PLANT STRESS-INDUCED MORPHOGENIC RESPONSE (SIMR): A STRATEGY OF ACCLIMATION TO ENVIRONMENTAL STRESSES.


Gaëlle Saladin

Abstract:

Plants can acclimate to various environmental stresses by inducing a common physiological response called “stress-induced morphogenic response” (SIMR). This SIMR was observed when plants were exposed to soil pollutions such as metallic trace elements, pesticides or salts, or when soils present an excess of water or a deficiency in several minerals. Moreover, UV-B, ozone or mechanical stress can generate a similar response on plants. SIMR is characterized by a reduction of principal roots and a proliferation of lateral roots and hairy roots. This phenotype is considered as a strategy to avoid stress by increasing root surface in different directions. It was also observed on aerial organs (but less frequently) with a reduction of the main stem and a more branching. This re-orientation of growth is first caused by reactive oxygen species (ROS) which accumulate in root and stem apical meristems and cause lipid peroxidation and lignification. At root level, the consequence is a reduction of mineral absorption and thus a lower growth. Moreover, ROS accumulated in root apical meristem inhibit directly several auxin transporters (or indirectly by modifying pH) and stimulate auxin oxidase, leading to a decrease of auxin concentration in meristem and a subsequent inhibition of cell division. Auxin produced by the aerial organs and transported to roots accumulates then above root meristem and promotes lateral root formation.

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NS05-21-28