Digestive enzyme inhibitors and storage pest resistance in cowpea (Vigna unguiculata) seeds

Summary Amylase and trypsin inhibitors are proteins which inhibit digestive enzymes. The loss of the activity of these enzymes produces a reduction of starch and protein digestion. Amylase and trypsin inhibitor activity have been investigated in seeds of 20 cowpea lines in trying to establish their role in the storage pest resistance. A broad variation has been observed for both the inhibitors. Correlation analysis between inhibitor levels and extent of attack has shown that neither amylase nor trypsin inhibitors can separately explain the resistance to Callosobruchus maculatus (F.). Lines bruchid resistant in fact, have high levels of both inhibitors. Conversely lines with low levels of amylase and trypsin inhibitors are bruchid susceptible. The breeding for high contents of both amylase and trypsin inhibitors can be an effective way to obtain lines with resistance to storage pest.     

Phenolic antioxidant-linked anti-hyperglycemic properties of rye cultivars grown under conventional and organic production systems

Rye (Secale cereale L.), is a temperate cereal food crop with diverse human health benefits partly linked to phenolic bioactives. Therefore targeting rye cultivars rich in phenolic bioactives and associated antioxidant properties has relevance to develop dietary support against chronic diseases, such as hyperglycemia linked to progression of type 2 diabetes. In this study we screened 9 rye cultivars and compared the impact of two different production practices (conventional and organic) on phenolic bioactive associated antioxidant and anti-hyperglycemic properties using in vitro assay models. Total soluble phenolic content (TSP), phenolic acids profile, protein content, antioxidant activity (AA), and hyperglycemia relevant α-amylase and α-glucosidase enzyme inhibitory activities of aqueous extracts of rye cultivars were evaluated using in vitro models. Overall, rye grown under organic production had higher yield, 1000 kernel weight, α-amylase inhibitory activity, and ferulic and benzoic acid content. On the contrary rye grown under conventional production had higher TSP content, AA, and α-glucosidase enzyme inhibitory activity. Further significant differences in phenolic antioxidant-linked anti-hyperglycemic properties among 9 rye cultivars were observed. This study indicated that differences in cultivars and production practices had significant impact on human health relevant phenolic antioxidant and associated anti-hyperglycemic properties of rye cultivars.     

Cl~-通道抑制剂对高氯条件下烤烟叶片超微结构和生理指标的影响

通过土培盆栽试验,研究了高氯条件下Zn~(2+)、NFA(尼氟灭酸)、9-AC(蒽-9-羧酸)3种Cl-通道抑制剂对烤烟叶片超微结构和相关生理指标变化的影响。结果表明:与对照相比,外施抑制剂可显著缓解氯含量较高的土壤对烤烟叶片的伤害作用,其中9-AC缓解作用最强,NFA次之,Zn2+作用较弱。施用抑制剂处理的烤烟叶片,其类囊体结构较发达,片层较多,垛叠能力强;抑制剂对烤烟生物量的积累有促进作用,其中地上部的干物质重提高显著;与对照相比,烤烟叶片MDA含量明显下降,在一定程度上缓解了膜脂的过氧化,同时,施用抑制剂有利于SOD、POD、CAT等抗氧化保护酶维持较高的活性。     

杜果乙烯抑制剂的筛选及其采后保鲜效果研究

比较研究不同浓度乙烯抑制剂AOA(aminooxyacetie acid)、AIB(α-amino-isobutyric acid)、AVG (Aminoethoxyvinyl glycine hydrochloride)、ATA(3-amino-1,2,4-triazole)、1-MCP(1-methylcyclopropene)、精胺、亚精胺对采后杧果(Mangifera indica L)乙烯释放的抑制效果,以期筛出最佳乙烯抑制剂并探究其对杧果的贮藏保鲜效果.结果表明:不同浓度乙烯抑制剂处理杧果,均可降低杧果果实乙烯释放量,其中1 mmol/L精胺、10 mmol/L亚精胺和50 mmol/LATA可有效延缓硬度、可滴定酸(Titratable acid,TA)下降,维持较高VC(Vitamin C)和TSS(Total soluble solids)含量.综合分析,精胺、亚精胺、ATA处理可有效延缓采后杧果果实软化,为采后杧果贮藏保鲜提供技术支持.     

