Factors Affecting Photosynthesis
Factor Affecting Photosynthesis:
The various factors affecting photosynthesis are light, carbon dioxide, water etc.
Light: Photosynthesis cannot occur in the dark and the source of light for the plants is sunlight. The longer the plant is exposed to light, the longer the process of photosynthesis will continue. As long as the temperature of the plant remains balanced, photosynthesis will occur.
Carbon Dioxide: The atmosphere contains 0.03% of carbon dioxide among other gases. Plants take in carbon dioxide from the air. The rate of photosynthesis increases on increasing the concentration of Carbon dioxide in the atmosphere.
Temperature: all biological processes that they occur best in a certain optimum range of temperature.
Water: Water is considered one of the most important factors affecting photosynthesis. When there is a reduced water intake or availability, the stomata begin to close to avoid loss of any water during transpiration. With the stomata closing down the Carbon dioxide intake also stops which affects photosynthesis.
NOTE:
The leaves of the croton plant have chlorophyll, but they appear dark red in color. This is because the higher percentages of other pigments anthocyanins and carotenoid present in them, hides the green color of the chlorophyll. So, the leaves of the croton plants can also make food by the process of photosynthesis.
Experiment to demonstrate that starch is formed during photosynthesis:
Pluck a healthy green leaf which was in the sunlight. Place it in a beaker containing boiling water for about two minutes. Now transfer the leaf to a beaker containing alcohol. Warm it over a water bath for a few minutes. You will observe that the leaf turns white, indicating that the chlorophyll has been removed. Now wash the leaf carefully in water without damaging it. Place the leaf in a dilute solution of iodine. This will turn the leaf bluish black. The changing of the leaf’s colour to bluish black after it has been treated with iodine solution shows that the leaf contains starch.
Experiment to demonstrate that carbon dioxide is essential for photosynthesis:
Get two healthy potted plants of almost the same size and place them in the dark for 24 hours to de- starch leaves. Now place them on a glass plate. Cover the plants with separate bell jars. Keep some crystals of potassium hydroxide (KOH) in a petri dish and place it under one of the jars. Make the set up airtight by applying Vaseline at the bottom of the bell jars. Keep the plants in sunlight for photosynthesis to take place. After 3 to 4 hours, pluck a leaf from each plant. Boil the leaves in water and subsequently in alcohol, using a water bath, to remove chlorophyll. Now use a few drops of iodine to test to starch in each leaf. Only one leaf turns blue black colour showing the presence of starch. This happens because KOH absorbs the CO2 present inside one bell jar. As a result, the leaves do not get CO2 for photosynthesis. Thus the process is inhibited and starch is not synthesized.
Experiment to show that sunlight is essential for photosynthesis:
Keep a potted plant in the dark for 24 hours. On one of the leaves, stick black paper strip (one below and one above the leaf) with the help of cello tape. Now, place this plant in sunshine for a few hours. Pluck the leaf and remove the black strips. Boil this leaf, first in water and then in alcohol, to remove chlorophyll. After washing the leaf with water, keep it in a petri dish. Add a few drops of iodine solution. The leaf turns blue- black except in the region that had been covered. This region did not receive light and hence no starch was formed. The uncovered region received light and starch was formed due to photosynthesis.
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