This work investigated the effects of SNP (sodium nitroprusside; an NO donor) on 100 µM cadmium (Cd) toxicity in 2-week-old Trifolium repens L. plants. Cd accumulated to a greater degree in roots ...than in shoots and resulted in oxidative stress, as evidenced by increased concentrations of hydrogen peroxide and malondialdehyde. In addition, Cd exposure markedly hindered root and shoot elongation and biomass production, reduced the activities of H⁺-ATPase in the plasma membranes (PMs) and tonoplasts (V), and inhibited the absorption of mineral nutrition. However, the addition of various SNP doses alleviated the inhibitory effects on plant growth caused by Cd, elevated the activity of the PM H⁺-ATPase in both shoots and roots, enhanced the activity of V-H⁺-ATPase in roots, and partially enhanced the uptake of minerals (shoots: Mg and Cu; roots: Ca, Mg, and Fe) in Cd-treated plants. Shoot and root Cd accumulation significantly diminished when plants were subjected to Cd plus SNP treatments, though the level of root Cd accumulation was not dependent on the SNP dosage level. Moreover, the addition of SNP considerably upregulated ascorbate peroxidases (APX), catalases and superoxide dismutase (SOD) activity in shoots under Cd stress, but downregulated APX and SOD activity in roots. The addition of SNP did not influence glutathione reductase (GR) activity in roots, but markedly increased its activity in shoots. Similar to root GR levels, shoot ascorbate content experienced no significant change between Cd plus SNP treatment and Cd treatment alone; however, root ascorbate and glutathione levels decreased in plant tissues in the treatments with Cd and SNP. The results obtained in this work indicate that SNP applied exogenously, particularly at lower doses, can effectively deplete the detrimental effects on white clover growth, likely by reducing oxidative damage, modulating mineral absorption, and re-establishing the levels of ATPases.
Purpose
Dredged sediments from waterways are often contaminated due to human activities. We tested an original remediation method consisting of mixing dredged contaminated sediments with contaminated ...soil to create a technosol and establish a phytoremediation technique. The objective was to determine if the
Miscanthus x giganteus
(MxG) and white clover co-culture could improve the PAH dissipation compared with monoculture.
Materials and methods
MxG and white clover were tested in mono- and co-culture on a technosol composed of sediments and soil in mesocosm during 263 days (a life cycle of MxG until its senescence). PAHs measurements and ecotoxicity and genotoxicity tests were performed at the beginning (T
0
) and the end (T
F
) of the phytoremediation experiment.
Results and discussion
PAH removal varied according to the planting patterns and the PAHs involved, but overall, the presence of vegetation significantly induced dissipation of total PAHs in the technosol. After 263 days of culture, 26.24% of the total 16 priority PAHs were removed with white clover monoculture, 29.27% with co-culture, and 31.65% with MxG monoculture. Moreover, after 263 days of culture, the index of additive cancer risk (IACR) values were 4.26 for the non-planted technosol, 3.43 for MxG monoculture, 3.31 for white clover monoculture, and 3.43 for co-culture. The different planting patterns improved the decrease of the IACR values in the technosol compared with the non-planted technosol, even if it remained above the reference value. Furthermore, co-culture significantly enhanced the dissipation of pyrene and anthracene and decreased the technosol ecotoxicity in contrary to MxG monoculture.
Conclusion
The present study showed the possibility to remediate dredged sediments after mixing them with soil, thus opening a new way to clean up contaminated excavated sediments. The presence of vegetation significantly promoted the dissipation of the total 16 priority PAHs and improved the decrease of the IACR values. Co-culture was more efficient for the dissipation of specific PAH, such as pyrene and anthracene, compared with MxG monoculture. Moreover, the co-culture improved the decrease of the technosol ecotoxicity contrarily to other planting patterns.
