Theodora Matsi

Influence of sewage sludge application on soil properties and on the distribution and availability of heavy metal fractions

Abstract The influence of sewage sludge application on some soil properties and on the growth of wheat and corn plants were studied with pot experiments. The distribution of heavy metals among the various soil fractions and their availability to plants were also investigated in relation to soil pH. The results showed that sewage sludge application significantly ifluenced pH, organic matter content, electrical conductivity and available phosphorus. Soil pH increased and tended to hold steady near neutrality while organic matter content, electrical conductivity and available phosphorus (P) increased. For the heavy metals investigated, only total copper (Cu) and zinc (Zn) increased but were below the limits set by the EC. A significant increase was observed in the concentrations of cadmium (Cd), nickel (Ni), Cu, and Zn extracted by DTPA while iron (Fe) and manganese (Mn) were reduced showing a strong relationship to soil pH. For the metals sequentially extracted it was observed that chromium (Cr), Ni, Cu, an...

Shoot Sr concentrations in relation to shoot Ca concentrations and to soil properties

This work was aimed to investigate whether shoot Sr concentrations of plant species are related to respective Ca concentrations and to soil properties and to compare the Sr-Ca observed ratios (OR), defined as the quotient of the ratios Sr/Ca in shoots and in the soil solution or in the extractable form, among species and soils. Ten pasture plant species were grown in pots (1-L volume) filled with eight soils differing in the various physicochemical characteristics. Each pot received 50 mg Sr except those of the soil with the highest cation exchange capacity (C.E.C.) that received 100 mg Sr per pot. For each soil, shoot Sr concentrations of species were linearly and positively related with the respective Ca concentrations. C.E.C, organic matter content and Ca in the soil solution or in the extractable form were the only soil properties that were related, all negatively, with shoot Sr concentrations. The ratio of extractable Sr and Ca was positively and linearly related with the ratio of Sr and Ca. in the soil solution. OR was affected by both species and soils. Most of OR values of all species in all soils ranged between 0.8 and 1.5, except for the grass Agrostis capillaris which had the highest values for most of soils. This indicates that Agrostis capillaris compared to other species, takes up proportionally more Sr than Ca.

Forms and distribution of heavy metals in soils of the axios delta of northern Greece

Abstract Distribution and availability of heavy metals to plants is important when assessing the environmental quality of an area. The objectives of this study, conducted in 1992–1993, were: a) to determine the levels of the heavy metals, cadmium (Cd), chromium (Cr), copper(Cu), lead (Pb), manganese (Mn), nickel (Ni), and zinc (Zn), in the soils of the Axios Delta (a Ramsar wetland site in Northern Greece) so that the degree of pollution could be ascertained, b) to identify the various heavy metal forms present in soils using a fractionation scheme based on sequential extraction, and c) to find possible dependence on soil physicochemical properties. Total heavy metal content of the soils studied was generally higher than the levels reported in the literature for similar soils, suggesting some degree of pollution with heavy metals. The exchangeable forms of the heavy metals, however, were very low indicating that under present conditions, the availability of the heavy metals to plants is at a minimum. Most...

Strontium Absorption by Two Trifolium Species as Influenced by Soil Characteristics and Liming

Strontium absorption by plants is specific to individual species and also depends on the underlying soil properties. The purpose ofthis study was to evaluate the effect of certain soil characteristics and liming on Sr absorption by twoTrifolium species. One-liter volume of two inorganic and three organic soilswere treated with a combination of three CaCO3 levels, 0, 3.6 and 7.2 g, × two Sr levels, 50 and 100 mg, (treatments) in four replications. Trifolium repens L. was grown in thetreated soils, in pots, harvested twice, and Sr in theabove-ground biomass of each harvest and soil exchangeable Caof each treatment were determined. The experiment was repeatedwith Trifolium subterraneum L., harvested once. For bothspecies, Sr transfer factor (T.F.) values of the varioustreatments were calculated. Shoot Sr concentrations weresignificantly affected by soil characteristics and Sr additionrates and were greater in T. repens. In all cases, theSr concentrations of plants grown in the organic soils, whichwere characterized by higher exchangeable Ca and cationexchange capacity (C.E.C.) values, were lower than those ofplants grown in the inorganic soils. Among the organic soils,Sr concentrations of the plants grown in the soil with thehighest values of C.E.C., organic matter and exchangeable Cawere the lowest. Liming decreased significantly the Srconcentrations in T. repens and T. subterraneumgrown in the two acid soils, while the pH and exchangeable Cawere increased. Shoot Sr concentration (log scale) wassignificantly, negatively correlated with soil exchangeable Ca. Strontium T.F. values were quite similar between the two Sr application rates and were affected by the same soil characteristics.

