植酸浓度对镁合金AZ31化学转化膜的影响

利用SEM分析、电化学测试、划格试验等手段研究了植酸浓度对化学转化膜膜厚、形貌及耐蚀性能、与基体结合力等的影响。结果表明:随着植酸浓度的增大,转化膜表面微裂纹增多、加宽;转化膜的膜厚与植酸浓度呈正比例变化,植酸浓度为13g/L时,膜层厚度达到最大值14.97μm;转化膜耐蚀性随植酸浓度的增大呈现先增大后减小的趋势,植酸浓度为9 g/L时,其腐蚀电位相比基体提高了85 m V,耐蚀性最好;划格试验结果显示植酸转化膜与基体结合力良好。

大气CO2浓度升高和施肥对粳稻产量和稻米营养品质的影响--FACE研究

利用稻田FACE(Free Air CO2 Enrichment)系统平台,以武运粳23为供试材料,设置裂区试验,研究不同肥料处理下大气CO2浓度升高对常规粳稻产量性状和营养品质的影响。主区为CO2浓度,设置环境CO2浓度(Ambient)和高CO2浓度(增200μmol/mol)2个水平;裂区为施肥量,设置常规施肥和不施肥2个水平。结果表明,与Ambient相比,高CO2浓度环境下武运粳23籽粒产量略增,但未达显著水平;与常规施肥处理相比,不施肥处理显著减产(-34.0%),这主要是有效穗数大幅减少所致。大气CO2浓度升高使稻米蛋白质、K、P和S浓度显著下降,分别下降6.6%、6.7%、10.5%和11.7%,而Fe浓度显著上升(+12.6%)。与常规施肥相比,不施肥使稻米蛋白质、K、P、S、Mn浓度显著下降(最大降幅为26.1%),但植酸浓度显著增加(7.4%)。从单位土地面积上收获稻米营养组分的累积量看,大气CO2浓度升高对稻米营养组分累积量无显著影响(Ca除外),但不施肥处理使稻米除Ca外所有测定指标的累积量均显著下降(最大降幅达51.3%)。方差分析表明,CO2与肥料处理对稻米K、Mg、P、S、Zn、Fe浓度和Fe含量均有不同程度的交互作用。以上数据表明,高CO2浓度环境下武运粳23产量略有增加,但稻米矿质元素浓度呈一致下降趋势(除Cu、Fe外);不施肥使籽粒产量和元素累积量均大幅下降,但植酸浓度显著增加;CO2与肥料处理对部分稻米矿质元素浓度和累积量有显著的交互作用。

The δ^15N response and nitrate assimilation of Orychophragmus violaceus and Brassica napus plantlets in vitro during the multiplication stage cultured under different nitrate concentrations

Natural nitrogen isotope composition(δ^(15)N) is an indicator of nitrogen sources and is useful in the investigation of nitrogen cycling in organisms and ecosystems. δ^(15)N is also used to study assimilation of inorganic nitrogen. However, the foliar δ^(15)N of intact plants, which is a consequence of nitrate assimilation occurring in the roots and shoots, is not suited for studying nitrate assimilation in cases where nitrate is the sole nitrogen source. In this study, Orychophragmus violaceus(Ov) and Brassica napus(Bn) plantlets, in which nitrate assimilation occurred in the leaves, were used to study the relationship between foliar δ^(15)N and nitrate assimilation.The plantlets were grown in vitro in culture media with different nitrate concentrations, and no root formation occurred for the plantlets during the multiplication stage.Nitrogen isotope fractionation occurred in both the Ov and the Bn plantlets under all treatments. Furthermore, the foliar nitrogen content of both the Ov and Bn plantlets increased with increasing nitrate concentration. Foliar nitrogen isotope fractionation was negatively correlated with foliar nitrogen content for both the Ov and Bn plantlets. Our results suggest that the foliar nitrogen isotope fractionation value could be employed to evaluate nitrate assimilation ability and leaf nitrate reductase activity.Moreover, high external nitrate concentrations couldcontribute to improved foliar nitrogen content and enhanced nitrate assimilation ability.

Characteristics of the δ15NNO3 distribution and its drivers in the Changjiang River estuary and adjacent waters

In this study, we conducted investigations in the Changjiang （Yangtze） River estuary and adjacent waters （CREAW） in June and November of 2014. We collected water samples from different depths to analyze the nitrogen isotopic compositions of nitrate, nutrient concentrations （including inorganic N, P, and Si）, and other physical and biological parameters, along with the vertical distribution and seasonal variations of these parameters. The compositions of nitrogen isotope in nitrate were measured with the denitrifier method. Results show that the Changjiang River diluted water （CDW） was the main factor affecting the shallow waters （above 10 m） of the CREAW, and CDW tended to influence the northern areas in June and the southern areas in November. 615Nrqo~ values in CDW ranged from 3.21%o-3.55%o. In contrast, the deep waters （below 30 m） were affected by the subsurface water of the Kuroshio Current, which intruded into the waters near 3 I^N in June. The ~iI^NNo3 values of these waters were 6.03%0-7.6%0, slightly higher than the values of the Kuroshio Current. Nitrate assimilation by phytoplankton in the shallow waters of the study area varied seasonally. Because of the favorable temperature and nutrient conditions in June, abundant phytoplankton growth resulted in harmful algae blooms （HABs）. Therefore, nitrate assimilation was strong in June and weak in November. The ~15NNo3 fractionations caused by assimilation of phytoplankton were 4.57%0 and 4.41%o in the shallow waters in June and November, respectively. These results are consistent with previous laboratory cultures and in situ investigations. Nitrification processes were observed in some deep waters of the study area, and they were more apparent in November than in June. The fractionation values of nitrification ranged from 24%0-25%o, which agrees with results for Nitrosospira tenuis reported by previous studies.