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Testing a leaf for starch experiment

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Introduction

Title: Testing a leaf for starch Date: February 20, 2012 Aim: To investigate the presence of starch in leaves. Materials: 2 small leaves (one green, one yellow), beaker, test-tube, ethanol, water, iodine solution, Petri dish, forceps, tripod, wire gauze, dropper, boiling tube. Method: Two leaves were taken from a dicotyledonous plant, one with a fresh green color and the other with a pale yellow color. The green leaf was first immersed in boiling water for roughly 10 seconds.

Middle

The iodine solution was then pourn off and the leaf was again rinsed in water. The reaction was observed and the process was repeated for the yellow leaf. Observation: The green leaf left a green solution in the ethanol while the yellow leaf left it with a pale yellow color. Both leaves were colorless after they were taken out of the ethanol but when the iodine solution was added to them respectively only the green leaf turned blue-black while the yellow leaf took the iodine's brick red color.

Conclusion

Since chlorophyll dissolves in ethanol (solvent), the leaves were placed in the ethanol and boilt so they could be decolorized and was then rinsed to remove any ethanol in it so that when the iodine solution is added it does not react with it. The green leaf turned blue-black when the iodine solution was added to it because it contained chlorophyll and was able to produce starch while the yellow leaf took the color of the iodine solution because it did not contain chlorophyll so it was unable to produce starch hence there was no reaction with the solution.

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