Oxygen
Is a vital root requirement. The roots convert sugar to energy with oxygen. The more oxygen available to the roots, the more energy they have to send nutrients up to the leaves, or fruit. Aerated soils and nutrients, or directly aerated roots, allow the plant to breathe to the maximum, and will increase root growth proportionately to the air supplied. The biggest advantage of a fine jet of air and nutrients being sprayed directly onto the roots, is not so much the sprays themselves, but the fact that all the nutrient is constantly being oxygenated.

Air Roots
In a plants natural life in the earth, the roots get moisture from rainfall. In soil, the water soon sinks down and the top dries quickly. For this reason, the top 1/3 of the plant roots are air specialized and the bottom 2/3 are water roots. One must be careful not to keep the air specialized roots constantly wet or the plant will drown. The bottom section of the root can be constantly wet, provided that the water has oxygen in it. Stagnant water will soon kill the plant. The roots should aleays be crisp and white. If the roots develop brown tips or general browning, the problem is usually lack of oxygen, or infection.

Root Size
The more extensive the root system, the better the plant will grow. Roots storing lots of energy are able to exchange lots of nutrients up to the leaves, and so the leaves can send down more sugar, etc.. The roots are important storage sites for starches, and the more energy the roots can store, the better the plant will grow. As you can see, it is important to have extensively healthy roots.