In gravitropism, in which direction do roots grow?

downward       is the answer

Roots will always grow down due to geotropism. It is caused by the statocytes in the root cap. They sense the force of gravity and grow down according to it. But if the root does not have a root cap, then the plant will not necesarily grow down. And if the seed is layed on a flat place like a counter, then the roots will grow any which-way

The answer is integumentary System.
 the integumentary system is the protection that make up most of our skin and its appendages. The main purpose of this system is to protect our internal body from any externalities that may cause damage to us, such as radiation, friction, thermal inbalance, etc.