Tue April 26, 2011 By: Nidhi Malik

write an activity to show that chlorophyll is important for photosynthesis.

Expert Reply
Tue April 26, 2011

First of all, we need to take a potted plant with variegated leaves like croton and keep it a dark region, away from sunlight for 3 days. This will halt photosynthesis and destarch the plant.

Next keep this plant in sunlight for 6-8 hours. The plant can now carry out photosynthesis and produce starch.

Next,luck a leaf from this plant and mark the green areas in it and trace them on a sheet of paper. Mark the regions as green and yellow. . As can be deduced, the green areas contain chlorophyll which is absent in the yellow areas. 

Next immerse the leaf in boiling alcohol so as to decolourise it. he leaf slowly loses its green color, which goes into the alcohol.Dip this decolorized leaf in iodine solution using a pair of forceps.   Now remove the leaf from iodine solution and rinse it in distilled water. Remove the leaf from distilled water and keep it on a petri dish. Two color regions are visible in the leaf. They are reddish brown and blue-black.Compare this leaf with the previously traced drawing on the graph paper. een parts of the tracing and blue-black regions of the leaf coincide. Similarly the reddish brown regions in the leaf coincide with the yellow areas on the traced figure. we can conclude that the earlier green parts of the leaf turn blue-black whereas the yellow parts have become reddish brown. Green parts of the leaf possess chlorophyll; hence they carry out photosynthesis and produce starch, which turns blue-black with iodine. The yellow regions of the leaf cannot carry out photosynthesis since they lack chlorophyll and hence no starch is produced here.

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