Analyzing And Modeling Of Root Architecture Of Individual Maize Plants Based On High-accuracy Field Data And Its Applications

Root system plays a pivotal role in water and nutrient acquisition and has strong plasticity to soil environment. Three-dimensional (3D) RSA models provide an opportunity to describe the shape and spatial arrangement of root systems. Quantifying the characteristics of different-order laterals based on the topological connection of root systems can provided valuable information for functional-structural root research and root modelling. Based on the measured dataset of root systems of adult, field-grown maize, the architectural characteristics of different-order lateral roots and the allometric relationships were analysed.3D RSA models were reconstructed according to the 3D digitised points of axile roots and the topological information of lateral roots. Based on the reconstructed 3D RSA models, the accuracies of different sampling strategies were assessed. The main results were as follows:(1) The basal diameter of the lateral roots (orders 1 to 3) was highly variable. Basal diameter was partly determined by the diameter of the bearing segment. Basal diameter defined a potential root length, however, the lengths of most roots fell far short this potential. This was partly explained by differences in the pattern of diameter change along roots. Diameter tended to decrease along most roots, the steepness of the gradient of decrease, depending on basal diameter. The longest roots were those that maintained (or sometimes increased) their diameters during elongation. The branching density of laterals was also determined by the diameter of the bearing segment. However, the location of this bearing segment along the mother root was also involved-intermediate positions were associated with higher densities of laterals.(2) The length and number of first-order laterals were not always related to the root insertion positions, but were strongly correlated with the diameter of their bearing roots. The first-order laterals with high-order laterals accounted for less than 50% of the total number, but contributed 85-91% to the total root length. The total branch number and total branch length of first-order laterals increased with the increasing length of first-order laterals and with the increasing rank of lateral roots unit (LRU). The higher the LRU rank, the larger the root length, root diameter and branch number of different-order laterals. The slopes for the linear relationship between the diameter of second-order laterals and the diameter of bearing roots, and the slopes for the linear relationship between the basal diameter and the length of first-order lateral roots, both increased with increasing LRU rank.(3) The 3D RSA models of maize groups were reconstructed using the measured dataset. Different core-sampling strategies were evaluated based on the 3D RSA models. The result shows that substantial deviations occurred for the estimation of RLD by using one-core sampling strategy. The deviation was still large for two-cores sampling strategy. The bias of estimated RLD from the reference RLD was low by using an 1:6 weighting proportion for two-cores sampling strategy. In this study, a multi-cores sampling strategy based on the area-weighting was proposed for the estimation of RLD. Three core-samplings between rows based on the area-weighting had a better estimation for the RLD vertical profiles by using 7.5 and 10 cm diameter cores. Moreover, ignoring the core which farthest from the root base and using only two core-samplings could also give a reliable estimation of RLD.Root diameter and branching were quantified at the root segment scale and the geometry and topology of the root systems were systematic detected. The relationships between diameter, length and branching density and their hierarchical connections are especially useful in simulations of root elongation and branching in source-sink models. Based on the topological connection, the architectural characteristics of different-order laterals in the morphogenetic continuum can be followed more fully. Virtual assessment based on 3D RSA model has great values in the optimization of core sampling strategies. The optimal sampling strategy was provided for the estimation of RLD of adult maize groups.