Evaluation of the NH4HCO3-DTPA soil test for assessing boron availability to wheat

Abstract The NH4HCO3‐DTPA (AB‐DTPA), 1 MNH4HCO3, 0.005 M DTPA, pH=7.6, was proposed as a multi‐element extractant, for evaluating macro and micronutrients availability to plants. AB‐DTPA was also evaluated as a soil test, for assessing boron availability and toxicity to alfalfa. In a pot experiment, ten soils of Northern Greece were used to assess AB‐DTPA as an extractant of available boron to wheat (Triticum aestivum L., cv. Yecora), in comparison with hot water and saturation extract. Boron (B) was added as borax (Na2B4O7*10H2O) to the ten soils, at rates equal to 0, 3, and 5 mg B kg‐1. Wheat was grown in pots containing the boron amended soils to the stage of tillering, and dry aboveground biomass, B concentration and B uptake by wheat were determined. AB‐DTPA extractable B was significantly greater than saturation extract and similar to hot water at each B application rate, and was correlated significantly with hot water (r=0.84), or with saturation extract (r=0.48). Extractable boron by all extractants, boron concentration in wheat and boron uptake were significantly affected by the soil x B application rate interaction. In assessing B availability to wheat using AB‐DTPA as a soil test, CEC should be included in the regression equation for B concentration, or pH for B uptake. However, the corresponding adjusted coefficients of determination for B concentration (adjusted R2=0.46) and B uptake (adjusted R2=0.48) were similar or lower to those of hot water (adjusted R2=0.45 and 0.60, respectively) and the saturation extract (adjusted R2=0.70 and 0.49, respectively), when the latter two soil tests were used in the regression equations without the inclusion of any soil property.

Silencing S-Adenosyl-L-Methionine Decarboxylase (SAMDC) in Nicotiana tabacum Points at a Polyamine-Dependent Trade-Off between Growth and Tolerance Responses

Polyamines (PAs) are nitrogenous molecules that are indispensable for cell viability and with an agreed-on role in the modulation of stress responses. Tobacco plants with downregulated SAMDC (AS-SAMDC) exhibit reduced PAs synthesis but normal levels of PA catabolism. We used AS-SAMDC to increase our understanding on the role of PAs in stress responses. Surprisingly, at control conditions AS-SAMDC plants showed increased biomass and altered developmental characteristics, such as increased height and leaf number. On the contrary, during salt stress AS-SAMDC plants showed reduced vigor when compared to the WT. During salt stress, the AS-SAMDC plants although showing compensatory readjustments of the antioxidant machinery and of photosynthetic apparatus, they failed to sustain their vigor. AS-SAMDC sensitivity was accompanied by inability to effectively control H2O2 levels and concentrations of monovalent and divalent cations. In accordance with these findings, we suggest that PAs may regulate the trade-off between growth and tolerance responses.

Soil application of sewage sludge stabilized with steelmaking slag and its effect on soil properties and wheat growth

The effect of sewage sludge, stabilized with steelmaking slag, on soil chemical properties and fertility and on wheat (Triticum aestivum L.) growth was evaluated. Dewatered sewage sludge [75% (wet weight basis)] stabilized with steelmaking slag (25%) and three soils with different pH values were used in a pot experiment with winter wheat. The following treatments were applied: (i) sludge addition of 30gkg-1 (≈ 120Mgha-1, rate equivalent to the common inorganic N fertilization for wheat, based on sludges water soluble NO3-N), (ii) sludge addition of 10gkg-1 (≈ 40Mgha-1, rate equivalent to the common inorganic N fertilization for wheat, based on sludges Kjeldahl-N), (iii) addition of the common inorganic N fertilization for wheat (120kgNha-1) as NH4NO3, (iv) control (no fertilizer, no sludge). Sludge application at both rates to all soils resulted in a significant increase of pH, electrical conductivity of the saturation extract (ECse) and soil available NO3-N and P, in comparison to the other two treatments and this increase remained constant till the end of the pot experiment. In sludge treatments pH did not exceed the critical value of 8.5, whereas ECse, although it did not reach the limit of 4dSm-1, exceeded the value of 2dSm-1 at the rate of 30gkg-1. Concentrations of heavy metals, which regulate the agronomic use of sewage sludge according to the established legislation, ranged from not detectable to lower than the respective permissible levels. Both rates of sludges addition in all soils improved wheats growth, as judged by the significant increase of the aboveground biomass yield and the total plant uptake of almost all nutrients, compared to the other two treatments. It was concluded that sewage sludge stabilized with steelmaking slag could be used in agriculture, applied at rates based on sludges Kjeldahl-N content and crops demand for N. However, potential environmental impacts must also be considered.

