Morphogenic effects of abiotic stress: Reorientation of growth in Arabidopsis thaliana seedlings

Abiotic stress responses include changes in physiological and biochemical processes as well as morphological and developmental patterns. It has remained an enigma which mechanisms are responsible for stress-induced morphogenesis. In this paper we demonstrate that stress induced phenotypes comprise a re-orientation rather than a cessation of growth. Moreover, strong similarities between the phenotypes induced by excess copper, paraquat, salicylic acid and a hydrogen peroxide analogue, indicate that a common molecular-physiological response system mediates these morphogenic stress responses. It is proposed that reactive oxygen species play a key role in controlling the architectural changes in stressed Arabidopsis thaliana seedlings. We found that phenotypes of plants exposed to stress resemble, in terms of the redistribution of growth, plants altered in phytohormone metabolism. We also found that plants in which polar auxin transport is blocked with TIBA, strongly resemble, but are not identical to, plants exposed to abiotic stress. Based on the stress induced formation of lateral roots, we surmise that stress induces local auxin accumulation near the root pericycle.