Importance of oxygen for soil and plants (Part 2)

In the first part, we will look at the role oxygen plays for soil, roots and plants and describe possible causes of oxygen deficiency (=hypoxia). Now it is essential to understand the effects on various mechanisms and finally on yield.

Consequences for root systems and stress in plants 

Speaking of roots. The roots also suffer from a lack of oxygen, e.g. due to excessively wet conditions. In extreme cases, the formation of new roots comes to a complete standstill. In addition, even under moist to wet conditions (‘no need to search for water’), new root formation decreases, as a pronounced deep root system is not required.   

Under waterlogged conditions, the atmospheric oxygen is also displaced from the coarse pores by water with a significantly lower O2 concentration. The diffusion of oxygen to the root system then becomes a limiting factor and plant growth stagnates.

All these factors have a direct influence on the development of crops, but also cause massive stress in the plant organism. But what exactly happens in the plant under these stress conditions?  

The lack of oxygen is recognised by special proteins in the plant and cell reactions that are essential for survival are triggered: 

• Switch to anaerobic cellular respiration. ATP is produced for a short time without oxygen; however, only 2 molecules are produced instead of 38 under aerobic conditions. 
• Increased ethanol production. This increases glucose to adapt the root architecture (additional root hairs for oxygen uptake).

In addition, more ethylene, a plant hormone that regulates physiological processes such as germination, cell elongation and fruit ripening, is produced under stress conditions. An increased ethylene content therefore promotes ripening, i.e. the plant wants to finish faster and save what is still there. It eventually prematurely ripened or dies.