Effects of simulated acid rain on uptake,accumulation, and retention of fluoride in forage crops

Forage crops accumulate F from exposures to the air pollutant HF and the rate and amount taken up can be affected by a number of external factors, one of which is precipitation. To assess how precipitation, including acidic precipitation, alters F uptake and retention in forage, alfalfa (Medicago sativa L. var. Saranac) and tall fescue (Festuca arundinacea Schreb. var. Kentucky 31) were subjected to extended exposures to HF and were treated periodically with various solutions (pH 5.6, 4.0, and 3.0) supplied as simulated rain or, for comparisons, as soil amendments. None of the treatments affected growth, but precipitation treatments significantly reduced the F content of both species relative to plants that received the same volumes of the same solutions added to the soil. Analyses of washed and unwashed foliage indicated that this loss of F was primarily due to the removal of F from foliar surfaces. There was no effect of pH of rain on the F content of tall fescue, but for alfalfa an increase in acidity from pH 4.0 to 3.0 resulted in a further decrease in the F content of foliage, suggesting that in addition to removing superficial F, the more acidic simulated rain resulted in the leaching of F from within foliage was well.     

Evaluation of Trace Element Pollution from Vehicle Emissions in Petunia Plants

Effects of environmental pollution from road traffic on traceelement accumulation and deposition were examined in washed andunwashed petunia leaves. The plants were grown in an urban and ina suburban area. Substantial amounts of elements were removedsimply by washing with demineralised water, which removed atleast 45% of Al, Fe and Pb and 15% of Mn, Cu and Zn in urbanareas, where the aerial deposition took place. Throughout thegrowing season, the concentrations of Fe, Cu, Al, Ni and Pbincreased in the washed leaves of the petunia plants grown inurban areas. However, the plant very specifically controlled thecontents of Mn and Zn. Concentrations of elements were significantly higher in washed leaves from the urban area thanthose from the surburban area, indicating that this ornamentalplant is able to absorb Fe, Al, Ni and Pb through its root andleaves. Periodic assessment of the accumulation of traceelements in urban areas with intense traffic is important inorder to evaluate the rate of environmental pollution.     

Uptake of fluoride and aluminum by plants grown in contaminated soils

Soils collected from areas at different distances from an aluminum smelter were studied to determine the soluble and labile F and soluble Al contents and availabilities to selected plants. Red maple seedlings (Acer rubrum L.) and orchard grass (Dactylis glomerata L.) were grown in pots containing the soils and after 3 mo foliar tissues were sampled and analyzed for the two elements. The soluble and labile contents of soil F as predictors of foliar F were compared. Significant decreases in soluble and labile F and soluble Al in soils were found with increasing distance from the smelter. As F levels in the soils increased, the F in the foliage of both orchard grass and maple increased. As Al in the soil increased, Al in maple foliage increased. Overall, F concentrations in plant foliage were below those considered as background. The results imply that, at least in the soils studied, the soil F content is not an important source of F to plants and therefore to herbivores in the area. Labile F values in the soils were significantly greater than soluble F at all sites, but, contrary to previous studies, soluble F was a better predictor of foliar F than was labile F.     

Hydroponic Study of Aluminum Accumulation by Aquatic Plants: Effects of Fluoride and pH

