Introducing an abundance index for assessing weed flora in survey studies

This study was carried out to propose a simple abundance index (AI) of weed species, to describe the ranking of weeds in weed communities, and to evaluate weed flora. Based on a 4 year weed survey program conducted in Tehran province, the Thomas methodology for determining the relative abundance (RA) in weed communities was applied and a new, improved method (called the AI method) was introduced. Sixty-one irrigated wheat fields were selected using a stratified sampling procedure. The boundaries of each county in the province formed the strata. For the Thomas method, the data were summarized for each county using five quantitative measures for determining the RA of each species. For the AI method, three quantitative measures were used, including frequency, uniformity, and mean field density. In the Thomas method, the mean field density had a significant role in determining the RA of a species, while the frequency and uniformity had a less significant role. However, for determining the AI, the frequency and uniformity had a higher value than the mean field density. Higher values for these two parameters for a particular species indicates that this species was more compatible with the soil and climate conditions in which it was growing, while higher values for the mean field density for a particular species indicates that the species had a higher competitive or reproductive ability than other species. In the Thomas method, the weed species with a low mean density were less abundant and not a serious weed for agroecosysytems but, in the AI method, an invasive weed could be detected before the colonization stage.     

重离子辐射玉米自交系田间性状的统计分析

利用7Li重离子辐射诱变永19玉米自交系, 跟踪记录从M1代到M3代植株的田间性状, 用生物统计学方法对当代植株的发芽率及后代植株的株高、穗位高、相对穗位等数据进行分析。结果表明, 重离子辐射永19玉米自交系后代植株变异较多, 其中10 Gy和40 Gy剂量处理得到的后代植株株高、穗位高与对照相比变异极显著;20 Gy、30 Gy和50 Gy剂量处理得到的后代植株株高、穗位高与对照相比变异明显;所有辐射后永19玉米自交系的相对穗位与穗位高呈线性相关, 与株高无明显相关, 且相对穗位与辐射剂量之间存在一定的线性相关, 但线性拟合优度较低。     

空间诱变育种研究进展及其在辣椒中的应用

通过简要介绍空间诱变育种的方法和诱变育种机理,综述了在空间环境影响下,植物体在形态学、细胞学、生理生化和遗传物质等方面发生的变化和空间诱变育种在粮食和经济等作物育种中取得的成就,并介绍了空间诱变育种技术在辣椒育种上的应用。     

Spatial variation in tree seedling density after the site preparation for planting in a cleared coniferous plantation in Hokkaido,northern Japan

To study spatial variation in natural tree seedling density and the relationship between variation in seedling density and seed dispersal mode at a cleared site, we surveyed natural tree seedlings after the site preparation for planting in a coniferous plantation cleared by a typhoon disturbance in 2004. The site was located near Sikotsuko Lake, Hokkaido, northern Japan. Twenty-five tree seedling species were found and the mean seedling density was 9.8 seedlings/m². Seedlings of non-animal-dispersed species (7.2 seedlings/m²) were approximately five times more abundant than those of animal-dispersed species (1.4 seedlings/m²), and 87% of all seedlings were current. The seedling density of non-animal-dispersed species (almost all wind-dispersed) decreased with distance from a natural forest; however, this trend did not hold for animal-dispersed species (almost all bird-dispersed). The spatial variation in seedling density was lower in animal-dispersed species than in non-animal-dispersed species. Seed dispersal patterns and the viability duration of buried seeds likely affected the variation in seedling density by seed dispersal mode.     

基于微波干燥的黑莓介电特性研究

以黑莓为对象,利用网络分析仪测量并研究了频率（1～3 000 MHz）、黑莓含水率（20%～80%）和温度（20～100 ℃）对相对介电常数ε′和介质损耗因数ε″的影响;计算了微波穿透深度,并分析频率、含水率和温度对其的影响;建立了部分频率下黑莓介电参数与主要影响因素的关系模型,检验了基于介电参数预测含水率的精度和可行性。结果表明,在1～3 000 MHz频率段内,黑莓的介电常数ε′和介电损耗因子ε″都随频率的增大而减小;ε′随含水率的增大而增加,但随温度的增大而减小;ε″随含水率的增大而下降,但随温度的增大而增加;能量穿透深度随温度、频率的升高而降低,随含水率的升高而增加。可用二元二次方程描述介电参数和主要影响因素的关系,且各模型的决定系数皆大于0.96。所构建的模型可以很好地描述黑莓的介电参数与各主要影响因素的关系,说明基于介电参数和温度预测黑莓的含水率是可行的。     

