Manuel Cantos

Is it possible to increase bioavailability but not environmental risk of PAHs in bioremediation

The current poor predictability of end points associated with the bioremediation of polycyclic aromatic hydrocarbons (PAHs) is a large limitation when evaluating its viability for treating contaminated soils and sediments. However, we have seen a wide range of innovations in recent years, such as an the improved use of surfactants, the chemotactic mobilization of bacterial inoculants, the selective biostimulation at pollutant interfaces, rhizoremediation and electrobioremediation, which increase the bioavailability of PAHs but do not necessarily increase the risk to the environment. The integration of these strategies into practical remediation protocols would be beneficial to the bioremediation industry, as well as improve the quality of the environment.

Growth and photosynthetic responses to copper in wild grapevine

The present study evaluates the tolerance and accumulation potential of Vitis vinifera ssp. sylvestris under moderate and high external Cu levels. A greenhouse experiment was conducted in order to investigate the effects of a range of external Cu concentrations (0-23mmolL(-1)) on growth and photosynthetic performance by measuring gas exchange, chlorophyll fluorescence parameters and photosynthetic pigments. We also measured the total copper, nitrogen, phosphorus, sulphur, calcium, magnesium, iron, potassium and sodium concentrations in the plant tissues. All the experimental plants survived even with external Cu concentrations as high as 23mmolL(-1) (1500mg Cu L(-1)), although the excess of metal resulted in a biomass reduction of 35%. The effects of Cu on growth were linked to a reduction in net photosynthesis, which may be related to the effect of the high concentration of the metal on photosynthetic electron transport. V. vinifera ssp. sylvestris survived with leaf Cu concentrations as high as 80mgkg(-1) DW and growth parameters were unaffected by leaf tissue concentrations of 35mg Cu kg(-1) DW. The results of our study indicate that plants of V. vinifera ssp. sylvestris from the studied population are more tolerant to Cu than the commercial varieties of grapevine that have been studied in the literature, and could constitute a basis for the genetic improvement of Cu tolerance in grapevine.

Tropane Alkaloid Distribution in Atropa baetica Plants

Fifteen different tropane alkaloids and derivatives were identified by GC-MS in various plant organs of Atropa baetica. The main root and leaves displayed the largest number of tropane alkaloids, most of which were also present in lateral roots. In contrast, only five of these alkaloids appeared in stem tissue. Quantitative analysis by HPLC showed the presence of the two major tropane alkaloids, atropine and scopolamine, in all the samples studied. Atropine was more abundant, with the highest concentration in the main root (ca. 10.0 mg/g dry wt) followed by leaves (ca. 3.0 mg/g dry wt); scopolamine was present in highest concentration in the main root (0.6 mg/g dry wt) followed by leaves (0.4 mg/g dry wt). The lowest concentrations of these compounds were detected in stem tissue, followed by the lateral roots. The main root constitutes the major tropane alkaloid storage site; moreover, the distribution of these compounds does not appear to be organ dependent. These latter two characteristics are in contrast to closely related Atropa genera.

Impact of dissolved organic matter on bacterial tactic motility, attachment, and transport.

Bacterial dispersal is a key driver of the ecology of microbial contaminant degradation in soils. This work investigated the role of dissolved organic matter (DOM) in the motility, attachment, and transport of the soil bacterium Pseudomonas putida G7 in saturated porous media. The study is based on the hypothesis that DOM quality is critical to triggering tactic motility and, consequently, affects bacterial transport and dispersal. Sunflower root exudates, humic acids (HA), and the synthetic oleophilic fertilizer S-200 were used as representatives of fresh, weathered, and artificially processed DOM with high nitrogen and phosphorus contents, respectively. We studied DOM levels of 16-130 mg L(-1), which are representative of DOM concentrations typically found in agricultural soil pore water. In contrast to its responses to HA and S-200, strain G7 exhibited a tactic behavior toward root exudates, as quantified by chemotaxis assays and single-cell motility observations. All DOM types promoted bacterial transport through sand at high concentrations (∼ 130 mg L(-1)). At low DOM concentrations (∼ 16 mg L(-1)), the enhancement occurred only in the presence of sunflower root exudates, and this enhancement did not occur with G7 bacteria devoid of flagella. Our results suggest that tactic DOM effectors strongly influence bacterial transport and the interception probability of motile bacteria by collector surfaces.

Growth responses of micropropagated cassava clones as affected by Glomus Intraradices colonization

ABSTRACT This study reports the effectiveness of an arbuscular mycorrhizal (AM) fungus Glomus intraradices on three clones (SOM-1, 05 and 50) of cassava (Manihot esculenta). Arbuscular mycorrhizal inoculation increased plant resistance to transplant stress from “in vitro” to “ex vitro” conditions and plant biomass (shoot and root) production was greatly enhanced by AM-colonization. The magnitude of AM growth stimulation over control clones was: 861% (SOM-1), 1042% (05) and 854% (50). Arbuscular mycorrhizal colonized cassava plants increased cassava water uptake in terms of percentage, 62% in clone SOM-1, 24% in clone 05, and 157% in clone 50. The highest effect of AM-colonization on water content in root of clone 50 was correlated with the greatest increment in leaf tissue production (1218% over control) and with the maximum shoot/root ratio determined. The biomass distribution between shoot and root was changed by AM symbiosis and such effect varied for each clone that may be caused by mycorrhizal changes in macro/micro-nutrients translocation/compartimentation. Cassava dependence on AM symbiosis was greatest in clone SOM-1 since AM-colonization provided the highest stem (weight, length, and diameters), leaf (weight and number), bud number, and root weight. These results lead to practical applications because AM inoculation is crucial for improving cassava yield (shoot and root) and nutrition irrespective of the clone involved. Thus, importance of AM symbiosis in micropropagated cassava clones is of great practical interest in agriculture and allows the selection of the most suitable clone for dry environments due to the particular effect on root water content that improves drought adaptation.

