Gravity provides a direction indicator in normal plant growth. In plant roots, two processes are seen: the diagonal path or "skewing" of the roots, and "waving" which is undulating changes in roots to avoid obstacles like rocks. Roots apparently do not need gravity to orient their directional skewing. Also, in the absence of gravity but in the presence of directional light, the roots show strong negative phototropism and grow in opposite direction of shoot growth. It has been now confirmed that although gravity is used by the plants as an orientating tropism, it is neither neccessary for root orientation, nor is it the only factor affecting patterns of plant growth. Other features of the environment are also required to ensure that a root grows away from its seed to enhance its chances of finding water and nutrients for its survival.