The potential of five common aquatic plant species (Typha latifolia, Myriophyllum exalbescens, Potamogeton epihydrus, Sparganium angustifolium and Sparganium multipedunculatum)to be used for Al phytoremediation was tested. The plants were exposed, for 14 days under hydroponic conditions, to synthetic effluents representing extreme conditions that could occur accidentally at an aluminum refinery site. Tested Al concentrationsranged between 0 and 400 μM, fluoride concentrations between 0 and 900 μM, and the pH varied from 4.5 to 7.5. The results indicate that all the plants tested accumulated aluminum, and as a result induced a decrease of Al in the ambient water. For individual species Al uptake (in mol g^-1 dw d^-1) decreased in the following order: Myriophyllum exalbescens > Sparganium sp. ≌Typha latifolia > Potamogeton epihydrus. M. exalbescens accumulated Al more rapidly in its leaves than in other tissues, whereas T. latifolia and Sparganium sp. accumulated Al essentially in their roots. For P. epihydrus the relative importance of the leaves and roots varied with exposure conditions. For all species, fluoro-Al complexes contributed to Al uptake, contrary to the predictions of the Free-Ion Model, according to which the bioavailability of aluminum should be best predicted by the concentration of the free ion, Al³⁺. The influence of pH on Al uptake varied among the different species and among the parts of the plant: competition between Al and the H⁺-ion was evident for the roots of T. latifolia and the leaves and stem of M. exalbescensand P. epihydrus, whereas the roots of M. exalbescens, P. epihydrus and Sparganium sp. showed an inverse trend (Al uptake increased at low pH). For the leaves of T. latifolia and Sparganium sp., no pH influence could be demonstrated. Overall, the results of this study indicate that aquatic plants have a potential for Al phytoremediation.     

铝和镉胁迫对两个大麦品种矿质营养和根系分泌物的影响

A hydroponic experiment was carried out to study the effect of aluminum （Al） and cadmium （Cd） on Al and mineral nutrient contents in plants and Al-induced organic acid exudation in two barley varieties with different Al tolerance. Al- sensitive cv. Shang 70-119 had significantly higher Al content and accumulation in plants than Al-tolerant cv. Gebeina, especially in roots, when subjected to low pH （4.0） and Al treatments （100 μmol L^-1 Al and 100 μmol L^-1 Al ＋1.0 μmol L^-1 Cd）. Cd addition increased Al content in plants exposed to Al stress. Both low pH and Al treatments caused marked reduction in Ca and Mg contents in all plant parts, P and K contents in the shoots and leaves, Fe, Zn and Mo contents in the leaves, Zn and B contents in the shoots, and Mn contents both in the roots and leaves. Moreover, changes in nutrient concentrations were greater in the plants exposed to both Al and Cd than in those exposed only to Al treatment. A dramatic enhancement of malate, citrate, and succinate was found in the plants exposed to 100 μmol L^-1 Al relative to the control, and the Al-tolerant cultivar had a considerable higher exudation of these organic acids than the Al-sensitive one, indicating that Al-induced enhancement of these organic acids is very likely to be associated with Al tolerance.     

Fluorine and boron effects on vegetation in the vicinity of a fiberglass plant

Fluorine and B concentrations in foliage and foliar injury symptoms produced by these contaminants closely followed the changing pattern of atmospheric emissions from a fiberglass plant. Typical F injury symptoms on foliage were replaced by B injury symptoms as F emissions were reduced. Foliar concentrations of B in excess of 300 ppm accumulated by plants exposed to atmospheric B emissions produced injury symptoms on sensitive species similar to those produced by toxic concentrations of B absorbed through roots. Water-soluble F and B concentrations in soil decreased with increasing distance from the fiberglass plant. Soluble B concentrations in soil within 150 m of the plant were above levels known to be injurious to many plant species. Water-soluble F in soil in the same area increased the F content of some native plants above 50 ppm by the end of the growing season. Silver maples (Acer saccharinum) growing near the fiberglass plant had delayed growth of new shoots in the spring and had increasingly higher contents of F and B in trunk sap with proximity to the fiberglass plant. Control of F and then B emissions by the company resulted in reduced concentrations of these elements in foliage and a reduction in the degree and extent of vegetation injury around the plant.     

Investigation of Aluminum‐Tolerant Species in Acid Soils of South China

Abstract

The low‐hilly regions in South China are mainly covered with Ultisols and Alfisols with a pH of 4.5–6.0. The major factor limiting crop performance is soluble aluminum (Al) in acid soils, resulting in phytotoxicity in susceptible species. An investigation in Jiangxi and Zhejiang provinces in South China showed that many plants including some native plants and cultivated crops (total of 27 species) could grow well in acid soils of these areas. The Al‐accumulating capacity in leaves varied greatly from species to species. Camellia oleifera Abel accumulated more than 13,500 mg kg^?1 Al in old leaves; Camellia sinensis (L.) O. Kuntze, Fagopyrum esculentum Moench, and Dicranopteris pedata (Houtt.) Nakaike accumulated more than 1000 mg kg^?1 Al in leaves; and Oryza sativa L., Eucalyptus globulus Labill., Citrus reticulata Blanco, and Brassica chinensis L. accumulated less than 200 mg kg^?1 Al in leaves. This investigation provides an important basis for further exploring Al accumulation and resistant mechanisms in plants.     

