Magnetite nanoparticles coated with citric acid are not phytotoxic and stimulate soybean and alfalfa growth.

In this work, the internalization and distribution of citric acid-coated magnetite nanoparticles (here, Fe3O4-NPs) in soybean and alfalfa tissues and their effects on plant growth were studied. Both legumes were germinated in pots containing an inert growing matrix (vermiculite) to which Hoagland solution without (control, C), with Fe3O4-NPs (50 and 100 mgironL-1, NP50 and NP100), or with the same amount of soluble iron supplied as Fe-EDTA (Fe50, Fe100) was added once before sowing. Then, plants were watered with the standard nutrient solution. The observation of superparamagnetic signals in root tissues at harvest (26 days after emergence) indicated Fe3O4-NPs uptake by both legumes. A weak superparamagnetic signal was also present in the stems and leaves of alfalfa plants. These findings suggest that Fe3O4-NPs are readily absorbed but not translocated (soybean) or scarcely translocated (alfalfa) from the roots to the shoots. The addition of both iron sources resulted in increased root weight; however, only the addition of Fe3O4-NPs resulted in significantly higher root surface; shoot weight also increased significantly. As a general trend, chlorophyll content enhanced in plants grown in vermiculite supplemented with extra iron at pre-sowing; the greatest increase was observed with NP50. The only antioxidant enzyme significantly affected by our treatments was catalase, whose activity increased in the roots and shoots of both species exposed to Fe3O4-NPs. However, no symptoms of oxidative stress, such as increased lipid peroxidation or reactive oxygen species accumulation, were evidenced in any of these legumes. Besides, no evidence of cell membrane damage or cell death was found. Our results suggest that citric acid-coated Fe3O4-NPs are not toxic to soybean and alfalfa; instead, they behave as plant growth stimulators.

Effects of salt concentration, pH, and their interaction on plant growth, nutrient uptake, and photochemistry of alfalfa (Medicago sativa) leaves.

In order to explore the main limiting factors affecting the growth and physiological function of alfalfa under salt and alkali stress, the effect of the salt and alkali stress on the growth and physiological function of alfalfa was studied. The results showed that effects of the excessive salt concentration (100 and 200 mM) on the growth and physiological characteristics were significantly greater than that of pH (7.0 and 9.0). Under 100 mM salt stress, there was no significant difference in the growth and photosynthetic function between pH 9.0 and pH 7.0. Under the 200 mM salt concentration the absorption of Na+ by alfalfa treated at the pH 9.0 did not increase significantly compared with absorption at the pH 7.0. However, the higher pH directly reduced the root activity, leaf's water content, and N-P-K content also decreased significantly. The PSII and PSI activities decreased with increasing the salt concentration, especially the damage degree of PSI. Although the photoinhibition of PSII was not significant, PSII donor and electron transfer from the QA to QB of the PSII receptor sides was inhibited. In a word, alfalfa showed relatively strong salt tolerance capacity, at the 100 mM salt concentration, even when the pH reached 9.0. Thus, the effect on the growth and photosynthetic function was not significant. However, at 200 mM salt concentration, pH 9.0 treatment caused damage to root system and the photosynthetic function in leaves of alfalfa was seriously injured.

Comparison of the Polyphenolic Profile of Medicago sativa L. and Trifolium pratense L. Sprouts in Different Germination Stages Using the UHPLC-Q Exactive Hybrid Quadrupole Orbitrap High-Resolution Mass Spectrometry.

Identification and quantification of polyphenols in plant material are of great interest since they make a significant contribution to its total bioactivity. In the present study, an UPLC-Orbitrap-MS/MS approach using the variable data acquisition mode (vDIA) was developed and applied for rapid separation, identification, and quantification of the main polyphenolic compounds in Medicago sativa L. and Trifolium pratense L. sprouts in different germination stages. Based on accurate MS data and fragment ions identification strategy, a total of 29 compounds were identified by comparing their accurate masses, fragment ions, retention times, and literatures. Additionally, a number of 30 compounds were quantified by comparing to the reference standards. Data were statistically analysed. For both plant species, the sprouts of the third germination day are valuable sources of bioactive compounds and could be used in phytotherapy and nutrition. Although Trifolium pratense L. (Red Clover) is considered to be a reference for natural remedies in relieving menopause disorders, alfalfa also showed a high level of biological active compounds with estrogenic activity.

