Explain the external conditions needed for growth.

Explanation

Plant growth is influenced by variety of external and internal factors. A brief account of these factors is given below:
External Factors:
1. Water:
i. Water is essential for cell enlargement as well as growth in the size of the cell.
ii. Turgidity of cells helps in growth extension. Water provides the medium for enzymatic activities needed for growth.
2. Nutrition:
i. Nutrition plays an important role in the formation of protoplasm.
ii. Macro and micro elements are very important as sources of energy.
iii. For example, carbon and oxygen in carbon - dioxide and hydrogen in water are assimilated in photosysnthesis.
3. Temperature:
i. Temperature plays a significant rolo in the growth of the plant.
ii. Proper growth of a plant occurs at a about `28^(@)C - 30^(@)C` temperature and above `45^(@)C` will damage the protoplasm and hinders the growth.
4. Oxygen:
i. Oxygen has a vital role in the growth of the plant.
ii. It helps in releasing metabolic energy essential for growth activities.
iii. It is necessary for respiration.
5. Light:
i. Light has its own contribution in the growth of the plant.
ii. Light is important for growth and photosynthesis. Light stimulates healthy growth.
iii. Absence of light lead to etiolation.