Showing papers in "Plant Soil and Environment in 2018"

Salt stress and phyto-biochemical responses of plants - a review

Abstract: The ability of plants to tolerate salts is determined by multiple biochemical pathways that facilitate retention and/or acquisition of water, protect chloroplast functions and maintain ion homeostasis Essential pathways include those that lead to synthesis of osmotically active metabolites, specific proteins and certain free radical enzymes to control ion and water flux and support scavenging of oxygen radicals No well-defined indicators are available to facilitate the improvement in salinity tolerance of agricultural crops through breeding If the crop shows distinctive indicators of salt tolerance at the whole plant, tissue or cellular level, selection is the most convenient and practical method There is therefore a need to determine the underlying biochemical mechanisms of salinity tolerance so as to provide plant breeders with appropriate indicators In this review, the possibility of using these biochemical characteristics as selection criteria for salt tolerance is discussed

Effect of coin coculation with phosphate and potassium solubilizing bacteria on mineral uptake and growth of pepper and cucumber

Abstract: Biofertilizers have been used as sources to improve plant nutrients in sustainable agriculture. Experiments were conducted to evaluate the potential of phosphate solubilizing bacteria (PSB) Bacillus megaterium var. phosphaticum and potassium solubilizing bacteria (KSB) Bacillus mucilaginosus inoculated in nutrient limited soil planted with pepper and cucumber. Results showed that rock P and K applied either singly or in combination did not significantly enhance soil availability of P and K, indicating their unsuitability for direct application. PSB was a more potent P-solubilizer than KSB, and co-inoculation of PSB and KSB resulted in consistently higher P and K availability than in the control without bacterial inoculum and without rock material fertilizer. Integrated rock P with inoculation of PSB increased the availability of P and K in soil, the uptake of N, P and K by shoot and root, and the growth of pepper and cucumber. Similar but less pronounced results were obtained when rock K and KSB were added concomitantly. Combined together, rock materials and both bacterial strains consistently increased further mineral availability, uptake and plant growth of pepper and cucumber, suggesting its potential use as fertilizer.

Effects of agricultural management on soil organic matter and carbon transformation - a review

Abstract: Soil organic carbon (SOC) is the most often reported attribute and is chosen as the most important indicator of soil quality and agricultural sustainability. In this review, we summarized how cultivation, crop rotation, residue and tillage management, fertilization and monoculture affect soil quality, soil organic matter (SOM) and carbon transformation. The results confirm that SOM is not only a source of carbon but also a sink for carbon sequestrati on. Cultivation and tillage can reduce soil SOC content and lead to soil deterioration. Tillage practices have a major effect on distribution of C and N, and the rates of organic matter decomposition and N mineralization. Proper adoption of crop rotation can increase or maintain the quantity and quality of soil organic matter, and improve soil chemical and physical properties. Adequate application of fertilizers combined with farmyard manure could increase soil nutrients, and SOC content. Manure or crop residue alone may not be adequate to maintain SOC levels. Crop types influence SOC and soil function in continuous monoculture systems. SOC can be best preserved by rotation with reduced tillage frequency and with additions of chemical fertilizers and manure. Knowledge and assessment of changes (positive or negative) in SOC status with time is still needed to evaluate the impact of different management practices.

Effect of osmotic stress on compatible solutes content, membrane stability and water relations in two maize cultivars

Abstract: The effect of osmotic stress on oxidative injury, compatible solutes content and water relations was investigated in two maize cultivars (Zea mays L. cv. Ankora – drought-sensitive and cv. Nova – drought-tolerant). Relative water content in leaves of both cultivars decreased after drought treatment, leaf water loss of sensitive cv. Ankora was higher than that of cv. Nova. The 24 h water stress induced by 0.3M sorbitol (–1.4 MPa) resulted in a damage of cell membranes. Lipid peroxidation rose in all studied organs of cv. Ankora and electrolyte leakage in roots of cv. Ankora was much higher than in cv. Nova. Similarly, proline content increased significantly in all studied organs of cv. Ankora. Content of soluble sugars increased in all studied organs of both cultivars, but the mesocotyl of cv. Nova accumulated the highest amount of sugars. The electrolyte leakage was the highest in the roots of both cultivars. Osmotic stress had deep influence predominantly on the roots of both cultivars. It is apparent that stress impact on the drought-sensitive cv. Ankora was deeper than on the drought-tolerant cv. Nova.