Influences of arbuscular mycorrhizae, phosphorus fertiliser and biochar on alfalfa growth, nutrient status and cadmium uptake.

The objective of the study was to explore the influences of arbuscular mycorrhizae (AM), phosphorus (P) fertiliser, biochar application (BC) and their interactions on Medicago sativa growth, nutrient, Cd content and AM fungi-plant symbioses. Applications of both P fertiliser and BC significantly increased total biomass and P and potassium (K) uptake, regardless of AM. When no P fertiliser or BC was used, the shoot biomass and nitrogen (N), P, and K contents in the +AM treatments were 1.39, 1.54, 4.53 and 2.06 times higher than those in the -AM treatments, respectively. AM fungi only elevated the total P uptake by 44.03% when P fertiliser was applied at a rate of 30 mg P kg-1 in the absence of BC addition. With BC application or high-P fertiliser input (100 mg P kg-1), the soil available P was significantly higher than that in the other treatments, and AM fungi significantly reduced the shoot biomass. The minimum Cd concentration occurred in the shoots of alfalfas treated with BC and high-P fertiliser inputs; this concentration was lower than the maximum permitted concentration in China. Although the BC and high-P inputs could eliminate the positive mycorrhizal response, the results suggested that BC application in combination with high-P fertiliser input could not only increase forage yields but also lower Cd concentrations to meet the forage safety standards by the dilution effect.

Arbuscular Mycorrhizal Symbiosis Mitigates Iron (Fe)-Deficiency Retardation in Alfalfa (Medicago sativa L.) Through the Enhancement of Fe Accumulation and Sulfur-Assisted Antioxidant Defense.

Iron (Fe)-deficiency is one of the major constraints affecting growth, yield and nutritional quality in plants. This study was performed to elucidate how arbuscular mycorrhizal fungi (AMF) alleviate Fe-deficiency retardation in alfalfa (Medicago sativa L.). AMF supplementation improved plant biomass, chlorophyll score, Fv/Fm (quantum efficiency of photosystem II), and Pi_ABS (photosynthesis performance index), and reduced cell death, electrolyte leakage, and hydrogen peroxide accumulation in alfalfa. Moreover, AMF enhanced ferric chelate reductase activity as well as Fe, Zn, S and P in alfalfa under Fe-deficiency. Although Fe-transporters (MsIRT1 and MsNramp1) did not induce in root but MsFRO1 significantly induced by AMF under Fe deficiency in roots, suggesting that AMF-mediated Fe enhancement is related to the bioavailability of Fe at rhizosphere/root apoplast rather than the upregulation of Fe transporters under Fe deficiency in alfalfa. Several S-transporters (MsSULTR1;1, MsSULTR1;2, MsSULTR1;3, and MsSULTR3;1) markedly increased following AMF supplementation with or without Fe-deficiency alfalfa. Our study further suggests that Fe uptake system is independently influenced by AMF regardless of the S status in alfalfa. However, the increase of S in alfalfa is correlated with the elevation of GR and S-metabolites (glutathione and cysteine) associated with antioxidant defense under Fe deficiency.

Different responses to soil petroleum contamination in monocultured and mixed plant systems.

