基于功能-结构模型的树体结构参与矮化砧木调控碳合成和分配的机理研究

As we all known, carbon assimilation and allocation are regulated by dwarfing rootstock, the mechanism involved is still under debate. Tree architecture connects organs by a network and determines spatial arrangements of organs and their activity by exchanging energy with surrounding environment and provides support for carbon transport. However, due to the complexity of tree architecture, studies on regulation of dwarf rootstock on carbon assimilation and allocation usually neglect the influence of tree architecture. Apple trees with dwarf interstem and vigorous rootstock and with various crop loads will be used in this study. Differences of tree spatial and topology structure response to treatments will be analyzed by combining 3D digiting, multi-scale tree graph and statistical Markov model. Then, the source-sink organ strength, vigour, carbon and nitrogen metabolites will be analyzed at organ scale dynamically. After that, validation and calibration of an apple functional-structural plant model at organ scale which has been established in our group will be carried out. In the end, the model will be used to run simulations according to parameters collected in our project and virtual experiments with fluctuated parameters, rootstock/interstem, crop load and tree architecture, to analyze the quantitative effect of rootstock/interstem, crop load and tree architecture on tree development and carbon assimilation and allocation. The research will be helpful to clarify the mechanism of carbon assimilation and allocation response to dwarf rootstock as the tree architecture involved, enrich the theory of source-sink and provide us good guidance to cultivation of apple with dwarf rootstock.

矮化砧木调控碳合成和分配被大家所熟知，但其中机理尚不明确。树体结构决定器官连接方式及空间分布，通过与外界能量交换调控器官活性，并为碳的转运提供支撑。但由于树体结构复杂，矮化砧木对碳合成和分配的研究常忽略树体结构影响。本项目拟以矮化中间砧和乔化苹果为试材，结合负载量调控试验，利用三维数字化、多重树图技术和马尔科夫模型分析处理间树体空间和拓扑结构差异；然后，在器官尺度研究处理间库、源器官强度、活力、碳氮代谢产物的动态差异；对项目组前期建立的基于器官尺度的苹果功能结构模型进行验证和校准，并利用模型进行实景模拟和虚拟试验，量化矮化中间砧、负载量和树体结构对树体生长及碳合成和分配的效应。本申请项目的实施有助于阐明整体植株尺度树体结构参与矮化砧木调控碳合成和分配的机理，丰富源-库理论，指导矮化栽培苹果生产，均具有重要的理论和实践意义。

果树普遍利用矮化砧木诱导植物矮化，通过影响其冠层结构和叶片功能性状调控碳合成和分配，但相关调控机制尚不明晰。本项目以不同矮化性砧木苹果为试材，结合负载量试验，利用三维数字化技术、气体交换测量、光合生理模型及结构功能模型重点开展了（1）三维虚拟模型重建及精度评价；（2）矮化砧木对叶片光合及气孔导度的影响；（3）矮化砧木对整体冠层空间结构、光截获效率、光合生产力及各类枝梢空间分布、光截获效率及光截获分配的影响；（4）基于虚拟试验的枝梢组成、主干数量、栽植密度、砧木类型对冠层光截获效率的影响以及矮化砧木树体结构和叶片功能对冠层光合生产力、水分利用及产量的影响；（5）负载量对果树生长、光合碳同化及代谢的影响。通过项目实施，构建了苹果叶面积估算模型及叶片、枝梢和冠层的三维结构模型，模型精度可满足冠层光截获分析要求，但枝梢尺度会低估长枝梢（>5cm）光能截获效率。果台副梢的光截获效率较营养枝高8-14%。同半矮化砧木处理相比，矮化砧木处理显著降低营养生长并优化营养枝叶的空间分布，进而著提高了挂果枝梢和营养短枝梢的光截获效率及光分布；矮化砧木处理叶片光合速率降低，可能由于叶片氮含量及最大羧化速率的调节，当温度、饱和水汽压差增加时，矮化砧木处理叶片气孔下降速率大于半矮化砧木处理叶片。负载量提高会降低枝梢生长、提升光合效率，但不影响枝梢停长时间。矮化砧对冠层光合能力的影响与树龄有关，可显著提高成年果树冠层光合及水分利用效率。构建了基于结构功能模型的苹果产量预测模型，矮化砧木提高了‘富士’品种的碳分配效率，但对‘嘎啦’品种无显著影响；基于虚拟试验，国台副梢比例提升及主干枝数量的增加，可显著改善冠层光能利用率；矮化砧木叶片分布可显著提升冠层光合速率、水分利用效率及产量。研究结果进一步阐明了树体结构参与矮化砧木调控碳合成和分配的机制，对于指导矮化砧木利用和开发相关高效管理措施具有重要的理论和实践意义。