Abstract Sugars accumulated in fruits are synthesized in leaves and translocated into the fruits. Quantitative measurement of phloem sap flow would enhance our understanding of the phenomenon and would facilitate efforts to ensure the production of high-quality fruits. The influence of girdling, which cuts off phloem, on sap flow rate determined using the heat balance method, was investigated in citrus. The present study aimed to measure the flow rates in phloem and xylem sap separately and to investigate the effect of gauge temperature on gauge output accuracy. When the gauge temperature was kept constant, the flow rate was consistent with the amount of water transpired from the branch. Immediately after girdling, the sap flow rate increased in a non-bearing branch, but decreased in a bearing branch. We conclude that the phloem sap flowed basipetally in the non-bearing branch and acropetally toward the fruits in the bearing branch. Regression lines for the sap flow before and after girdling were almost parallel, and the difference in the intercept of the two regression lines can be regarded as the flow rate change caused by girdling. Our results indicate that it is possible to determine separate flow rates for phloem and xylem sap by combining the heat balance method with girdling.

中文翻译：

---

柑橘中使用热平衡法和环剥相结合的韧皮部汁液流速测定

摘要 果实中积累的糖分在叶子中合成并转移到果实中。韧皮部汁液流量的定量测量将增强我们对这一现象的理解，并有助于确保生产优质水果。在柑橘中研究了切断韧皮部的环剥对使用热平衡法确定的树液流速的影响。本研究旨在分别测量韧皮部和木质部汁液中的流速，并研究仪表温度对仪表输出精度的影响。当仪表温度保持恒定时，流速与从分支蒸发的水量一致。环剥后，非承载分支的树液流速立即增加，但承载分支的树液流速下降。我们得出结论，韧皮部汁液在非承载分支中向基部流动，向承载分支中的果实向上流动。环割前后的树液流回归线几乎平行，两条回归线截距的差异可认为是环割引起的流量变化。我们的结果表明，通过将热平衡方法与环剥相结合，可以确定韧皮部和木质部汁液的单独流速。