White clover (Trifolium repens L.) is one of the legume herbages with high feed quality, but it is sensitive to water deficiency. The objectives of this study were to compare morpho-physiological ...responses to drought stress and post-drought recovery in four-leafed white clover cultivars. Under well-watered conditions, drought stress (3 d, 6 d, 9 d and 12 d), and rehydration, the relative water content (RWC), membrane lipid permeability, osmoregulatory substances, photosynthetic characteristics and stomatal features of Chinese native Longping No.1 (LP, small-leafed) and three introduced cultivars, namely Pudi (PD, small-leafed), Rivendel (RD, medium-leafed) and Koala (KL, large-leafed), were evaluated. Results showed that small-leafed white clover maintained higher RWC and better membrane stability and osmotic regulation with increased drought intensities, compared to the medium-leafed and large-leafed cultivars. Following rewatering, small-leafed white clover recovered more rapidly with all of the parameters than the other cultivars. The increase of drought stress intensity led to the decline of net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Cs). However, the decreased range of Pn, Tr and Cs in the small-leafed white clover was significantly smaller than that in the medium-leafed and large-leafed white clovers. Meanwhile, the small-leafed white clover showed a smaller size and higher density of stoma either under normal or drought conditions than the intermediate- and large-leafed cultivars. Taken together, the results indicated that the adaptability of small-leafed white clover to drought stresses and post-drought recovery was better than that of medium-leafed and large-leafed white clovers. The study will provide better insights into the mechanism of drought response and recovery potential in different white clover cultivars.
•We examined the biocontrol services of ground cover vegetation in peach orchards.•The key insect pests (aphids and Grapholitha molesta) abundance was decreased.•The generalist predators (spiders, ...ladybirds and lacewings) abundance was increased.•The pests were better repelled by the predators in ground cover peach orchards.•Ecological engineering of ground cover vegetation promoted biocontrol services.
We conducted a 2-year field experiment at two sites in eastern China, examining the effects of the ground cover by Trifolium repens L. on the biocontrol services in peach orchards. The results indicated that compared to those in control areas, the abundances of aphids and Grapholitha molesta decreased, respectively, by 31.4% and 33.3% in Shanghai and by 30.1% and 33.3% in Jiangsu, while the abundance of generalist arthropod predators increased by 116.7% in Shanghai and by 115.8% in Jiangsu in ground cover areas. Compared to that in control areas, the ratio of generalist predator abundance to aphid abundance and to G. molesta abundance increased, respectively, by 260.0% and 384.2% in Shanghai and by 213.3% and 253.1% in Jiangsu in ground cover areas. Our study revealed that the ecological engineering of ground cover by T. repens promoted biocontrol services in peach orchards.
•We hypothesize ground cover affects the diversity and stability of arthropod.•We presented five diversity and four stability indices to evaluate the effect.•Ecological engineering of ground cover ...enhanced the diversity and stability.•The correlations between diversity and stability were not always significant.
Ecological engineering of ground cover vegetation in agro-ecosystem may affect the diversity and stability of arthropod communities. Factors affecting the stability of arthropod community in turn influence the relationship between arthropod diversity and stability, which has been rarely investigated. We conducted a 2-year field-experiment in Shanghai and Jiangsu province in eastern China, examining the effects of the ecological engineering of ground cover plant Trifolium repens on the diversity and stability of canopy arthropod community in peach orchards. The results indicated that five diversity indices (abundance, species richness, Simpson's index, Shannon–Wiener index and Pielou's evenness index) and four stability indices (Nn/Np, Sn/Sp, (Nn+Nd)/Np and (Sn+Sd)/Sp) were all significantly higher but the coefficient of variation (ds/dm) was significantly lower in ground cover areas than control areas. The results of Pearson's correlations were significantly negative for abundance/richness and the above four stability indices both in ground cover areas and control ones in both sites; correlations between Pielou evenness index and the above four stability indices were all positive in control areas, while those in ground cover areas were not the same. Our study provides a more comprehensive understanding for arthropod community stability, suggesting that regulating harmful arthropods by beneficial and neutral arthropods was the basic implication of arthropod stability, and demonstrates that the ecological engineering of ground cover T. repens can enhance the diversity and stability of canopy arthropod communities but increased arthropod diversity will not always positively affect arthropod stability.
