Plants absorb nutrients mostly through their roots from the soil and they can also absorb nutrients applied to the leaves as well. On the whole, the absorption by roots is the major route for the entry of nutrients into the plants. For this a soil must furnish each nutrient in exactly the chemical forms in which the roots want them.
The supply of plants with carbon dioxide through leaves as a result of foliar nutrition is usually steadier than via root nutrition. Photosynthesis requires light, heat, humidity and sufficient amounts of nutrients. The above factors plus the biological characteristics of plants and the thickness of their stand determine the intensity or rate of the process.
Similar to other plants, grape also absorb major portion of most of the nutrients through their roots. However, some quantity of nutrients can be also absorbed through their vegetative parts mainy leaves. For efficient and uninterrupted absorption of ions by plant roots, ions must some in contact with root surface. There are mainly three ways by which ions reach to the root surface from soil solution.
1) Root interception
2) Diffusion of ions
3) Mass flow