Translocation and distribution of assimilated carbon in peanut plant

An attempt was made to monitor ¹³C that had been photosynthetically assimilated in the foliage of the main stem and branches of peanut plant, as well as in a single leaf at different positions on a branch.

When the foliage of the main stem or branch was supplied with ¹³CO₂ for 8 h at the vegetative stage, ¹³C assimilated in the branches was detected in the roots and nodules in addition to the foliage immediately after the exposure, whereas when the main stem was supplied with ¹³CO₂, ¹³C was not detected in the roots and nodules immediately after ¹³CO₂ feeding. At the reproductive stage, ¹³C assimilated in the main stem or branch was found in the leaves, stems, fruit (shell, seed coat, and seed), roots, and nodules immediately after assimilation.

Photoassimilates from each leaf of the branch at the reproductive stage were exported to the fruit and leaves that were attached to the same branch. Namely, photoassimilates in the leaves of odd nodes were mainly translocated to the fruits attached to the first node, whereas such photoassimilates from the leaf of even nodes were mainly translocated to the fruit attached to the second node.

When the foliage of a branch had been fed ¹³CO₂ at the vegetative stage, the loss of the assimilated ¹³C by respiration was about 40% of the total assimilated ¹³C within 23 d and about 65% within 93 d after the exposure, and a small amount of photoassimilates was detected in the fruit. On the other hand, at the seed-filling stage, about 35% of the photoassimilates were utilized for seed growth within 10 d after the end of exposure.

These results suggest that in the peanut plant, the carbon source of nodules mainly depends on the branch, and the main stem plays an important role as carbon source for the fruit, that a sink organ for carbon is connected with a specific sources leaf by the vascular bundles, and that most of the carbon sources for the growth of peanut fruit depend on the photoassimilates at the reproductive stage.     

Mechanisms of aluminum‐induced growth stimulation in tea (Camellia sinensis)

Beneficial effects of aluminum (Al) on plant growth have been reported for plant species adapted to acid soils. However, mechanisms underlying the stimulatory effect of Al have not been fully elucidated. The aim of this study was to determine the possible contribution of photosynthesis, antioxidative defense, and the metabolism of both nitrogen and phenolics to the Al‐induced growth stimulation in tea (Camellia sinensis [L.] Kuntze) plants. In hydroponics, shoot growth achieved its maximum at 50 μM Al suply (24 μM Al³⁺ activity). A more than threefold increase of root biomass was observed for plants supplied with 300 μM Al (125 μM Al³⁺ activity). Total root length was positively related to root Al concentrations (r = 0.98). Chlorophyll a and carotenoid concentrations and net assimilation rates were considerably enhanced by Al supply in the young but not in the old leaves. Activity of nitrate reductase was not influenced by Al. Higher concentrations of soluble nitrogen compounds (nitrate, nitrite, amino acids) and reduction of protein concentrations suggest Al‐induced protein degradation. This occurred concomitantly with enhanced net CO₂‐assimilation rates and carbohydrate concentrations. Aluminum treatments activated antioxidant defense enzymes and increased free proline content. Lowering of malondialdehyde concentrations by Al supply indicates that membrane integrity was not impaired by Al. Leaves and roots of Al‐treated plants had considerably lower phenolic and lignin concentrations in the cell walls, but a higher proportion of soluble phenolics. In conclusion, Al‐induced growth stimulation in tea plants was mediated by higher photosynthesis rate and increased antioxidant defense. Additionally, greater root surface area may improve water and nutrient uptake by the plants.     

