Sergio Mugnai

HEAVY METAL DISTRIBUTION BETWEEN CONTAMINATED SOIL AND PAULOWNIA TOMENTOSA, IN A PILOT-SCALE ASSISTED PHYTOREMEDIATION STUDY: INFLUENCE OF DIFFERENT COMPLEXING AGENTS

The distribution of Cd, Cu, Pb and Zn between a contaminated soil and the tree species Paulownia tomentosa was investigated in a pilot-scale assisted phytoremediation study. The influence of the addition of EDTA, tartrate and glutamate at 1, 5 and 10mM concentrations on metal accumulation by the plant and on metal mobilization in soil was evaluated. Root/shoot metal concentration ratios were in the range of 3-5 for Zn, 7-17 for Cu, 9-18 for Cd and 11-39 for Pb, depending on the type and concentration of complexing agent. A significant enhancement of metal uptake in response to complexing agent application was mainly obtained in roots for Pb (i.e. 359 mg kg(-1) for EDTA 10mM and 128 mg kg(-1) for the control), Cu (i.e. 594 mg kg(-1) for glutamate 10mM and 146 mg kg(-1) for the control) and, with the exception of glutamate, also for Zn (i.e. 670 mg kg(-1) for tartrate 10mM and 237 mg kg(-1) for the control). Despite its higher metal mobilization capacity, EDTA produced a metal accumulation in plants quite similar to those obtained with tartrate and glutamate. Consequently the concentration gradient between soil pore water and plant tissues does not seem to be the predominant mechanism for metal accumulation in Paulownia tomentosa and a role of the plant should be invoked in the selection of the chemical species taken up. Metal bioavailability in soil at the end of the experiment was higher in the trials treated with EDTA than in those treated with tartrate and glutamate, the latter not being significantly different from the control. These findings indicated the persistence of a leaching risk associated to the use of this chelator, while an increase of the environmental impact is not expected when glutamate and tartrate are applied.

Spatiotemporal dynamics of the electrical network activity in the root apex

The study of electrical network systems, integrated with chemical signaling networks, is becoming a common trend in contemporary biology. Classical techniques are limited to the assessment of signals from doublets or triplets of cells at a fixed temporal bin width. At present, full characteristics of the electrical network distribution and dynamics in plant cells and tissues has not been established. Here, a 60-channels multielectrode array (MEA) is applied to study spatiotemporal characteristics of the electrical network activity of the root apex. Both intense spontaneous electrical activities and stimulation-elicited bursts of locally propagating electrical signals have been observed. Propagation of the spikes indicates the existence of excitable traveling waves in plants, similar to those observed in non-nerve electrogenic tissues of animals. Obtained data reveal synchronous electric activities of root cells emerging in a specific root apex region. The dynamic electrochemical activity of root apex cells is proposed to continuously integrate internal and external signaling for developmental adaptations in a changing environment.

Marine bioactive substances (IPA extract) improve foliar ion uptake and water stress tolerance in potted Vitis vinifera plants

The effect of marine bioactive substances (IPA extract) on K + and Ca 2+ fluxes and water stress tole- rance was evaluated on potted Vitis vinifera plantlets. Different foliar treatments were compared during the experiment: a control treatment (distilled water), a pure fertilizer treatment (9-5-4 at 2%), and a marine bioac - tive substances (IPA extract, supplied by BiotechMarine, Roullier Group, Pontrieux, France) treatment added to a fertilizer (0.1% solution of IPA extract with distilled water and 9-5-4 at 2%). Ion fluxes, measured by selec- tive non-invasive microelectrodes, were monitored in leaves. IPA extract significantly enhanced both potassium and calcium fluxes compared to the other treatments. Total dry weight and macro- and micro-nutrient content were subsequently measured: results showed an improved growth in IPA extract plants, together with a better capacity in accumulating macronutrients in plant organs, but not micronutrients, especially in leaves. Marine bioactive substances were finally tested for their effectiveness in promoting water stress tolerance: IP A extract was very effective in inducing waterstress tolerance, maintaining a higherleaf water potential and stomatal con- ductance during the stress period, and inducing a quick recovery in rehydrated plants.

Phospholipase Dζ2 Drives Vesicular Secretion of Auxin for Its Polar Cell-Cell Transport in the Transition Zone of the Root Apex

Auxin (IAA) is versatile signaling molecule of plants, currently classified as plant hormone. But there are data suggesting that auxin is acting also as plant-specific morphogen, electric-responses inducing transmitter, and as general signaling molecule used for plant-bacteria communication. Our previous data revealed that auxin is associated with secretory endosomes and also highly enriched within cell walls of cells active in transcellular auxin transport. Our present data, based on in vivo non-invasive auxin flux recordings, reveal that auxin is secreted out of synaptic-like domains specialized for efflux of auxin in root apex cells highly active in polar cell-cell transport of auxin. We obtained both genetic and pharmacological evidence that phospholipase Dζ2 drives vesicular secretion of auxin for its polar transcellular transport in the transition zone of the root apex. Secretion of auxin via secretory vesicles has far-reaching consequences not only for our understanding of cell-cell auxin transport but also for plant sciences as a whole.

