乌桕不同种源种子性状的地理变异

测定了乌桕不同种源间种子性状的地理变异情况。结果表明：乌桕不同种源间种子带蜡和去蜡百粒质量均呈极显著差异。有7个种源的种子外形大,带蜡百粒质量在14 g以上,为大粒型;有3个种源的种子较小,带蜡百粒质量在10 g以下,为小粒型;其余种源种子为中粒型,带蜡百粒质量为10～14 g。湖南新宁、江西上饶、湖北房县、浙江宁海4个种源种子去蜡百粒质量在所有种源中最大（〉10 g）,带蜡百粒质量也很高,为大粒果用乌桕良种选育的种源材料;贵州龙里、开阳、道真,四川广元,湖北房县,江西新建、于都、上饶,广东阳春9个种源净籽率较高（75%～90%）,为梓油果用良种选育的种源材料;浙江杭州,广西南宁,江西遂川、赣县,贵州石阡,湖南新宁,安徽黄山、贵池8个种源净籽率较低（60%～70%）,为皮油果用乌桕良种选育的种源材料。相关分析表明,与纬度密切相关的年均温度与≥10℃积温是影响乌桕种子性状的主要环境因子。     

植物DNA甲基化与体细胞无性系变异的研究进展

为更好地理解植物DNA甲基化在植物体细胞无性系变异中表观遗传的调控作用,为体细胞无性系变异研究及作物遗传改良提供理论参照,对DNA甲基化的产生及维持机制、生物学作用以及体细胞无性系变异中DNA甲基化模式重建进行了综述。     

降水变化对中国农作物病虫害的影响

基于已有研究成果,采用农作物病虫害发生危害时空变化对降水时空变化响应事实检测的方法,系统分析降水变化对农作物病虫害影响的已有观测事实及其变化规律性,提出其影响的最新认知,并对今后的发展方向进行了展望。已有影响事实检测表明：一定区域、时段的降水偏少、高温干旱有利于部分害虫的繁殖加快、种群数量增长,降水、雨日偏多有利于部分病害发生程度和害虫迁入数量的明显增加,病虫危害损失加重;暴雨洪涝可使部分病害发生突增,危害显著加重;暴雨可使部分迁入成虫数量突增、田间幼虫数量锐减;降水强度大,可使部分田间害虫的死亡率明显增加、虫口密度显著降低。高温干旱年可使部分病虫害大发生、飞蝗可比常年多发生1代,持续多雨年可使部分病虫害发生界限北移。梅雨期长且梅雨量多的年份有利于江淮地区稻飞虱、稻纵卷叶螟的迁入危害,稻纵卷叶螟迁入早的年份可比常年多繁殖1代。西太平洋副热带高压偏强年份有利于害虫迁入始见期提早、数量增加、范围扩大、危害加重。台风暴雨可使部分病害突发流行、田间虫口密度显著降低,台风多雨有利于害虫的迁入危害。厄尔尼诺年的当年、次年易暴发农作物病虫害。降水变化对农作物病虫害影响的时空变化及其规律性、发生与灾变的影响预估、风险评估及适应对策将是未来需要重点解决的关键问题。     

Seasonal Variations in Physicochemical and Textural Properties of North Atlantic Cod (Gadus morh.ua) Mince

Abstract

Seasonal variations in physicochemical and textural properties of minced cod muscle from Icelandic coastal areas were evaluated. Measurements were performed on mince from the white muscle. Compared to the winter and summer values, hardness and cohesiveness, as measured by Instron, showed a drop in March to May and another drop was observed for cohesiveness during the autumn months. Expressible moisture changed slightly from March to August whereas results from the winter months indicate greater fluctuations. A minimum was observed for protein solubility in March and July. The surface hydrophobicity of proteins, increased gradually from November to May followed by a sudden drop, then a gradual increase again.     

Diagnostic value of rectal temperature of African cattle of variable coat colour infected with trypanosomes and tick-borne infections

Diagnosis of major endemic bovine parasitic diseases in sub-Saharan Africa such as trypanosomosis, theileriosis, anaplasmosis, babesiosis and cowdriosis is increasingly relying on clinical diagnosis due to deterioration of veterinary services and laboratory facilities. Pyrexia is a common clinical feature of aforementioned diseases whose detection relies on measurement of rectal temperature. The research undertaken in this study was aimed at assessing the effects of diurnal changes and variable coat colour of indigenous Nkedi Zebu cattle on the diagnostic value of rectal temperature under tropical conditions. The results revealed that variation in rectal temperature was significantly influenced by time of day it was taken and by the coat colour of the Nkedi Zebu cattle (P < 0.001). Rectal temperature experienced diurnal changes: steadily rising to reach a peak at 17.00 h before declining. The mean rectal temperature of unhealthy cattle was significantly higher (P < 0.05) than that of the healthy ones only between 13.00 and 17.00 h of the day. During which period the proportion of unhealthy cattle having a rectal temperature of 39.4 °C or higher was significantly higher than that of healthy ones (P < 0.001). Regarding the variable coat colour of indigenous breeds, rectal temperature among cattle of different coat colours was significantly different (P < 0.05). In conclusion it is important to consider diurnal changes in rectal temperature and differences due to variable coat colour of indigenous African breeds when measuring rectal temperature for assessing pyrexia, during clinical diagnosis of bovine trypanosomosis and tick-borne diseases that are endemic in many countries in sub-Saharan Africa.     