Soil degradation: a problem threatening the sustainable development of agriculture in Northeast China

Abstract: Soil degradation that results from erosion, losses of organic matter and nutrients, or soil compaction are of great concern in every agricultural region of the world. The control of soil erosion and loss of organic matter has been proposed as critical to agricultural and environmental sustainability of Northeast China. This region is bread bas ket of China where the fertile and productive soils, Mollisols (also called Black soils), are primarily distributed. In this paper, we introduce the importance of Northeast China’s grain production to China, and describe the changes of sown acreage and grain production in past decades. This paper also summarizes the distribution, area and intensity of water erosion, changes in the number of gullies and gully density, thickness of top soil layer, soil organic matter content, bulk density, field water holding capacity, and infiltration rates; the number of soil microorganism and main enzyme activities from soil erosion in the region are also summarized. The moderately and severely water-eroded area accounted for 31.4% and 7.9% of the total, and annual declining rate is 1.8%. Erosion rate is 1.24–2.41 mm/year, and soil loss in 1°, 5° and 15° sloping farmlands is 3 t/ha/year, 78 t/ha/year and 220.5 t/ha/year, respectively. SOC content of uncultivated soil was nearly twice that of soil with a 50-year cultivation history, and the average annual declining rate of soil organic matter was 0.5%. Proper adoption of crop rotation can increase or maintain the quantity and quality of soil organic matter, and improve soil chemical and physical properties. Proposed strategies for erosion control, in particular how tillage management, terraces and strip cultivation, or soil amendments contribute to maintain or restore the productivity of severely eroded farmland, are discussed in the context of agricultural sustainability with an emphasis on the Chinese Mollisols.

Effects of hydrogel amendment on water storage of sandy loam and loam soils and seedling growth of barley, wheat and chickpea

Abstract: The hydrogel amendments may improve seedling growth and establishment by increasing water retention capacity of soils and regulating the plants available water supplies, particularly under arid environments. The effects of dif ferent levels of a locally prepared hydrogel were studied on the moisture properties of sandy loam and loam soils (fine-loamy, mixed, hyperthermic Typic Haplargids, USDA, Luvic Yermosol, FAO) and on growth response of three plant species, viz. barley (Hordeum vulgare L.), wheat (Triticum aestivum L.) and chickpea (Cicer arietinum L.). Water absorption by gel was rapid and highest in distilled water and was inhibited by an increase in water salinity. The addition of 0.1, 0.2 and 0.3% hydrogel increased the moisture retention (θr) at field capacity linearly ( r = 0.988) and thus the amount of plant available water significantly in both sandy loam and loam soils compared to the untreated soils. Seed germination of wheat and barley was not affected but seedling growth of both species was improved by the gel amendment. In loam soil, seed germination of chickpea was higher with 0.2% gel and seedling growth increased with increase in gel level compared with control conditions. The hydrogel amendment caused a delay by 4–5 days in wilting of seedlings grown in both soils compared with control conditions. The hydrogel amendment was effective in improving soil moisture availability and thus increased plant establishment. However, the varied responses of plant species in sandy loam and loam soils warrant further studies on the behaviour of different soil types with gel amend ments.

Effect of cadmium and lead on growth, biochemical parameters and uptake in Lemna polyrrhiza L.

Abstract: Aquatic plants are known to accumulate heavy metals. In this study, Duckweed plants (Lemna polyrrhiza L.) were exposed to different concentrations of Cd and Pb. Various physio-biochemical parameters (fresh weight, chlorophyll content, soluble protein, soluble sugars, proline content and metal absorption) were studied. At lower metal concentrations, an increase in proline, protein and sugar was observed but at higher concentrations (above 30 mg/l) their decrease was noticed. Uptake of the metals was concentration and time dependent. Treatment with 1, 10 and 20 mg/l of Cd and Pb showed synergistic relation while 30 and 40 mg/l treatments showed antagonistic relation during the metal uptake. The results suggest that the L. polyrrhiza can be effectively used as a phytoremediator for wastewater polluted with more than one heavy metal at moderate concentrations.

Root excretion and plant tolerance to cadmium toxicity - a review

Abstract: Significant quantities of Cd have been added to soils globally due to various anthropogenic activities, posing a serious threat to safe food production and human health. Rhizosphere, as an important interface of soil and plant, plays a significant role in the agro-environmental system. This article presents a review of relationship between root excretion and microorganisms and plant resistance to Cd toxicity and possible mechanisms. Root exudates markedly altered in species and quantity under Cd stress. Root exudates can affect Cd absorption by plants through changing the physical and chemical characteristics of rhizospheres. The influence of root exudates on Cd bioavailability and toxicity may include modifying the rhizosphere pH and Eh, chelating/complexing and depositing with Cd ions, and altering the community construction, the numbers and activities of rhizospheric microbes. In this paper, the methods to reduce the transfer of Cd in soil-plant system by adjusting rhizosphere environment are discussed, and some aspects are also proposed that should be emphasized in the future research work.

