Plants require different nutritious substances present in soil solution.
Soil solution is a mixture of soil particles, water and air etc.
Different nutritional elements are dissolved in water, which plants have to absorb.
These nutritional elements only can be absorbed in solution form by roots.
The root hairs are single celled, living structures which are directly in contact of soil solution.
The water gradient in root hair is lower than the soil solution .
The water enters the root hairs by means of osmosis. The diffusion and osmosis collectively passes the water and minerals into the xylem channel.
This continuous process of entering water and minerals exert root pressure necessary for ascent of sap in plants. In higher plants transpiration pull co-act along with root pressure.

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I peli delle radici sono escrescenze epidermiche nella regione di maturazione della punta della radice. è responsabile dell'assorbimento acqua.it è nella regione dei peli della radice le piante assorbono l'acqua per osmosi.