Levels of Lead and other Metals in Citrus Alongside a Motor Road

The present study investigates the accumulation of Pb, Cu, Mn and Zn in leaves of Citrus limon (L.) Burm picked up from a field situated near a busy road. Samples were collected at different distances of 1–500 m from the road. Washed and unwashed foliage of citrus were analyzed by AA. Differences between washed and unwashed samples were found only for lead which indicated a significant reduction in concentration in all distances that come up to 52.35%, the differences evidence that this metal mainly reaches leaves by aerial deposition. Lead concentration in leaves of citrus with regard to distance from the roads decreases rapidly with increasing distance. Lead levels were higher than typical background concentrations. These concentrations indicated that lead pollution on a local scale is caused by emissions from motor vehicles that are still using leaded gasoline, that is, the only source of contamination known in this place. The content of the other metals did not present significant differences between washed and unwashed samples and the concentrations are not a function of the distance from the road.     

Effects of acidity in precipitation on terrestrial vegetation

Over the last several decades rain in the Northeastern United States has become more acidic presumably as a result of anthropogenic inputs of SO_x and NO_x to the atmosphere and their conversion to H₂SO₄ and HNO₃. Present experimental results suggest that acidic precipitation would initially affect organisms on leaf surfaces and epidermal cells of leaves of higher plants. More internal cell layers would be affected with increasing duration or frequency of exposure. Differences in responses of plant foliage among plant species to acidic precipitation appear to be due to the degree of leaf wetting and differences in responses of leaf cells to low pH rain. Moreover, within the same plant, particular structures or cell types may be more sensitive than others. If the United States is to utilize coal reserves for electric power generation that might increase rainfall acidity in the future, an assessment of the impact that acidic rain might have on terrestrial vegetation is necessary. In one experiment, field-grown soybeans were exposed to short duration rainfalls of either pH 4.0, 3.1, 2.7, or 2.3 to provide inputs of 50, 397, 998, or 2506 μeq of H⁺, respectively, above ambient levels throughout the growing season. Control plots received only ambient rainfalls. These additional H⁺ decreased seed yield, 2.6, 6.5, 11.4, and 9.5%, respectively. A treatment response function determined between H⁺ treatments and seed yield wasy=21.06?1.01 logx had a correlation coefficient of ?0.90. Researchers must design additional experiments with adequate experimental controls to assess the impact that acidic rain, at the present pH levels of 3.0 to 4.0 or at anticipated worst-case levels, that could occur if the acidity of rain should increase. Only a holistic view of the impacts that acid precipitation may have on vegetation will enable optimal energy and environmental policy decisions to be made.     

超累积植物油茶中Al的吸收和累积

Oiltea camellia (Camellia oleifera Abel.), an aluminium (Al) hyperaccumulator, grows well on acid soils in tropical or subtropical areas. In this study, the growth of oiltea camellia in response to Al application and the characteristics of Al uptake and accumulation were investigated using laboratory and field experiments. The growth of oiltea camellia seedlings in the nutrient solution tended to be stimulated by addition of Al. Results of the field experiment showed that oiltea camellia accumulated 11000 mg kg-1 Al in leaves within 10 months, and the average rate of Al accumulation in new leaves was about 1100 mg kg-1 month?1; however, the monthly rate varied and was highest in spring and autumn. The results of the laboratory experiment on Al uptake by oiltea camellia seedlings in CaCl2 solutions with various forms of Al showed that large amounts of Al supplied as Al3+ and Al complexes Al-malate (1:1) and Al-F (1:1) were influxed into oiltea camellia roots, whereas Al supplied as Al-citrate (1:1), Al-F (1:6), Al-oxalate (1:3), and Al-oxalate (1:1) complexes exhibited low affnity to oiltea camellia roots. The kinetics of Al3+ cumulative uptake in excised roots and intact plants showed a biphasic pattern, with an initial rapid phase followed by a slow phase. The Al cumulative uptake was una?ected by low temperature, which indicated that Al uptake in oiltea camellia was a passive process. The effcient influx of Al into the roots and the high transport rate in specific seasons were presumed to account for the plentiful Al accumulation in leaves of oiltea camellia.     

