196,061 research outputs found
Root foraging and avoidance in hyperaccumulator and excluder plants: a rhizotron experiment
No full textAims: Metal hyperaccumulation is a rare phenomenon described for an increasing number of plant taxa. In this study we investigated the root growth responses of the well-known nickel, zinc, cadmium hyperaccumulator Noccaea caerulescens and of the metal tolerant (non-accumulator) Stellaria media, in order to observe root foraging vs avoidance responses to nickel. Methods: To allow for observations of root growth and foraging preferences, two accessions of Noccaea caerulescens and two accessions of Stellaria media orginating from high nickel and low nickel habitats were grown in rhizotrons with localized nickel enrichment. Results: The root density in the control and nickel-enriched soil areas in the rhizotrons with different N. caerulescens accessions had distinct responses: moderate nickel avoidance was recorded for the non-nickel accession, while a clear foraging response was observed in N. caerulescens from the nickel accession. In contrast, nickel rooting avoidance was observed for both S. media accessions and was more pronounced in the non-nickel accession. Conclusions: This study shows that N. caerulescens originating from different accessions responded differently to soil nickel enrichment, with the nickel accession of N. caerulescens actively foraging for nickel, suggesting a physiological adaptation and demand for this metal. In contrast, a clear nickel avoidance response by a metal tolerant species, S. media, was observed in this study, a phenomenon which has not been previously described; this suggests that root avoidance responses might play a role in the adaptation of metal tolerant species to Ni-rich soils
Accumulation of cadmium, zinc and copper by Helianthus annuus L.: impact on plant grawth and uptake of nutritional elements
No full textWe investigated the effects on physiological response, trace elements and nutrients accumulation
of sunflower plants grown in soil contaminated with: 5 mg kg−1 of Cd; 5 and 300 mg
kg−1 of Cd and Zn, respectively; 5, 300, and 400 mg kg−1 of Cd, Zn, and Cu, respectively.
Contaminants applied did not produce large effects on growth, except in Cd-Zn-Cu treatment
in which leaf area and total dry matter were reduced, by 15%. The contamination with
Cd alone did not affect neither growth nor physiological parameters, despite considerable
amounts of Cd accumulated in roots and older leaves, with a high bioconcentration factor
from soil to plant. By adding Zn and then Cu to Cd in soil, significant were the toxic effects
on chlorophyll content and water relations due to greater accumulation of trace elements in
tissues, with imbalances in nutrients uptake. Highly significant was the interaction between
shoot elements concentration (Cd, Zn, Cu, Fe, Mg, K, Ca) and treatments. Heavy metals
concentrations in roots always exceeded those in stem and leaves, with a lower translocation
from roots to shoots, suggesting a strategy of sunflower to compartmentalise the potentially
toxic elements in physiologically less active parts in order to preserve younger tissues
Assessment of cadmium uptake and nutrient content in sunflower plants grown under Cd stress
No full textCadmium accumulation and physiological response of sunflower plants to Cd during the vegetative growing cycle
No full textThe effects of soil Cd contamination on Cd accumulation and distribution, growth and physiological responses of sunflower plants were investigated. Plants were subject to six levels of soil contamination (from 2.5 to 15 mg Cd kg/soil) with an untreated control, from the emergence of the cotyledon leaves until the harvest, when plants were at the flower bud stage. An overall increase of Cd concentration was found in all tissues of the plants (roots, stem, young, mature and old leaves) by increasing the Cd contamination in the soil. Regardless of treatments, Cd concentration in roots always exceeded those in the aboveground dry matter with a low translocation from roots to shoots. At early stage of growth, Cd concentration in plants was higher than at the flower bud stage. Soil Cd contamination did not affect plant growth, relative water content and gas exchange parameters. Negative and significant correlation was only found between Cd concentration in the young leaves and chlorophyll concentration at the end of vegetative growing stage. Roots and old leaves are the main metal sinks suggesting a defense or tolerance mechanism of the plants to avoid toxic levels in physiologically most active apical tissues.
These results should be tested in open field to verify the suitability of sunflower in the area of phytotechnologies
Aluminium-phosphate interactions in the rhizosphere of two bean species: Phaseolus lunatus L. and Phaseolus vulgaris L.
No full textBACKGROUND:
Plants differ in their response to high aluminium (Al) concentrations which typically cause toxicity in plants grown on acidic soils. The response depends on plant species and environmental conditions such as substrate and cultivation system. The present study aimed to assess Al-phosphate (P) dynamics in the rhizosphere of two bean species, Phaseolus vulgaris L.
var. Red Kidney and Phaseolus lunatus L., in rhizobox experiments.
