Morphological and anatomical effects of abscisic acid (ABA) and fluridone (FLU) on the growth of rice mesocotyls

Abstract

It has been reported that abscisic acid (ABA) promotes the growth ofrice mesocotyls. We investigated the effects of ABA and fluridone (FLU), aninhibitor of ABA biosynthesis, on the morphological and anatomicalcharacteristics of the mesocotyl of dark-grown rice seedlings. By 5 days aftersowing (DAS), the mesocotyl of control seedlings had reached their a maximumlength of 50.0 mm. In ABA treated seedlings, the mesocotylcontinued growing until 12 DAS, reaching a length of 152.6 mm.Mesocotyls treated with FLU elongated until 4DAS attaining a final length ofonly 10.5 mm. The data indicated that the greater length ofmesocotyls in seedlings treated with ABA was mainly due to their longer growingperiod. An anatomical study showed that the cell division activity of themesocotyl localised near the coleoptilar node and that ABA prolonged the celldivision activity of the meristem. The results suggested that ABA regulates thegrowth of rice mesocotyls by controlling the activity of the meristem localisednear the coleoptilar node.