Growth Analysis And Characteristics Of Wheat Root System Architecture In Southern China

South of China is an important base for grain production and a typical economic development zone.In these areas,rice-wheat rotation is one of the major grain crops with high mechanization level.However,there are still some problems to be sloved,such as low yield and low mechanization efficiency;in China,agricultural mechanization techanization technology and management system with high efficiency and increased production is not perfect;root system distribution determines the absorption efficiency of water and fertilizer,which plays very important role in crop yield,weak in the evaluation of tillage effect;the study of root architecture is limited by methods and evalution indicies.For the above problems,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 root system architecture under two tillage methods of no tillage and rotary tillage in 2010-2013,to explore the root distribution characteristics of wheat stubble and its response to soil condition with indices of root system.The specific research contents are as follows:(1)Digitization and visualization of field crop root system.A specialized plant root architecture digitizer was designed and produced,which was applied for field-grown wheat root system digitizing.The measured data was transferred to Pro-E software platform to re-fabricate the virtual wheat root system architecture for further scientific calculation;the proposed plant root architecture digitizer provided a measurement resolution of less than 1 mm.The digitizer was both convenient to use and highly tolerable to dirt,proving its suitability for 3D plant root architecture measurement.The root distribution along soil depth and circular directions can be observed directly base on 3D reconstruction technology of root system.During winter season the soil exploiting capacity of wheat root system was largely and laterally restricted.But a rapid exploration of soil at early stem elongation stage was noticed in the surface soil layer,and this rapid outburst moved to deeper soil layers in the later stem elongation stage.The distribution of root in each soil layers varied from time to time,this proved a highly dynamic process of wheat root system during the winter period;to sum up,the virtual plant root pack,constructed with both hardware and software,can be used for 3D plant root system architecture analyzing,and can accurately quantify root architecture dynamical behavior and evolution.(2)Phenotyping for the dynamics of field wheat root system.They are depicted the 3D topology of wheat RSA based on visualization of field root with a set of indices of mm scale precision.The phenotyping procedure,proposed for understanding the spatio-temporal variations of root-soil interaction and the RSA dynamics in the field.With the time increased,the distribution of root system in horizontal direction and root length were following the same trend,increased slowly at first then rapidly;root foraging potential,explained by MaxW/MaxD ratio(Maximum RSA width/Maximum RSA depth),changed obviously then went gently.No-till post-paddy wheat root length density decreased exponentially in both depth and circular directions.Root vertical angle in the 40 mm surface soil layer was the largest,but steadily decreased along the soil depth.After 98d,larger root vertical angle appeared in the deep soil layers.Wheat root elongation rate along soil depth was either positive or negative,depending on specific soil layers and the sampling time.(3)2D fractal analysis of wheat root system architecture in field.Virtualization of field wheat root system based on the plant root architecture digitizer,Pro-E modeling reconstruction technology and fractal theory,then projected it on 3 coordinate planes.The projected 2-D root architecture was then analyzed to derive fractal dimensions and fractal abundances.Results showed that both root fractal dimension and fractal abundance increased over time.Fractal dimension and fractal abundance in the top plane were always higher than that in the right plane.Starting from the 98th day after sowing,a rapid increase of fractal dimension and fractal abundance was observed in the front plane.Then the virtual root was projected on a set of planes along the soil depth that have 10 deg apart from each other.Fractal dimension and fractal abundance of the root projections on each viewport were calculated.Results showed significant differed characteristics of fractal indices on each planes in the seeding stage,indicating a strong orientation of no-tillage root development.From seeding to regeneration period,large fluctuation of fractal indices was observed,which revealed a continued dynamical process of root development.In the jointing stage,fractal indices again revealed differences in each orientation.Root distribution resumed its directionality.The distribution of root architecture in each dimension did not have the obvious seasonal characteristics under rotary-tillage condition.The comparison results above showed that this method could be used to distinguish the effects of tillage on root system architecture.