The role of plant composition should be considered during ecological risk assessment of soil petroleum contamination. To evaluate the influences of plant composition on phytotoxicity, petroleum degraders, and petroleum degradation, four treatments were arranged in the present study: unplanted, bristle grass only, alfalfa only, and bristle grass and alfalfa mixed planted in uncontaminated soil or petroleum contaminated soil (w/w, 1.0%). Petroleum contamination inhibited the growth of bristle grass and alfalfa significantly, and alfalfa growth inhibition was significantly alleviated when mixed planted with bristle grass (p < 0.05). MPN analysis indicated that the mixed plant treatment can gather the benefits of two species, and facilitate the development of alkane, total hydrocarbon and PAH degraders in contaminated soil, but not occur in uncontaminated soil. Compared with alfalfa only treatment, the degradation rates for total petroleum hydrocarbons (TPH) and aliphatic fraction were significantly increased in the mixed plant treatment (p < 0.05). However, the degradation of aromatic petroleum fraction was not received substantial improvement in the mixed plant treatment, despite containing an abundant PAH degraders. Overall, mixed plant cultivation had the significant influences on plant growth, microbial community and petroleum degradation in contaminated soils. The study provides valuable insights for vegetation restoration and remediation systems in petroleum contaminated sites of study area.

Arbuscular mycorrhizal fungi alleviate arsenic toxicity to Medicago sativa by influencing arsenic speciation and partitioning.

In a pot experiment, Medicago sativa inoculated with/without arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis were grown in four levels (0, 10, 25, and 75 mg/kg) of arsenic (As)-polluted soil to investigate the influences of AM symbiosis on plant As tolerance. The results showed that mycorrhizal inoculation significantly increased plant biomass, while As addition decreased mycorrhizal colonization and hyphal length density. Mycorrhizal inoculation dramatically improved plant phosphorus (P) nutrition, restricted As uptake and retained more As in roots by upregulating the expression of the AM-induced P transporter gene MsPT4 and the metallothionein gene MsMT2. High soil As content downregulated MsPT4 expression. Dimethylarsenic acid (DMA) was detected only in the shoots of mycorrhizal plants, indicating that AM fungi likely play an essential role in As detoxification by biological methylation. The present investigation allowed deeper insights into the As detoxification mechanisms of AM associations and demonstrated the important role of AM fungi in plant resistance under As-contaminated conditions.

Interactions of plant growth-promoting rhizobacteria and soil factors in two leguminous plants.

Although the rhizomicrobiome has been extensively studied, little is known about the interactions between soil properties and the assemblage of plant growth-promoting microbes in the rhizosphere. Herein, we analysed the composition and structure of rhizomicrobiomes associated with soybean and alfalfa plants growing in different soil types using deep Illumina 16S rRNA sequencing. Soil pH, P and K significantly affected the composition of the soybean rhizomicrobiome, whereas soil pH and N had a significant effect on the alfalfa rhizomicrobiome. Plant biomass was influenced by plant species, the composition of the rhizomicrobiome, soil pH, N, P and plant growth stage. The beta diversity of the rhizomicrobiome was the second most influential factor on plant growth (biomass). Rhizomicrobes associated with plant biomass were identified and divided into four groups: (1) positively associated with soybean biomass; (2) negatively associated with soybean biomass; (3) positively associated with alfalfa biomass; and (4) negatively associated with alfalfa biomass. Genera assemblages among the four groups differentially responded to soil properties; Group 1 and Group 2 were significantly correlated with soil pH and P, whereas Group 3 and Group 4 were significantly correlated with soil N, K and C. The influence of soil properties on the relative abundance of plant biomass-associated rhizomicrobes differed between soybean and alfalfa. The results suggest the rhizomicrobiome has a pronounced influence on plant growth, and the rhizomicrobiome assemblage and plant growth-associated microbes are differentially structured by soil properties and leguminous plant species.

Breaking continuous potato cropping with legumes improves soil microbial communities, enzyme activities and tuber yield.

