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林业科学 ›› 2017, Vol. 53 ›› Issue (10): 22-28.doi: 10.11707/j.1001-7488.20171003

• 论文与研究报告 • 上一篇    下一篇

杨树苗木完整植株根压的昼夜节律及其影响因素

郭建荣, 万贤崇   

  1. 中国林业科学研究院林业新技术研究所 北京 100091
  • 收稿日期:2016-03-25 修回日期:2016-04-21 出版日期:2017-10-25 发布日期:2017-11-29
  • 基金资助:
    国家自然科学基金项目(31270648)。

Circadian Rhythm of Root Pressure in Intact Poplar Seedlings and the Influencing Factors

Guo Jianrong, Wan Xianchong   

  1. Institute of New Forestry Technology, Chinese Academy of Forestry Beijing 100091
  • Received:2016-03-25 Revised:2016-04-21 Online:2017-10-25 Published:2017-11-29

摘要: [目的]对84K杨树(Populus alba×P.glandulosa)苗木完整植株的根压进行连续测定,研究根压昼夜节律和蒸腾作用、木质部汁液渗透质的关系,为揭示在自然条件下完整植物的根压昼夜节律及发生规律提供参考。[方法]在自然条件下,运用侧面开孔法对杨树苗木完整植株的根压昼夜周期进行测定,并测定叶片水势、根系和茎干木质部汁液的渗透势、无机离子及可溶性糖含量的日变化。[结果]完整杨树植株的根压可以通过侧面开孔法进行监测,测定结果可靠性强。在自然条件下完整植株的根压和去顶根系的根压具有相似的昼夜节律,即昼高夜低,但是完整植株的最大根压值相对较小,且受蒸腾作用的影响。上午蒸腾拉力导致的水势下降并没有抑制根压的上升,中午水势降到一定程度后,根压才迅速下降。1天内任何时间,杨树苗木茎干不同部位木质部汁液存在自上而下渗透势梯度,越到上部渗透势越低,中午尤为突出。此外,茎干木质部汁液渗透势比根系木质部汁液低,根系木质部汁液渗透势在凌晨最低。根系木质部汁液的渗透物质主要是由矿质元素组成,其次是可溶性糖。[结论]完整植株的根压和去顶根系的根压一样,具有明显的昼夜节律,但是在蒸腾作用的影响下最大根压值较小。根压具有较强的自主性,在一定程度上能够抗衡蒸腾拉力。茎干木质部汁液渗透势比根系木质部汁液低,根系木质部汁液的渗透势在凌晨最低,吸水动力最强。

关键词: 完整植株, 根压, 84K杨, 渗透势, 无机离子, 可溶性糖

Abstract: [Objective] In this study, we continuously measured the root pressure of intact seedlings of 84 K popular (Populus alba×P. glandulosa) with the pressure transducer technique, and investigated relationships between diurnal rhythm of root pressure and transpiration and xylem sap osmotic osmolytes, in order to reveal the diurnal rhythm of root pressure and its occurrence pattern in intact plants under natural conditions.[Method] A hole was drilled through the bark into the xylem of the stemnear the base, and a compression fitting was inserted into the hole and connected to a pressure transducer. With this method, we measured in situ the diurnal rhythm of root pressure of intact popular seedlings in field. We also measured diurnal variations of the leaf water potential, as well as the osmotic potential, ions and soluble sugarscontent in xylem sap from roots and stems.[Result] The root pressure of intact seedling could be measured in situ by side hole opening method, and the result was reliable.The root pressure of intact plantshad similar diurnal rhythm to that obtained with the decapitated root systems, that is, root pressure was high in daytime and low at night. However, the maximum root pressure of intact plants was relatively lower than that by the decapitation method, which might be due to the influence of transpiration. The reduction of water potential caused by transpiration in the morning did not conceal the root pressure. Until noon,when water potential descended to a threshold,the root pressure declined rapidly. There existed a top down osmotic potential gradient in xylem sap across popular stem,and it was lower in the upper position and higher in the bottom of the stem.The gradient maintained at any point within a day, particularly at noon. Osmotic potential of stem xylem sap was lower than that of roots. Osmotic potential of root xylem sap was lowest at the predawn time. The osmotic substance inxylem sap from roots was mainly composed by mineral ions,but the role of soluble sugar couldnot be ignored too.[Conclusion] Root pressure of intact seedlings possesses a similar daily rhythm with that of decapitated roots, but the maximum value of intact root pressure is lower than that by the traditional destructive method, possibly due to the influence of transpiration.Root pressure can counter-balance the transpiration to a certain extent. Osmotic potential in root xylem sap was lowest at the predawn time,thereby providing the maximum driving force for upward water transport due to the existence of a osmotic gradient between stem and root. The osmotic substance in xylem sap from roots was mainly composed by mineral ions but the soluble sugars components can not be ignored.

Key words: intact seedling, root pressure, Populus alba×P. glandulosa, osmotic potential, ions, soluble sugar

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