Effects of copper on growth, antioxidant enzymes and phenylalanine ammonia-lyase activities in Jatropha curcas L. seedling

Abstract: The effects of different concentrations of copper (0 –800 µmol) on growth, protein contents, peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), and phenylalanine ammonia-lyase (PAL) in Jatropha curcas L. se edlings were assessed by means of pot experiments. Results suggested that increased copper concentrations lead to decreased shoot elongation and seedling biomass. Protein content in the leaves and roots reached their highest levels at the copper concentrations of 400 µmol, while the highest protein content in the stem was observed at 800 µmol copper. POD activity in leaves and stems was unaffected at low copper concentrations, but showed a considerable variation at high copper concentrations. In roots, the highest POD activity was observed at 200 µmol copper. Under copper stress, SOD activity in leaves increased concomitantly with increasing copper up to 400 µmol, and SOD activity in stems and roots showed a slight increase. Catalase activity significantly elevated in leaves and roots but showed no significant changes in stems of the seedlings exposed to copper. A gradual increase of PAL activity in leaves and roots at the copper concentration of 400 and 200 µmol was observed, while PAL activity remained unchanged in stems.

Performance index as a sensitive indicator of water stress in Triticum aestivum L.

Abstract: Polyphasic chlorophyll a fluorescence represents a promising tool for detection of plant tolerance to various environmental stresses. In pot vegetation experiments, plants of seven winter wheat varieties were screened for their drought tolerance. The drought stress was initiated in plants by withholding water at the beginning of anthesis. While water content was measured continuously as relative water content (RWC), fast chlorophyll a fluorescence kinetics was measured and analysed on dehydrating intact leaves by the JIP-test (analysis of O-J-I-P fluorescence transient). Maximum quantum efficiency of PS II photochemistry (FV/FM) parameter was almost unaffected by dehydration until the severe water stress occurred. In contrast to this a continuous decrease of performance index (PIabs) parameter (Strasser et al. 1995) was observed from the very beginning of dehydration following the decrease of RWC. Statistically significant differences were also found in the PIabs parameter among all tested varieties. The results show that PIabs may serve as an index of plant/variety vitality and/or sensitivity to water stress reflecting their different drought tolerance.

Low-cost agricultural measures to reduce heavy metal transfer into the food chain - a review

Abstract: Heavy metal contamination affects large areas of Europe and worldwide. Hot spots of pollution are located close to industrial sites, around large cities and in the vicinity of mining and smelting plants. Agriculture in these areas faces major problems due to heavy metal transfer into crops and subsequently into the food chain. This paper gives an overview on simple but effective countermeasures to reduce the transfer of heavy metals to edible parts of crops. Since crop species and varieties largely differ in their heavy metal uptake, choosing plants with low transfer factors (e.g., legumes, cereals) may reduce metal concentration in edible parts significantly. Cultivating crops with higher

Effects of heavy metal concentrations on biological activity of soil micro-organisms

Abstract: The distribution of cadmium, lead and zinc in exchangeable, organic, and 2M HNO 3 -extractable fractions as well as the effect of heavy metal concentrations on soil microflora was investigated. Six sampling transects were chosen in the Litavka River alluvium in 1999–2001. Concentrations of all metals increased with decreasing distance from the source of contamination. The concentrations of Cd and Zn in exchangeable fraction were higher than in organically bound fraction, a reverse trend was found in Pb speciation. All measured parameters of soil microbial activity were affected by heavy metal concentrations. The decrease in CFU was most significant in the case of oligotrophic bacteria and spore-forming bacteria. Significant inhibition of C-biomass occurred in soils highly contaminated by heavy metals. The C biomass :C ox ratio decreased with increasing soil pollution. Generally, the values of enzymatic activities were highest in the soil above the source of contamination and they were decreased as approaching the source of contamination. Our results demonstrate that several parameters of microbial activity could be used as good indicators of increasing concentrations of Cd, Pb, and Zn in soil.

