BS-Biotech 4th Term
Presentation Of Plant Physiology
Factors Effecting Respiration
• 1. Temperature:
Affecting the activity of enzymes. Q10 = 2
or 3. Optimum temperature is 20 - 30°C. At high
temperature the rate of respiration declines
with time and at very low temperature, the
respiration rate is insignificant.
• 2. CO2:
• Increase in CO2 concentration and absence of
O2 adversely affect the rate of aerobic
• 3. Light:
• Control respiration by raising the temperature
of an organism.
• 4. O2-Extinction point:
• i.e., minimum oxygen concentration at which
aerobic respiration takes place which is 3 10% of oxygen. In some cases a direct relation
between the respiration rate and oxygen
concentration has been reported.
• 5. Water:
• Very low water content in dry seeds and
stored tubers is responsible for very feeble
rate of respiration. In wilted tissues the stored
starch converted into sugars which increase
the rate of respiration while in well hydrated
plants the rate of respiration is not likely to be
affected much by slight changes in the water
• 6. Respiratory substrates:
• Higher availability of respiratory substrates
increases the rate of respiration upto a certain
• 7. Stimulation:
• Mechanical disturbance, injury or infection
increases respiration. Hopkins (1927) found that
in wounded plant tissue the sugar content is
suddenly increased which is responsible for
temporary increase in the respiration rate.
• 8. Climacteric fruits:
• Such fruits have high rate of respiration during
their ripening e.g.. Banana, Apple.
• 9. Inhibitors:
• A number of chemicals inhibit respiration e.g.,
azide, cyanide, malonate, carbon monoxide etc.
• 10. Protoplasmic factor:
• Young growing cells exhibit high rate of
respiration as compared to mature cells.