大豆胰蛋白酶抑制因子对獭兔氮平衡和养分消化率的影响

试验选择（63±4）日龄、平均体重为（1150.5±124.0） g的健康美系獭兔20只,随机分为5组,每组4只兔,公母各半。试验日粮分别含有25%生大豆、25%化学钝化大豆、25%热处理大豆、25%豆粕和13%生大豆+12%豆粕。胰蛋白酶抑制因子含量（实测值）分别为6.55、 1.99、1.73、 0.81和3.97 mg/g。试验结果表明,25%生大豆组显著降低饲料氮表观消化率（P<0.05）,显著增加粪氮排出（P<0.05）,对尿氮无显著影响;化学钝化、热处理及生大豆+豆粕组粪氮、氮消化率同豆粕组间无显著差异（P>0.05）。饲料干物质、有机物质、无氮浸出物、粗脂肪、粗纤维表观消化率5组间无显著差异（P>0.05）。     

A standardized method for the determination of the intrinsic carbon and nitrogen mineralization capacity of natural organic matter sources

A new method was developed for the simultaneous determination of the intrinsic carbon and nitrogen mineralization capacity of organic matter (OM) sources by means of an aerobic incubation in suspension. The proposed method is based on determination of the oxygen consumption, monitored indirectly via pressure measurement, and on determination of nitrogen mineralization, through the periodical measurement of NH₄⁺-N, in a liquid suspension of the samples. The suspension is standardized in terms of nutrient composition and pH, and well-controlled incubation conditions that can be enforced as desired. This method rules out the effect of soil conditions and thus reflects the intrinsic properties of the OM. The method is faster and more reproducible than soil incubation tests that are currently used. In such a system, it is important that nitrification is inhibited to avoid oxygen consumption by nitrifiers and prevent the production of gaseous nitrogen compounds. Two nitrification inhibitors, N-allylthiourea and 2-ethynylpyridine, were tested at different concentrations for three reference samples, soil, bark and manure. Both inhibitors completely suppress NO₃⁻ formation without suppressing the heterotrophic microbial activity, thus allowing the correct determination of the oxygen uptake rate (OUR). When nitrification inhibitors were added, nitrous oxide could not be detected anymore in the gas phase of the system, which confirms that nitrification was inhibited and indicates that denitrification and nitrifier denitrification activity was negligible. N mineralization rates were determined by frequent sampling from the liquid phase of the system without disturbing the pressure measurement during the incubation and subsequent determination of NH₄⁺-N. The method presented allows for the reliable and relatively easy and cheap, simultaneous determination of carbon and nitrogen mineralization rates for a wide range of OM sources.     

Urea N uptake efficiency of ryegrass (Lolium perenne L.) in the presence of urease inhibitors

Summary A greenhouse experiment was conducted to study the comparative efficiency of urea as an N fertilizer with and without the addition of different urease inhibitors. Ryegrass (Lolium perenne L.) was used as the test plant and the N balance technique with ¹⁵N was applied. Three urease inhibitors, hydroquinone, phenyl phosphorodiamidate (PPDA), and N-(n-butyl) phosphorothioic triamide (NBPT), were evaluated for their effects on urea-N uptake as well as on grass yield. The addition of urease inhibitors, except for hydroquinone in the later growth period, did not significantly influence the dry matter weight. Throughout the whole growth period, only NBPT significantly increased the total urea-N uptake. In the uninhibited system, the major fertilizer N loss occurred during the first period of grass growth, presumably via NH₃ volatilization, since the environment did not favour the other pathways of N loss. However, an appreciable amount of urea N was lost during the later growth period in all inhibited systems, especially in the hydroquinone-treated system. This indicates that the application of urease inhibitors could not eliminate the urea N loss. The greater N loss in the hydroquinone-treated soil appears to be related to the inhibition by hydroquinone of nitrification.     

湿热处理对大豆粉品质的影响

在不同的时间、温度以及蒸气压条件下,对大豆粉进行湿热处理,测定其尿素酶活性(UA)和蛋白质溶解度(PS)及胰蛋白酶抑制因子(TI)的活性.结果表明:在温度为110 ℃(0.05 MPa)的条件进行湿热处理,5 min即可将TI灭活96%,PS为66.1%,与其它各处理组相比,是较合适的加工处理条件.