Effect of zinc foliar application on grain yield of maize and its yielding components

Abstract: Actual yields of maize harvested by farmers are at level much below attainable yield potential of currently cultivated varieties. Among many growth factors zinc was recognized as one of main limiting factors of maize crop growth and yielding. This hypothesis has been verified within a three-year field study, where zinc fertilizer was applied to maize plants at the 5 th leaf stage. Maize crop responded significantly to zinc foliar application in two of three years of study. The optimal rate of zinc foliar spray for achieving significant grain yield response was in the range from 1.0 to 1.5 kg Zn/ha. Grain yield increase was circa 18% (mean of three years) as compared to the treatment fertilized only with NPK. Plants fertilized with 1.0 kg Zn/ha significantly increased both total N uptake and grain yield. Yield forming effect of zinc fertilizer revealed via improvement of yield structure elements. The number of kernels per plant showed the highest response (+17.8% as compared to the NPK plot) and simultaneously the highest dependence on N uptake (R 2 = 0.79). For this particular zinc treatment, however, the length of cob can also be applied

Arbuscular mycorrhizae improves photosynthesis and water status of Zea mays L. under drought stress

Abstract: The influences of arbuscular mycorrhizal (AM) fungus on growth, gas exchange, chlorophyll concentration, chlo rophyll fluorescence and water status of maize ( Zea mays L.) plants were studied in pot culture under well-watered and drought stress conditions. The maize plants were grown in a sand and black soil mixture for 4 weeks, and then exposed to drought stress for 4 weeks. Drought stress significantly decreased AM colonization and total dry weight. AM symbioses notably enhanced net photosynthetic rate and transpiration rate, but decreased intercellular CO 2 concentration of maize plants regardless of water treatments. Mycorrhizal plants had higher stomatal conductance than non-mycorrhizal plants under drought stress. The concentrations of chlorophyll were higher in mycorrhizal than non-mycorrhizal plants under drought stress. AM colonization significantly increased maximal fluorescence, maximum quantum efficiency of PSII photochemistry and potential photochemical efficiency, but decreased prima ry fluorescence under well-watered and droughted conditions. Mycorrhizal maize plants had higher relative water content and water use efficiency under drought stress compared with non-mycorrhizal plants. The results indicated that AM symbiosis alleviates the toxic effect of drought stress via improving photosynthesis and water status of maize plants.

Phytoremediation based on canola (Brassica napus L.) and Indian mustard (Brassica juncea L.) planted on spiked soil by aliquot amount of Cd, Cu, Pb, and Zn

Abstract: The use of plants to remove heavy metals from soil (phytoremediation) is expanding due to its cost-effectiveness as compared to conventional methods and it has revealed a great potential. Since contaminants such as Pb or Cd have a limited bioavailability in the soil, methods to facilitate their transport to the shoots and roots of plants are required for successful phytoremediation. The objective of this study was to investigate the effects of addition of different rates (0, 3, 6 and 12 mmol/kg) of ethylene diaminetetraacetate (EDTA) on heavy metal availability in soils contaminated with 50 mg/kg Cd (CdCl 2 ), 50 mg/kg Cu (CuSO 4 ), 50 mg/kg Pb [Pb(NO 3 ) 2 ] and 50 mg/kg Zn (ZnSO 4 ), and on the capacity of canola (Brassica napus L.) and Indian mustard (Brassica juncea L.) plants to uptake Cu, Cd, Pb and Zn in a growth chamber. Results indicated that EDTA application increased heavy metal availability and uptake by plants. Significant differences were obtained in both species and plant parts. As for plant species tested, canola was more effective in the uptake of Cu, Cd, Pb and Zn. Root heavy metal uptake of both species was higher than shoot heavy metal uptake.

Microbial enzyme-catalyzed processes in soils and their analysis.

Abstract: Currently, measuring enzyme activities in soils or other lignocellulose-based materials is technically feasible; this measurement is particularly suitable for evaluating soil processes of biopolymer (cellulose, hemicelluloses, lignin, chitin and others) degradation by microbes and for assessing cycling and mobilization of principal nutrients including nitrogen, phosphorus and sulfur. With some considerations, assay methods can provide reliable information on the concentration of enzymes in soil or the rates of enzyme-catalyzed processes. Enzyme analyses in recent studies demonstrated a high level of spatial variability of soil enzyme activity both in depth and in space. The vertical gradients of enzyme activities are most developed in forest soils. Furthermore, enzyme activity in soils is regulated by seasonally-dependent variables such as temperature, moisture and the input of fresh litter. While several enzymes are widely produced by different groups of soil microorganisms, some of them can be used as indicators of the presence or activity of specific microbial taxa.

Selenium biofortification and antioxidant activity in lettuce plants fed with selenate and selenite

Abstract: Selenium is an important element associated with enhancement of antioxidant activity in plants, microorganisms, animals, and humans. In Brazil, the information on Se in agricultural crops is lacking, though there are indications that low levels of Se are consumed by the population. The experiment was conducted under greenhouse conditions with pots containing 3 l of nutritive solution in a completely randomized factorial design, with seven Se concentrations (0, 2, 4, 8, 16, 32, and 64 µmol/l) and two forms of Se (sodium selenate – Na 2 SeO 4 and sodium selenite – Na 2 SeO 3 ), with six replicates. The application of Se as selenate at low concentrations is more appropriate for let tuce biofortification because it favors shoot biomass growth and Se levels in the shoot biomass. Selenium in both forms had two effects on lettuce plant metabolism: at low doses it acted as an antioxidant and enhanced plant growth, whereas at higher levels it reduced yield.