Local Root Apex Hypoxia Induces NO-Mediated Hypoxic Acclimation of the Entire Root

Roots are very sensitive to hypoxia and adapt effectively to a reduced availability of oxygen in the soil. However, the site of the root where oxygen availability is sensed and how roots acclimate to hypoxia remain unclear. In this study, we found that the root apex transition zone plays central roles in both sensing and adapting to root hypoxia. The exposure of cells of the root apex to hypoxia is sufficient to achieve hypoxic acclimation of the entire root; particularly relevant in this respect is that, of the entire root apex, the transition zone cells show the highest demand for oxygen and also emit the largest amount of nitric oxide (NO). Local root apex-specific oxygen deprivation dramatically inhibits the oxygen influx peak in the transition zone and simultaneously stimulates a local increase in NO emission. The hypoxia-induced efflux of NO is strictly associated with the transition zone and is essential for hypoxic acclimation of the entire root.

Effect of Hypoxic Acclimation on Anoxia Tolerance in Vitis roots: Response of Metabolic Activity and K+ Fluxes

The effect of a hypoxic pre-treatment (HPT) on improving tolerance to prolonged anoxia conditions in two contrasting Vitis species (V. riparia, anoxia tolerant; V. rupestris, anoxia sensitive) was evaluated. The energy economy of root cells was studied by measuring heat production, the activity of pyruvate decarboxylase (PDC) and alcohol dehdrogenase (ADH), ethanol and ATP production, and K(+) fluxes. The results showed that HPT is an effective tool in order to maintain a sustainable metabolic performance in both the species under anoxia conditions, especially in sensitive species such as V. rupestris. Our results showed that the improved tolerance was mainly driven by: (i) an enhanced activity of key enzymes in alcohol fermentation (ADC and PDC); (ii) the capability to maintain a higher level of respiration, evidenced by a lesser decrease in heat development and ATP production; and (iii) the maintenance of a better ion homeostasis (highlighted by measurement of K(+) fluxes) and K(+) channel functionality.

Influence of the Application Renewal of Glutamate and Tartrate on Cd, Cu, Pb and Zn Distribution Between Contaminated Soil and Paulownia Tomentosa in a Pilot-Scale Assisted Phytoremediation Study

The influence of repeated applications of tartrate (TAR) and glutamate (GLU) at 50-mmol kg−1 of soil on Cd, Cu, Pb, and Zn distribution between a contaminated soil and Paulownia tomentosa was investigated. TAR and GLU were applied by a single or a double dosage, the latter carried out with an interval between the two applications of thirty days. The comparison of the differences in mean amounts of metals accumulated in the whole plant at the end of single and double TAR and GLU application experiments indicated the positive effect of repeated GLU applications on the accumulation of Cu, Pb, and Zn by Paulownia tomentosa as compared to untreated controls. A similar effect was not observed for the TAR treatments. When soil treated with either TAR or GLU was compared with untreated controls, no significant effect on heavy-metal concentrations in the soil solution was observed 30 days after treatment, suggesting the absence of an increase of the long-term leaching risk of heavy metals in aquifers and surface waters due to the ligand application. A cost analysis of the treatment is also reported.

Artificial neural networks as a tool for plant identification: a case study on Vietnamese tea accessions

Seventeen tea accessions belonging to Chinese (Camellia sinensis), Assamic (C. sinensis var. assamica), and Shan tea (C. sinensis var. pubilimba) groups, which are either commercially planted or new promising tea germplasm, were morphologically described at Phu Tho province (Viet Nam) and assessed for their diversity. Fourteen phyllometric parameters were qualitatively and quantitatively investigated using digital image analysis. The accessions were then discriminated by a dedicated artificial neural network for univocal plant identification and a hierarchical cluster analysis was performed in order to build a dendrogram reporting the relationships among them. Results proved the diversity of investigated tea morphotypes from Phu Tho province based on a morphological screening. More, the artificial neural network was able to perform a correct identification for almost all the accessions using simple dedicated instruments.

The plant as a biomechatronic system

Our vision of plants is changing dramatically: from insensitive and static objects to complex living beings able to sense the environment and to use the information collected to adapt their behavior. At all times humans imitate ideas and concepts from nature to resolve technological problems. Solutions coming from plants have the potential to face challenges and difficulties of modern engineering design. Characteristic concepts of the plant world such as reiteration, modularity and swarm behavior could be of great help resolving technological problems. On the other hand a biorobotic approach would facilitate the resolution of many biological problems. In this paper, the concept of a plant-inspired robot is proposed for the investigation of both biological and technological issues.

Camellia japonica L. genotypes identified by an artificial neural network based on phyllometric and fractal parameters

The potential application of phyllometric and fractal parameters for the objective quantitative description of leaf morphology, combined with the use of Back Propagation Neural Network (BPNN) for data modelling, was evaluated to characterize and identify 25 Camellia japonica L. accessions from an Italian historical collection. Results show that the construction of a BPNN based on phyllometric and fractal analysis could be effectively and successfully used to discriminate Camellia japonica genotypes using simple dedicated instruments, such as a personal computer and an easily available optical scanner.