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Analyzing variations in silicon (Si) isotopes can help elucidate the biogeochemical Si cycle and Si accumulation processes of higher plants. Importantly, the composition of Si isotopes in higher plants has yet to be studied comprehensively and our knowledge of the distribution of Si isotopes in higher plants lags behind that of Si isotopes in marine organisms, such as diatoms. In the present study, we investigated the isotope fractionation that occurs during the uptake and transport of Si in rice, using a series of hydroponic experiments with different external concentrations of Si. We found that an active mechanism was responsible for the majority of Si uptake and transport at lower Si levels and that the uptake of Si by rice roots was significantly suppressed by both low temperature and metabolic inhibitors. In addition, light Si isotopes (28Si) entered roots more readily than heavy Si isotopes (30Si) when the active mechanism was inhibited. Therefore, we conclude that biologically mediated isotope fractionation occurs during the uptake of Si by rice roots. In addition, both active and passive Si uptake components co-exist in rice, and the fractionation effect is enhanced when more Si is absorbed by plants. [ABSTRACT FROM AUTHOR]

Plant can directly take up the intact amino acids, thus bypass the microbial mineralization of organic nitrogen. As an excellent carbon and nitrogen source, there exists competition for amino acid absorption between plant roots and soil microorganisms. And the total flux of amino acids in soil may be enormous due to the extensive sources and short hall-life. Studies on amino acid nitrogen nutritional contribution for plant by the technique of nitrogen isotopic tracer, has become a research topic in recent years, which will help us better understand the principle of soil fertility. This paper summarized the recent researches on amino acid morphological characteristics in soil and its metabolic mechanism and nitrogen nutritional contribution for plant in different ecosystems, and discussed the present status and development trend of the amino acid circulation mechanism in the plant-soil-microorganism ecosystem and its bioavailability for plant. Finally, the topics of environmental regulating mechanism of amino acid bioavailability, amino acid carbon-nitrogen metabolism, and how to improve the field organic nitrogen management were all the core issues to be resolved. [ABSTRACT FROM AUTHOR]

A pot experiment was conducted to study the effect of spent mushroom compost ( SMC) in alleviating greenhouse soil secondary salinization and cabbage salt stress. With the amendment of SMC, the salinized soil after 60 day cabbage cultivation had a pH value close to 7. 0, its organic matter and available phosphorous contents increased significantly, and the increment of total water-soluble salt content reduced, compared with the control. When the amendment amount of SMC was 10 g ∙ kg-1 the increment of soil water soluble salt content was the least, suggesting that appropriate amendment with SMC could reduce the salt accumulation in greenhouse soil. Amendment with SMC increased the cabbage seed germination rate, plant height, plant fresh mass, chlorophyll SPAD value, and vitamin C content, and decreased the proline content significantly. All the results indicated that SMC could improve the growth environment of greenhouse cabbage, and effectively alleviate the detrimental effect of salt stress. [ABSTRACT FROM AUTHOR]

Abstract: A climate-controlled greenhouse experiment was conducted to determine the influence of soil water stress on the nutrient status of a climbing plant, Parthenocissus tricuspidata (Sieb.et Zucc) Planch. The results showed that water stress constrained N uptake more than P and K uptake in P. tricuspidata. Soil water supply significantly affected N efficiency ratio, but had no effect on P and K efficiency ratios. P. tricuspidata had low K concentration (<10mgg−1) in all its plant tissues, which allowed the plant to limit its stomatal opening and reduce its water loss. The study revealed that P. tricuspidata is able to adjust biomass distribution, nutrient uptake and nutrient use efficiency in response to soil water stress and that nutrient management for this plant under water stress should focus on N more than on P and K. [Copyright &y& Elsevier]

Abstract: A method of vegetation establishment with rocky slopes was conducted by planting three climbing plant species (Parthenocissus tricuspidata (Sieb.et Zucc) Planch, Hedera helix and Euonymus fortunei (f. minimus)) an artificial hole drilled on a rocky slope surface of an abandoned quarry. During the experiment period for 18 months, plant growth and dynamics of soil moisture content in holes were surveyed. The results indicated that artificial holes may save soil on the rocky slope for plant growth, but water deficit was the key limiting factor to plant growth in the hot summer. P. tricuspidata and E. fortunei had higher survival and growth rates than H. helix. They showed good adaptability to the disadvantageous growing conditions of rocky slope. The experiment demonstrated that P. tricuspidata and E. fortunei could be used as pioneer plant species for revegetation of rocky slopes. [Copyright &y& Elsevier]