A interferência das plantas daninhas é um dos principais fatores que influencia no estabelecimento das pastagens e, dentro das pastagens, o trevo branco é uma importante Fabaceae utilizada na ...alimentação animal. O objetivo deste trabalho foi determinar os períodos de interferência das plantas daninhas sobre o trevo branco, o qual foi submetido a períodos de convivência e de controle do mato. Foram realizados levantamentos fitossociológicos em cada período de convivência da cultura com a comunidade infestante e aos 119 dias para os períodos de controle de convívio. Os dados de produção de matéria seca de trevo branco foram ajustados ao modelo de regressão não linear sigmoidal de Boltzmann, adotando-se um nível de redução da produtividade de 5%. Os resultados revelaram que o período anterior à interferência (PAI) foi de 20 dias após a emergência (DAE), o período total, de prevenção à interferência, foi 82DAE e o período crítico, de prevenção à interferência, foi de 62 dias. As perdas de produtividade por matocompetição podem chegar a 96%, sendo necessário o controle das plantas daninhas aos 20DAE, prolongando-se até aos 62DAE.
En la zona central de México existen sistemas de producción animal que tienen como componente importante el uso de praderas puras y asociadas. El objetivo de esta investigación fue evaluar cuatro ...asociaciones, dos gramíneas y una leguminosa, sembradas en diferentes proporciones. Los tratamientos consistieron de las siguientes asociaciones: 20-40-40, 00-50-50, 40-20-40, y 50-00-50 % de ovillo (Ov), ballico perenne (Ba) y trébol blanco (Tr), respectivamente. Los tratamientos se distribuyeron aleatoriamente en 12 parcelas experimentales de 9 por 8 m, de acuerdo con un diseño de bloques completamente al azar con tres repeticiones. Se evaluó rendimiento de materia seca, tasa de crecimiento, composición botánica y morfológica y altura de la planta. En rendimiento anual las asociaciones que presentaron mayor rendimiento fueron; 40-20-40 y 20-40-40 con 20,182 y 19,146 kg MS ha-1, respectivamente y la menor, la asociación 00-50-50 con 15,896 kg MS ha-1. La asociación; 40-20-40 es la que mayor tasa de crecimiento anual presentó con 56 kg MS ha-1 d-1. Independientemente de la estación, en composición botánica y morfológica las asociaciones; 20-40-40, 40-20-40 y 50-00-50 fue la que mayor hoja de ovillo presentó con un promedio de 50%. La estación de invierno fueron las que mayor porcentaje de hoja de ballico presentó para la asociación 00-50-50 con 32%. Independientemente de la asociación, en la estación de primavera fue donde se obtuvo mayor altura con un promedio de 37 cm y la menor fue en invierno con un promedio de 15 cm. En conclusión, la asociación; 40-20-40 fue mejor en rendimiento anual, tasa de crecimiento y altura y la menor fue la asociación 00-50-50.
