Laboratory evaluation of some pesticides on the cabbage aphid,Brevicoryne brassicae L. and their side effects on some important natural enemies

The susceptibility of adults of the cabbage aphid,Brevicoryne brassicae and two of the most important predators,Coccinella undecimpunctata andChrysopa carnea to pesticides was assessed. Most of the organophosphorus and carbamate compounds tested were toxic to the aphids. Profenophos was highly toxic to the adult virginoparous aphid at Lc50 level. Malathion demonstrated the highest toxicity to, the aphids. The application of profenophos for the cabbage aphid at Lc50 level exhibited no toxicity forCoccinella but was highly toxic forChrysopa. Pirimicarb proved to be the most selective of the compounds tested for the control of aphids when it was used at a concentration that caused 50% mortality as it was found to be unharmful to bothChrysopa andCoccinella. Dimethoate, on the other hand, was found to be very harmful and highly toxic to bothCoccinella andChrysopa adults and would probably be destructive to those natural enemies in the field. Laboratory evaluation indicates that both pirimicarb and malathion have potentials for use, in IPM program for vegetable pest control.     

Differential physiological and morphological responses of two hybrid Populus clones to water stress

Hardwood cuttings of Populus clones Tristis #1 and Eugenei were grown in pots in a controlled environment chamber to observe early patterns of growth and water relations in response to changing conditions of water stress. Height and dry weight growth, dry matter partitioning, leaf area production, stomatal conductance and leaf water potential were measured periodically during the 73-day experiment. The two clones reacted in a similar way to an initial period of stress, showing reduced growth, stomatal conductance and leaf water potential. However, when stress was interrupted by ample watering and then reimposed, substantial differences between the clones were evident. Growth of Eugenei fully recovered after stress was relieved, especially leaf growth, but when water deficiency was reimposed, the plants wilted and some leaves died. Tristis #1, in contrast, showed a greater adaptation to changing stress conditions; it grew less than Eugenei after drought was interrupted, but showed little adverse effect of renewed water deficits. These responses were partially explained by the higher root/leaf weight ratios of Tristis #1 which enabled it to maintain a more favorable plant water status than Eugenei.     

A study of lignification in loblolly pine tracheids by the SEM-EDXA technique

Summary The lignification process in different morphological regions of loblolly pine tracheids was studied by the SEM-EDXA technique. Prior to S₂ layer formation, lignification was initiated in the cell corner middle lamella and compound middle lamella regions. Subsequently a rapid lignin deposition was observed in both regions, whereas secondary wall lignification was a more gradual process and initiated when the middle lamella lignin concentration was approximately 50% of maximum. Within the secondary wall, the S₁ layer is lignified first. Then, lagging just behind cell wall formation, lignification of the S₂ layer is initiated adjacent to the S₁ layer and extends toward the lumen. Finally, the S₃ layer lignified. Upon completion of lignification, the cell walls had a higher concentration of lignin in both the S₁ and S₃ layers than in the S₂ layer.This Paper is an excerpt from the Ph.D. dissertation of Shiro Saka     

Diuretic, laxative and toxicity studies of Cocculus hirsutus aerial parts

The aqueous extract of the Cocculus hirsutus aerial parts (100 and 200 mg/kg, p.o.) showed significant diuretic activity and laxative effect in rats. The acute toxicity, orally evaluated in mice, was found to be higher than 3000 mg/kg.     

The use of the green fluorescent protein as a biomarker for sapstain fungi

To understand wood colonization by sapstain fungi and their potential biocontrol agents, it is necessary to differentiate these organisms directly on their natural substrates. In the present study the feasibility of transforming with the green fluorescent protein (GFP), the sapstain fungus Ophiostoma piceae and a potential biocontrol agent Cartapip^®, an Ophiostoma piliferum albino strain was assessed. Transformants of the two fungal species were screened by polymerase chain reaction and Southern blot analyses. The GFP was expressed in spores, synnemata and mycelia of the transformants grown in artificial media or wood. The growth, pigmentation and wood colonization of the transformants were similar to that of the non‐transformants, suggesting that the presence of the gfp gene had no negative effect on the biology of the transformants. Using fluorescence and confocal microscopy, the GFP‐expressing fungi were easily differentiated from the wild‐type strains and other fungal species in wood, even 4 months after inoculation. The results show that the use of the GFP system is feasible to monitor Ophiostoma fungi in wood.     

Effect of thermo-mechanical refining on properties of MDF made from black spruce bark

The effects of thermo-mechanical refining conditions on the properties of medium density fiberboard (MDF) made from black spruce (Picea mariana) bark were evaluated. The bark chips were refined in the MDF pilot plant of Forintek Canada Corporation under nine different refining conditions in which preheating retention time was adjusted from 3 to 5 to 7 min and steam pressure was set at either 0.6, 0.9 or 1.2 MPa. The resulting bark fibers were blended with 12% UF resin (based on oven-dry fiber weight) using a mechanical blender. The resinated fibers were manually formed into fiber mats and hot-pressed into MDF panels using consistent parameters. Two panels for each refining condition were produced, resulting in a total of 18 panels. Analysis of variance (ANOVA) was used to analyze the significance of factors. Regression coefficients and 3D contour plots were used to quantify the relationship between panel properties and the two test factors. The results from this study indicated that the preheating retention time was a significant factor for both modulus of rupture (MOR) and modulus of elasticity (MOE), the steam pressure was a significant factor for internal bond strength (IB), MOR and MOE, whereas both factors were insignificant for thickness swelling, water absorption and linear expansion. The properties of MDF panels were quadratic functions of retention time and steam pressure. Compared to the ANSI standard for 120-grade MDF, most panels with a nominal density of 950 kg/m³ had very high IB (>1 MPa) and acceptable MOR, MOE and dimension stabilities. These results suggest that black spruce bark residues can be considered as a potentially suitable raw material for manufacturing MDF products.     

