Tropisms of Underground Shoots—Stolons and Rhizomes

Abstract

In the review, the problem of plant movements (photo- and gravitropism) is discussed. The contemporary data on physiological and molecular mechanisms of tropisms in underground shoots and roots are presented. Special attention is paid to diagravitropism phenomenon in underground shoots (stolons and rhizomes) that grow in perpendicular direction to the Earth's gravitational axis. The role of phytochrome control in maintaining the horizontal growth of stolons and rhizomes is demonstrated, and physiological mechanisms of photo- and diagravitropism are discussed. It is shown that switching of an underground shoot tip from diatropic to ortotropic (vertical) growth is dependent on the carbohydrate and phytohor-mone balance. The perspectives are outlined for further exploratory studies on mechanisms of growth orientation and morphogenesis of underground diagravitropic shoots.