is a key determinant of tree architecture. The mechanisms leading to the precedence of certain buds over the others are not yet fully explained, but the availability of soluble sugars may play a significant role, especially those in the xylem sap at the onset of the growing period. Here, we measured carbon availability in the different tissues (bud, xylem and bark). To assess the capacity of buds to use the xylem sap carbohydrates, the fluxes between xylem vessels and parenchyma cells, bark and buds of walnut (Juglans regia cv `Franquette') were measured during the rest period until bud break. This uptake capacity varies according to the temperature, the sugar and the position on the branch of the fragment studied. Between December and March, in xylem tissues, the active component of sucrose uptake was predominant compared with diffusion (90% of the total uptake), whereas the active component accounted for more moderate amounts in buds (50% of the uptake). The active uptake of hexoses took place belatedly (April) in xylem. The flow rates between xylem vessels and buds increased 1 month before bud break and reached 2000 mu g sucrose h(-1)gDW(-1). Fluxes seemed to depend on bud position on the branch. However, this study strongly suggests that they were mainly dependent on the sink strength of the buds and on the sink competition between bud, xylem parenchyma and bark.