The roots of corn seedlings grow downwards with gravity. Credit: Darkves/Getty ImagesNew research has discovered how the plant hormone auxin guides roots to grow downwards in the direction of gravity, a process known as gravitropism. Charles Darwin was one of the first to write about gravitropism when he observed that plant roots grow downwards and shoots grow upwards. This allows a plant’s stem to grow upwards towards the light it needs for photosynthesis, while the roots anchor it and collect water and nutrients from the soil. Their study found ABA influences the angles at which rice and corn roots grow by promoting the production of auxin.