基于虚拟植物技术的冬小麦根系3D构型测试与分析

Measurement and Analysis of 3D Wheat Root System Architecture with a Virtual Plant Tool Kit

【目的】构建一套由硬件和软件集成且完整而适用的虚拟植物根系技术,定量描述稻茬田冬小麦根系的三维几何构型特征。【方法】自主设计制作"根系构型数字化仪",该数字化仪为纯机械结构,分别设有一个水平回转臂、一个横向滑动臂和一个竖向滑动臂,回转臂与滑动臂都配有标尺,且3者的组合运动能保证测头在3D范围测取任一点的空间坐标。测量时将置于工作台的根区土壤按3—5 mm厚度逐层清除并进行根系构型数字化,从而测取田间小麦根系的真实空间拓扑数据,实现小麦根系实体构型的数字化。将实测的小麦根系构型数据导入Pro-E软件平台,利用软件的3D造型技术完成小麦根系构型的虚拟重构,实现计算机虚拟根系与实体根系的一致性。利用软件的分析工具对虚拟重构的小麦根系构型进行计算分析,定量小麦不同时期根系的三维空间构型、根系的土体空间搜寻能力、根系总长以及根系平均增长率等指标的变化,通过不同的指标反映田间土壤环境下真实小麦根系构型的时空动态。【结果】植物根系构型数字化仪能够提供<1 mm的测试分辨率,操作使用方便,耐污染、抗干扰能力强,对工作环境要求不高,可满足作物根系三维空间几何构型测试要求,而使用Pro-E的小麦根系三维空间几何构型重构技术也便于根系构型的深度计算与分析。冬小麦的根系构型分析结果表明,该虚拟根系技术能够直观展示小麦生长期不同时间节点的根系构型状态特征及土体空间搜寻动态,根系构型图可以反映各时期小麦根系在土体中的纵深拓展和周向扩展状态。同一时期植株个体的根系构型变异性较大,越冬期小麦根系很浅,在返青及分蘖旺期小麦的根系迅速向深层土层中伸展,拔节期根系爆发迅速。【结论】由软硬件单元组构的虚拟植物根系三维空间几何构型的测试与分析方法是准确定量根系动态、根-土关系、根系拓扑特征、根系动态空间行为指标等作物根际生理生态行为的技术保障,其不仅直观展示了水稻土条件下冬小麦根系空间几何构型在不同时期的空间拓展状况,也能够定量根系构型的动态,因此能够满足作物根系三维空间几何构型分析的实用要求。

[Objective]A consistent and useful system for virtual crop root system simulation was constructed with integrated hardware and software, and applied to quantify post-paddy wheat RSA. [Method] A crop RSA digitizer was designed and fabricated in a purely mechanical manner. The digitizer was constructed with a leveled rotating beam, a cross slider and a vertical＆amp;nbsp;slider. All the beam and sliders were calibrated with rulers. The coordinated movements of the three moving parts allows the measuring tip to access any possible point within the 3D root-soil volume. Root zone soil sample, installed on the platform of the digitizer, was stripped in layers, each in 3-5 mm thickness. The positions of the exposed roots were digitized. This laminated treatment continued until the whole RSA was digitized. Collected RSA data was then transferred to Pro-E, where the virtual RSA was reconstructed. As the data set used for RSA reconstruction came directly from undisturbed field-grown crop, the reconstructed virtual RSA was able to represent the actual RSA state and the dynamical process of RSA in situ. The virtual RSA was then analyzed with tools supplied in the Pro-E, where the 3D RSA parameters were calculated, such as soil exploration ability of root system, root total length and mean root elongation rate, etc. Wheat RSA dynamics was also quantified with these parameters.[Result] Being easy to operate, suitable for dusting environment and highly stable under noisy conditions, the proposed RSA digitizer provides a measurement resolution of ＆lt;1 mm and can be used as a satisfactory tool for RSA measurement. Pro-E provides a means of realizing the virtual RSA, and also an in-depth computation of RSA parameters. Results shown that the proposed virtual RSA method was able to illustrate structural characteristics and soil exploitation abilities of root system in each stage of wheat seedling development, as well as the root-colonized soil depth and circumferential root expanding dynamics. High heterogeneity of RSA was observed in each wheat seedling stage. Wheat root was confined in shallow soil layers in winter, but rapidly expanded to deeper layers in standing and tillering stages. More rapid development of root was observed in the shooting stage. [Conclusion] The proposed virtual RSA, integrated with hardware and software, is a technical solution for accurate quantification of root system dynamics, root-soil relation, root topology and the dynamics of soil space exploration. This tool kit provides a solution for RSA quantification in each post-paddy wheat seedling stage, thus illustrating the dynamics of wheat RSAs and satisfying the practical needs for crop RSA study.