Vertical distribution of sodium in roots of rice plants exposed to salinity as analyzed by cryo time-of-flight secondary ion mass spectrometry

Abstract

Distribution of Na+ along the root axis under salinity stress was analyzed in two rice (Oryza sativa L.) cultivars with different salt resistance (salt-sensitive IR 24 and salt-resistant Pokkali). Rice plants were grown hydroponically and NaCl was applied with nutrient solution at concentrations of 0, 25 and 50 mM for 7 d after germination. The distribution of Na+ in roots under salinity was analyzed by the cryo time-of-fl ight secondary ion mass spectrometry (cryo TOF-SIMS). The Na+ content in the root was higher in salt-sensitive IR 24 than in salt-resistant Pokkali under NaCl stress. The content was highest at the root tip and was decreased basipetally along the root axis. The difference in Na+ content between the cultivars was apparent in all regions from the root tip.