珠江三角洲三水市种植业耕作模式的综合评价

采用层次分析法对广东三水市种植业18种耕作模式进行综合评价。结果表明，生态效益和经济效益相互协调的模式有：稻-荸荠、菜-萝卜-萝卜、瓜-豆-番茄和瓜-豆-菜等；两效益相互矛盾的模式有：瓜-瓜-菜-较好的发展前途。但有待优化作物结构和管理技术，提高系统功能和效益。     

珠江源头区占马地小流域不同用地水土保持作用研究

 对珠江源头区占马地小流域灌木林地、疏林地、耕地及荒草地4类不同用地的土壤含水量、理化性状、土壤侵蚀特性等进行测定分析,结果表明:1)在土层60 cm深度范围内,随着土层的加深,灌木林地和疏林地的土壤水分含量呈下降趋势,而耕地和荒草地则呈上升趋势。2)土壤在持水能力、通透性能等方面排列顺序是灌木林地>荒草地>疏林地>耕地;土壤有机质含量以荒草地最高,为2.34%,分别是灌木林地、疏林地和耕地的1.08、1.89和3.46倍;全氮含量顺序是荒草地>灌木林地>疏林地>耕地;全磷和全钾含量顺序是疏林地>荒草地>灌木林地>耕地。3)不同用地的初渗速率、稳渗速率与渗透系数均为灌木林地最大,荒草地最小,灌木林地的稳渗速率、渗透系数分别是耕地、疏林地、荒草地的1.142、.06和2.7倍。4)不同用地的土壤最大持水量,在020cm土层,排列顺序为耕地>灌木林地>疏林地>荒草地;在2060cm土层,则为疏林地>灌木林地>荒草地>耕地。5)在坡度相同的情况下,不同用地的降雨产流时间为荒草地>疏林地>灌木林地>耕地;地表径流量为荒草地>疏林地>灌木林地>耕地;土壤侵蚀量以耕地最大,分别是灌木林地、疏林地和荒草地的2.51、2.26和1.32倍。研究结果可为珠江源头区土地合理利用提供理论依据。     

Allozyme Variation Among Some Pearl Millet (<Emphasis Type="Italic">Pennisetum glaucum</Emphasis> L.) Cultivars Collected from Tunisia and West Africa

Allozyme variation was assessed in a collection of pearl millet cultivars derived from three different regions of traditional cultivation of this cereal in Tunisia and West African countries. Using starch gel electrophoresis, 11 loci corresponding to seven enzyme staining systems were identified. Important within-cultivar genetic diversity was detected. Genetic diversity within Tunisian cultivars was similar and was more pronounced than for West African ones. This result could be explained by the low level of the human selection characterizing the Tunisian cultivars. Most of the total genetic diversity is maintained within subregions suggesting little genetic differentiation. Cluster analysis did not reveal separate clusters for the various subregion cultivars. However the cluster analysis should help in the selection of interesting genotypes for future breeding programs.     

Polyembryony in species of the genus Allium

Polyembryony has been detected in 26 Allium species during a series of germination tests. Additionally to those species already known for their polyembryonic tendency, high rates (up to 32%) of twin seedlings have been found in A. splendens and some other species. Genotype effects were obvious between several accessions within the species A. tuberosum. In A. tuberosum, enzymatic embryo sac isolation has been used for demonstration of polyembryonic development in early stages. Genotype and ploidy dependence of the polyembryonic process and ploidy alterations in plants derived from polyembryony are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

植物胚囊发育的细胞与分子生物学研究

综述了植物胚囊发育的细胞及分子生物学研究进展 ,并对该领域的进一步研究和发展提出了问题     

平邑甜茶的无融合生殖及单性胚的发育

平邑甜茶的胚囊是由胚囊母细胞直接有丝分裂产生,而胚囊内无助细胞,因此为6核5细胞。胚由未经受精的卵细胞发育而成,因此在无融合生殖中届孤雌生殖。单性胚具有苹果属合子胚相同的发育途径,可分为8个时期:1.球胚前原胚期;2.小球胚期;3.球胚期;4.大球胚期;5.心形胚期;6.鱼雷胚期;7.幼胚期;8.成熟胚。原胚的发育属茄型。胚乳的发育属核型,当胚乳发育处于大球胚形成前,胚乳为游离核,当幼胚形成时,胚乳已形成细胞。当幼胚体积膨大为成熟胚时,则胚乳已解体。     

珠三角地区养殖及野生淡水鱼类的甲基汞积累现状

汞（尤其是甲基汞）易在鱼体内富集,进而危害人类健康。为了解珠三角地区淡水鱼类的甲基汞积累现状,本研究对该区域内常见的养殖和野生鱼类进行了采样和甲基汞测定,并探讨了影响鱼类甲基汞积累差异的原因。结果发现,珠三角地区鱼类甲基汞含量总体较低,均未超过我国水产品食用安全标准,其中养殖鱼类肌肉甲基汞含量为0.26-331 ng g-1 dw,平均含量为62 ng g-1 dw;野生鱼类肌肉甲基汞含量为0.71-1 006 ng g-1 dw,平均含量为111 ng g-1 dw,养殖鱼类甲基汞含量显著低于野生鱼类。鱼类甲基汞累积主要受食物组成及食物甲基汞浓度影响,饲料甲基汞含量是决定养殖鱼类甲基汞水平的关键性因素。食用该地区鱼肉的甲基汞摄入水平总体较低,其中食用野生鱼类的甲基汞摄入水平较养殖鱼类高,食用野生鳜（Siniperca chuatsi)）存在甲基汞暴露风险。     

Determination of mortality in exploited freshwater pearl mussel (Margaritifera margaritifera) populations

Estimates of mortality, based on relative numbers of live mussels and empty shells observed were obtained for a sample of seven exploited Scottish freshwater pearl mussel (Margaritifera margaritifera) populations. Total mortality (Z) estimates ranged from 0.058 to 0.189 year⁻¹ and fishing mortality (F) estimates ranged from 0.005 to 0.129 year⁻¹. General trends of increasing Z and F with age were apparent. Pearl fishers generally targeted larger, older mussels. In one heavily exploited population, the Z and F estimates converged, indicating that most of the mortality in older mussels (>50 years) was due to the effects of destructive pearl fishing. Since a complete ban on pearl fishing was introduced in 1998, illegal pearl fishing has continued albeit at a reduced level.