The force of gravity makes things fall to earth.

引力使物体落面。

The geotropism growth was a response of hypha to gravity and the geotropic sensitive was at the hyphal apex.

丛枝菌根真菌菌丝延伸生部位是菌丝尖端，其生是引力感应，感应敏感部位也在生菌丝尖端。