Question
What are the external factors which affects photosynthesis?
✓
Answer
External factors which affect photosynthesis are as follows:
$1.$ Light:
$a.$ It is an essential factor as it supplies the energy necessary for photosynthesis.
$b.$ Quality and intensity of light affects the photosynthesis.
$c.$ Highest rate of photosynthesis takes place in red light followed by blue light.
$d.$ The rate of photosynthesis considerably decreases in plants which are growing under a forest canopy.
$e.$ In most of the plants, photosynthesis is maximum in bright diffused sunlight.
$f.$ Uninterrupted and continuous photosynthesis for a very long period of time may be sustained without any visible damage to the plant.
$2.$ Carbon dioxide:
The main source of $CO_2$ in land plants is the atmosphere, which contains only $0.3\%$ of the gas.
$b.$ Under normal conditions of temperature and light, carbon dioxide acts as a limiting factor in photosynthesis.
$c.$ Increase in concentration of $CO_2$ increases the photosynthesis.
$d.$ Increase in $CO_2$ to about $1\%$ is advantageous to most of the plants.
$e.$ Higher concentration of the gas has an inhibitory effect on photosynthesis.
$3.$ Temperature:
$a.$ Like all other physiological processes, photosynthesis also needs a suitable temperature.
$b.$ The optimum temperature at which the photosynthesis is maximum is $25-30 ^\circ C.$ Except in plants like Opuntia, photosynthesis takes place at as high as $55 ^\circ C.$
$c.$ This is the maximum temperature. Minimum temperature is temperature at which photosynthesis process just starts.
$d.$ In the presence of sufficient light and $CO_2,$ photosynthesis increases with the rise of temperature till it becomes
maximum. After that there is a decrease or fall in the rate of the process.
$4.$ Water:
$a.$ Water is necessary for photosynthetic process.
$b.$ An increase in water content of the leaf results in the corresponding increase in the rate of photosynthesis.
$c.$ Thus, the limiting effect of water is not direct but indirect.
$d.$ It is mainly due to the fact that it helps in maintaining the turgidity of the assimilatory cells and the proper hydration of their protoplasm.
$1.$ Light:
$a.$ It is an essential factor as it supplies the energy necessary for photosynthesis.
$b.$ Quality and intensity of light affects the photosynthesis.
$c.$ Highest rate of photosynthesis takes place in red light followed by blue light.
$d.$ The rate of photosynthesis considerably decreases in plants which are growing under a forest canopy.
$e.$ In most of the plants, photosynthesis is maximum in bright diffused sunlight.
$f.$ Uninterrupted and continuous photosynthesis for a very long period of time may be sustained without any visible damage to the plant.
$2.$ Carbon dioxide:
The main source of $CO_2$ in land plants is the atmosphere, which contains only $0.3\%$ of the gas.
$b.$ Under normal conditions of temperature and light, carbon dioxide acts as a limiting factor in photosynthesis.
$c.$ Increase in concentration of $CO_2$ increases the photosynthesis.
$d.$ Increase in $CO_2$ to about $1\%$ is advantageous to most of the plants.
$e.$ Higher concentration of the gas has an inhibitory effect on photosynthesis.
$3.$ Temperature:
$a.$ Like all other physiological processes, photosynthesis also needs a suitable temperature.
$b.$ The optimum temperature at which the photosynthesis is maximum is $25-30 ^\circ C.$ Except in plants like Opuntia, photosynthesis takes place at as high as $55 ^\circ C.$
$c.$ This is the maximum temperature. Minimum temperature is temperature at which photosynthesis process just starts.
$d.$ In the presence of sufficient light and $CO_2,$ photosynthesis increases with the rise of temperature till it becomes
maximum. After that there is a decrease or fall in the rate of the process.
$4.$ Water:
$a.$ Water is necessary for photosynthetic process.
$b.$ An increase in water content of the leaf results in the corresponding increase in the rate of photosynthesis.
$c.$ Thus, the limiting effect of water is not direct but indirect.
$d.$ It is mainly due to the fact that it helps in maintaining the turgidity of the assimilatory cells and the proper hydration of their protoplasm.
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