不同生长期苦瓜对瓜实蝇产卵选择的影响

瓜实蝇(Bactrocera cucurbitae)是苦瓜(Momordica charantia)的一种重要入侵性害虫，评估其在不同生长期苦瓜上的产卵偏好，旨在摸清该虫的防治适期。本研究选取了不同生长期的苦瓜，通过设定选择性和非选择性测试，在室内研究了不同生长期损伤和未损伤的苦瓜对瓜实蝇产卵偏好的影响。结果表明：不同生长期的苦瓜显著影响了瓜实蝇的产卵偏好。针对无损伤的苦瓜，瓜实蝇偏好在谢花2～5和6～8 d后的苦瓜上产卵；针对损伤的苦瓜，除谢花1 d的苦瓜外，瓜实蝇在其它生长期苦瓜上的产卵偏好无显著性差异。基于本研究，对于无损伤的苦瓜，谢花2～8 d是预防和防治瓜实蝇的关键时期；而苦瓜一旦损伤，除谢花1 d外所有生长期均应提防瓜实蝇的为害。     

转型期中国城市生长影响因素的实证研究

在界定城市生长概念的基础上,选取城市建设用地占市区面积比重X1、建成区绿化覆盖率X2、第二产业从业人员比重X3、人均地区生产总值X4等共计47个指标,依据2008年《中国城市统计年鉴》各指标相关数据,利用SPSS软件,采用因子分析和回归分析探讨了转型期中国城市生长影响因素。结果表明,影响城市生长的要素可分为经济与制度因子、区位因子、环境因子、社会文化服务与功能因子四大类,而在影响中国城市生长的因子中,地方财政一般预算内支出与地方财政一般预算内收入首当其冲;通过逐步剔除法得到的地方财政一般预算内支出、地方财政一般预算内收入、城市建设用地面积等共计15项因子,可以很好地表征城市生长系数。     

Assessment of metabolic and immune changes in postspawning Pacific oyster Crassostrea gigas: identification of a critical period of vulnerability after spawning

This study investigates the vulnerable period in postspawning Pacific oysters (Crassostrea gigas) through physiological and immunological assessments. After spawning, the oyster condition index reduced by 50% and required 70 days to recover to the prespawning level. The mantle glycogen reduced quickly while the reduction in tissue protein occurred slowly. The mantle tissue also lost more protein than gills. The analysis of adenylate energy charge indicated that oysters were stressed in the first 8 days after spawning. As a result of spawning, haemocyte phagocytosis was reduced and remained at a low level for 3 days. In contrast, the reduction of haemolymph antimicrobial activity did not occur until 3 days after spawning and continued to decline until day 8. This immunesuppression was not directly correlated to the changes in haemocyte density. Our study suggests that the first 8 days after spawning are a critical period for oyster survival due to the loss of energy and low immunity. This study further improves our understanding of the coincidence between spawning and summer mortality in oyster aquaculture.     

黔中地区杂交稻播始历期与若干经济性状的相关性分析

贵州黔中地区是典型的喀斯特山区,生态复杂,气候多变,水稻生长后期易受低温影响造成减产。为选育适合黔中地区特殊气候环境种植的杂交水稻,选用安顺市农业科学研究所选育的耐冷性三系不育系与大面积推广的恢复系配组进行试验,结果表明:播始平均温度与穗总粒、穗实粒呈负相关;通过逐步回归和通径分析,发现每穗总粒对单株粒重的直接贡献最大,而每穗实粒数的直接作用负效应最高。该地区的育种栽培目标是严格控制生育期,选择大穗型,协调穗粒与群体间结构。     

3种宿根花卉花期控制技术的研究

通过增加越冬保护、施用植物生长调节剂的方法,提早千叶蓍、桔梗的花期.其中温室盆栽能使千叶蓍、桔梗花期提早到"五一"期间,千叶蓍花期提早23 d,桔梗花期提早54d,效果显著.对假龙头进行延迟花期的实验研究,其中通过延迟播种能延迟花期48 d;通过品种筛选,品种间自然花期相差40 d;通过不同时期重压剪,能延迟花期40～...     

离心泵在启动阶段的瞬态三维数值模拟

为研究离心泵启动瞬态过程的内部流动机理,建立了求解叶轮启动和加速过程非定常流动的数学模型,以三维模型泵为对象进行启动过程内部流动的数值模拟.采用RNGk-ε湍流模型计算叶轮启动过程内部非定常流动结构和演化过程,得到不同时刻的瞬态外特性曲线,并与定常计算结果进行对比.定性分析了离心泵在启动过程中的瞬态效应,得到叶片及蜗壳压力分布的变化规律.从叶片的压力分布图也清楚地看出压力的不平衡分布,说明存在严重的压力脉动现象,这是引起叶轮不稳定振动的主要原因.     

Eco-physiological studies on desert plants: germination of Halothamnus iraqensis Botsch. seeds under different conditions

With the aim to investigate if the halophyte Halothamnus iraqensis Botsch. can be suitable for re-vegetation and remediation of salt-affected lands, this study evaluated(1) the effects of photoperiod, thermoperiod, storage period and wings' presence on its seed germination, and(2) the ability of its seeds to have successful germination recovery after salt stress. Germination tests in different photoperiods(12 h light/12 h darkness and total darkness) and thermoperiods(15℃/20℃ and 20℃/25℃) were conducted for seeds collected in 2012, 2013, 2014, 2015 and 2016. The seeds collected in 2016 were sown under different salinity levels(0, 100, 200, 400 and 600 m M Na Cl) to assess the salinity tolerance during the germination. Wings' presence highly inhibited seed germination of this species in both photoperiods and thermoperiods under all salinity level treatments. In addition, the germination recovery occurred well when seeds were deprived of their wings. The photoperiod of 12 h light/12 h darkness and the thermoperiod of 15℃/20℃ were the best conditions for seed germination. Germination percentages of H. iraqensis seeds decreased with the increasing storage duration, especially after three years of the collection. In addition, H. iraqensis seeds were able to germinate under different salinity levels, and their germination percentages decreased with increasing salinity levels. H. iraqensis seeds have the ability to recover their germination after alleviating the salt stress, irrespective of photoperiod, highlighting the halophilous character of this species.     

Critical period for weed control in sesame production

Planning effective weed control in cropping systems requires exact appraisal of the weed intensity and duration of their competition with the crops. This 2‐year study was carried out in order to determine the critical weed control period in sesame fields. Related and relative crop yields were monitored and analyzed using a four‐parametric log‐logistic model. We recorded data from weed‐free plots and compared these with data from different periods of weed interference. In both the study years, the longer period of weed interference decreased the relative yield of sesame, whereas the yield was increased with increasing duration of the weed‐free period. A 51–78.7% decline in sesame yield was noted if the weeds were allowed to compete with the crop from planting to harvest. In the first year, the duration of the critical period for weed control (CPWC) was 177–820 growing degree days (GDD), which corresponded to 14–64 days after crop emergence (DAE), and between 170 and 837 GDD (13–64 DAE) in the second year; this was based on a 5% acceptable yield loss. The results of this study clearly elaborated that maintaining weed‐free conditions is compulsory from as early as the second week after the emergence of sesame plants, and this should be maintained at least until the ninth week to avoid sesame yield losses by more than 5%. These findings show that growers can benefit from CPWC to improve weed control in sesame production, including the efficacy of a weed control program and its cost.