Root Oxygenation
Oxygen is a vital component of root physiology. The superior oxygenation of the root zone and nutrient solution that hydroponics provides helps improve root health, as without enough oxygen to complete the respiration process, roots will suffocate. Plants will exhibit a strategy called oxytropism, where roots will avoid growing in oxygen-deprived areas such as water-logged soils, overwatered hydroponic substrates and stagnant nutrient solutions.
Some plants require large amounts of oxygen within the root zone, particularly when growing in the protected, warm conditions provided year-round with indoor gardens. A restricted root zone is limited in how much oxygen it can hold, so it relies heavily on oxygen replenishment. This can be carried out by dissolved oxygen in the nutrient solution, or by oxygen percolation down into the root zone during irrigation.
If roots require more oxygen than what they can get through replenishment, their function begins to slow, as does the uptake of water and nutrients.
Eventually, a lack of oxygen can cause root-cell death and increase the risk of root diseases such as pythium. The more restricted the root zone volume, the greater the replenishment rate of oxygen must be. In hydroponics, this can be achieved in a number of ways. Some grow mediums contain larger pores than others and allow oxygen to diffuse faster down into the root zone. Second, nutrient solutions carry dissolved oxygen, so increasing the dissolved oxygen content of the solution via aeration and making sure the root zone is not oversaturated with water will ensure more oxygen is available for root uptake.