With two rice genotypes (cv. Zhongbu 51 and Azucena) differing in their root-secreted acid phosphatase activity (APA) under low P condition as test materials, an agar culture experiment was conducted to investigate their P utilization from myo-inositol hexaphosphate (IHP) under conditions of sterilization and inoculating with soil microorganisms. Under sterilization, the shoot dry mass, P absorption and P concentration of test genotypes supplied with hexaphosphate (IHP) as the P source were significantly higher than those with no P supply, but significantly lower than those supplied with inorganic P, indicating that rice plants could partly acquire P from IHP under sterilized condition. The root-secreted APA of the two genotypes was significantly higher under low P than under sufficient P supply, and the higher APA of Zhongbu 51 under low P could be one of the mechanisms of higher P utilization capability of Zhongbu 51 than Azucena under deficient P supply. When supplied with high level IHP (0.96 mmol P · L-1), the shoot dry mass, P absorption and P concentration of both Zhongbu 51 and Azucena were higher than those when supplied with low level IHP (0.16 mmol P · L-1), indicating that substrate availability could be one of the limiting factors to the utilization of phytate by rice. Inoculation with soil microorganisms had no significant effects on the shoot dry mass, P absorption and P concentration of rice plants, regardless of IHP level and rice genotypes, implying that the utilization of IHP by rice could not be improved via inoculation with soil microorganisms. [ABSTRACT FROM AUTHOR]

Abstract: In this study, soil column was used to study the new nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on nitrate (NO3--N) and potassium (K) leaching in the sandy loam soil and clay loam soil. The results showed that DMPP with ammonium sulphate nitrate (ASN) ((NH4)2SO4 and NH4NO3) or urea could reduce NO3--N leaching significantly, whereas ammonium (NH4+-N) leaching increased slightly. In case of total N (NO3--N+NH4+-N), losses by leaching during the experimental period (40 d) were 37.93 mg (urea), 31.61 mg (urea+DMPP), 108.10 mg (ASN), 60.70 mg (ASN+DMPP) in the sandy loam soil, and 30.54 mg (urea), 21.05 mg (urea+DMPP), 37.86 mg (ASN), 31.09 mg (ASN+DMPP) in the clay loam soil, respectively. DMPP-amended soil led to the maintenance of relatively high levels of NH4+-N and low levels of NO3--N in soil, and nitrification was slower. DMPP supplementation also resulted in less potassium leached, but the difference was not significant except the treatment of ASN and ASN+DMPP in the sandy loam soil. Above results indicate that DMPP is a good nitrification inhibitor, the efficiency of DMPP seems better in the sandy loam soil than in the clay loam soil and lasts longer. [Copyright &y& Elsevier]

Abstract: Five field experiments were conducted to study the effects of continuous plastic film mulching on rice yield, water use efficiency and soil properties on different soils with great environmental variabilities in Zhejiang Province, China, under non-flooding condition. The experiment started in 2001 at five sites and ended in 2003 with one rice crop annually. Three treatments included plastic film mulching with no flooding (PM), no plastic film mulching and no flooding (UM), and traditional flooding management (TF). Soil samples were collected after the third year of the experimentation and were analyzed for soil properties. PM increased soil temperature, accelerated decomposition of organic carbon and root growth, there was a slight but statistically insignificant trend of decline in soil bulk density. PM produced the similar rice grain yield as TF at two sites, significantly higher grain yield (5.8% and 20.0% higher) at other two sites, but significantly lower (34.3% lower) yield at one site where no irrigation water was applied and rainfall was the sole water source for rice growth. PM increased water use efficiency by 69.6–106.0% and irrigation water use efficiency by 273.7–519.6%. Compared to TF, PM decreased soil organic matter content by 8.3–24.5%, soil total N by 5.2–22.0%, and available K by 9.6–50.4% at all sites. PM treatment also reduced soil available N by 8.5–26.5% at four sites. Soil total P content in PM treatments reduced by 13.5–27.8% at three sites, and increased by 6.6–8.2% at other two sites. However, PM increased soil available P by 20.9–64.7% at all sites. Systematic cluster analysis indicated the PM treatment distinctively clustered from the other treatment. These results suggested PM could gain higher yield under appropriate water condition and PM may change soil nutrient cycle. [Copyright &y& Elsevier]

The influence of nitrification inhibitor (NI) 3,4-dimethylpyrazole phosphate (DMPP) on nitrate accumulation in greengrocery (Brassica campestris L. ssp. chinensis) and vegetable soil at surface layer were investigated in field experiments in 2002 and 2003. Results showed that NI DMPP took no significant effect on yields of edible parts of greengrocery, but it could significantly decrease NO_3^--N concentration in greengrccery and in vegetable soil at surface layer. In addition, NI DMPP could reduce the NO_3^--N concentration during the prophase stage of storage. [ABSTRACT FROM AUTHOR]