A model for vertical distribution of fine roots in Robinia pseudoacacia plantations on the Loess Plateau

Based on a detailed investigation of vertical distributions of fine roots in Robinia pseudoacacia plantations at the Ansai Soil and Water Conservation Station, Shaanxi Province, a model was developed for the deep distribution of fine roots of R. pseudoacacia, which reflects the growth of fine roots affected by the mixed process of infiltration water and deep soil water. The maximum depth of the distribution h _max and the depth of the highest fine root density (FRD) h _p were determined and the maximum depth of infiltration water supplied for fine root growth h _q could also be calculated, h _q was considered as the approximate boundary between infiltration water and deep soil water in support of the growth of fine roots. According to the model, the soil water of R. pseudoacacia woodland in the profile could be classified into three layers: the first layer from the soil surface to h _p was the active water exchange layer, very much affected by precipitation; the second was the soil water attenuation layer, between h _p and h _q and largely affected by the vertical distribution of fine roots; the third was the relatively stable soil water layer below h _q, below which soil water did not change much. The percentage of infiltration water supplied for the growth of fine roots reached a level of 88.32% on the shaded slopes and 85.21% on sunny slopes. This indicated infiltration of precipitation played a crucial role in the growth of R. pseudoacacia in the gully region of the Loess Plateau. The research of interaction between the distribution of fine roots and soil water in the profile will help to explain the reasons for the complete drying out of soils and provide a theoretical basis for continuing the policy of matching tree species with sites on the Loess Plateau. Translated from Scientia Silvae Sinicae, 2006, 42(6): 40–48 [译自: 林业科学]     

火炬树克隆植株生长和生物量特征的研究

通过随机选取样木后进行室内外测定 ,揭示了外来种火炬树水平侧根形态特征、生物量积累格局与克隆繁殖的关系。结果表明 :火炬树克隆子株前端水平侧根直径超过后端水平侧根直径的形态不对称性随树龄而日趋显著 ,随地形起伏变化几乎呈现完全一致形态特征 ;火炬树子株前端水平侧根直径与其地径、冠幅、树高的相关性高于后端水平侧根直径 ;生长于荒山石隙生境 1～ 6a火炬树的生物量分配比例为树冠大于根系 ,单位长度水平侧根生物量却以子株前端水平侧根高于子株后端水平侧根 ,由此形成的生物量冠根复合分配格局成为火炬树克隆繁殖快速占据新生境的营养物质前提。火炬树具有营养物质在水平侧根趋前储备的特征 ,为其快速克隆繁殖准备最小空间间隔的相对充足的营养库。火炬树是一个入侵力正在表达的外来种。     

鲜切莲藕贮藏中的酚类物质变化及控制褐变的抑制剂组合筛选

挑选、清洗、预冷、切分后的鲜切莲藕采用不同褐变抑制剂组合处理 ,并贮藏于 4℃下。贮藏期间定期测定鲜切莲藕的褐变度 (BD)、总酚 (TP)、游离酚 (FP)和儿茶酚含量。试验结果表明 ,鲜切莲藕中FP占总酚的 70 %以上 ,且FP又以儿茶酚为主 ;鲜切莲藕在贮藏期间TP、FP和儿茶酚的量先上升后下降 ;效果最好的褐变抑制剂的组合是4 0mg·mL-1L Cys +1 5mg·mL-1EDTA 2Na +2 0mg·mL-1Zn(Ac) 2 。     

茶树根愈伤组织及发状根诱导的研究

为了获得茶树发状根，生产茶叶中的有用物质，以大田茶树的根为材料，在离体培养下对其诱导发状根．结果表明，从茶树根愈伤组织中诱导出的发状根具有生长快、无向地性、密生白色根毛和较强的分枝能力．发状根分枝，存在直接分枝和在发状根上出现瘤状突起后在其附近发生侧根2种类型．发状根及其愈伤组织轮换在不同组分的培养基上继代培养，对发状根的分化与增殖有明显的促进作用．根外植体在本研究的所有培养基上都诱导出了愈伤组织，不同品种的根外植体愈伤组织诱导率存在明显差异．     

虚拟植物根系生长模型分析和比较

虚拟植物根系生长可视化研究开始于20世纪80年代，该研究对于提高虚拟植物生长研究整体水平具有十分重要的意义。介绍了国内外近年来对虚拟植物根系生长研究的进展，分析和比较了常见根系建模模型，预测该研究的发展前景，对理论研究和实际应用有一定的参考价值。     

