Factors affecting low temperature preservation of the marine rotifer Brachionus rotundiformis Tschugunoff

Experiments were performed to determine suitable conditions for low temperature preservation of small S (Fukuoka) and ultra-small SS (Thai) strains of B. rotundiformis. For this, single rotifers (an adult bearing one egg or a 4-h neonate) were incubated for 10 days in 1 ml seawater (22 ppt salinity). The highest survival was achieved at 10 and 12 °C for S-strain and 12 °C for SS-strain. The effect of salinity, change of culture medium and feeding regime were further tested on rotifers (300 ind. ml^–1) cultured in vials containing 10 ml seawater and microalgae at 12 °C. Survival of S-strain was highest (55.5±0.8%) at 35 ppt, while SS-strain survived best (43.1±2.6%) at 17 ppt. Survival was suppressed by changing the culture medium every 4 days. Feeding rotifers every 2 days yielded better survival (66.2±6.6%: S-strains, cultured at 35 ppt and 81.8±5.2%, SS-strains cultured at 17 ppt) than feeding them only at the beginning of the experiment or at 4-day intervals. An acclimation at 20 °C for 24 h before transferring them from their usual culture temperature (28 °C) to 12 °C resulted in higher survival of SS-strain. For S-strain, however, no significant improvement resulted from acclimation. SS-strain was more susceptible to lower temperature and higher salinity than S-strain.     

Influence of the green spruce aphid on defoliation and radial stem growth of Sitka spruce

Premature abscission of older Sitka spruce foliage on trees within forests in Northern Ireland was compared with green spruce aphid population levels 2 to 3 months earlier. Each aphid has a lower relative impact on needle loss at higher aphid population density; nevertheless, more aphids on a tree results in greater rates of needle loss. Evidence from horizontal stem increment sequences suggested that aphid feeding inhibited incremental growth, and that this inhibition might be delayed for up to two field seasons. However, the effect of aphids on stem growth in most years and on most trees seems relatively small compared with the potential of other tree-or year-specific processes.     

Factors affecting survival of bacteriophage on tomato leaf surfaces

The ability of bacteriophage to persist in the phyllosphere for extended periods is limited by many factors, including sunlight irradiation, especially in the UV zone, temperature, desiccation, and exposure to copper bactericides. The effects of these factors on persistence of phage and formulated phage (phage mixed with skim milk) were evaluated. In field studies, copper caused significant phage reduction if applied on the day of phage application but not if applied 4 or 7 days in advance. Sunlight UV was evaluated for detrimental effects on phage survival on tomato foliage in the field. Phage was applied in the early morning, midmorning, early afternoon, and late evening, while UVA plus UVB irradiation and phage populations were monitored. The intensity of UV irradiation positively correlated with phage population decline. The protective formulation reduced the UV effect. In order to demonstrate direct effects of UV, phage suspensions were exposed to UV irradiation and assayed for effectiveness against bacterial spot of tomato. UV significantly reduced phage ability to control bacterial spot. Ambient temperature had a pronounced effect on nonformulated phage but not on formulated phages. The effects of desiccation and fluorescent light illumination on phage were investigated. Desiccation caused a significant but only slight reduction in phage populations after 60 days, whereas fluorescent light eliminated phages within 2 weeks. The protective formulation eliminated the reduction caused by both of these factors. Phage persistence was dramatically affected by UV, while the other factors had less pronounced effects. Formulated phage reduced deleterious effects of the studied environmental factors.     

Factors affecting the survival of Neisseria sicca

Cultures of Neisseria sicca incubated at 37 degrees C died rapidly (within 36 h) after growth ceased. Re-suspending cells in a brain heart infusion broth and storing at 4 degrees C greatly reduced the rate of decline in viability (decimal reduction time 6 days). An important factor in maintaining viability was apparently the presence of external energy source(s). Survival comparable to that in broth was obtained by incubation in Ringer's solution with pyruvate plus glucose (but not with pyruvate or glucose alone). Medium pH had little effect on survival in the range pH 7.0 to 8.5. Energy sources also promoted survival of cells in Ringer's solution or a buffered salts solution at 37 degrees C. Highest levels of survival (up to 30% at 24 h) were obtained with pyruvate, lactate, proline and glutamate. A number of other amino acids and the tricarboxylic acid cycle intermediates, isocitrate, oxoglutarate, succinate, fumarate, malate and oxaloacetate, enhanced survival to a lesser extent.     

