Question

Write an experiment to show that chlorophyll is necessary for photosynthesis.

Answer 1

Experiment:

1. Take a potted plant with variegated leaves like croton and keep it in a dark region, away from sunlight for 3 days. This will halt photosynthesis and de-starch the plant.
2. Then keep the plant facing the sunlight for 6 to 8 hours
3. The plant can now carry out photosynthesis and produce starch.
4. Mark the green areas in the leaf and trace them on a sheet of paper. Mark the regions as green and yellow.
5. The green areas contain chlorophyll which is absent in the yellow areas.
6. Immerse the leaf in boiling alcohol to decolorize it. The leaf slowly loses its green color, which goes into the alcohol.
7. Dip this decolorized leaf in iodine solution. Now remove the leaf from the iodine solution and rinse it in distilled water.
8. Remove the leaf from distilled water and keep it on a petri dish.

Observation

1. Two-color regions are visible in the leaf.
2. They are reddish-brown and blue-black.

Conclusion

1. It can be concluded that the earlier green parts of the leaf turn blue-black whereas the yellow parts have become reddish-brown.
2. Green parts of the leaf possess chlorophyll; hence they carry out photosynthesis and produce starch, which turns blue-black with iodine.