Responses of Biomass Production and Reproductive Development to Ozone Exposure Differ Between European Wild Plant Species

A screening study with 25 common European wild plant species were performed over three consecutive growing seasons to investigate the effects of ozone on plant growth, reproductive development, and resource allocation. Species were grown from seedling stage until the flowering stage or seed maturity, respectively, in open-top chambers in different ozone-enriched atmospheres at environmentally-relevant concentrations. Ozone treatments covered a range of concentrations from 20 to 55 ppb ozone (seasonal 8 h daily mean). The experiments revealed significant differences between species with respect to the sensitivity of different end points toward ozone exposure. Ozone caused a significant reduction in leaf biomass of more than 20% in six species, and a significant increase in leaf biomass in three species. The relative ozone sensitivities of the species in terms of leaf biomass were different from those inferred from total shoot biomass or seed production, indicating that ozone alters resource allocation patterns in wild plants but there was considerable variation between species in effects on the allocation to leaves, stems, flowers/fruits and seeds. Germinability of seeds was affected by ozone such that germination rate was up to 30% lower in ozone-treated plants compared to control plants. Based on the genotypes screened and by combining different sensitivity criteria (vegetative growth, reproductive growth, exposure-growth response relationships) Malva sylvestris must be regarded as the most sensitive species in this study.     

Genotypic differences in uptake and translocation of cadmium in bean and maize inbred lines

For better understanding of mechanisms responsible for genotypic differences in uptake and translocation of cadmium (Cd) in different plant species, two maize (Zea mays L.) inbred lines (B37 and F2) and a bean (Phaseolus vulgaris L.) cultivar (Saxa) were grown in a complete nutrient solution with additional 0.5 μM Cd and 250 μM buthionine sulfoximine (BSO), an inhibitor of PC synthesis, alone or in combination. The maize line B37 had a much higher Cd content in shoots (116.2 mg Cd kg^?1 dry wt.) than F2 (32.7 mg Cd kg^?1 dry wt.) and bean (1.83 in leaves, and 2.85 mg Cd kg^?1 dry wt. in stems), whereas in roots the Cd content was much higher in bean (602.6 mg Cd kg^?1 dry wt.) than in maize (427.1 mg Cd kg^?1 dry wt. in B37, and 428.2 mg Cd kg^?1 dry wt. in F2). Application of BSO markedly decreased Cd contents in roots of bean and maize lines, and also Cd contents in shoots and stem basis of both maize lines, while Cd contents in leaves, stems and stem basis of bean were not reduced by BSO. In root extracts (Tris-HCl buffer, pH 8.0) the proportion of Cd in the soluble fraction was much lower in bean (29.6%) than in the maize lines B37 (58.6%) and F2 (60.1%). Compared with the whole root tissue, Cd contents in the stele of the roots were much lower, especially in bean, and decreased by BSO in both maize lines, but not in bean. Gel-chromatography of root extracts strongly suggested that in the soluble fraction about 80% of the Cd was present as Cd-phytochelatin (PC) complexes in B37, whereas in F2 this Cd fraction accounted for about 50%, and in bean only for a few percent in the soluble fraction, Our results suggest that Cd-PC complexes constitute a mobile form in plants. The lower proportion of Cd in the soluble fraction as well as lower PC production in roots of bean compared to maize lines may be the main reasons for the very low Cd translocation from roots to shoots in bean plants.     

Aluminium chemistry and acidification processes in a shallow podzol on the Swedish westcoast