Cyanobacteria from paddy fields in Iran as a biofertilizer in rice plants

Abstract: In this research cyanobacteria (Blue-Green Algae, BGA) were isolated, identified, multiplied and used as an inoculum in pot rice experiment. The pH, moisture and algal population were measured in four seasons. The highest and lowest pH (6.7, 6.2), moisture of soil (43%, 34%) and algal population (12, 20 Colony-Forming Units/50 ml on A and B medium and 4, 5 Colony-Forming Units/50 ml on A and B medium) were recorded in spring and winter, respectively. The only heterocystous cyanobacteria were found in soil samples identified as Anabaena with four species (A. spiroides, A. variabilis, A. torulosa and A. osillarioides). The germination of rice seeds treated with cyanobacte ria was faster than control. The result of pot experiment were: increase of 53% in plant height; 66% in roots length; 58% in fresh leaf and stem weight; 80% in fresh root weight; 125% in dry leaf and stem weight; 150% in dry root weight; 20% in soil moisture; 28% in soil porosity and a decrease of 9.8% in soil bulk density and 4.8% in soil particle density. There were significant differences (P < 0.05) in pot treated with BGA as compared with control.

Red and purple coloured potatoes as a significant antioxidant source in human nutrition - a review

Abstract: Potatoes regarding their consumption are a significant antioxidant source in human nutrition. The main potato an tioxidants are polyphenols, ascorbic acid, carotenoids, tocopherols, α-lipoic acid, and selenium. The most contained polyphenolic antioxidants in potatoes are L-tyrosine, caffeic acid, scopolin, chlorogenic and cryptochlorogenic acid and ferulic acid. In red and purple potatoes are in addition contained acylated anthocyanins and pigmented potatoes display two to three times higher antioxidant potential in comparison with white-flesh potato. Red potato tubers con tain glycosides of pelargonidin and peonidin, purple potatoes glycosides of malvidin and petunidin. New red and purple flesh potato varieties are breeded for their use in food and in the non-food industry. Anthocyanins of potatoes are also useful in the protection against potato blight.

Effects of root interaction and nitrogen fertilization on the chlorophyll content, root activity, photosynthetic characteristics of intercropped soybean and microbial quantity in the rhizosphere

Abstract: A pot experiment using root separation technique was conducted to further understand the effect of root interac tion played in intercropping system under different nitrogen levels The results showed that root interaction and increasing nitrogen application increased the green leaf area per plant and chlorophyll content of soybean, but their effects gradually decreased with increasing nitrogen fertilization level Root interaction and increasing nitrogen application can improve photosynthetic characteristics of soybean, but root interaction only had a significant ef fect under low nitrogen level The number of bacteria, fungi, actinomycetes and Azotobacteria was also obviously affected by root interaction and nitrogen fertilization, and the number of Azotobacteria presented a changing trend of first increased and then decreased with increasing nitrogen fertilization level Root interaction and increas ing nitrogen application improved soybean yield and its components, but their effects gradually decreased with increasing nitrogen fertilization level The root activity of soybean was obviously affected by root interaction, and was significantly positively correlated with green leaf area per plant, chlorophyll content, photosynthetic rate and economic yield per plant Our results indicate that the advantage effect of root interaction and increasing nitrogen application will be partially inhibited with an increasing nitrogen fertilization level

Cadmium and zinc phytoextraction potential of seven clones of Salix spp. planted on heavy metal contaminated soils

Abstract: The Cd and Zn accumulation and phytoextraction potential of seven willow clones was investigated in a pot experiment for two vegetation periods. Heavily polluted Fluvisol-Litavka, moderately contaminated Cambisol-Pribram, and unpolluted control Chernozem-Suchdol were used. Significant differences were found in Cd and Zn accumulation between the willow clones. Cd and Zn were transferred from roots to aboveground tissues and all tested clones confirmed higher Cd and Zn accumulation in leaves than in twigs. Cd and Zn amounts removed by willow leaves were the highest from the most polluted soil (up to 83% Cd and 71% Zn of total removal). Therefore the harvest of leaves is necessary if willows are planted for heavy metal phytoextraction. Although the extremely high Zn contamination of Fluvisol-Litavka significantly reduced biomass production, willows planted in this soil showed the highest Zn removal because of extremely high Zn accumulation (max. 5061 ppm in leaves). Clones planted in moderately contaminated soil achieved the highest Cd removal. Clones showed different abilities to remove Cd and Zn, which was dependent on soil type and contamination level. Remediation factors were determined less than 1% for Zn in the heavily polluted soil and also unsatisfactory for Cd. However, it was shown that willows were suitable phytoextractors of moderately contaminated soil. About 20% of Cd and 4% of Zn were removed by harvested biomass from the total content of soil after two vegetation periods.

