Root Dynamics and Mycorrhizal Amelioration of Root Stress

The pollution caused by modern mining efforts is well documented, but the practice can also disturb soil structure and damage root systems, hampering restoration efforts in coal mines. The difficulty of studying roots and other below-ground parts of plants compounds the problems scientists face in remedying root stress. Using a miniaturized, scan-based rhizotron system, scientists followed root dynamics over time to show how arbuscular mycorrhizal fungi help damaged plants deal with root stress.

Soil Subsidence Causes Below-Ground Problems

Mining for coal takes place at the surface or underground, depending on the location of the resource. Underground mining involves excavating soil below the ground and if the roofs of underground mines are destroyed for any reason, the danger of topsoil subsidence is increased.

Soil subsidence is reported to create problems for above-ground vegetation in restoration projects of abandoned coal mines. During subsidence, soil becomes fissured. As a result, there is root damage or roots are exposed to the air, causing stress.

Any stress or damage to roots will affect plant growth. For successful restoration, plants need help to recover from the effects of subsidence.

The soil fissures and subsidence make in situ research to suggest remedies difficult. A team of Chinese scientists subverted this problem by conducting experiments in the laboratory by simulating soil fissures. These studies showed that the root damage due to fissures affects plant hormonal balance, which reduces biomass accumulation. The change in root morphology also affects the uptake of plant nutrients and the resistance plants have to stress.

Repairing Root Damage

Root morphology can be influenced not just by soil structure, but also by the availability of nutrients and arbuscular mycorrhizal fungi (AMF).

AMF stimulates the growth of lateral roots and root hairs. Hence, the use of AMF to help plants in restoration projects is a possible solution to repair root damage and help in biomass accumulation.

However, the interaction between roots and AMF is symbiotic and depends on give and take. When roots are damaged by fissuring, their functions are affected, and it is possible that they cannot provide the photosynthetic assimilates that AMF needs, like carbohydrates. In this scenario, the symbiotic interaction may not take place. Also, the relationship between AMF and the plant roots does not always have to be positive. The scientists were able to resolve this issue by showing that AMF does alleviate the negative effects of root damage due to fissures.

However, the way AMF achieved this remained a mystery. They also did not know the dynamics of the root response to damage and stress symbionts.