辐照对鲜切苦瓜杀菌效果及感官品质的影响

本试验将60Co-γ辐照引入苦瓜的鲜切加工过程,研究不同辐照剂量对苦瓜杀菌效果和感官品质的影响。结果表明:辐照剂量0.52kGy以上的辐照处理对鲜切苦瓜细菌、大肠菌群、肠炎沙门氏菌(D10=0.33),英诺克李斯特菌(D10=0.29)杀灭效果显著;1.86kGy以下的辐照对鲜切苦瓜色度、硬度的影响在5%水平上差异不显著。0.52～1.86kGy辐照处理对苦瓜的色泽、气味、质地和滋味、组织状态等方面可接受性没有显著影响。因此,0.52～1.86kGy辐照剂量可以有效控制鲜切苦瓜中的微生物而不影响其感官品质,能满足糖尿病人的食用要求,货架期可达6d。     

苦瓜抗虫物质与抗虫作用初探

不同有机溶剂(乙醚、丙酮、乙醇)处理苦瓜叶片,用超敏感银染SDS-PAGE电泳进行蛋白质分析。结果表明：不同化学试剂处理后的蛋白质谱带组分和着色程度都出现了比较明显的差异。乙醚处理后的样品出现21条谱带,其中9号、5号、18号谱带较为清晰,着色较深;丙酮处理出现21条谱带,其中9号、10号、13号谱带较为清晰,着色较深,乙醇处理则有18条,其中只有6号谱带较为清晰,着色较深。这些蛋白质的异同将为进一步分离和研究苦瓜抗虫物质与抗虫作用提供依据。     

氮磷钾配施对苦瓜产量和品质的影响

采用田间试验的方法研究了氮磷钾配施对苦瓜产量和品质的影响。结果表明,氮肥、磷肥和钾肥以及适宜配合施用可显著提高苦瓜的产量。氮肥可提高苦瓜粗蛋白和氨基酸的含量,降低苦瓜维生素C和糖分含量,磷肥可提高粗蛋白和糖分含量,钾肥可以提高苦瓜维生素C、糖分和氨基酸含量,减缓施氮不合理带来的负面影响。充足的钾素供应和适宜的氮磷钾配比是保证苦瓜产量和品质的关键。     

Logging pattern and landscape changes over the last century at the boreal and deciduous forest transition in Eastern Canada

Forestry practices associated with the industrial era (since ~1900) have altered the natural disturbance regimes and greatly impacted the world’s forests. We quantified twentieth century logging patterns and regional scale consequences in three sub-boreal forest landscapes of Eastern Canada (117,000, 49,400 and 92,300 ha), comparing forestry maps depicting age and forest cover types for early industrial (1930) and present-day (2000) conditions. Results were similar for the three landscapes, indicating large-scale forest change during the twentieth century. In 1930, previous logging activities had been concentrated in the lowlands and along the main hydrographical network, as compared to a more even distribution over the landscapes in 2000, reflecting a decreasing influence of the environmental constraints on forest harvesting. In 1930, old-aged forests (>100 years) accounted for more than 75% of the unlogged areas of the three landscapes, as compared to less than 15% for the present-day conditions. Logging practices have thus inverted the stand age distribution of the landscapes that are currently dominated by young and regenerating stands. The 1930 forest cover types showed a clear relationship with elevation, with conifers located in the lowlands and mixed and deciduous stands restricted to the upper slopes. Between 1930 and 2000, 58–64% of the conifer areas transformed to mixed and deciduous forests, such that no clear altitudinal relationships remained in 2000. We conclude that twentieth century logging practices have strongly altered the preindustrial vegetation patterns in our study area, to the point that ecosystem-based management strategies should be developed to restore conifer dominance, altitudinal gradients, as well as the irregular structure inspired from old forest stands.     

连栋大棚苦瓜立体套种试验

通过研究在连栋大棚中立体套种苦瓜、大白菜、芹菜对土地利用率及产量和效益的影响。试验结果表明,套种栽培模式土地利用率可达175%;常规苦瓜栽培模式1hm2种植13500株,产量为46200kg;套种模式1hm2栽苦瓜6750株,产量达78450kg,比常规栽培增产69.81%,1hm2净收入132960.0元,比常规栽培增收346%,效益明显高于常规种植。     

农优1号苦瓜与丽华苦瓜比较试验初报

为了解农优1号苦瓜与丽华苦瓜在熟性、结果习性、产量、抗病性等方面的对比情况,在春季进行品比试验.结果表明农优1号苦瓜表现早熟、产量高、抗病强.值得进一步示范推广.     

A variance-covariance structure to take into account repeated measurements and heteroscedasticity in growth modeling

This study proposes a within-subject variance-covariance (VC) structure to take into account repeated measurements and heteroscedasticity in a context of growth modeling. The VC structure integrates a variance function and a continuous autoregressive covariance structure. It was tested on a nonlinear growth model parameterized with data from permanent sample plots. Using a stand-level approach, basal area growth was independently modeled for red spruce (Picea rubens Sarg.) and balsam fir [Abies balsamea (L.) Mill.] in mixed stands. For both species, the implementation of the VC structure significantly improved the maximum likelihood of the model. In both cases, it efficiently accounted for heteroscedasticity and autocorrelation, since the normalized residuals no longer exhibited departures from the assumptions of independent error terms with homogeneous variances. Moreover, compared with traditional nonlinear least squares (NLS) models, models parameterized with this VC structure may generate more accurate predictions when prior information is available. This case study demonstrates that the implementation of a VC structure may provide parameter estimates that are consistent with asymptotically unbiased variances in a context of nonlinear growth modeling using a stand-level approach. Since the variances are no longer biased, the hypothesis tests performed on the estimates are valid when the number of observations is large.     

不同处理方法对苦瓜种子萌发的影响

[目的]研究机械损伤、壳聚糖、赤霉素和硝酸钾对苦瓜种子萌发的影响。[方法]通过机械损伤及适宜浓度的壳聚糖、赤霉素、硝酸钾处理苦瓜种子,测定种子的发芽率、发芽势及发芽指数。[结果]机械损伤处理苦瓜种子发芽率为93.3%,与对照差异显著,发芽势高达92.3%,与对照差异极显著;壳聚糖处理种子最适宜的浓度是100 mg/L,发芽势与发芽率高达84.7%、93.0%,与对照差异显著;赤霉素浸种最适宜浓度为10 mg/L,发芽率为94.3%,与对照差异极显著;硝酸钾浸泡苦瓜种子最佳浓度为20 mg/L,发芽率达到最高99.0%,处理效果最显著。[结论]该研究为苦瓜种子工厂化育苗提供理论依据。     

灰色系统理论应用于苦瓜主要品种的评估

 利用灰色系统理论对苦瓜品种进行综合评估, 结果证明, 各品种的灰色关联排序综合评估与品种的实际表现一致。此方法对苦瓜遗传育种工作将会有重要作用。     

苦瓜杂交制种技术研究

苦瓜杂交制种父母本在上午7～9时,且每朵雄花授2～4朵雌花,授粉后30天左右采收,种子各项生理指标均达到较理想的水平,可显著提高杂交种子的产量和质量.