Arbuscular-Mycorrhizal Contributes to Alleviation of Salt Damage in Cassava Clones

ABSTRACT This study determined how arbuscular-mycorrhizal (AM) colonization by Glomus intraradices affected plant biomass and salt tolerance (in terms of growth) of three cassava clones (SOM-1, 05, and 50). Survival, root, stem and leaf production, and nutrient accumulation were determined in AM-inoculated and non-inoculated cassava clones under a range of sodium chloride (NaCl) levels (0, 68.4, or 136.8 mM) in the medium. The AM colonization stimulated plant growth and increased survival at 136.8 mM of salt. Clone SOM-1 showed to be the most salt tolerant of the three clones tested. G. intraradices-inoculation was important not only for growth promotion, but also played a crucial role in protecting cassava clones against salt (particularly the most salt sensitive clones). Mycorrhizal clones growing under 136.8 mM of NaCl showed greater dry weight than non-mycorrhizal clones growing without salt. Results show that AM-colonization provides a biological mechanism by which cassava clones increased plant biomass and salt tolerance being required for the best cassava clone development under non-stress and stress conditions.

FEASIBILITY AND ANATOMICAL DEVELOPMENT OF AN IN VITRO OLIVE CLEFT-GRAFT

SummaryThe feasibility and anatomical development of an in vitro olive cleft-graft method were studied. Grafting survival after 60.d in vitro was 85% which then dropped slightly to 67% after hardening. Three days after grafting, callus formation was observed along the cut surfaces of the rootstock and scion, after 6.d the first healing cellular unions were observed, and by 12.d after grafting a strong union developed. The first cellular differentiation to form vascular tissues was observed 12.d after grafting and continued rapidly until a total connection was reached 10.d later. Thus a complete graft union of the in vitro olive cleft-grafts was achieved in three weeks, and vigorous plants were established after 60.d of in vitro culture followed by 10.d of hardening. The in vitro olive cleft graft is suggested as an effective and useful method for germplasm multiplication.

Heavy metals and trace element concentrations in intertidal soils of four estuaries of SW Iberian Peninsula

Soils from four estuaries of SW Iberian Peninsula, affected by anthropogenic influence (urban, industrial and agricultural activities), were analyzed for the occurrence of a variety of metals and trace elements including Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, S and Zn. The soils presented very high levels of salinity (high concentrations of Na, K and Mg), organic matter and, consequently, of C and N concentrations. In contrast, very low values of CaCO3, Ca and P were found. In addition, it should be highlighted that in certain localities (Piedras 1 and 2 and Guadiana in Huelva, Spain, and Ria Formosa, Faro, Portugal) the concentrations of Pb, S and Zn were extremely high, reaching levels of pollution.

Induction and development of adventitious shoots of Atropa baetica as a means of propagation

In vitro propagation of Atropa baetica was established employing axillary buds. Single buds were cultured through a multiple shoot induction phase, rooting phase, and then followed by acclimatization in soil. For multiple shoot induction, Murashige and Skoog (MS) medium with 3% sucrose, supplemented with either 0.75 or 1.25 mg l-1 of BAP provided the best results with an average of 5.6 shoots per explant after 31 days of culture. Similar results were obtained with higher BAP concentrations (1.75–2.0 mg l-1); however, these media had a negative effect on the subsequent root induction due to residual BAP effect. Medium containing only 0.25 mg l-1 of BAP induced a significantly lower number of shoots. Root induction occurred spontaneously after transferring the shoots onto MS medium lacking any plant growth regulator. Moreover, root induction also occurred on media supplemented with 0.125 and 0.25 mg l-1 of NAA. On these two rooting media, this response was more prominent and with a higher number of roots per explant. Nevertheless, after 28 days on root induction medium, the number of rooted plantlets was similar on the three media. Acclimatization of plantlets in soil was very successful (95.52%). However, all plantlets which died during acclimatization were rooted on medium containing 0.25 mg l-1 NAA suggesting a negative carry over effect of this medium upon plantlet survival, irrespective of the initial BAP treatment used. On the other hand, karyological studies showed no variation in the number of chromosome (2n=72) in root tips of the plantlets produced.

Effects of different arbuscular mycorrhizal fungal backgrounds and soils on olive plants growth and water relation properties under well-watered and drought conditions.

The adaptation capacity of olive trees to different environments is well recognized. However, the presence of microorganisms in the soil is also a key factor in the response of these trees to drought. The objective of the present study was to elucidate the effects of different arbuscular mycorrhizal (AM) fungi coming from diverse soils on olive plant growth and water relations. Olive plants were inoculated with native AM fungal populations from two contrasting environments, that is, semi-arid - Freila (FL) and humid - Grazalema (GZ) regions, and subjected to drought stress. Results showed that plants grew better on GZ soil inoculated with GZ fungi, indicating a preference of AM fungi for their corresponding soil. Furthermore, under these conditions, the highest AM fungal diversity was found. However, the highest root hydraulic conductivity (Lpr ) value was achieved by plants inoculated with GZ fungi and growing in FL soil under drought conditions. So, this AM inoculum also functioned in soils from different origins. Nine novel aquaporin genes were also cloned from olive roots. Diverse correlation and association values were found among different aquaporin expressions and abundances and Lpr , indicating how the interaction of different aquaporins may render diverse Lpr values.