萱草根素对家兔中枢神经损害的病理学研究

本研究旨在对萱草根素中毒家兔中枢神经系统进行病理学研究。从北黄花菜根中提取萱草根素，用1％的淀粉溶液配制成2％混悬液，试验组家兔每只每天灌服萱草根素混悬液4mL／kg，对照组灌服等量的1％淀粉溶液。于处理后第4、7、10、13、16、19天进行常规病理学检查。试验第4天大脑、小脑、脊髓和视神经中的神经纤维出现脱髓鞘变化，在小脑从白质中央向两侧进行性扩展，在脊髓从边缘向中央扩展，最终呈丝瓜络样变；第7天起，蒲肯野氏细胞和脊髓神经细胞发生固缩、坏死；第10天，大脑神经细胞出现坏死、凋亡，并且数目逐渐增多，出现噬神经现象，视网膜萎缩，节细胞固缩、溶解消失。超微结构观察显示，髓鞘变薄，板层崩解、断裂、分离，失去原来的致密结构；神经细胞染色体边集，线粒体肿胀、消失并空泡化、粗面内质网扩张，结构模糊。结果表明，萱草根素可引起神经纤维脱髓鞘和神经细胞的广泛性坏死，并最终导致家兔失明和死亡。     

表油菜素内酯对烤烟植株根系活力和碳氮代谢影响的研究

根据二年的试验结果表明,用表油菜素内酯(24—Epibrassinolide 简称BR)0.01或0.05ppm 叶面喷施烟株,可以提高根系活力,并使其在相当长时期内维持较高的活力。用BR0.05ppm 处理的烟株根系内ATP 含量、总游离氨基酸含量及~(32)P 吸收分别为138.5×10~(-9)发光强度·克鲜重、612.11mg/g干重、2637.5CPM/100mg 干重,而对照分别为50.4×10~(-9)发光强度·克鲜重、467.50mg/g 干重、1260.3CPM/100mg 干重。BR0.01ppm 处理的根系内IAA 含量高于对照5倍以上,但其ABA 含量低于对照。在试验中还观察到,用BR0.01或0.05ppm 处理的烟叶内尼古丁、游离氨基酸、多酚类、总酯、还原糖等化学成分含量显著高于对照。     

硒对玉米生长发育影响的研究

1984—1987四年中,应用亚硒酸钠溶液浸玉米种,对玉米生长发育各时期均有明显的促进作用。苗期可促根壮苗;拨节期根系发达生物产量明显捉高;孕穗期生殖器官发育早而快;成熟期有明显增产作用,浸种的适宜浓度范围是40—70ppm,最佳浓度是60ppm,试验表明硒是玉米植株正常生长发育必需的微量元素之一。     

The effect of woodland growth on a containment landfill site in Hertfordshire, UK

Below-ground growth of four tree species (ash (Fraxinus excelsior L.), alder (Alnus spp.), sycamore (Acer pseudoplatanus L.) and Corsican pine (Pinus nigra var. maritima (Ait.) Melville)) was investigated on a 15-year-old containment landfill in Hertfordshire, UK. The site was restored using a variable but predictable thickness of soil-forming material over the mineral cap and this permitted a study of the relationship between soil thickness and indices of tree root growth. Tree root habit was affected by soil thickness, and the likelihood of root penetration into the cap was significantly reduced when soil cover was greater than 1.25 m. Penetration into the cap appeared to occur because bulk density was often lower than threshold values set to meet permeability criteria necessary for pollution control. The study results suggest that previously published guidance on minimum soil thickness over unprotected landfill caps (1.5 m) should be adhered to, and that risk of root penetration into the cap will be acceptable if it is.     

不同放牧梯度下高寒小嵩草草甸植被根系和土壤理化特征的变化

以野外样地调查和室内分析法研究了不同放牧梯度下高寒小嵩草草甸的植被根系空间变化和土壤环境因子间的关系.结果表明,放牧干扰不仅改变了高寒小嵩草草甸植被根系分布、根土比例,改变了植物群落的结构和功能,而且使土壤的物理和化学特性发生了明显的改变.随着放牧强度的增加,蕴育土壤根系的基质量逐渐减少,根土比特别是0～10 cm土层的根土比例增加;"载体"量减少导致大部分地下根系由于营养供给水平的降低而死亡,归还土壤中有机质的数量逐渐减少;不同放牧梯度下,植被根系(0～40 cm)的垂直分布、根土比与土壤容重、土壤含水量以及土壤中全氮、硝态氮和铵态氮含量存在一定的相关性;放牧主要通过影响土壤环境及其养分含量来改变草地群落生物量(地上、地下).