100,567 research outputs found
Rhizodeposition of Zea mays L. as affected by heterosis
No full textThe objective of the present work was to investigate in a field experiment the quantity and quality of rhizodeposits of different parental inbred lines (Lo1016 and Lo964, B73 and H99) and hybrids of Zea mays L. Rhizosphere soil was collected after 40 days and several properties were determined: pH, organic carbon, total nitrogen, acid and alkaline phosphatases, organic acids, bioavailable phosphorous, a-amino nitrogen, total phenols, total root-derived rhizodeposits. The results showed that heterosis
induced more qualitative differences within the genotypes as d13C, TOC and TN did not show any significant differences. The two groups of genotypes enhance phosphorous availability adopting two different strategies. In the first group, B736H99 shows the best phenological performance as well as the highest concentration of bioavailable P, result which is correlated with a high organic acid
concentration (in particular succinic and acetic acid), total phenols, a-amino nitrogen and acid phosphatase activity. There is thus a strict relationship between the phenological superiority of this particular hybrid and its ability to modify the chemistry of its rhizosphere whereas the second hybrid (Lo10166Lo964) seems to have developed different strategies as for example changing the root morphology, stimulating microbial biomass or favouring mycorrhizal symbiosis
La sostenibilità del modello glocale. Per una pedagogia dell’abitare.
No full textThe glocal dimension constitutes a virtuous example of anthropological sustainability of our age, not only as a socio-economic phenomenon but above all as a cultural and educational resource. It can be thought of as a pacification of identity between globalisms and localisms, giving rise to a new way of perceiving the concept of world citizenship that would probably constitute a solution and a noble compromise to the social tensions that the local/global dichotomy generates in the international arena.La dimensione glocale, non solo come fenomeno socio-economico ma soprattutto come risorsa culturale ed educativa, costituisce un esempio virtuoso di sostenibilità antropologica del nostro tempo. Essa può essere pensata come una pacificazione identitaria tra globalismi e localismi, dando vita a un nuovo modo di percepire il concetto di cittadinanza mondiale che probabilmente costituirebbe una soluzione e un compromesso nobile alle tensioni sociali che in ambito internazionale la dicotomia locale/globale genera
Organic acid extraction from rhizosphere soil: effect of field-moist, dried and frozen samples
No full textThis study investigates the effect of soil
treatment and storage on organic acid extraction.
For this study one clayey-loamy (Typic Udochrept) and
one sandy-loamy (Aquic Ustifluvent) soil were selected
and used to grow Lupinus albus L. plants in a climate
chamber. After 4 weeks the rhizosphere soil was
sampled and divided into five portions: (a) field moist,
no storage; (b) air-dried; (c) oven-dried, (d) field-moist
at +4°C for 8 weeks; (e) field-moist at −20°C for
8 weeks. Organic acid extraction (1:4 w/v) was carried
out for each soil portion both in water and in 10 mM
NaH2PO4. Organic acid concentration was subsequently
determined by reversed-phase high performance
liquid chromatography (HPLC). Oxalic,
fumaric, malonic and α-ketoglutaric acid were identified
in the rhizosphere of both soils but the extractable
concentration was significantly higher in the sandyloamy
soil. For both soils NaH2PO4 extracted significantly
higher organic acid concentrations than water.
Oven drying increased the extractability of organic
acids in both soils. Field moist samples (i.e. where no
storage occurred) of the sandy-loamy soil showed a
similar behaviour than −20° stored samples whereas
the one of the sandy-loamy soil were more close to the
air-dried samples. These results indicate that organic
acid extraction strongly depends on soil storage as
well as on the soil type. Sample storage seems thus to
be a crucial issue for the determination of organic
acids in rhizosphere soil and needs to be considered
prior analysis
Does the degree of pectin esterification influence aluminium sorption by the root apoplast?
No full textAbstract This study investigates the influence of the
degree of pectin esterification (DE) on the sorption of
aluminium (Al) by plant roots. Ca-pectates, with
varying degrees of esterification, are major constituents
of the soil–root interface and of the root apoplast. Capectate
networks (Ca–PG and Ca–Al–PG) were formed
at three DEs (0%, 26%, 65%) with custom-made cells
and used as a model system for the root cell wall.