(4)3D fractal analysis of wheat root system architecture.RSA has significant effect on water uptake and nutrient absorption.However,related indices for the quantification of crop RSAs were limited to 2D fractal analysis.Analytical tools for 3D fractal analyzing on crop RSAs were lacking.Thus there is a need to investigate the related parameters and operational procedures suitable for the analyzing of the 3D characteristics of crop RSAs.A self-fabricated digitizer for crop RSAs was used to measure the topological parameters of the field-grown wheat root,providing the spatial dimensions of wheat RSAs.Virtual wheat RSAs were then modeled and reconstructed with Matlab programming,which guaranteed a realization of the real-world wheat RSAs with virtual reality.The fractal theory was then introduced to the computing software to calculate the fractal parameters of the modeled virtual wheat RSAs,including 3D fractal dimension,3D fractal abundance,2D fractal dimension,2D fractal abundance and total root length.These parameters were used to quantify the dynamics of wheat RSAs,in both the 2 experimental years and the 2 tillage treatments.Co-relationships among 3D fractal dimension,3D fractal abundance,2D fractal dimension,2D fractal abundance and total root length were also analyzed.It was found that all the RSA-related parameters were steadily increased along wheat developmental stages,in either different years or under different tillage treatments.Differences between the 2 years appeared as the 2010-2011 crop season revealed a steadily increase of RSA-related parameters,while the 2011-2012 crop season observed a more radical increase of root elongation rate.A comparison between the 2 years revealed that tillage treatment has contrasting effect from year to year,with a better crop performance under rotary till than no-till in the first year,whereas the no-till treatment in 2011-2012 outperformed the first year.In the early stages(0-98 d)the crop season has pronounced influences on wheat RSAs,as compared with tillage treatments.In the ensuing stages(98-112 d),however,annual difference of wheat RSA parameters was as similar as the tillage treatments.A comparison between 3D fractal parameters with the 2D parameters revealed that 3D parameters were markedly contrasted with the 2D parameters,indicating that introducing the 3D parameters for crop RSA analysis is necessary.Disregard annual difference and tillage treatment,all the dynamics of 3D fractal dimension,3D fractal abundance,2D fractal dimension,2D fractal abundance and total root length satisfied power law functions and were all co-related significantly.This means that the effects of crop season and tillage treatment were only related to the coefficients of the power law models.It was concluded that the visualization and analytical tools developed with hardware and software integration and combined with fractal theory was a guarantee for precise quantification of crop root system architectures.Such an analyzing tool allows recasting the spatio-and-temporal dynamics of field crop RSAs with modeled virtual roots.3D fractal parameters could be used as a precision analytical tool for crop RSAs.In selecting root elongation tactics and optimizing the root-soil interactions an important consideration should be taken to match the crop root with its soil environment and the tillage system.(5)Root-soil interaction of paddy wheat under rotary tillage system and no-tillage system.Engineered crop root system architecture(RSA)guarantees an optimized root-soil interaction for improved crop yield where suboptimal or heterogeneous soil environment presents.In a 2yr experiment wheat RSAs was sampled,digitized,modeled and parameterized in Pro-E,yielding a set of RSA-derived parameters for the root-soil interactions.Time-series presentation of these parameters was illustrated and the correlations among them were statistically analyzed.Results showed that relative horizontal angle was significantly influenced by crop seasons,while the effect from tillage systems(no-till v.s.rotary till)was minimal.The variation range of the relative horizontal angle of the root system is mainly around 55 degrees.Rotary-tillage was better than no-tillage during 2010-2011 according to the indices of axial root expansion volume,enveloped soil volume and effective volume per unit root length,furthermore,there was a significant decreased in the 56 days after sowing both tillage system.On the contrary,no-tillage was better than rotary-tillage during 2010-2011 with these indices,and the significant decrease occurred in 70 days after sowing.The analysis of variance test showed that the effect of annual change was significantly higher than that of tillage system.The quantification of root-soil interaction provided a method to describe root architecture and soil exploration ability caused by tillage and annuals.The wheat root configuration evolution process of quantitative analysis and correlation test were also carried out.And the influence of the annual growth of wheat root and root-soil relationship was significantly higher than that caused by the tillage system in this study.(6)Relationship between root architecture and aboveground growth indices of paddy wheat.Based on the root architecture and soil interaction quantitatively,and combined with the aboveground growth indices of paddy wheat.This part analyzed the post-paddy wheat which consisted of dynamic changes of root system architecture and the aboveground growth states,and then established the relationship between the belowground and aboveground.The results showed that there was no significant difference for post-paddy wheat between the two tillage systems,but the correlation coefficient changes of different indices caused by different tillage system was notable.For the aboveground parts of wheat under different tillage system,the relevance of indices between different years was very high besides leaf angle,and the effect of annual change on wheat growth was not significant.It was found that the correlation between the change trend of the root level angle of wheat and the growth indices of aboveground part was not obvious.There had a significant difference between the wheat root indices such as axial root expansion volume,enveloped soil volume and total root length and aboveground indices during 2010-2011.There had no obvious difference between the wheat root indices except total root length and aboveground indices during 2011-2012.In addition,the correlation between leaf angle and all root indexes of two different tillage systems were very low in 2010-2011;while in the 2011-2012,there was a negative correlation between the leaf angle and all root indexes under the two tillage methods,and the correlation of rotary-tillage system was higher than no-tillage system.However,the reasons for the above phenomena have yet to be verified by further experiments.