灌水量和滴灌频率对甘肃省河西地区春玉米生长和水分利用的影响

为探究适合河西地区春玉米生长的灌水量和滴灌频率的最佳组合,采用‘咸科858’为试验材料,设置作物蒸发蒸腾量(ETc)60%(W_1)、80%(W_2)和100%(W_3)3个灌水水平和间隔4(D_1)、8(D_2)和12d(D_3)3个滴灌频率,共9个处理。生育期内,对春玉米株高、茎粗、叶面积指数(LAI)、干物质累积量和产量等进行测定。结果表明:同一滴灌频率下,W_3处理的株高、茎粗、LAI和干物质累积量均显著高于W_1和W_2处理,灌水量对春玉米产量、水分利用效率(WUE)和灌溉水利用效率(IWUE)影响极显著,其中产量在W_3最高,平均达到15 769kg/hm~2,比W_1和W_2分别提高29.68%和8.90%,而其IWUE最低,较W_1和W_2分别减少22.17%和12.68%,灌水量对春玉米耗水量有显著影响,且春玉米耗水量随灌水量增加而增加;同一灌水量下,亏缺灌溉(W_1和W_2)中D_1处理的生长指标、产量、WUE和IWUE最大;充分灌水(W_3)水平下,春玉米产量、WUE和IWUE均在D_2处理达到最大,分别为16 658kg/hm~2、3.16kg/m~3和4.3kg/m~3;灌水量和滴灌频率二者交互作用对春玉米株高、产量、WUE和IWUE有极显著影响;主成分分析法得出W_3D_2处理得分最高。综上,W_3D_2(100%ETc,间隔8d)处理高产且WUE较高,可作为河西地区春玉米生产的最佳滴灌灌水组合。     

Biomass yield and nutrient content of a tropical mulberry forage bank: effects of season,harvest frequency and fertilization rate

Effects of season (SEAS), organic fertilization with laying hen manure (N) and harvest frequency (FREQ) on forage yield and composition were evaluated in a high‐density mulberry forage bank, established under low‐input tropical farming conditions. The experiment, replicated over two consecutive years, was arranged in 18 treatments resulting from a 3 × 3×2 factorial design which combined three FREQ (60, 90 and 120 d), 3 N rates (100, 300 and 500 kg N ha^?1 year^?1) and the two seasons (RAIN and DRY). Forage yield, leaf‐to‐stem ratio, the edible fraction (EDIB, %), nutrient content and the maturity indexes were monitored. Either forage yield or qualities by plant fraction were strongly affected by SEAS, FREQ, N rate and by their interactions. Effects of FREQ and N were modulated by SEAS. Increasing FREQ during RAIN negatively affected EDIB yield and quality after 90 d, while increasing ligneous fraction. During DRY, longer FREQ allowed higher total forage and EDIB yields. Leaves were more abundant in RAIN, and its yield was increased with fertilization but only during this season. Maturity indexes were higher in DRY than in RAIN. Under the conditions of this experiment, harvesting at 60 and 90 d in RAIN and DRY, respectively, with an N rate of 300 kg N ha^?1 year^?1 seems the best agronomic choice for an optimal compromise between forage yield and nutritive value.     

基于ABAQUS不同动刀排列方式下树枝削片粉碎机振动特性研究

为了探明不同动刀排列方式下树枝削片粉碎机的动力学特征以及抗振性能,借助ABAQUS仿真平台等效刚度的方法模拟计算了树枝削片粉碎机刀盘转子在实际工况下的振动特征,分析计算了对称式排列、星型排列、十字型排列3种动刀排列方式下刀盘转子的自然共振频率、有效质量分布、振动形态以及规避共振变形的特性.结果表明:十字型排列的刀盘转子...     

灌水频率对甘蓝抗病性及品质和产量的影响

【目的】探究灌水频率对甘蓝栽培中抗病性、品质和产量3个主要性状指标的影响,为确定甘蓝生产的最适宜灌水频率及制定其标准化栽培技术提供参考。【方法】选用国家审定甘蓝品种"秦甘60"为试材,秋季栽培后于第1片莲座叶展开时进行1次统一灌水后,采用相同灌水量不同灌水频率,即间隔6,8,10(CK),12和14d灌水共5个处理,在甘蓝结球中后期调查处理间病毒病和黑腐病的发病株数和发病程度,在叶球采收期统计产量并测定品质,比较灌水频率对"秦甘60"甘蓝品种抗病性、品质和产量等性状指标的影响。【结果】在"秦甘60"甘蓝品种栽培中,灌水频率为8d时病害最轻,病毒病和黑腐病的病情指数分别为1.48(HR)和1.85(HR),产量最高,可达71896.0kg/hm2,较对照增产9.3%;5个灌水处理中灌水间隔越短,结球越紧实,帮叶比较大,中心柱变长,可溶性糖和干物质含量增加,叶球鲜食口感更为脆甜,品质更优。【结论】"秦甘60"甘蓝品种在秋季栽培的水分管理中,当第1片莲座叶展开统一灌水后,以灌水频率为8或10d的灌水效果较好。总体而言,灌水频率为6,12,14d时,甘蓝植株容易感染病害,叶球品质变差,产量较低;而灌水频率为8或10d时,甘蓝植株高抗病毒病并兼抗黑腐病,叶球紧实度≥0.6g/cm3,帮叶比≤25.3%,中心柱≤5.86cm,营养丰富、质地脆甜、品质优良,产量高,可实现"秦甘60"甘蓝品种抗病优质丰产的标准化栽培目标。