Actually most carbohydrate (energy) filled veggies, like the potatoes are tubers. a modified stem that stays underground-not a root! Plants store extra energy as starch, which can come in a wide range of forms.Potato plants store them in big underground tubers that we know as the edible vegetable, as do carrots, parsnips, turnips, etc. Apples, tomatoes, grapes and oranges are all other examples of energy storage sites.You may realise that these often correlate with the plant's seed location/vessel, for obvious reasons.otato plants store them in big underground tubers that we know as the edible vegetable, as do carrots, parsnips, turnips, etc. Apples, tomatoes, grapes and oranges are all other examples of energy storage sites. You may realise that these often correlate with the plant's seed location/vessel, for obvious reasons.