Processes pertinent to soil acidification with special emphasis on the solution chemistry of A1, were studied in three adjacent small catchments on the Swedish westcoast, with mixed coniferous forest and shallow podzols (average soil depth 50 cm). Soil solution from different depths, groundwater and stream-water were sampled. Separation of organic and inorganic Al species was done with an ion exchange technique. The concentration of organic A1 species was linearly correlated with the concentration of dissolved organic C (r,², varied from 0.38 to 0.69 with p, < 0.001). In the A horizon 83 to 97 % of the dissolved A1 consisted of organic species. The average concentration of total A1 varied from 3.3 to 9.8 μmole 1^?1, in soil leachates collected below the A₀, horizon, and from 29.3 to 47.0 pmole 1^?1, in leachates collected below the A₂, horizon. The organic Al species decreased in importance with increasing soil depth. Leachates collected below the B horizon had average total A1 concentrations ranging from 95.3 to 115 pmole 1^?1, with a contribution of organic species varying between 8 and 20% of the total concentration. Activity calculations indicated an equilibrium with A1(OH)SO₄, (pK _S = 17.23) in the lower part of the B horizon, while groundwater together with some of the leachates from the upper B horizon showed a better fit with A1₁₄(OH)₁₀SO₄ (pK₁ = 117.51). Streamwater was obviously influenced by the soil organic matter in the outflow areas in terms of A1- organic matter complexes and protolysis of dissolved organic acids. There was a net outflow of Al and sulphate from the lower part of the B horizon compared to input in throughfall precipitation. The relative concentration increase varied from 64.4 to 78.0 (A1) and from 1.52 to 1.92 (sulphate). The relative increase due to evapotranspiration was estimated to be 1.4. The corresponding concentration factors for Mg and Ca were from 2.06 to 2.38, and from 0.81 to 1.07, respectively, indicating a very low Ca weathering. Data were compared with other studies, both recent and older ones. The possible influence from present-day levels of H⁺ and sulphurous compounds in the atmospheric deposition is evaluated.     

Speciation and Solubility Control of Aluminium in Soils Developed from Slates of the River Sor Watershed (Galicia,NW Spain)

The Al species in the soid and liquid phases were studied in eight soils developed from slates in a watershed subjected to acid deposition. From soil solution data the mechanisms possibly controlling Al solubility are also discussed. The soils are acidic, organic matter rich and with an exchange complex saturated with Al. In the solid phase, more than 75% of non-crystalline Al was organo-Al complexes, mostly highly stable. In the soil solutions, monomeric inorganic. Al forms were predominant and fluoro-Al complexes were the most abundant species, except in soil solutions of pH<4.8 and Al L/F ratio >3, in which Al³⁺ predominated and sulphato-Al complexes were relatively abundant. The most stable phases were kaolinite, gibbsite and non-crystalline Al hydroxides. In most samples, Al solubility was controlled by Al-hydroxides. Only in a few cases (solutions of pH 4-5, Al³⁺ activity >40 µmol L-¹ and SO₄ content >200 µmol L-¹), Al-sulphates such as jurbanite also could exert some control over Al solubility. In adition to these minerals, a possible role of organo-Al complexes or the influence of adsorption reactions of sulphate is considered, especially for samples with very low Al³⁺ content (<0.5 µmol L-¹).     

ALUMINIUM TOXICITY AND TOLERANCE IN THREE HEATHLAND SPECIES

Arnica montana and Cirsium dissectum are characteristic species of species-rich heathlands and adjacent grasslands, which declined during the last decades in the Netherlands. It has been shown in a recent field survey that the decline of A. montana and C. dissectum might be caused by soil acidification. Calluna vulgaris is not susceptible to soil acidification. It was hypothesized that increased aluminium concentrations in the soil as a result of acidifying atmospheric inputs caused the decline of A. montana and C. dissectum whereas C. vulgaris would not be sensitive to enhanced aluminium concentrations. We studied the effects of different Al:Ca-ratios and of Al concentrations on the development of A. montana, C. dissectum and C. vulgaris in nutrient solution experiments. All three species showed aluminium accumulation in the shoots related with increased aluminium concentrations in the nutrient solutions. This accumulation was correlated with a reduction in growth when plants were cultured at high Al concentrations (200–500 µmol l^-1), in both A. montana and C. dissectum. In addition, indications of Al toxicity were observed in these plant species, e.g. poor root development, yellowish leaves and reduced contents of Mg and P in the plants. C. vulgaris did not show reduced growth or poor plant development due to high Al concentrations. The negative effects of aluminium in A. montana and C. dissectum were partly counterbalanced when plants were grown on the same Al concentrations but with increased Ca concentrations, resulting in lower Al:Ca-ratios. No effects of enhanced calcium concentrations on C. vulgaris have been observed.     

