Biochemical indicators of root damage in rice (Oryza sativa) genotypes under zinc deficiency stress
Zn deficiency is one of the major soil constraints currently limiting rice production. Although recent studies demonstrated that higher antioxidant activity in leaf tissue effectively protects against Zn deficiency stress, little is known about whether similar tolerance mechanisms operate in root tissue. In this study we explored root-specific responses of different rice genotypes to Zn deficiency. Root solute leakage and biomass reduction, antioxidant activity, and metabolic changes were measured using plants grown in Zn-deficient soil and hydroponics. Solute leakage from roots was higher in sensitive genotypes and linked to membrane damage caused by Zn deficiency-induced oxidative stress. However, total root antioxidant activity was four-fold lower than in leaves and did not differ between sensitive and tolerant genotypes. Root metabolite analysis using gas chromatography–mass spectrometry and high performance liquid chromatography indicated that Zn deficiency triggered the accumulation of glycerol-3-phosphate and acetate in sensitive genotypes, while less or no accumulation was seen in tolerant genotypes. We suggest that these metabolites may serve as biochemical indicators of root damage under Zn deficiency.
KeywordsZn deficiency Oxidative stress Rice Root solute leakage Acetic acid Glycerol-3-phosphate
This research was part of the PhD dissertation of JSL at the College of Agriculture, University of the Philippines Los Baños. The study was partially funded by the SCPRID programme of BBSRC/DIFID (BB/J011584/1) and by IRRI. We wish to thank Sarah E. Johnson-Beebout and Glenn B. Gregorio (IRRI) and Yoshiaki Ueda and Michael Frei (University of Bonn) for their advice during the study; and James A. Egdane, Ricardo L. Eugenio, Myrish A. Pacleb and Francis H. Rubianes (IRRI) for technical support and Fiona R. Hay (IRRI) for English language editing.
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