This study was conducted to explore the changes in soil microbial populations, enzyme activity, and tuber yield under the rotation sequences of Potato-Common vetch (P-C), Potato-Black medic (P-B) and Potato-Longdong alfalfa (P-L) in a semi-arid area of China. The study also determined the effects of continuous potato cropping (without legumes) on the above mentioned soil properties and yield. The number of bacteria increased significantly (p < 0.05) under P-B rotation by 78%, 85% and 83% in the 2, 4 and 7-year continuous cropping soils, respectively compared to P-C rotation. The highest fungi/bacteria ratio was found in P-C (0.218), followed by P-L (0.184) and then P-B (0.137) rotation over the different cropping years. In the continuous potato cropping soils, the greatest fungi/bacteria ratio was recorded in the 4-year (0.4067) and 7-year (0.4238) cropping soils and these were significantly higher than 1-year (0.3041), 2-year (0.2545) and 3-year (0.3030) cropping soils. Generally, actinomycetes numbers followed the trend P-L>P-C>P-B. The P-L rotation increased aerobic azotobacters in 2-year (by 26% and 18%) and 4-year (40% and 21%) continuous cropping soils compared to P-C and P-B rotation, respectively. Generally, the highest urease and alkaline phosphate activity, respectively, were observed in P-C (55.77 mg g-1) and (27.71 mg g-1), followed by P-B (50.72 mg mg-1) and (25.64 mg g-1) and then P-L (41.61 mg g-1) and (23.26 mg g-1) rotation. Soil urease, alkaline phosphatase and hydrogen peroxidase activities decreased with increasing years of continuous potato cropping. On average, the P-B rotation significantly increased (p <0.05) tuber yield by 19% and 18%, compared to P-C and P-L rotation respectively. P-L rotation also increased potato tuber yield compared to P-C, but the effect was lesser relative to P-B rotation. These results suggest that adopting potato-legume rotation system has the potential to improve soil biology environment, alleviate continuous cropping obstacle and increase potato tuber yield in semi-arid region.

Heated blends of phosphate waste: Microstructure characterization, effects of processing factors and use as a phosphorus source for alfalfa growth.

Microstructure of expandable lightweight aggregates (LWAs), which was composed of phosphate waste (PW), cement kiln dust (CKD) and raw clay (RC) was investigated, and the effects of processing factors (temperature, waste content, soaking time) on their physical properties were quantified by using response surface methodology (RSM). The potential use of LWAs as a phosphorus source was assessed through the use of seeds of alfalfa. It was found that the main minerals of the waste, namely carbonates and fluorapatite, were involved in the formation of labradorite/anorthite and melt respectively. Stability of mullite- the main constituent of CKD- was sensitive to the melt content. The assemblage of the identified phases was discussed based on the CaO-SiO2-Al2O3 phase diagram. The results of RSM showed that the change of compressive strength, firing shrinkage and water absorption of LWAs versus processing factors was well described with a polynomial model and the weights of the effects of the factors increased in the following order: sintering temperature > waste content (in the case of PW-RC) > soaking time. On the other hand, it was found that due to the release of phosphorus by soil-embedded pellets, the growth of alfalfa plants improved, and the rate enhanced in this order: PW-RC > PW-CKD > PW-CKD-RC. The absorbed quantity of phosphorus (0.12%) was still lower than the common uptake amount.

The effects of Mg enrichment of vegetable sprouts on Mg concentration, yield and ROS generation.

BACKGROUND: Two-thirds of the world's population do not consume the recommended amount of Mg, hence the demand for the production of Mg-enriched plants. Sprouts represent promising targets for enrichment. This study evaluated the effects of enriching broccoli, radish, alfalfa and mung bean sprouts with Mg (50-300 mg L(-1) ) on (i) the concentration of Mg and other ions, (ii) biomass accumulation, (iii) levels of reactive oxygen species (ROS), and (iv) the activity/content of enzymatic and non-enzymatic components of antioxidative systems. RESULTS: Enrichment of sprouts with Mg led to a significant increase in Mg concentration, especially in alfalfa (increase of 23-152 %), without depletion of other ions. A higher Mg concentration had a minor effect on biomass accumulation, but increased, often significantly, ROS generation and affected enzymatic and non-enzymatic antioxidative systems. The level of O2 (•-) increased most in broccoli, by 59-158%, while OH(•) increased most in radish, by 200-350%. CONCLUSIONS: Enrichment of sprouts with Mg is possible, but attention must be paid to elevated ROS levels in food. Mung bean sprouts are best suited to enrichment as they make a considerable contribution to the daily supplementation of Mg, at still low levels of ROS in enriched plants. © 2015 Society of Chemical Industry.

