Root-System Development and Water-Extraction Model Considering Hydrotropism.pdfVIP

Root-System Development and Water-Extraction Model Considering Hydrotropism D. Tsutsumi,* K. Kosugi, and T. Mizuyama ABSTRACT certain conditions. However, because root-system de- velopment is not considered in these water-extractionA two-dimensional model that combines root-system development models, the root length per unit soil volume should beand water extraction by roots is proposed to simulate the dynamic interaction between root growth and soil-water flow. Both of hydrotro- given a priori as a function of soil depth. That is, the pism and gravitropism were considered as the controlling factors of water-extraction model alone cannot simulate the be- root growth in the proposed root-system development model. The havior of soil-water extraction by roots with active finite-element method was employed to compute the soil-water flow growth, which changes the distribution of the root sys- caused by water extraction, evaporation, and irrigation. We succeeded tem over time. in simulating the plagiogravitropic elongations of lateral roots under As a pioneer study of modeling plant-root system de-a plane condition, and the asymmetric architecture of root system under velopment, Lungley proposed a two-dimensional modela slope condition by the proposed model in which the root hydrotro- (Lungley, 1973). Diggle and Pages developed three-pism is considered. On the other hand, we cannot simulate such mor- dimensional root-system architecture models, and theyphological characteristics of a root system by the use of the conven- tional model in which a random elongation factor is employed, and successfully simulated crop plant-root system develop- root hydrotropism is not considered. The results support the impor- ment and morphological architecture three-dimension- tance of hydrotropism in root-system development and the availability ally (Diggle, 1988; Pages et al., 1989). It seems that the of the proposed model in which the hydrotropism is considered. fundamental part of root-