Few studies have examined if perennial leguminous cover crops are able to transfer nitrogen (N) via common mycorrhizal networks (CMNs) to neighboring fruit trees; the gradient of such N transfer ...could affect the N nutrition of both plants. Using separated three-column chambers to grow plants in a greenhouse, 99 atom% 15N as (15NH4)2SO4 was applied to leaves of white clover (Trifolium repens L.) and 15N was then traced in neighboring citrus (Citrus sinensis (L.) Osbeck) seedlings interconnected by an arbuscular mycorrhizal fungus (AMF, Rhizophagus intraradices). A range of 66.85–68.74% mycorrhizal colonization in white clover (mycorrhizal and/or Rhizobium trifolii inoculated) and 19.29–23.41% in citrus (non-mycorrhizal inoculated) was observed after 12 months of AMF inoculation in the white clover, indicating a successful CMN linkage was established between these two plant species. This CMN establishment resulted in significant increases in biomass, N accumulation, and 15N content of citrus when accompanied with nodulated and mycorrhizal fungus colonized white clover. N transfer from white clover to citrus was significantly greater under nodulation plus mycorrhization (46.23 mg N per pot, 1.71% of N transferred) than under non-inoculated control (4.36 mg N per pot, 0.21% of N transferred), and higher than sole mycorrhization (36.34 mg N per pot, 1.42% of N transferred). The percentage of N in citrus derived from white clover under nodulated/mycorrhization was 1.83–1.93%, and was highest in leaves (3.31%), moderate in stems (2.47%), and lowest in roots (0.41%) of citrus. In summary, results from this experiment demonstrated that nearly 2.0% of N transferred from white clover to citrus via CMN. Further studies are needed to quantify N transfer between white clover and citrus by other routes, including soil or root exudation pathways.
For pastures, root turnover can have an important influence on nutrient and carbon cycling, and plant performance. Turnover was calculated from mini‐rhizotron observations for chicory (Cichorium ...intybus), lucerne (Medicago sativa), perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) grown in the Manawatu, New Zealand. The species were combined factorially with four earthworm species treatments and a no‐earthworm control. Split plots compared the effects of not cutting and cutting the shoots at intervals. Observations were made c. 18 days apart for 2.5 years. This article concentrates on differences between plant species in root turnover in the whole soil profile to 40 cm depth. At this scale, earthworm effects were generally small and short lived. For ryegrass and white clover, root length and mass were linearly related (R² = 0.82–0.99). For chicory and lucerne, the relationships were poorer (R² = 0.38–0.77), so for those species length turnover may be a poor indicator of mass turnover. Standing root length, total growth and death generally decreased in the sequence ryegrass > lucerne > chicory = white clover. In length terms, scaled turnover (growth divided by average standing root length) generally followed the sequence lucerne > white clover > perennial ryegrass = chicory. Across species the scaled turnover rate averaged 3.4 per year or 0.9% per day. Cutting shoots reduced standing root length, growth and death, but increased scaled turnover. These results indicate fast and prolonged root turnover. For ryegrass and white clover, at least there is need to reappraise how to measure and model shoot : root ratios, dry matter production and carbon cycling.
The objective of this present investigation was to study the different response on drought tolerance and post-drought recovery for two different genotypes of white clover (a drought-tolerant ...small-leafed white clover and a drought-sensitive large-leafed white clover) associating with antioxidative enzyme and lignin metabolism. Two materials were exposed to 12 days of drought stress and 6 days of rewatering in a greenhouse. Significantly higher activities of superoxide dismutase, ascorbate peroxidase, catalase, guaiacol peroxidase and root activity as well as lower electrolyte leakage and malondialdehyde levels of the small-leafed in leaves and roots were observed as compared to the large-leafed under drought stress and rewatering. Lignification-related enzymes (polyphenol oxidase, cinnamyl alcohol dehydrogenase) activities of two materials in leaves gradually increased from 0 to 9 days of drought stress; then declined at 12 days of drought stress and after rewatering. After 12 days of drought stress, lignin content of two materials in roots was significantly higher relative to the well-watered. Lignin content of leaves in the small-leafed also increased significantly after 6 days of rewatering, but not in the large-leafed. The small-leafed exhibited more sensitive lignin metabolism and faster lignification in leaves and roots than the large-leafed regarding the response of drought stress. These results indicated that antioxidant efficiency and lignin metabolism played important roles in response to drought stress and rewatering for different white clovers. Comparatively higher reactive oxygen species scavenging system and more sensitive lignin metabolism could be associated with better drought tolerance and post-drought recovery in white clover.
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