Describe how different environmental factors affect the direction of growth of roots and shoots.

The growth and roots and shoots is caused by the plant hormone auxin. Shoots grow towards light, known as phototropism, they also grow upwards against the force of gravity which is known as geotropism. In shoots auxin causes faster growth and therefore the unequal distribution of this hormone on the lower side of the shoot causes it to bend upwards towards light and away from gravity. Roots on the other hand grow downwards towards moisture (hydrotropism) and towards gravity (geotropism). This growth is also a result of the unequal distirbution of the hormone auxin, however in roots auxin inhibits growth. This in turn means that growth rates on the upper side of the root are faster, casuing it to bend, growing down towards moisture and towards the force of gravity.