Yacon (Smallanthus sonchifolia (Poepp. et Endl.) H. Robinson) chemical composition and use - a review

Abstract: Yacon (Smallanthus sonchifolia (Poepp. et Endl.) H. Robinson), a native plant of the Andes, belongs to the family Com- positae (Asteraceae) and it represents a traditional crop of the original population of Peru used in traditional medicine. A major portion of tuberous root biomass is composed of water (> 70% of fresh weight). Saccharides, especially oligo- fructans, form 70-80% of dry weight, protein content ranges between 0.3% and 3.7%. Fructooligosaccharides of inulin type β (2→ 1), mainly oligomers (GF 2 -GF 16 ), are known for their ability to keep the colon healthy. Yacon sweetness is predominantly caused by fructose, which is by some 70% sweeter than sucrose. Other oligosaccharides are 1-kestose and nystose. Diabetics and persons suffering from digestive problems are recommended to consume yacon because its sugars are not available from the small intestine. The mean tuberous root composition per 100 g of fresh matter is 81.3, 13.8, 0.9, 1.0, 0.1 and 1.1 g of water, saccharides, fibre, proteins, lipids and ash, respectively. Mean mineral contents per 100 g of fresh matter are 334, 34, 12, 8.4, 0.4 and 0.2 mg of potassium, phosphorus, calcium, magnesium, sodium and iron, respectively. Vitamins B 1 , B 2 , C, β-carotene and polyphenols in the same weight are present at mean concentrations 0.07, 0.31, 5.0, 0.13 and 203 mg, respectively. Yacon can be considered an industrial crop, particularly as a source of inulin. The used forms are flour, syrup, extract from tuberous roots and moreover leaf extract for the preparation of yacon infusion with hypoglycaemic effect. In yacon leaves di- and sesquiterpenes with protective effects against insects are present, among them mainly ent-kaurenic acid (ent-kaur-16-en-19-oic acid) and its derivative - 15- α -angeloyloxy-ent- kauren-19-oic acid 16-epoxide. Other components are polyphenolic antioxidants, esp. hydroxycinnamic acids and chlo- rogenic acid. A new antifungal melampolide - sesquiterpene lactone named sonchifolin, as well as three known melampolides, polymatin B, uvedalin and enhydrin, were isolated from leaf extracts of yacon. Three major phytoalexins were isolated: 4'-hydroxy-3'-(3-methylbutanoyl)acetophenone, 4'-hydroxy-3'-(3-methyl-2-butenyl)acetophenone and 5-acetyl-2-(1-hydroxy-1-methylethyl)benzofuran.

Alleviation of salt stress in citrus seedlings inoculated with mycorrhiza: changes in leaf antioxidant defense systems

Abstract: Citrus is a salt-sensitive plant. In the present study, the salt stress ameliorating the effect of arbuscular mycor rhizal fungi through antioxidant defense systems was reported. Three-month-old trifoliate orange ( Poncirus trifoliata) seedlings colonized by Glomus mosseae or G. versiforme were irrigated with 0 and 100 mmol NaCl solutions. After 49 days of salinity, mycorrhizal structures were obviously restrained by salt stress. Mycorrhizal inoculation especially G. mosseae significantly alleviated the growth reduction of salinity. There were notably lower malondialdehyde and hydrogen peroxide contents in the leaves of mycorrhizal seedlings than in non-mycorrhizal ones. Mycorrhizal seedlings recorded notably greater activity of catalase and contents of ascorbate, soluble protein and glutathione under salinity or non-salinity conditions. The seedlings colonized by G. mosseae showed significantly higher antioxidant defense systems response to salinity than by G. versiforme. Our data demonstrate that mycorrhizal (especially G. mosseae) citrus seedlings exhibited greater efficient antioxidant defense systems, which provide better protection against salt damage.

