Iron Nutrition in Plants and Rhizospheric Microorganisms

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Therefore, in order to overcome potential bacterial failure, the use of bacterial metabolites appears as an encouraging alternative.

Iron nutrition in plants and rhizospheric microorganisms [2006]

Two siderophore-producing bacterial strains were studied; Chryseobacterium spp. C isolated from the rhizosphere of Oryza sativa unpublished and Pseudomonas fluorescens N Bacterial strains were grown in modified M9 medium MM9 without added iron Alexander and Zuberer The composition of this media was KH 2 PO 4 0.

Siderophore content was checked as described in " Siderophore production media, quantitative determination and iron-binding capacity " section. Tomato seeds of Lycopersicon esculentum var.

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Thirty-five days after the emergence, when the upper leaves turned yellow, treatments were delivered as follows: Seven days after treatment delivery, plants were harvested and dried for further nutrient determination. The following determinations were done: For nutritional analyses, plants from each treatment were pooled, and analyses were carried out on the mixture of expanded upper leaves of each plant. Total N was analyzed by Kjeldhal digestion.

Nutritional analyses were carried out by Albion Laboratories. Chlorophyll content was determined on the last fully expanded leaf of plants from each treatment. Determination was done according to Lichtenthaler and Buschmann During the incubation period, pH decreased with C by 1. Siderophore production by C was more abundant and, therefore, it was selected for further experiments. UV—Vis spectra of bacterial culture filtrates revealed that the nature of the siderophore produced by each strain was different, while C filtrate does not absorb light in visible region while N Data obtained from biometrical analysis of tomato plants appear in Fig.

Bacterial siderophores with BS or without bacteria S , both supplemented with Fe affected biometrical features of plants. Values of stem diameter and shoot dry weight were significantly higher in treated plants than in the negative controls iron-free Hoagland solution and water. Shoot length and weight were affected differentially by the siderophore S or the bacteria BS. Conversely, shoot dry weight was highest on bacterial BS -treated plants 0.

Interestingly, delivering living bacteria BS to the plants resulted in a significant increase in shoot dry weight, comparing to full Hoagland solution-treated plants H. Chlorophyll content analysis showed non-significant differences in total chlorophylls between siderophore treatments S or BS and the Hoagland-treated plants Fig.

The nutritional status of plants is shown in Fig.


The amounts of copper, boron, aluminium and sodium were highest in S-treated plants. Interestingly, aluminium uptake was moderate under bacterial influence and peaked on S-treated plants. Iron is an essential element for plants, and, therefore, it is absolutely necessary to close plant cycle.

Hence, relevance in agriculture is beyond any doubt, especially since its solubility is conditioned by pH. Although the high concentrations of EDTA itself are not toxic for humans, the main risk remains in its ability to bind heavy and toxic metals and rend them water soluble, therefore, contaminating drinking water Kaparullina et al. In view of this, it is vital to find alternative ways to deliver iron to the plants which are sensitive to iron deficiency.

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Furthermore, organic farming and ecological agriculture call for a natural product able to cover up the needs in these handling procedures. In this experiment, the production of organic chelates by two PGPR strains was evaluated in an iron-free medium, seeking the induction of siderophore production. The two strains were selected for their excellent results obtained on CAS agar medium plates Ramos-Solano et al.

The yellow-orange halos on CAS agar medium produced by C and the quick change of colour of CAS reagent suggest that it is of the catechol type Schwyn and Neilands However, its chemical structure has not been determined yet. According to UV—Vis spectra of bacterial culture filtrates Fig.

Bioassay on iron-starved tomato plants revealed that iron-chelated bacterial siderophores were suitable for plants. Plants treated with bacterial chelates S and BS showed better growth parameters than plants deprived of any Fe source, reaching similar values than plants supplied with full Hoagland solution Fig. Interestingly, delivering siderophores and bacteria to plants BS resulted in a significant increase in shoot dry weight, compared to full Hoagland solution H , and higher than plants treated only with siderophores S , indicating that the bacteria are conferring an additional benefit to the plant other than providing Fe-chelates.

Although in vitro test for auxin production or ACC degradation was recorded negative for C unpublished , production of plant growth regulators is within the putative mechanisms of plant growth promotion. Despite the negative record for auxin production by C, it is a fact that the effective amount of a plant growth regulator is conditioned by the plant species, physiological status and concentration of other plant growth regulators Peleg and Blumwald Plant dry matter was well correlated with chlorophyll concentration in the upper leaves Fig. Nutritional analysis of shoots confirmed the improved iron uptake by siderophore-treated plants.

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  8. Although the fate of the siderophore has not been evaluated yet, the similar efficiency of the organic and chemical agents appears as a promising alternative to reduce chemical inputs due to Fe chemical fertilization Orera et al. A positive side effect was also observed for N, P, K and Na, indicating that a fast recovery of nutrients was occurring in BS-treated plants Nikolic et al. Since the siderophore was provided to plants with Fe, effects should only refer to this ion. However, in addition to increased Fe levels on plants treated with the culture filtrate S or with the bacteria BS , a strong side effect is evidenced for aluminium, specially marked in the case of the culture filtrate S as compared to the bacterial treatment BS , and similar to that of full Hoagland solution.

    This supports the notion of siderophores being able to bind Fe and other metals with variable specificity Schalk et al. It has been described how plants follow two strategies to solubilise unavailable Fe III forms from soil. In addition, plants manage to select microorganisms able to release siderophores into their rhizosphere Ramos-Solano et al. However, despite its well-demonstrated effect to provide iron to plants Crowley et al. According to our results, it seems feasible that the bacterial siderophore is not absorbed by the plant, and iron is obtained through a reduction-based mechanism Cesco et al.

    Rare and Exotic Orchids Joel L. Plants and Microclimate Hamlyn G. Making Eden David Beerling. Scripture, Culture, and Agriculture Ellen F.

    Iron Nutrition in Plants and Rhizospheric Microorganisms - Google Книги

    Flora Unveiled Lee Taiz. Seaweed Ecology and Physiology Kai Bischof. Carnivorous Plants Lubomir Adamec. Healthy Crops Francis Chaboussou. Multiaged Silviculture Kevin O'Hara. Physiological Plant Ecology Walter Larcher. Monarchs and Milkweed Anurag Agrawal. The Botany of Mangroves P. Ecological Statistics Vinicio J. Organism and Environment Sonia E. The Economy of Nature Robert E. Biological Diversity Brian J. Introduction to Bryophytes Bernard Goffinet.


    The arrows indicate a common band determined to be plastid DNA top arrow and a second predominant band bottom arrow that was cloned and sequenced for all root locations. Ordination diagram of microbial communities associated with different root locations on iron-stressed and nonstressed barley plants generated by correspondence analysis of 16S rDNA profiles for individual root segments and adhering rhizosphere soil. Each profile shown was generated from root tips of replicate plants in different containers.

    The profiles reveal the very consistent community structure associated with this root zone and the impact of iron stress on community species composition. Canonical correspondence analysis, showing the relative similarities of microbial communities associated with specific barley root locations as affected by plant iron nutritional status. Iron is included as a covariable on the x axis. A New root tips. B Secondary, nongrowing root tips. C Sites of lateral root emergence.