断根对杨树切口处不同根序细根的形态特征、解剖结构及生理代谢的调控机理研究

Root pruning acts on the root system directly, and can make the incision germinate a large number of fine roots. However, information is lacking on research of fine root architecture and function in the incision. Fine root morphological characteristics, anatomical structure, physiological metabolism and fine root function among different root orders had a close inner link. Consequently, we inferred that discussion about the variation law of fine root architecture and function in the incision of poplar by root pruning, could reveal the regulation mechanism of fine root growth, and would be likely to effectively solve the “little old tree” problem by means of guidance the closed-canopy poplar production. To prove the conjecture，this study sets up different root pruning treatments and the fine roots germinating in the incision were classified systematically using root order method. Firstly, the functional mechanism of root pruning was investigated from the perspective of morphological characteristics, anatomical structure and stoichiometric characteristics of fine roots, and the root pruning treatments were screened preliminarily. Then, the root pruning treatments of preliminary screening were screened further by analysis of the variation characteristics of endogenous hormones and carbon and nitrogen metabolism, to determine the best root pruning measure and discuss the internal relationship among morphological characteristics, anatomical structure, stoichiometric characteristics and physiological metabolism. The results of this study will provide theoretical basis and technical support for the effective implementation of root pruning.

断根直接作用于根系，且能刺激切口处萌发出大量细根，但目前关于切口处细根构型与功能方面的研究鲜有报道。资料显示，不同根序细根的形态特征、解剖结构、生理代谢与细根功能有密切的内在联系。我们推测，探讨断根对杨树切口处萌发出的细根构型与功能的变化规律，能揭示断根对细根生长的调控机理，并将之用于指导杨树郁闭林分的生产，很可能会有效解决杨树的“小老树”问题。为证实该推测，本研究拟设置不同的断根处理，采用根序法对切口处萌发出的细根进行系统分级，首先从细根形态特征、解剖结构和化学计量特征的角度剖析断根的作用机理，并对断根处理进行初筛；然后从细根内源激素与碳、氮代谢的层面对初筛的断根处理进一步筛选，确定最佳断根措施，并探析各级根序细根的形态特征、解剖结构、化学计量特征及生理代谢的内部关联，进而为断根的有效实施提供理论依据和技术支撑。

断根直接作用于根系，且能刺激切口处萌发出大量细根，但目前关于切口处细根构型与功能方面的研究鲜有报道。资料显示，不同根序细根的形态特征、解剖结构、生理代谢与细根功能有密切的内在联系。我们推测，探讨断根对杨树切口处萌发出的细根构型与功能的变化规律，能揭示断根对细根生长的调控机理，并将之用于指导杨树郁闭林分的生产，很可能会有效解决杨树的“小老树”问题。为证实该推测，本研究设置六倍胸径两侧(6-2)、八倍胸径两侧(8-2)、十倍胸径两侧(10-2)等不同断根处理，采用根序法对切口处萌发出的细根进行系统分级，并从细根形态特征、解剖结构、化学计量特征及生理代谢的角度剖析断根的作用机理。研究结果表明：1）在断根处理中，8-2处理1-2级根的直径和根长最小、比根长最大，而3-5级根的直径和根长最大、比根长最小。2）8-2处理1-2级根的维管束直径与维根比显著小于6-2和10-2处理，而3-5级根则明显大于6-2、10-2处理。3）与未断根(CK)相比，6-2处理1-5级根的C、N、P含量和C/N、C/P明显减小，10-2处理变化较小，而8-2处理则显著增大。4）8-2处理1-5级根的吲哚乙酸(IAA)、赤霉素(GA)与玉米素(ZT)含量均显著高于其他处理，而脱落酸(ABA)含量最低，其中IAA含量的平均值较CK、6-2与10-2处理分别提高22.89%、36.04%与21.76%。综上，距离树干八倍胸径两侧的断根措施是最佳的。项目研究结果阐明了断根对杨树切口处细根生长的调控机理，可为断根的有效实施提供理论依据与技术支持。