Phytoextraction of lead, zinc and cadmium from soil by selected plants

Abstract: The Pb, Zn and Cd phytoextraction potential of 14 different plants was assessed in a chelate induced phytoextraction experiment. In the used soil heavy metals mainly reside in carbonate, organic matter, and residual soil fractions. The addition of a chelate, 5 mmol/kg ethylenediamine-tetracetic acid (EDTA), increased the proportion of phytoavailable Pb, Zn and Cd in the soil (dissolved in soil solution and exchangeable from soil colloids), and also their uptake by tested plants up to 48 times (Sinapis alba), 4.6 times (Raphanus sativus oleiformis), and 3.3 times (Amaranthus spp.), respectively, compared to the control. The biodegradable chelate ethylenediamine-disuccinic acid (EDDS) was generally less effective (tested on a selection of 4 plant species), except for Cannabis sativa. In a treatment with 10 mmol/kg EDDS, Pb, Zn and Cd concentrations of 1053 ± 125, 211 ± 16 and 5.4 ± 0.8 mg/kg, respectively, were measured in the biomass of Cannabis sativa and were 105, 2.3 and 31.7 times higher, respectively, than in the control treatment. The calculated Pb phytoextraction potential of Cannabis sativa amounted to 26.3 kg/ha.

The effect of salinity stress on ions and soluble sugars distribution in leaves, leaf sheaths and roots of rice (Oryza sativa L.) seedlings

Abstract: In order to investigate the solutes accumulation associated with salt tolerance of rice (Oryza sativa L.), two rice genotypes including IR651 (salt-tolerant) and IR29 (salt-sensitive) were grown hydroponically in the Youshida nutrient solution. Salinity treatment was imposed 3 weeks after sowing using NaCl in two levels 0 and 100 mmol. Samples were separately collected from the youngest (sixth) leaves, leaf sheaths and roots at 72 and 240 h after salinization; then Na + , K + , Ca 2+ , Mg 2+ , P, Mn 2+ , Cl – and total soluble sugars concentration and Na + /K + ratio were determined. Total dry weight of both genotypes decreased with the application of NaCl. Salinity caused higher accumulation of Na + and Cl – in the sixth leaf and leaf sheath of IR29 than in IR651 while their concentration in root of IR651 was higher. K + concentration was decreased in the sixth leaf and leaf sheath of IR29 under NaCl stress. Reduction in Ca 2+ and Mg 2+ concentrations were observed in sixth leaves of both genotypes. P concentration was increased in leaf sheath and root of IR29 under saline conditions while it showed no changes in IR651. Our results indicated that the tolerant genotype had mechanisms to prevent high Na + and Cl – accumulation in the sixth leaf. High total soluble sugars concentration in shoot of IR651 is probably for adjusting osmotic potential and better water uptake under salinity. These mechanisms help plant to avoid tissue death and enable to continue its growth and development under saline conditions.

Halopriming improves vigor, metabolism of reserves and ionic contents in wheat seedlings under salt stress

Abstract: The present study was conducted to investigate whether salt tolerance may be induced in wheat at germination stage by halopriming with different inorganic salts (CaCl 2 , NaCl and CaSO 4 ), and how far these salts affect the mobilization of different nutrients to different parts of seedlings. Seeds of two wheat cultivars (Inqlab-91 and SARC-1) were primed in 50 mmol solutions of CaCl 2 , NaCl or CaSO 4 for 12 h separately and germinated under non-saline and saline (125 mmol NaCl) conditions. All seed treatments hastened germination under saline and non-saline conditions as compared to those of non-primed seeds. However, priming with CaSO 4 enhanced germination of both cultivars under saline conditions more than any other treatment. Maximum root length and fresh and dry weights were obtained in plants raised from seeds primed with CaSO 4 followed by CaCl 2 . Concentrations of Na + and K + in seedlings obtained after priming changed significantly. However, Na + was highest in seedlings raised from seeds primed with NaCl whereas the concentration of K + was highest in the seedlings primed with CaSO 4 . Maximum total sugars and reducing sugars were observed when seeds were treated with CaCl 2 followed by CaSO 4 . In addition, SARC-1 overcame Inqlab-91 in all growth parameters of the seedlings. In conclusion, different salts used for priming in wheat seeds improved the salt stress tolerance; however, CaSO 4 and CaCl 2 proved to be the most effective priming agents in inducing salt tolerance in both wheat cultivars whereas NaCl was a less effective priming agent.