Deregulation of apoplastic polyamine oxidase affects development and salt response of tobacco plants

Polyamine (PA) homeostasis is associated with plant development, growth and responses to biotic/abiotic stresses. Apoplastic PA oxidase (PAO) catalyzes the oxidation of PAs contributing to cellular homeostasis of reactive oxygen species (ROS) and PAs. In tobacco, PAs decrease with plant age, while apoplastic PAO activity increases. Our previous results with young transgenic tobacco plants with enhanced/reduced apoplastic PAO activity (S-ZmPAO/AS-ZmPAO, respectively) established the importance of apoplastic PAO in controlling tolerance to short-term salt stress. However, it remains unclear if the apoplastic PAO pathway is important for salt tolerance at later stages of plant development. In this work, we examined whether apoplastic PAO controls also plant development and tolerance of adult plants during long-term salt stress. The AS-ZmPAO plants contained higher Ca2+ during salt stress, showing also reduced chlorophyll content index (CCI), leaf area and biomass but taller phenotype compared to the wild-type plants during salt. On the contrary, the S-ZmPAO had more leaves with slightly greater size compared to the AS-ZmPAO and higher antioxidant genes/enzyme activities. Accumulation of proline in the roots was evident at prolonged stress and correlated negatively with PAO deregulation as did the transcripts of genes mediating ethylene biosynthesis. In contrast to the strong effect of apoplastic PAO to salt tolerance in young plants described previously, the effect it exerts at later stages of development is rather moderate. However, the different phenotypes observed in plants deregulating PAO reinforce the view that apoplastic PAO exerts multifaceted roles on plant growth and stress responses. Our data suggest that deregulation of the apoplastic PAO can be further examined as a potential approach to breed plants with enhanced/reduced tolerance to abiotic stress with minimal associated trade-offs.

Comparison of Two Sequential Extraction Methods and the DTPA Method for the Extraction of Micronutrients from Acidic Soils

Two sequential extraction methods (the modified BCR—Community Bureau of Reference, now the Standards, Measurement and Testing Program, of the European Commission—and the original Tessier) were compared for the assessment of various forms of copper (Cu), zinc (Zn), iron (Fe), and manganese (Mn) in 29 cultivated acidic soils of northern Greece. In addition, the different forms of the micronutrients extracted by the two methods were compared to the plant-available micronutrients extracted by diethylenetriaminepentaacetic acid (DTPA) and their relation to certain soil physicochemical properties was examined. Because the soils were acidic, the second step of the original method of Tessier (related to micronutrients bound to carbonates) was omitted. Consequently, four micronutrient fractions were assessed by both methods, namely water-soluble + exchangeable, bound to Fe-Mn oxides, bound to organic matter, and residual. Each of the two methods extracted different amounts of the same micronutrients in similar fractions, which amounts were significantly and positively correlated. The order of Fe and Mn distribution in the various fractions was similar in the two methods, within the same element, whereas Zn was slightly different and Cu was detectable only in the residual fraction of both methods. Clay and Fe-Mn oxide–bound Fe, cation exchange capacity (CEC), and organic matter–bound Fe were significantly and positively correlated in the case of the original Tessier method. In the modified BCR method, organic matter–bound Fe and Zn were significantly and positively correlated with CEC. In both methods, significant and positive correlation coefficients were found for the following relations: clay and Mn in the water-soluble + exchangeable fraction, organic C and organic matter–bound Mn, CEC and Mn in the three first fractions. The DTPA-extractable micronutrients were significantly and positively correlated with the respective micronutrients in the fractions bound to Fe-Mn oxides and bound to organic matter of the original method of Tessier for Zn; the fraction bound to Fe-Mn oxides of the same method for Fe; and the three first fractions of both sequential extraction methods for Mn.

Cation selectivity in cotton ( Gossypium hirsutum L.) grown on calcareous soil as affected by potassium fertilization, cultivar and growth stage

Background and aimsSelective uptake of K over Na has been proposed as a mechanism employed by plants to tackle high soil salinity. However, the impact of other dominant soil cations such as Ca and Mg and essentiality of higher K/Ca and K/Mg selectivity for plant performance under adverse growing conditions have been studied much less. We addressed this topic by looking at cation selectivity in cotton grown on calcareous soil supplemented by K.MethodsCation selectivity in leaves was determined as a ratio of two cations to the respective ratio in the soil over two growth seasons, three growth stages, and two cotton cultivars. Concurrently, instantaneous and long-term leaf traits related to CO2 assimilation, N and water use efficiency were assessed.ResultsPotassium addition did not affect on cation selectivity; growth stages and their interaction with years were allotted with the most of the variation found for cation selectivity and many of the physiological traits. Cultivar Carmen compared to Elina had higher K selectivity, was water conservative and had higher fiber quality. Elina took up Na selectively over Mg in an effort to sustain stomata open.ConclusionsThe reported results indicated an importance of improved cation selectivity to optimize K+ nutrition in plants grown on calcareous soils. Under conditions of low K+ availability, cotton cultivars took up selectively Na and Mg over Ca, to optimize its water relations and photosynthetic performance. Cation selectivity was largely affected by growth stages and was correlated with stomata functioning.