Rhizosphere properties of rice genotypes as influenced by anoxia and availability of zinc and iron

Roghieh Hajiboland,Naier Beiramzadeh

doi:10.1590/s0100-204x2008000500009

Abstract

The objective of this work was to study possible mechanisms involved in root-induced changes of rhizosphere physicochemical properties of rice genotypes, under anoxia and low supply of Zn and Fe. Two rice genotypes, including an upland and a lowland ones, were grown in hydroponic medium under adequate and low supply of Zn and Fe, with or without aeration. Anoxia increased shoot dry weight, root length and uptake of Zn and Fe in lowland Amol genotype, but reduced these parameters in upland Gasrol-Dashti genotype. The amount of oxygen released by roots was statistically higher in 'Amol'. The highest acidification potential of roots was observed in the lowland genotype under low supply of Zn, and in the upland genotype under Fe starvation. The highest oxalate (only organic acid detected) exudation from roots was observed in Zn and Fe deficient Gasrol-Dashti genotype. Zinc deficiency caused reduction of alcohol dehydrogenase and stimulation of lactate dehydrogenase activity, particularly in shoot. The ability to induce changes in the rhizosphere properties has a great contribution for the adaptation of both lowland and upland rice genotypes to specific soil conditions.

Highlights

Zinc deficiency is found to be a widespread phenomenon in lowland (Quijano-Guerta et al, 2002) and upland rice (Fageria & Baligar, 2005); and Fe deficiency is a common disorder of rice growing on well drained soils (Nerkar et al, 1984), whether these are neutral, calcareous or alkaline
The objective of this work was to investigate possible mechanisms involved in root-induced changes of rhizosphere physicochemical properties in two contrasting rice genotypes
Higher acidification potential of roots in lowland genotype, under Zn deficiency conditions, is an important factor in adaptation to soils with sparingly available Zn; in contrast, release of oxalate under low supply of Zn is a mechanism for adaptation in upland genotype

Summary

Introduction

Zinc deficiency is found to be a widespread phenomenon in lowland (Quijano-Guerta et al, 2002) and upland rice (Fageria & Baligar, 2005); and Fe deficiency is a common disorder of rice growing on well drained soils (Nerkar et al, 1984), whether these are neutral, calcareous or alkaline. Most of the world’s rice is cultivated under irrigated or rainfed lowland conditions. Under reductive conditions in flooded soils, the availability of Zn is extremely low, due to formation of Zn sulfide, which presents very low solubility, and adsorption or co-precipitation of Zn onto calcium carbonate particles, in the presence of a large amount of carbon dioxide. Beiramzadeh the most widespread nutrient disorder in lowland rice (Quijano-Guerta et al, 2002)

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