PLANT NUTRITION PART 5: IS LIGHT NEEDED?

The objective of this experiment is to investigate if light is one of the requirements for plants to photosynthesize.

PROCEDURE

• Destarch a potted plant.
• Cover one leaf of this destarched plant with a black paper with patterns cut in it (See the following figure).
• Expose the plant to bright sunlight for two hours.
• After 2 hours, test the leaf for the presence of starch using Iodine solution (Remember the procedure outlined in the previous post)
  

OBSERVATION

• The Iodine solution will change colour to Blue-black in the uncovered region whereas in the regions which is covered with black paper, the Iodine solution remain unchanged.

CONCLUSION

• Light is unable to penetrate in the region which is covered with the black paper, so no photosynthesis and therefore no starch is produced.
• Light penetrates in the uncovered region, so photosynthesis takes place and therefore starch is produced and detected when the leaf is tested with Iodine solution.
• The experiment shows that light from the sun is necessary for photosynthesis to take place.