ALLELOPATHIC POTENTIAL OF RASPBERRY FOLIAR LEACHATES ON GROWTH OF ECTOMYCORRHIZAL FUNGI ASSOCIATED WITH BLACK SPRUCE

In vitro bioassays on seven species of ectomycorrhizal fungi associated with black spruce (Picea mariana (Mill.) BSP) were tested under allelopathic action of raspberry (Rubus idaeus L.). Radial growth inhibitions were observed when fungi were confronted with increasing concentrations (0%–0.1%–0.5%–2.5%) of foliar leachates made from May, July, and September material (1986). For the 2.5% treatment, species Paxillus involutus, Laccaria proximo, Laccaria bicolor, Thelephora terrestris, and Cortinarius pseudonapus grew only 6, 8, 32, 42, and 46% of their control, whereas Hebeloma cylindrosporum and Cenococcum geophilum were stimulated. Tree seedlings from raspberry invaded plantation showed mycorrhizal infection rate over 75%, with fine roots mainly colonized by C. geophilum. In combination with efforts of tree improvement and based on the results of this study, it seems important to select a well-adapted my-corrhizae, when interference by raspberry is involved.     

IS DIOECY ASSOCIATED WITH FLESHY FRUIT?

The floras of the northeastern U.S. and California were analyzed with respect to the question whether dioecy is associated with fleshy fruit. These analyses control for mode of pollination, woodiness, and flower color. Weak associations between dioecy and fleshy fruit were observed, unconvincing because of the difficulty of controlling for phylogenetic constraint. Other such studies are reviewed, however, and, because the better studies all do show a weak association, it is concluded that the weak association may be real. An ecological explanation is postulated and defended. The much stronger association between dioecy and floral biology is noted.     

青虾生长性状相关的微卫星标记筛选

青虾,学名日本沼虾(Macrobrachium nipponense),又称河虾.属于甲客纲(Crustacea),十足目(Decapoda),长臂虾科(Palaemonidae),沼虾属(Macrobrachium)[1].具有适应性强、分布广、食性杂、生长快、养殖经济效益高等特点,是我国淡水虾类的一个重要养殖品种[2].也是主要淡水名特优养殖品种之一.目前,我国养殖青虾出现了个体小型化、性早熟以及生长速率慢等种质退化现象,极大地影响了日本沼虾养殖业的效益,迫切需要对其进行遗传改良[3,4].     

GENETIC PATTERNS ASSOCIATED WITH GROWTH VARIABILITY IN PONDEROSA PINE

Variability in annual growth increment in Pinus ponderosa was measured and heterozygosity level estimated in order to examine the relationship between genetic heterozygosity and phenotypic homeostasis in natural populations of a long-lived perennial plant. Pollen was collected from 190 ponderosa pine trees in the upper montane region of the Front Range in Colorado and four isozyme systems were resolved electrophoretically from these samples. Each tree was cored, aged, and each annual ring width measured. Statistics estimating within-tree variation in growth increment were then related to heterozygosity levels. The results indicated a significant positive association between level of heterozygosity and growth variability. Two speculations are offered to account for this relationship.