Sorption of Al was conducted for 24 h at a range of
oxalic acid concentrations (0–500 μM) at pH 4.50 to
examine two different metal resistance mechanisms of
plants. In fact, plants release organic acids either to
desorb or to complex metals to prevent their sorption by
plant roots.Thermal analysis showed that Al sorption
did not seem to affect the stability of the pectate gels and
the presence of hydrophobic groups (–CH3) at DE>0%
seemed to even increase the stability of the gels
decreasing thermal decomposition. Results suggest
two potential Al tolerance mechanisms: (a) high oxalic
acid concentrations (500 μM) were able to desorb
almost 100% and 72% at DE 65 and 0%, respectively;
(b) high oxalic acid concentrations (500 μM) and thus
molar ratios of 5:1 (oxalate/Al) reduced Al sorption by
98% and 86% at DE 65 and 0%, respectively. In
conclusion, both mechanisms indicate that high
degrees of esterification as 65% are much more
efficient in excluding Al from the apoplast and might
therefore contribute to Al resistance in plants
Dynamics, thermodynamics and kinetics of exudates: crucial issues in understanding rhizosphere processes
No full textBackground: In this issue, Schenkeveld and coworkers described the potential of phytosiderophores (a class of root exudates) to mobilize metals in the rhizosphere by an equilibrium modelling approach.
Scope: The rhizosphere is a complex and dynamic environment where several different organic and inorganic compounds coexist. Due to the different concentration and chemical characteristics there might be competitive and synergistic interactions. However the rhizosphere is strongly influenced by root activity: water and nutrient uptake, root respiration that might modify the pH and redox status of the rhizosphere. Thus, how does the complexity of the system and the dynamics influence the thermodynamics of the single process? Can chemical equilibria be really reached in the rhizosphere? Issues related to kinetics vs thermodynamics are discussed. The study of the single processes is important but more complex researches, being thus more realistic (i.e. field-like conditions), are necessary. Hence, what are the available tools/methods in rhizosphere research? What are the drawbacks? How can the results of these methods be related to thermodynamic and kinetic models?
Conclusions: Besides stimulating further awareness around the rhizosphere complexity, tentative answers are given highlighting the future challenges in rhizosphere research, essential knowledge for the development of agronomic practices ensuring a better exploitation of soil endogenous resources of nutrients by crops
Tendril-based climbing plants to model, simulate and create bio-inspired robotic systems
No full textBioinspiration can be considered one of the keys for future smart and versatile robotic systems. Plants could be an important source of ideas despite the fact that they have not yet been deeply observed and considered. In this paper, climbing tendril-bearer plants that, by means of irritable filiform organs called tendrils, search for a support, grasp it and climb to gain height, have been used to study and develop an effective climbing robot. The study aimed first to evaluate the main movements and behaviors of the tendril from a biomimetic point of view. The tendril complexity was then simplified, a robotic model was developed and a kinematic simulator was designed and implemented to visualize and evaluate the chosen system. Finally, based on the biological, technical and numerical evaluations, the main tendril behaviors were replicated by proof of concept devices made of smart materials to move towards a practical realization and to replicate the simulated results. The designed proof of concept prototypes showed good repeatability and feasibility
Phosphorus deficiency changes carbon isotope fractionation and triggers exudate reacquisition in tomato plants
No full textPlant roots are able to exude vast amounts of metabolites into the rhizosphere in response to phosphorus (P) deficiency. Causing noteworthy costs in terms of energy and carbon (C) for the plants. Therefore, it is suggested that exudates reacquisition by roots could represent an energy saving strategy of plants. This study aimed at investigating the effect of P deficiency on the ability of hydroponically grown tomato plants to re-acquire specific compounds generally present in root exudates by using 13C-labelled molecules. Results showed that P deficient tomato plants were able to take up citrate (+ 37%) and malate (+ 37%), particularly when compared to controls. While glycine (+ 42%) and fructose (+ 49%) uptake was enhanced in P shortage, glucose acquisition was not affected by the nutritional status. Unexpectedly, results also showed that P deficiency leads to a 13C enrichment in both tomato roots and shoots over time (shoots—+ 2.66‰, roots—+ 2.64‰, compared to control plants), probably due to stomata closure triggered by P deficiency. These findings highlight that tomato plants are able to take up a wide range of metabolites belonging to root exudates, thus maximizing C trade off. This trait is particularly evident when plants grew in P deficiency. © 2020, The Author(s)
Ca-polygalacturonate as a useful model to study the interaction of ions at the soil-root interface: aluminium as a case study.
No full textThis chapter presents results of the adsorption of aluminium and its influence on the mobility of nutrients, in particular phosphate at the soil-root interface. Ca-polygalacturonate (Ca-PG) is the major constituent of the root mucilage and thus the soil-root interface. A Ca-PG network, which resembles the natural root mucilages and thus constitutes a good system model of natural systems, was used to study the interaction with aluminium. The first part of the chapter discusses the effect of aluminium adsorption on the structure of a Ca-membrane. The Ca-PG membrane is organised in a fibrillar and porous network acting as a bio-filter for ions and water and playing thereby a fundamental role in plant nutrition. Metal sorption alters this fibrillar structure and consequently its functionality. Structural modifications determined by FT-IR spectroscopy, Thermogravimetric (TG), Differential Thermal Analysis (DTA) and Scanning electron microscopy (SEM) are described. The final part of the chapter examines alterations induced by aluminium of the functionality of the root mucilage
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