RESULTS:
Root activity of the bean species induced up to a 7-fold increase in exchangeable Al and up to a 30-fold decrease of extractable P. High soluble Al concentrations triggered the release of plantspecific carboxylates, which differed between soil type and plant species. The results suggest that P. vulgaris L. mitigates Al stress by an internal defence mechanism and P. lunatus L. by an external one, both mechanisms involving organic acids.
CONCLUSION:
Rhizosphere mechanisms involved in Al detoxification were found to be different for P. vulgaris L. and P. lunatus L., suggesting that these processes are plant species specific. P. vulgaris L.
accumulates Al in the shoots (internal tolerance mechanism) while P. lunatus L. prevents Al
uptake by releasing organic acids (exclusion mechanism) into the growth media
Microbial community structure and proteolytic activity in the rhizosphere of maize plants differing in nitrogen use efficiency
No full textThe rhizosphere, the thin soil layer influenced by the presence of plant roots has different physico-chemical properties from the bulk soil because of the active or passive rhizodepositions, which sustain larger and more active microbial populations in the rhizosphere than in bulk soil, and this plays a key role in soil organic matter decomposition and nutrient solubilization. The rhizosphere is chemically complex and dynamic microenvironment and this makes it difficult to study. Progresses in the study of the rhizosphere can be achieved by using rhizoboxes allowing the plant growth and precise sampling of rhizosphere. Plants select microbial bacterial and fungal populations in the rhizosphere during the plant growth, and while plant mechanisms involved in increased N uptake efficiency have been clarified, the importance of the rhizosphere microbial communities in nutrient availability to plants are still poorly understood.
Nitrogen is the main nutrient limiting the plant growth and the crop yields and today, the nitrogen use efficiency (NUE) of crops at field scale is still relatively low, with detrimental effects on groundwater quality and atmosphere due to NO3- leaching and NH3 and nitrous oxide emissions caused be excessive fertilization, and large efforts have been carried out to increase the NUE to enhance the crop production and reduce the environmental impact of agriculture, especially through plant breeding and preparation of fertilizers with slow N release.
We evaluated the changes in the biochemical activity and microbial community structure induced by the inbred maize (Zea mais L.) lines Lo5 and T250 characterized by high and low NUE using rhizobox experiments. The adopted experimental approach allowed to describe the relative plant induced changes on the different rhizosphere chemical and microbiological components and provide information to improve the crop NUE. In this work we studied the changes in the biochemical activity and microbial community structure in the rhizosphere of the inbred maize (Zea mais L.) lines Lo5 and T250 characterized by high and low NUE, repectively, using rhizobox experiments. Because of the importance of the proteolytic activity in soil N mineralization, the proteolytic activity in the rhizosphere of the two maize lines was also studied by the assessment of the diversity and abundance of the apr and npr genes coding for coding for alkaline protease and neutral metalloprotease, respectively, and determination of the protease activity.
The results showed that the Lo5 plant, having the higher NUE, induced the greater modification in the rhizosphere chemical properties, induced significantly faster depletion of inorganic N, higher bacteria diversity, proteolytic populations and protease activity. The importance of the plant activity in modifying microbial community structure, protease functions and rhizosphere biochemical activity will be presented
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
Identification of specific interactions between bacteria and heavy metals accumulating plants
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Interactions between accumulation of trace elements and macronutrients in Salix caprea after inoculation with rhizosphere microorganisms.
No full textAlthough the beneficial effects on growth and trace element accumulation in Salix spp. inoculated with
microbes are well known, little information is available on the interactions among trace elements and
macronutrients. The main purpose of this study was to assess the effect of phytoaugmentation with
the rhizobacteria Agromyces sp., Streptomyces sp., and the combination of each of them with the fungus
Cadophora finlandica on biomass production and the accumulation of selected trace elements (Zn, Cd, Fe)
and macronutrients (Ca, K, P and Mg) in Salix caprea grown on a moderately polluted soil. Dry matter production
was significantly enhanced only upon inoculation with Agromyces sp. Regarding the phytoextraction
of Cd and Zn, shoot concentrations were mostly increased after inoculation with Streptomyces sp. and
Agromyces sp. + C. finlandica. These two treatments also showed higher translocation factors from roots to
the leaves for both Cd and Zn. The accumulation of Cd and Zn in shoots was related to increased concentrations
of K. This suggests that microorganisms that contribute to enhanced phytoextraction of Cd and
Zn affect also the solubility and thus phytoavailability of K. This study suggests that the phytoextraction
of Zn and Cd can be improved by inoculation with selected microbial strains
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