Anatomical variations in wood among four native species of Leguminosae grown in arid areas of China

Morphological features and anatomical variations are described and illustrated in detail for four native species of Legumi-nosae grown in arid sandy regions in China, which are Hedysarum scoparium Fisch.et Mey., Caragana korshiskii Kom., Lespedeza bicolor Turcz. and Ammopiptanthus mongolicus (Maxim. ex Kom.) Cheng f. All species showed similar morphological features: distinct growth ring boundaries, ring to semi-ring-porosity, simple perforation plates, alternate intervessel pitting, nonseptate fibers, para...     

Growth change of young Picea sitchensis in response to deer browsing

Taking advantage of the introduction of the black-tailed deer to the Queen Charlotte Islands (British Columbia, Canada), we used dendrochronological analyses to understand the consequences of deer browsing on Sitka spruce growth. We compared shape, radial growth, height growth and age of young spruce in three sites. We identified two types of trees growing side by side: (1) stunted and heavily browsed spruce, smaller than the browsing limit and (2) escaped spruce that were taller than the browsing limit but still browsed in their lower part. The compact and heavily ramified shape in stunted spruce was the result of repeated and intense browsing. In escaped spruce this was also the case below the browsing limit (1.16 m±0.07 m), in sharp contrast with the normal shape that escaped spruce resumed above the browsing limit. We show that the release of browsing pressure, once the tree reaches the browsing limit, is characterised by an abrupt increase in radial growth. Before release, trees show a growth stagnation characterized by narrow rings (0.5 mm per year) and small annual height increments (<5 cm per year). After release, trees show a growth stabilisation characterised by wider rings (3 mm per year) and larger annual height increments (20 cm per year). We use this pattern to estimate frequency and age at release and their possible variation over time. Age differences between stunted and escaped spruce are highly significant and indicate that, despite of browsing, most if not all trees will ultimately reach the browsing limit and escape. Heavy deer pressure (30 deer per km²) delays spruce sapling recruitment by about 8 years. This delay varies in relation to site quality and seems to have increased over time, suggesting an increase in browsing pressure.     

Cardamom, mandarin and nitrogen-fixing trees in agroforestry systems in India's Himalayan region. II. Soil nutrient dynamics

A study on seasonal soil nutrient dynamics was made in large cardamom (Amonum subulatum) and mandarin (Citrus reticulata) agroforestry systems in the Sikkim Himalaya, India. Alnus nepalensis was the N₂-fixing associate in the large cardamom system, and Albizia stipulata in the mandarin agroforestry system. Sites without N₂-fixing species in both agroforestry types comprised native non-symbiotic mixed tree species. Soil was acidic in the cardamom agroforestry and slightly acidic to neutral in the mandarin agroforestry system. Total-N in soils was the highest in the forest-cardamom stand and the lowest in the mandarin-based agroforestry systems. Soil ammonium-N and nitrate-N concentrations were highly seasonal, and the ratio of seasonal maximum and minimum varied up to six times. The C/N ratio was higher in cardamom agroforestry indicating lower N availability than in the mandarin agroforestry. Cardamom stand with Alnus showed a relatively narrower C/N ratio. N₂-fixing species help in maintenance of soil organic matter levels with higher N-mineralization rate as land use change from natural-forest system to agroforestry systems with sparse tree populations. Ratios of inorganic-P/total-P were lower in cardamom agroforestry than the mandarin agroforestry. Seasonal fluctuation in Ca-PO₄, Al-PO₄ and Fe-PO₄ contents regulated the availability of phosphates to some extent for plant uptake.     

日本落叶松自由授粉家系纸浆材材性遗传变异的研究

对12年生日本落叶松自由授粉子代测定林纸浆材材质性状进行了遗传变异分析、遗传参数估计、相关分析及综合评价和选择。结果表明:家系间综纤维素含量、基本密度、早材和晚材纤维长度、早材和晚材壁腔比差异极显著或显著,10g·L-1NaOH抽出物差异也达10%水平显著。各性状受强度或中等强度的遗传控制,对日本落叶松进行家系水平的材性改良具有很大的潜力。木材密度与早、晚材壁腔比、10g·L-1NaOH抽出物呈显著正相关,与综纤维素含量呈显著负相关,与早、晚材纤维长度相互独立;晚材纤维长度与早材纤维长度存在紧密正相关,纤维长度与早材壁腔比存在显著负相关关系,与晚材壁腔比、综纤维素含量和10g·L-1NaOH抽出物相互独立;综纤维素含量与早材壁腔比呈显著负相关,与晚材壁腔比相关不显著;10g·L-1NaOH抽出物与综纤维素含量、早、晚材壁腔比均相互独立。根据对日本落叶松材质性状的综合评价结果,选出最适合作纸浆林培育的249、340、346、217和364号家系。     

三江源地区1961−2019年降水量时空变化特征

利用三江源地区13个气象站1961?2019年共59年的降水量资料,基于一元线性回归、滑动平均法、气候倾向率和重标极差分析等方法,研究源区降水量的时空演变规律和未来变化趋势.结果表明:三江源地区年均降水量为470.7?mm,并以10.31?mm·10?a?1的速率增加.黄河源区春季降水量最大,其余三季以澜沧江源区最高,...