First of all, I want to compliment you on making this difficult question!
I will try to explain my way of thinking and answering this question:
This is pure thinking, so not based on any sources:
Why do certain nutrients occur in high levels in particular foods? Example:
An orange contains a lot of dietary fibre. Dietary fibre is known to
be contained in high concentration by cell walls of plants. Because
the orange contains a lot of cell walls (it is the seed of the orange
plant), it contains a lot of dietary fibre.
I do not think there is a relation between the function of the derived
tissue, the nutrient was extracted from, and the level of nutrient
value. It is just because of the concentration of building material.
Starchy foods like potatoes are made up of a high concentration of
carbohydrates such as glucose, because starch is made up of many
glucose molecules bind together.
I hope this helps you.