The role of phytohormones in the root system response to environmental conditions

During their life cycle, plants form several important anatomical structures in roots, which are crucial for the proper function of the root system and for survival of plant organisms in variable environmental conditions. These structures enable plants to adapt to various stress factors of the environment. Among them, apoplastic barriers are very important. They are formed by cells of the endodermis and exodermis. These cell layers develop Casparian bands and suberin lamellae, modifications of cell walls, that block the apoplastic pathway and are necessary for selective nutrient uptake. Another structure is aerenchyma, a tissue containing many intercellular spaces, which is primarily associated with growth in flooded soils. Development of these structural adaptations is associated with the abscisic acid (ABA) and ethylene. These phytohormones are known mainly for their involvement in stress responses but they are also important in many developmental processes. Work published so far have shown that ABA stimulates deposition of suberin lamellae in the endodermis in unfavourable conditions. Ethylene on the other hand suppresses the deposition of suberin and can even trigger a degradation of previously developed suberin lamellae. In many cases ethylene plays a crucial regulatory role in development of..