Factors affecting respiration are divided into two categories.
(1) External or environmental factors
(2) Internal or plant factors.
(1) External factors
- Temperature
- Oxygen
- Water
- Light
- Carbon dioxide
(2) Internal factors
- Protoplasm
- Respiratory substrate
- Age of Cell
- Wound and injury
1. External factors or Environmental Factors:
1. Temperature: It is the most important factor affecting the rate of respiration. Normally the rate of respiration increases to a certain limit by an increase in temperature from 5.0°C to 30.0°C. In this range, the rate of respiration increases as per Vont Hoff’s rule. According to this a rise in temperature by 10°C, the rate of respiration becomes double. Increase in temperature beyond 35.0°C results into decrease in rate as the enzymes begin to denaturalize. At very low temperatures also enzymes become inactive and the rate of respiration decreases. In cold storage, the fruits and vegetables escape spoilage because of this.
2. Oxygen: Oxygen is necessary for aerobic respiration because it acts as a terminal acceptor of electrons. At low concentration of oxygen both aerobic and anaerobic respiration may take place, but when the concentration of oxygen becomes zero only anaerobic respiration takes place. Under such a condition value of R.Q. becomes infinite (∞)
3.Water: Water acts as a medium for all metabolic activities. The protoplasm contains up to 90-95% of water. Water plays an important role in enzyme activation, gaseous diffusion, transportation etc. In dry seeds and fruits rate of respiration is extremely low due to the shortage of water and so these can be stored for a long duration. In the presence of water stored carbohydrates convert into soluble sugar and the rate of respiration increases.
4. Light: Rate of respiration is not influenced directly by light and so it takes place in the presence as well as an absence of light.
5. Carbon dioxide (CO2): Increase in concentration of CO2 inhibits respiration. Hence it has an adverse effect on the germination of seeds and rate of growth of plants. Heath experimentally proved that an increase in the concentration of CO2 causes the closure of stomata and the rate of respiration decreases due to a shortage of oxygen.
Internal factors or Plant Factors:
1. Protoplasm: Meristematic cells have dense and active cytoplasm and so the rate of respiration is relatively high in these cells as compared to the mature cells. The activity of protoplasm is affected by several factors such as hydration, pH, temperature etc.
2. Respiratory substrate: Different types of sugars such as glucose, fructose, maltose etc. present in the cell are quickly used in respiration. In comparison to these starch and fats need to be first converted into a soluble form and only then they can be used as a respiratory substrate. This is the reason why in hospitals a patient is administered directly with, glucose, whereas the normal diet of healthy persons contains starch and fats.
3. Age of Cells: The rate of respiration is much higher in the young cells as compared to mature and old cells.
4. Wound and Injured part: Rate of respiration sharply increases in the wound and injured part to promote healing.
