Question

How does root system architecture change in response to phosphorus deficiency?

Answer 1

Plant root systems are highly plastic in nature and are adaptable to the prevailing environmental conditions. Phosphorus is a critical macronutrient required for the plants' energy generation, nucleic acid synthesis, photosynthesis, glycolysis, nitrogen fixation, etc,. The concentration of phosphorus in the soil solutions is less than 10µM which is way lesser than the required concentration. This can be solved using concentrated fertilizers but is inefficient as phosphorus is highly immobile. Therefore, plant systems have evolved a complex array of tightly controlled adaptive mechanisms such as alteration of root architecture for maintaining the homeostasis.   

Low availability of phosphorus modifies the root architecture traits such as primary root length, root branching, number and length of lateral roots, enhancement of root hair and cluster root formation. These alterations are associated with changes in phytohormone composition and concentration. The localized concentration, transport of sugars, sensitivity to sugars and hormonal signals play an important role in the root development when phosphorus concentrations are low.

In response to low phosphorus, primary roots have a reduced growth in plants such as Arabidopsis. Rice plants display longer roots under these conditions.In maize, there is no reduction or enhancement in the root length. Root cap is the site of sensing and response to low phosphorus conditions. Reduced growth of roots in phosphorus-deficient plants have reduction of cell differentiation and inhibition of cell proliferation in the root elongation zone. The reduced growth of primary root system results in a shallow root system that exploits the topsoil resources efficiently. However, this may result in the reduced water acquisition.