EFFECT OF SILICON APPLICATION ON SORGHUM ROOT RESPONSES TO WATER STRESS

Abstract

To analyze how silicon (Si) fertilizer improves plant growth under water stress, we investigated the growth and root responses of sorghum seedlings to Si application. Seedlings were grown hydroponically at two Si levels (0 and 1.78 mM) and under two water stress conditions simulated with polyethylene glycol. The reduction in dry weight due to stress was alleviated by Si application, accompanied by an increase in root water uptake. Silicon application decreased the osmotic potential of the roots without affecting their water content, showing that osmotic adjustment occurred to increase water uptake. An assessment of root solutes suggested that soluble sugar and amino acids (alanine and glutamic acid) were osmolytes responsible for this adjustment. Root anatomical traits related to water transport were not affected by the Si application. These results improved our understanding of the physiological mechanisms that underlie the Si-induced increases in sorghum growth and water uptake under water stress.

Keywords:

• root
• silicon
• sorghum
• water uptake
• water stress

ACKNOWLEDGMENT

This study was supported by a grant from the 21st Century Center of Excellence (COE) program of the Japan Society for the Promotion of Science.