Differential uptake of silver, copper and zinc suggests complementary species-specific phytoextraction potential.

The aim of our study, conducted as a pot experiment, was to assess the potential of willow (Salix miyabeana), alfalfa (Medicago sativa), tall fescue (Festuca arundinacea), and Indian mustard (Brassica juncea) to remediate two brownfield soils differentially contaminated with Ag, Cu and Zn (up to 113.60, 47.50, and 117.00 mg kg(-1) respectively). While aboveground Ag accumulation was highest in B. juncea (4.60 ± 2.58 mg kg(-1)), lower levels were also measured in M. sativa and F. arundinacea. Cu accumulation was observed in all species, but only in underground parts, and was highest in F. arundinacea (269.20 ± 74.75 mg kg(-1)), with a bioconcentration factor of 13.85. Salix miyabeana was found to have the highest Zn aerial tissue concentration (119.96 ± 20.04 mg kg(-1)). Because of its high Ag uptake, the remediation potential of B. juncea should be evaluated more extensively on the site from which we excavated the soil for this study. Given the multiple forms of contamination on the site and the differential specie-related uptake evident in our findings, we hypothesize that an optimal plantation allowing expression of complementary remediation functions would include B. juncea for extraction of Ag, in combination with F. arundinacea for stabilization of Cu and S. miyabeana for extraction of Zn.

Risks and benefits of compost-like materials prepared by the thermal treatment of raw scallop hepatopancreas for supplying cadmium and the growth of alfalfa (Medicago sativa L.).

Scallop hepatopancreas, fishery waste, contains relatively high levels of Cd and organic nitrogen compounds, the latter of which represent a fertilizer. In this study, raw scallop hepatopancreas tissue was thermally treated with sawdust and red loam in the presence of an iron catalyst to produce compost-like materials (CLMs). Two CLM samples were prepared by varying the content of raw scallop hepatopancreas tissue: 46 wt.% for CLM-1 and 18 wt.% for CLM-2. Mixtures of control soil (CTL) and CLMs (CLM content: 10 and 25 wt.%) were examined for the growth of alfalfa (Medicago sativa L.) to evaluate the risks and benefits of using this material for fertilization. The Cd content in shoots and roots of alfalfa, that were grown in the presence of CLMs, was significantly higher than those for the plants grown in the CTL, indicating that Cd had accumulated in the plants from CLMs. The accumulation of Cd in the alfalfa roots was quite high in the case of the 25% CLM-1 sample. However, alfalfa growth was significantly promoted in the presence of 10% CLM-1. This can be attributed to the higher levels of nitrogen and humic substances, which serve as fertilizer components. Although the fertilization effect in case of CLM-1showed a potential benefit, the accumulation of Cd in alfalfa was clearly increased in the presence of both CLMs. In conclusion, the use of CLMs produced from raw scallop hepatopancreas tissue can be considered to have a desirable benefit from standpoint of its use as fertilizer, but is accompanied by a risk of the accumulation of Cd in alfalfa plants.

Phytotoxicity of three plant-based biodiesels, unmodified castor oil, and Diesel fuel to alfalfa (Medicago sativa L.), lettuce (Lactuca sativa L.), radish (Raphanus sativus), and wheatgrass (Triticum aestivum).

