The root is the underground part of a plant. It develops from radical of the germinating seed. The network of roots and their branches form the root system of the plant.
It is positively geotropic (growing towards gravitational force). Chloroplasts are absent in roots. So it is not green in colour, but colourless plastids (leucoplasts) for storage of food. Roots grow towards water (positively hydrotropic) and grow away from light (negatively phototropic). Nodes and internodes are absent in roots.
Two types of root systems are seen.
- Tap root system
- Fibrous root system
- They help to anchor the plant in the soil.
- They absorb and transport water and nutrients from the soil to the stem.
- In many plants roots may be modified to perform other functions storage, additional support, nutrition, respiration etc.