Intraclonal Variation in Wood Density of Trembling Aspen in Alberta

Four trees from each of three putative clones of trembling aspen (Populus tremuloides Michx.) at one site in north-central Alberta were sampled to determine the patterns of wood density variation within stems and within clones. Sample disks were removed at five heights from each tree to examine variation among cardinal directions and across the southern radius at each height. Although only three clones were sampled, there were significant differences (0.05 level) among clones. Wood density tends to be high at the bottom of the tree, decreases to a minimum at midheight, then increases again near the top of the tree. In the radial direction, wood density is high near the pith (at all heights), decreases, then increases again in the mature wood zone (after rings 15-20+). Average wood density values within the twelve stems varied from 0.348 g/cc to 0.402 g/cc

Purification and Characterization of an Extracellular Acid Proteinase from the Ectomycorrhizal Fungus Hebeloma crustuliniforme

Hebeloma crustuliniforme produced an extracellular acid proteinase in a liquid medium containing bovine serum albumin as the sole nitrogen source. The proteinase was purified 26-fold with 20% activity recovery and was shown to have a molecular weight of 37,800 (as indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) and an isoelectric point of 4.8 ± 0.2. The enzyme was most active at 50°C and pH 2.5 against bovine serum albumin and was stable in the absence of substrates at temperatures up to 45°C and pHs between 2.0 and 5.0. Pepstatin A, diazoacetyl-dl-norleucine methylester, metallic ions Fe(2+) and Fe(3+), and phenolic acids severely inhibited the enzyme activity, while antipain, leupeptin, N-α-p-tosyl-l-lysine chloromethyl ketone, and trypsin inhibitor inhibited the activity moderately. The proteinase hydrolyzed bovine serum albumin and cytochrome c rapidly compared with casein and azocasein but failed to hydrolyze any of the low-molecular-weight peptide derivatives tested