Aluminium impact on respiration of lotic mayflies at low pH

Three species of stream-living mayfly nymphs were exposed to total inorganic (labile) monomeric aluminium levels of 0, 0.5, and 2.0 mg L^?1 at pH 4.0 and 4.8 for 10 days. Oxygen consumption rate of the nymphs was measured, using a closed-cylinder technique and micro-Winkler titration. The animals showed significant increases in respiration with raised Al concentrations. The mayfly species Ephemera danica, which is restricted to the less heavily acidified region of South Sweden, was most affected by Al. The response of the two Heptagenia species to elevated Al was less pronounced. The effect of pH, however, seemed less important. Two possible reasons for the respiration increase at high Al levels are: (1) A “chemical impact route”, consisting of a compensatory mechanism due to decreased O₂ transport efficiency, because of impaired osmoregulation and ion transport; and/or (2) a “mechanical impact route” with Al hydroxide precipitation and mucus formation on the gills, causing lowered respiration efficiency. This stress of the increased respiration rate costs energy. Thus less will be available for growth and reproduction. A model of the proposed impact routes is presented.     

Aluminium Induced Magnesium Deficiency in Oats

It was the objective to study the effect of Al on Mg uptake by plants, precluding as far as possible the effect of Al on root growth. Oat plants were grown in a complete standard nutrient solution without any differential treatment, in order to obtain a set of plants which did not differ in the size, the morphology and the physiology of the root system. After the first harvest at the beginning of the stem elongation stage 4 different treatments were introduced: pH 5.5-6.0, pH 5.5-6.0 without Mg, pH 3.8-4.1, pH 3.8-4.1 + 0.3 mmole Al/l. Apart from these variations the composition of the nutrient solution remained unaltered. After another 10 days 2 vessels of each treatment were harvested. The final harvest was 14 days after the beginning of the differential treatments. The growth (in terms of dry matter yield) of neither the shoots nor the roots was adversely affected by the differential treatments, although the plants in the Al and Mg₀ treatments showed distinct symptoms of nutritional disorder. The plants in the low and the high pH treatments differed neither in Mg uptakte nor in Mg concentration in the plants. However, the addition of Al to the nutrient solution reduced Mg uptake in the shoots to about 30% of that in the Al₀ treatments, while there was a net loss of Mg in the roots in spite of the fact that dry matter increased. This means that net uptake of Mg was less than was translocated to the shoot during the period of differential treatments. With no Al in the nutrient solution the Mg concentration in the shoots declined by 3–8% between the first and the final harvest, whereas it increased by 22–35% in the roots. If, however, Al was added to the nutrient solution the Mg concentration dropped by 46% in the shoots and 70% in the roots. With the exception of Ca in the roots, the differential treatments had no effect on the uptake and concentration of Ca, K and P in the plants. In terms of dry matter the differential treatments did not influence root growth and it was concluded that Al had a direct effect on Mg uptake by either inactivating or competing for uptake sites or carriers.     

Evaluation of the Suitability of Sewage and Recycled Water for Irrigation of Ornamental Plants

The present study was conducted to evaluate the potential benefits and risks of the sewage water and recycled treated water on three ornamental plant species, including Umbrella plant (Cyperus alternifolius), Euonymus (Euonymus japonicas), and Dracaena (Cordyline terminalis). Plants in the pots were irrigated with equal volumes of water in 2-day intervals. Treatment plants were analyzed for sodium (Na), potassium (K), copper (Cu), iron (Fe), and lead (Pb) concentrations, in roots and shoots. The experiment was conducted by using a completely randomized design (CRD) with five replications. Data were analyzed using analysis of variance technique and least significance difference (LSD) test was applied at 5% probability level. Plants species performed better in sewage water after recycled water, in terms of growth, number of leaves, chlorophyll content, and leaf thickness, which proved sewage water accelerates the growth and development of ornamental foliage plants, but plants irrigated with this water exhibited greater concentration of Pb than other treatments.