Role of Phi Cells Under Abiotic Stress in Plants

Abstract

Phi thickening in cortical cells of the roots was discovered in the nineteenth century. Phi thickenings of cell walls can be present in the different cell layers of the cortical cells forming in many cases a continuous cell layer. We have found that more than 100 species present phi thickening in roots, including angiosperms and gymnosperms. A mechanical role was originally suggested for this structure, although it has never been demonstrated. In the last decade, new studies have demonstrated that phi thickening can be altered by the environmental conditions. Different abiotic and biotic stresses may be modifying the distribution, structure and/or development of phi thickening. Abiotic stresses such as salinity, heavy metals and flooding are altering phi thickening distribution and lignification. A physiological role for phi thickenings has also been proposed, acting as a barrier, altering cation movement through the apoplast and regulating the symplastic ion movement through the plasmodesmata system.