Unit 1 - Auxin and Plant Growth

In this GCSE Biology quiz we look at plant growth - both phototropism and geotropism - and how they are affected by auxins.

Auxins are plant hormones which cause growth. They are produced by cells in the actively growing parts of a plant - the tips of the shoot and root. Auxins can diffuse through the plant and can therefore affect more than just the growing tip of the shoots. High concentrations of auxins have different effects on the different cells of a plant. They make the shoot cells grow more and root cells grow less. Shoots grow towards the light (phototropism) and roots need to grow down into the soil towards moisture. Roots grow downwards due to gravitropism which is also known as geotropism. The responses of shoots and roots to stimuli is the result of unequal growth due to unequal distribution of auxin. Plant growth hormones are used in agriculture as weedkillers and as rooting hormones.