Question

how do plant get nutrient explain in simple and short

Answer 1

Plants get nutrients from air, water and soil.
From air it gets C02 and O2
From water it gets Fe, K, etc
From soil it gets N2 , P, K etc.

For your onion peel practical .

Answer 2

Plants absorb nutrients and water through their roots, but photosynthesis — the process by which plants create their fuel — occurs in the leaves. Therefore, plants need to get fluids and nutrients from the ground up through their stems to their parts that are above ground level.