Effect of zinc-solubilizing bacteria and organic acids on zinc uptake and growth of rice applied with zinc sulfate

Nur Maizatul Idayu O,M.S Halimi,Radziah O

doi:10.26656/fr.2017.4(s5).009

Abstract

An Investigation on the influence of Zinc-solubilizing bacteria (ZSB) inoculation, Zn fertilizer and organic acids on growth of rice was done at Microbiology lab, Universiti Putra Malaysia. Commercial oxalic acid (BDH), malic acid (SIGMA), citric acid (SIGMA), succinic acid (SIGMA) was used to solubilise Zn oxide, Zn carbonate and Zn sulfate at four different rates (0, 0.1, 1.0 and 10 mM). Selected organic acid and its rate was then combined with ZSB and Zn sulfate using sand culture experiment for rice plant treatment. Highest Zn sulfate solubilisation activity at 0.421 mg/L was found using citric acid as a solubilizer. Similar observation found for malic acid and oxalic acid in Zn sulfate at 0.331 mg/L and 0.249 mg/L respectively. Then, selected organic acids were malic acid and citric acid for plant treatment with Zn-solubilizing bacteria (ZSB) and Zn sulfate. Highest plant biomass was found in inoculated plants treated with 0.1 mM malic acid in the presence of Zn sulfate at 135.67 mg/3 plants. The same treatment was also observed for the highest plant height at 29.57 cm. With the addition of malic acid, the population of the rhizosphere, endosphere and non-rhizosphere varied, but higher than control treatment Application of ZSB inoculation, with Zn sulfate at 0.2 mg/L worked best with malic acid at 0.1 mM concentration due to high increase of rice plant growth parameters, Zn uptake and Zn concentration. Bacterial populations also varied due to different organic acids and their rate

Highlights

Organic acids have good potential to solubilise Zn because both proton and ligand-mediated mechanisms of mobilization play an integral role in the chemical attack on mineral’s surface (Fomina et al, 2005)
The results showed that the application of malic and citric acids highly affected the solubilisation of Zn from zinc sulfate both in the presence and in the absence of zinc-solubilizing bacteria (ZSB) inoculation
There was a significant effect of organic acids rate and Zn types on zinc solubilisation

Summary

Introduction

Organic acids have good potential to solubilise Zn because both proton and ligand-mediated mechanisms of mobilization play an integral role in the chemical attack on mineral’s surface (Fomina et al, 2005). Plant roots release organic acids into the rhizosphere. Some of these organic acids like citric acid and malic acid are intermediates in the tricarboxylic (TCA) cycle for energy production while malic acid, malonate acid and oxalic acid are primarily present in cells for cation charge (Uren, 2000). Solubilisation of zinc sulfate is dependent on exudation of citrate from rice in a small amount. Organic acids are more advantageous than highmolecular-weight compounds as they are mobile and readily assimilated by a wide range of microorganisms like zinc-solubilizing bacteria (ZSB) (Szmigielska et al, 1985; Robert, 1986). Previous studies showed that ZSB produced high organic acids during zinc sulfate solubilisation but it varied during the plant growth period

Methods

Results

Discussion

Conclusion