The direction in which roots and shoots move after germination of a seed is guided by two opposing properties. On germination, the roots emerge first. They are guided downwards by the action of hormones which sense gravity. This property is called geotropism. The shoots, on the other hand, are guided upwards by hormones that sense light. This property is called phototropism. Together these two properties ensure that the roots and shoot grow the right way irrespective of the position of the germinating seed in the soil.