Not light or gravity but water guiding root to grow

The plant root elongation and growth-oriented mechanism is the research focus. The main viewpoints are three, which are the growth of backlight, to gravity and to water and fertilizer. This paper believes that the viewpoint of the root growth to water and fertilizer is more reasonable. The random structured soil model, and the soil water evaporation model in weightlessness and gravity environment are established. The numerical simulation is performed. The phenomena, that root faster grows on the earth's gravity than in weightless environment, the root near the surface soils is more disorderly in weightless environment, the main root is more taproot growing faster in both environments than the lateral roots, and the roots have some bifurcation and tilt, are explained. The water evaporation near the surface causes the water gradient, and the water gradient drives root elongation and growth, which shows the illusion of the root elongating to gravity. This study can be referred in the subsequent root growth-oriented, random structured soil, soil cracking, and soil water seepage/evaporation.