Evidence for the formation of organic matter (starch) in chloroplasts

Some plants, such as pelargonium (edged geranium) or chlorophytum, have variegated leaves. Their white areas are formed by cells without chloroplasts.

Cut off one leaf of chlorophytum and put it in boiling water for 2-3 minutes, then in hot alcohol. Wash the leaves in water and fill them with a weak solution of iodine for 2-3 minutes.
In a solution of iodine, the leaf will not completely turn blue: the white stripe along the edge of the leaf will not be colored. Why?

The cells of the green part of the leaf contain chloroplasts containing chlorophyll. It is in these cells that sugar is formed, and then starch. There is no chlorophyll in the cells of the white stripe along the edge of the leaf, and starch is not found here.

Conclusion: starch is formed only in cells with chloroplasts.

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