The wide use of plant-based oils and their derivatives, in particular biodiesel, have increased extensively over the past decade to help alleviate demand for petroleum products and improve the greenhouse gas emissions profile of the transportation sector. Biodiesel is regarded as a clean burning alternative fuel produced from livestock feeds and various vegetable oils. Although in theory these animal and/or plant derived fuels should have less environmental impact in soil based on their simplified composition relative to Diesel, they pose an environmental risk like Diesel at high concentrations when disposed. The aim of the present study was to ascertain the phytotoxicity of three different plant-derived biodiesels relative to conventional Diesel. For phytotoxicological analysis, we used seeds of four crop plants, Medicago sativa, Lactuca sativa, Raphanus sativus, and Triticum aestivum to analyze the germination of seeds in contaminated soil samples. The toxicological experiment was conducted with two different soil textures: sandy loam soil and silt loam soil. The studied plant-based biodiesels were safflower methyl-ester, castor methyl ester, and castor ethyl-ester. Biodiesel toxicity was more evident at high concentrations, affecting the germination and survival of small-seeded plants to a greater extent. Tolerance of plants to the biodiesels varied between plant species and soil textures. With the exception of R. sativus, all plant species were affected and exhibited some sensitivity to the fuels, such as delayed seedling emergence and slow germination (average=10 days) at high soil concentrations (0.85% for Diesel and 1.76% for the biodiesels). Tolerance of plants to soil contamination had a species-specific nature, and on average, decreased in the following order: Raphanus sativus (0-20%)>Triticum aestivum (10-40%) ≥ Medicago sativa> Lactuca sativa (80-100%). Thus, we conclude that there is some phytotoxicity associated with plant-based biodiesels. Further, the findings of this study can be useful for selecting the least fuel-tolerant species as a soil contamination bio-indicator and for determining the risks of biodiesel contamination.

The effect of dietary alfalfa and flax sprouts on rabbit meat antioxidant content, lipid oxidation and fatty acid composition.

The aim of this study was to determine the effect of dietary supplementation with flax and alfalfa sprouts on fatty acid, tocopherol and phytochemical contents of rabbit meat. Ninety weaned New Zealand White rabbits were assigned to three dietary groups: standard diet (S); standard diet+20g/d of alfalfa sprouts (A); and standard diet+20g/d of flax sprouts (F). In the F rabbits the Longissimus dorsi muscle showed a higher thio-barbituric acid-reactive value and at the same time significantly higher values of alpha-linolenic acid, total polyunsaturated and n-3 fatty acids. Additionally n-3/n-6 ratio and thrombogenic indices were improved. The meat of A rabbits showed intermediate values of the previously reported examined parameters. Dietary supplementation with sprouts produced meat with a higher total phytoestrogen content. The addition of fresh alfalfa and flax sprouts to commercial feed modified the fat content, fatty acid and phytochemical profile of the meat, but the flax ones worsened the oxidative status of meat.

Estimation of biomass and canopy height in bermudagrass, alfalfa, and wheat using ultrasonic, laser, and spectral sensors.

Non-destructive biomass estimation of vegetation has been performed via remote sensing as well as physical measurements. An effective method for estimating biomass must have accuracy comparable to the accepted standard of destructive removal. Estimation or measurement of height is commonly employed to create a relationship between height and mass. This study examined several types of ground-based mobile sensing strategies for forage biomass estimation. Forage production experiments consisting of alfalfa (Medicago sativa L.), bermudagrass [Cynodon dactylon (L.) Pers.], and wheat (Triticum aestivum L.) were employed to examine sensor biomass estimation (laser, ultrasonic, and spectral) as compared to physical measurements (plate meter and meter stick) and the traditional harvest method (clipping). Predictive models were constructed via partial least squares regression and modeled estimates were compared to the physically measured biomass. Least significant difference separated mean estimates were examined to evaluate differences in the physical measurements and sensor estimates for canopy height and biomass. Differences between methods were minimal (average percent error of 11.2% for difference between predicted values versus machine and quadrat harvested biomass values (1.64 and 4.91 t·ha(-1), respectively), except at the lowest measured biomass (average percent error of 89% for harvester and quad harvested biomass < 0.79 t·ha(-1)) and greatest measured biomass (average percent error of 18% for harvester and quad harvested biomass >6.4 t·ha(-1)). These data suggest that using mobile sensor-based biomass estimation models could be an effective alternative to the traditional clipping method for rapid, accurate in-field biomass estimation.

