Soils and Rice-Fields

DOI: 10.1007/0-306-46855-7_8

ABSTRACT Cyanobacteria are an important component of many soils. including the surface crusts that sometimes cover extensive areas
in semiarid regions and mine spoil wastes. They are also abundant in many areas which are wet or submerged for part of the
year. especially rice-fields. Most soils forms have sheaths or mucilage and this polysaccharide has important effects onthe
soil. mostly beneficial. such as improved soil structure. but sometimes adverse where a dense surface layer impedes drainage.
Nitrogen-fixing species often constitute half or more of the species present in soils not enriched with nitrogenous fertilizer
and these can contribute combined nitrogen in several ways to adjacent vascular plants.

Attempts to enhance crop yield by adding cyanobacteria to soils have mostly focussed on paddy rice. Although many studies
have reported positive effects of such ‘algalization’. the number of locations where it has been adopted as routine practice
appear to be few. in contrast to the relatively widespread use of Azolla with rice culture. Algalization is most successful where local species are used to prepare the inoculum. but there is considerable
scope for other improvements. It is important to obtain a much more detailed understanding of cyanobacterial population dynamics
over the whole annual cycle in agricultural systems where rice is grown for only part of the year.

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    ABSTRACT: Four non-heterocystous cyanobacterial strains isolated from rhizosphere and soil surface mat of rice, wheat, and maize were identified by 16S rRNA gene sequencing and evaluated for auxin production as well as growth promotion of wheat. Isolated strains produced a diverse amount of auxin in BG11 media supplemented with different concentrations of L-tryptophan. The amount of auxin detected with colorimetric methods was higher as compared to GC-MS analysis. Auxin production by cyanobacterial strains in BG 11 medium supplemented with 250 µg ml(-1) L-tryptophan ranged from 0.20 to 1.63 µg ml(-1) IAA as revealed by gas chromatography and mass spectrometric (GC-MS) analysis. In a hydroponic growth system, the vegetative growth of wheat was stimulated appreciably by inoculation with cyanobacterial strains. The endogenous auxin content of wheat was significantly correlated with the exogenous auxin production of the cyanobacterial strains. It was observed that cyanobacterial strains produced more endogenous and exogenous auxin in the presence of a plant, showing that plants might be releasing some signals responsible for higher auxin production by cyanobacterial cultures. It was concluded that the auxin producing potential of cyanobacterial strains can be exploited for the promotion of wheat growth.
    Journal of Basic Microbiology 12/2013; 53(12). DOI:10.1002/jobm.201100563 · 1.20 Impact Factor
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    ABSTRACT: Phosphorous (P) starved cells of the cyanobacterium Anabaena oryzae showed higher phosphate uptake rates than P-sufficient cells. The P-uptake obeyed saturation kinetics. The Km value for P-deficient cells was lower (54.34 μM) than P-sufficient cells (82.64 μM) while Vmax was higher in P-deficient and lower in P-sufficient cells. Salinity (NaCl) stimulated phosphate uptake significantly in the cyanobacterium which is followed by greater amount of P-accumulation in the form of polyphosphate bodies. Inhibition of P-uptake in P-deficient cells was 45% in dark grown compared to light grown cells. P-uptake was inhibited 52 and 85% in culture treated with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU; 10 μM) and carbonyl cyanide m chloro phenylhydrazone (CCCP; 100 μM), respectively, suggesting that energy for uptake could be derivedfrom oxidative phosphorylation and photophosphorelation.
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    ABSTRACT: Studies of cyanobacterial nostocacean taxa are important to the global scientific community, mainly because a significant number of beneficial strains that belong to the order Nostocales fix atmospheric nitrogen, thus contributing to the fertility of agricultural soils worldwide, while others behave as nuisance microorganisms in aquatic ecosystems due to their involvement in toxic bloom events. However, in spite of their ecological importance and environmental concerns, their identification and taxonomy are still problematic and doubtful, often being based on current morphological and physiological studies, which generate confusing classification systems and usually vary under different conditions. Therefore, the present research aimed to investigate through a polyphasic approach differences in morphological, biochemical and genotypic features of three nostocacean cyanobacterial strains isolated from central-western Portuguese shallow freshwater bodies. Morphometric, genetic (16S rRNA, nifH and hetR fragments) and biochemical (fatty acid methyl ester; FAME profiles) data were used to characterize the strains. Morphological analysis and sequencing of 16S rRNA fragments showed that the strains belonged to Anabaena cylindrica (UTAD_A212), Aphanizomenon gracile (UADFA16) and Nostoc muscorum (UTAD_N213) species. These strains showed clear distinct morphological and genetic features, allowing easy allocation to their respective genera. The same happened by using partial sequences of hetR and nifH genes, in spite of the scarcity of deposited sequences. Biochemical characterization showed that the FAME profiles obtained were consistent with both morphological and molecular analyses. It was suggested that the ratio of monounsaturated to polyunsaturated FAMEs, together with the unsaturation index, could be used as genus-specific chemotaxonomic biomarkers. KeywordsPolyphasic taxonomy–Cyanobacteria– 16S rRNA – hetR – nifH –Fatty acid methyl esters
    Hydrobiologia 01/2011; 663(1):187-203. DOI:10.1007/s10750-010-0572-5 · 2.21 Impact Factor


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Jan 24, 2015