Internal stucture of root :- In T. S. of root given in previous class, root hairs are visible surrounded by soil particles. Just behind epidermis, there is a cortex ( a group of parenchymatous cells ) . Last layer of cortex is called the endodermis. Xylem tissue is present behind endodermis. Water from soil enter to root hair cell by endosmosis process. From here the water move from cell to cell from cortex and reach to  endodermis. The endodermis does not allow water to return back from xylem vessels.

Root pressure :- Pressure created by the water in  xylem vessels by continuous entry of water from root hairs to xylem vessels via cortex of root, is called root pressure.
 Root pressure is important for plants for ascent of sap. It is initial pushing force.

Note :-  Water column is continue, without any air bubbles in the xylem of root, xylem of stem and xylem of leaves.

Transpiration :- Loss of water in the form of water vapour through the aerial parts of plants ( leaf, stem etc. ) is called the transpiration.

Transpiration pull :- Transpiration pull is the force which pull water through xylem vessels of leaf, stem and root. This pull force plays a vital role in the ascent of sap.

Minerals :- Minerals are important for proper growth and development of plants and for proper functioning of its different physiology.
More than 60 elements are found in different plants out of which approx. 17 elements come under category of essential elements and rest all are considered as non-essential elements.