Canny M J
Biology Department, Carleton University, Ottawa, Canada K1S 5B6.
New Phytol. 1990 Jul;115(3):511-516. doi: 10.1111/j.1469-8137.1990.tb00478.x.
The apoplastic tracer sulphorhodamine G (SR) was used as an indicator of the flumes, the sites where water left the apoplast and entered the symplast, in a selection of dicotyledon leaves. At these flumes the dye is deposited as crystals after a pulse of dye is fed to the transpiration stream, followed or not by a water chase. In contrast to wheat, the dicotyledons showed SR cystals inside the tracheary elements of the finest leaf veins. At short pulse times the crystals were in the stems of the branch-trees of the fine veins, but after longer pulses, had moved to the vein termini. The dye solution was moving very slowly in the tracheary elements as it approached the ends of the branch-trees, since the axial flow there is nearly balanced by radial leakage. These results are interpreted as evidence that most of the transpiration water enters the symplast in the vein sheaths of the fine veins, and that these veins are places where many of the natural solutes of the xylem sap will be enriched to quite high concentrations.
质外体示踪剂磺基罗丹明G（SR）被用作一种指标，来研究一系列双子叶植物叶片中的“水槽”，即水分离开质外体并进入共质体的部位。在这些“水槽”处，当向蒸腾流中注入一剂染料，随后或不随后进行水冲洗后，染料会以晶体形式沉积下来。与小麦不同，双子叶植物在最细叶脉的管状分子内部显示有SR晶体。在短脉冲时间下，晶体位于细脉分支树的茎中，但在较长脉冲后，晶体已移至叶脉末端。当染料溶液接近分支树末端时，其在管状分子中的移动非常缓慢，因为那里的轴向流动几乎被径向渗漏所平衡。这些结果被解释为证据，表明大部分蒸腾水在细脉的维管束鞘中进入共质体，并且这些叶脉是许多木质部汁液中的天然溶质将富集到相当高浓度的地方。