The role of land tenure in conservation of tree and shrub species diversity in miombo woodlands of southern Malawi

Biodiversity is declining throughout southern African miombo woodlands due to poor land use practices that are detrimental to soil, vegetation and habitat. We aimed at examining tree and shrub species diversity and distribution in Uapaca kirkiana-dominated woodlands under three land tenure types; forest reserves, customary and leasehold land. The study was conducted at different forest sites within similar agroecological zone in southern Malawi. Study sites were located at a range of altitudes between 900 and 1,200 m a.s.l. Three circular plots each with 32.60 m radius were established at each study site to sample tree and shrub species composition, structure and distribution under three land tenure types. We found that forest reserves had higher species diversity with an average of 16 tree families, 27 genera and 34 species as compared to only 10 tree families, 6 genera and 6 species on customary forest lands. Comparisons of diameter at breast height size class distributions showed that customary land had significantly low numbers of small (5.0–10.0 cm) and very large (≥30 cm) diameter classes suggesting lower levels of regeneration and high rate of anthropogenic activities. The high species diversity and richness in forest reserves and leasehold land indicate high potential for protected lands to restore tree species diversity. It is concluded that levels of human activities as influenced by land tenure type reduce tree species diversity, composition and distribution at the different sites, and this confirms the hypothesis that open access lands are not compatible with conservation of tree and shrub species diversity because of high anthropogenic activities.     

Prevention of Blue-stain in Unpeeled Scots Pine Logs: (With 2 Plates)

Blue-stain causes degrade of saw logs during the inevitabledelays between felling and conversion. Chemicals of potentialvalue in blue-stain control have been tested in the laboratoryand trials have been made of their use on unpeeled logs storedin the forest. End treatments with fungicides were not very effective duringsummer storage of logs. Whole log treatments with a combinedfungicide and insecticide containing 2 per cent. Santobrite,2 per cent. borax, and 0?75 per cent. BHC gave very good protectionfor 3 months. End treatment with fungicides followed by whole-logtreatment with insecticides was also effective. Protection byeither method of treatment was lessened during longer storageperiods especially in the warmer months of the year. Whole-logtreatment with insecticide alone gave a good measure of controlof stain. Short delays after felling before the application of whole-logtreatments may be acceptable especially on logs which have previouslyreceived end treatments. Attack by bark-boring insects must be controlled if effectiveall-the-year protection against blue-stain is required. Insectattack appears to be secondary only to time of felling in relationto incidence of blue-stain. The value of winter felling hasbeen confirmed.     

Characterization of juvenile wood to mature wood transition age in black spruce (Picea mariana (Mill.) B.S.P.) at different stand densities and sampling heights

The radial pattern of both maximum ring density and ring area of 36 black spruce trees were used to determine the transition age from juvenile wood to mature wood. The data were obtained by X-ray densitometry and both segmented linear and polynomial regressions were used to point out the age of the juvenile wood boundary. Three stand densities (1,790, 2,700 and 3,400 stems/ha) and three sampling heights (2.4, 5.1 and 7.8 m) were studied. Although maximum ring density and ring area presented similar radial patterns, they gave two significantly different results of transition ages. The maximum ring density over-estimated the transition age (17.6 years) in contrast to ring area (14 years). The results show that the transition from juvenile wood to mature wood occurred after 12 years at 7.8 m (versus 13.1 years at a height of 5.1 m, and 17.6 years at 2.4 m). Although transition age occurred later in the high stand density group (21 years), the difference was not significant between the three stand density groups. Nevertheless, transition age remains difficult to determine since no standard definition exists. The transition occurs over years, and most probably a transition wood exists between juvenile wood and mature wood. Estimation of the juvenile wood proportion in volume shows that it remains constant along the stem and it increases with stand density.     

Carbonic anhydrase in Tectona grandis: kinetics, stability, isozyme analysis and relationship with photosynthesis

Carbonic anhydrase (CA, EC: 4.2.1.1) activity in teak (Tectona grandis L.f.) was studied to determine its characteristics, kinetics and isozyme patterns. We also investigated effects of leaf age, plant age and genotype on CA activity and gas exchange parameters. Carbonic anhydrase extracted from leaves in 12 mM veronal buffer, pH 7.8, had a K(m) for CO(2) of 15.20 mM and a V(max) of 35,448 U mg(-1) chlorophyll min(-1), which values declined by 50 and 70%, respectively, after 1 week of storage at 4 degrees C. A 15% native polyacrylamide gel revealed the absence of CA isozymes in teak, with only a single CA band of 45 kD molecular mass observed across 10 segregating half-sib families and groups of trees ranging in age from 10 to 25 years. Activity remained stable during the first month in storage at 0 degrees C, but gradually declined to 25% of the initial value after 1 year in storage. During the period of active growth (February-May), maximal CA activity was observed in fully expanded and illuminated leaves. Significant variation was observed in CA activity across 10 1-year-old half-sib families and 21 5-year-old half-sib families. There was a positive correlation between CA activity and photosynthetic rate in a population of 10-year-old trees (P < 0.005). Positive correlations between CA activity and photosynthetic rate were found in 10 of 21 5-year-old half-sib families (P < 0.005 to P < 0.05), which showed greater diversity in CA activity than in photosynthetic characteristics. Thus, CA may serve as a biochemical marker for photosynthetic capacity in teak genotypes.