Question

potatoes are grown underground.how do they obtain starch when photosynthesis occurs in the green leaves above the ground

Answer 1

small buds on potato help them to growing it's new plant.

Answer 2

hello mate ,
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Photosynthesis takes place on the leaves of the potato plant . Potatoes are modified to store food that's why all the starch made by leaves get stored in Potatoes.
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I hope it will help you :-)