Effects of rapeseed oil on the rhizodegradation of polyaromatic hydrocarbons in contaminated soil.

Plants have the ability to promote degradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil by supporting PAH degrading microorganisms in the rhizosphere (rhizodegradation). The aim of this study was to evaluate if rapeseed oil increases rhizodegradation because various studies have shown that vegetable oils are able to act as extractants for PAHs in contaminated soils and therefore might increase bioavailability of PAHs for microbial degradation. In this study different leguminous and grass species were tested. The results suggested a significant impact of vegetable oil (1 and 3% w/w) on plant growth (decrease of plant height and biomass). The results of the pot experiment showed a decrease in the PAH content of the soil without amendment of rapeseed oil after six months. In soil amended with 1% and 3% of oil, there was no decrease in PAH content within this period. Although no enhancement of PAH degradation by plants could be measured in the bulk soil of the pot experiments, a rhizobox experiment showed a significant reduction of PAH content in the rhizosphere of alfalfa (Medicago sativa cv. Europe). Our investigations also showed significant differences in the degradation behaviour of the 16 individually analysed PAHs.

[Effects of shading on the aboveground biomass and stiochiometry characteristics of Medicago sativa].

In order to provide scientific basis for inter-planting alfalfa in abandoned farmland, a shading experiment was conducted to simulate the effects of different light intensities on the aboveground biomass, the contents of carbon, nitrogen, phosphorus and potassium, and the stoichiometric characteristics of alfalfa under the plantation. The results showed that the aboveground biomass of alfalfa correlated significantly with the light intensity, and shading treatment reduced the aboveground biomass of alfalfa significantly. The aboveground alfalfa tissues under the 62% shading treatment had the highest contents of carbon, nitrogen and phosphorus, which was 373.73, 34.38 and 5.47 g · kg(-1), respectively, and significantly higher than those of the control. However, shading treatments had no significant effect on the potassium content of aboveground part. The C/N ratio in aboveground tissues under the 72% shading treatment was significantly higher than that of the control, but no significant differences among other treatments were found. The ratios of N/P and C/P in aboveground tissues showed a tendency that decreased firstly and then increased with the increase of light intensity.

[Effects of continuous cropping of wheat and alfalfa on soil enzyme activities and nutrients].

Based on a long-term rotation and fertilization experiment in Changwu, Shaanxi, China, we determined the enzymatic activities and nutrients in soils after 27 years continuous cropping of alfalfa and wheat, respectively. The activities of invertase, urease and phosphatase were not affected by fertilization treatment within each cropping system, but they were significantly higher in the alfalfa continuous cropping system than in the wheat continuous cropping system under each fertilization treatment. The activity of hydrogen peroxidase was not affected by the type of cropping system or fertilization treatment. Across the cropping systems, the activities of soil urease, phosphatase and hydrogen peroxidase were higher while soil invertase activity was lower in N, P and manure (NPM) combined treatment compared with the other fertilization treatments. The accumulations of soil organic matter, total nitrogen and available nitrogen were greater in the alfalfa cropping system than in the wheat continuous cropping system, and the NPM treatment could improve the soil fertility.

Study of selenocompounds from selenium-enriched culture of edible sprouts.

Selenium is recognised as an essential micronutrient for humans and animals. One of the main sources of selenocompounds in the human diet is vegetables. Therefore, this study deals with the Se species present in different edible sprouts grown in Se-enriched media. We grew alfalfa, lentil and soy in a hydroponic system amended with soluble salts, containing the same proportion of Se, in the form of Se(VI) and Se(IV). Total Se in the sprouts was determined by acidic digestion in a microwave system and by ICP/MS. Se speciation was carried out by enzymatic extraction (Protease XIV) and measured by LC-ICP/MS. The study shows that the Se content of plants depends on the content in the growth culture, and that part of the inorganic Se was biotransformed mainly into SeMet. These results contribute to our understanding of the uptake of inorganic Se and its biotransformation by edible plants.