Mobility of lead, zinc and cadmium in alluvial soils heavily polluted by smelting industry

Abstract: In order to determine the mobility of Pb, Zn and Cd in soils from the Přibram region (Czech Republic) heavily contaminated by metallurgy, two profiles of alluvial soils were closely studied. Total contents of heavy metals were determined a�er digestion with a mixture of HF and HClO4. Heavy metal mobility was assessed using the mobility factor (MF) that represents the proportion of heavy metals present in the exchangeable and carbonate bound fraction based on the Tessier’s sequential extraction procedure. The MF ranged from 2 to 46% for lead, 19 to 62% for zinc and 61 to 94% for cadmium. The profile distribution of zinc and cadmium showed a variable development with depth, which is caused by high amounts of these metals present in labile forms. The profile distribution of lead (the least mobile metal) is characterized by a gradual decrease with depth. The results indicate a higher contamination of the soil profile situated 2.5 km away from the smelter in comparison with the profile in its close vicinity. This fact confirms the existence of extreme fluvial contamination.

The effect of brassinosteroids on radish (Raphanus sativus L.) seedlings growing under cadmium stress

Abstract: The effect of 24-epibrassinolide and 28-homobrassinolide on seed germination and seedling growth of radish (Raphanus sativus L.) was studied under cadmium toxicity. The impact of brassinosteroids (BRs) on free proline levels and the activity of antioxidant enzymes catalase (CAT; EC 1.11.1.6), peroxidase (POD; EC 1.11.1.7), superoxide dismutase (SOD; EC 1.15.1.1), ascorbic peroxidase (APOX; EC 1.11.1.11) and guaiacol peroxidase (GPX; EC 1.11.1.7) in radish seedlings under Cd toxicity was evaluated. The effect of BRs on the activity of ascorbic acid oxidase (AAO; EC 1.10.3.3) and lipid peroxidation in radish seedlings challenged with Cd stress was also investigated. BRs supplementation alleviated the toxic effect of the heavy metal and increased the percentage of seed germination and seedling growth. Out of the two substances, HBL was found to be more effective than EBL in stress alleviation. HBL (3μM) alleviated the toxic effect of the heavy metal and increased the percentage of seed germination by 57% over Cd and 20% over unstressed control. Similarly supplementation of HBL (3μM) caused an increase of 156%, 78% and 91% in length, fresh weight and dry weight of seedling, respectively, over Cd treatment alone. The amelioration of seedling growth by BRs under metal toxicity was associated with enhanced levels of free proline. The activities of antioxidant enzymes CAT, SOD, APOX and GPX were increased in the seedlings from treatments with Cd along with BRs. Brassinosteroid treatment reduced the activity of POD and AAO in heavy metal stressed seedlings. Lipid peroxidation induced by Cd was found reduced with the supplementation of BRs. The results obtained in the study clearly indicated the ameliorative influence of brassinosteroids on the inhibitory effect of Cd toxicity.

Antioxidative protection in wheat varieties under severe recoverable drought at seedling stage

Abstract: The antioxidative protection in leaves of four winter wheat ( Triticum aestivum L) varieties with different field drought resistance was studied under severe recoverable soil drought at seedling stage by withholding irrigation for 7 days (57–59% leaf water deficit) followed by rewatering A 3-fold raise in electrolyte leakage and a sharp increase in proline accumulation corresponded to drought severity Hydrogen peroxide content and catalase (CAT) activity were maintained low under stress Peroxidase (GPX) activity increased, whereas superoxide dismutase (SOD) activity only slightly changed The content of ascorbate and low-molecular thiols diminished under severe drought and was restored in recovery Malondialdehyde level was not changed significantly in drought-treated plants but raised after re-watering In recovery CAT activity became significantly higher whereas GPX activity diminished Three isoforms of SOD, one of catalase and three of GPX were revealed Proline accumulation had a predominant role in drought response As for varieties, drought sensitivity or tolerance was not necessarily correlated with differences in the antioxidative response at early vegetative stage

Application of chlorophyll fluorescence performance indices to assess the wheat photosynthetic functions influenced by nitrogen deficiency.

Abstract: Nitrogen deficiency influences importantly the plant photosynthetic capacity and crop productivity. Here, we employed the rapid, non-invasive measurements of chlorophyll a fluorescence kinetics for calculation of the integrative fluorescence parameters related to the leaf photosynthetic performance. In pot experiments with winter wheat (Triticum aestivum L.) we cultivated plants during the whole growing period in the soil substrate supplied with four different doses of nitrogen. The leaf nitrogen and chlorophyll content as well as the plant dry mass were analyzed after chlorophyll fluorescence records in three growth stages. Our results indicate that the commonly used parameter F-v/F-m (the maximum quantum yield of photochemistry) was almost insensitive to nitrogen treatment. In contrary, the performance index (PIabs) and total performance index (PItot) were much more responsive and significant differences among plants of different nitrogen treatments as well as between the youngest and third leaf from the top were observed. Parameter PItot shown to express only small diurnal changes, thus being more reliable and more useful for comparison of different samples in field conditions than more frequently used parameter PIabs.