Interactions between green spruce aphid (Elatobium abietinum (Walker)) and Norway and Sitka spruce under high and low nutrient conditions

1 Green spruce aphid (Elatobium abietinum) is a serious pest of spruce (Picea spp.) in north‐west Europe, causing defoliation of one‐year‐old and older needles. 2 Relationships between population development of E. abietinum, needle loss and tree growth were compared for five pure genotypes of Sitka spruce and mixed‐genotype material of Sitka and Norway spruce, grown under high and low nutrient conditions. 3 Despite wide differences in flushing date between spruce genotypes, E. abietinum populations peaked on the same date on each genotype and on the mixed‐genotype material, irrespective of nutrient supply. 4 Larger aphid populations developed on trees grown under high nutrient conditions than under low nutrients. However, more needles were lost per aphid in the low nutrient treatment and overall defoliation rates in the two nutrient treatments were similar. 5 Total aphid numbers differed significantly between Sitka spruce genotypes within nutrient treatments, but not in relation to bud‐burst or needle terpene content. Reductions in height growth caused by infestation were greater (15–44%), and related to mean aphid densities and defoliation, in the low nutrient treatment, but were smaller (11–27%) and not related to aphid density and defoliation in the high nutrient treatment. 6 Development of E. abietinum populations was similar on Norway and Sitka spruce, but Norway spruce lost fewer needles. However, the effects of infestation on tree growth were more closely related to aphid density and were similar for Norway and Sitka spruce. 7 Infestation caused a decrease in total root dry weight of Norway and Sitka spruce in proportion to the reductions observed in above‐ground growth.     

Within-crown distribution of male and female cones on clonal Sitka spruce trees

The within-crown distribution of cones (strobili) was mapped on 48 mature grafts of Sitka spruce [Picea schensis (Bong.) Carr.]. The total number of cones per tree was increased by a mainstem injection of 20 mg GA_4/7 and 8 mm wide bark ring. The cones and buds were classified as either lateral or terminal on each individual branch. The distribution of lateral female, terminal female, lateral male and terminal male cones, showed a general progression from the upper distal to lower proximal regions of the tree crown in all 12 clones. Evidence for preferential allocation of cones to particular branch types is presented. The region of the tree with the greates number of cones varied with treatment and reflected differences in the sex ratio of the individual trees. There is evidence for a relationship between branch length, position within the crown and the type of cone produced.     

The effect of some aspects of low temperature and radiation on the survival of Latheticus oryzae eggs

In an attempt to delay hatching without affecting their viability, the eggs ofLatheticus oryzae W. were subjected to cold treatment at 5° for varying periods and at different stages of their development. A small dose of 0.5 krad of gamma radiation was also given at each of those temperature treatments. Most of the eggs hatched at 30° following low-temperature exposures of 1 and 2 days. There was a significant decrease in hatch as the exposure period increased further (P<0.05). An egg exposure to 5° also led to an increase in egg period and the increase was nearly equal to the period of cold exposure. Radiation did not alter the situation.     

Promotion of cone and seed production on Sitka spruce by gibberellin application

Gibberellin mixtures were applied to large, mature scions of Sitka spruce, growing in the open at Wauchope Tree Bank in 1975, 1976 and 1977. Large increases in coning and seed production, and in the numbers of clones producing seed, occurred in the year after treatment. Cone and seed yields varied with the timing and concentration of hormone treatment, and were greatest when applications were made in the top two branch whorls on the tree. Clonal differences in seed production were observed among gibberellin-treated branches. Seed quality, judged by seed weight and percentage germination, appeared normal. Promotion of male strobili was greater in lower branch whorls than in the top branch whorl on the tree. Ways in which these findings can be applied in breeding and seed production are discussed.     

Insects associated with the Sitka spruce weevil,Pissodes Strobi [Col.: Curculionidae] on Sitka spruce,Picea sitchensis in British Columbia,Canada

BioControl - Insects associated with the Sitka spruce weevil,Pissodes strobi (Peck), on Sitka spruce,Picea sitchensis (Bong.) Carr. were sampled at 9 locations in British Columbia. Fourteen species...     

Factors affecting the survival of frozen-thawed mouse spermatozoa

Mouse epididymal spermatozoa were frozen in solutions containing various compounds with different molecular weights, and the factors affecting the postthawing survival were examined. Monosaccharides (glucose, galactose) had almost no protective effect regardless of the concentration and the temperature of exposure. On the other hand, disaccharides (sucrose, trehalose) and trisaccharides (raffinose, melezitose) resulted in higher survival rates, especially at a concentration of around 0.35 mol/kg H(2)O (0.381-0.412 Osm/kg). Macromolecules, such as PVP10, Ficoll 70, bovine serum albumin, and skim milk had almost no effect, but compounds with a molecular weight of about 800, such as metrizamide and Nycodenz, had some protective effect. When a raffinose solution was supplemented with 10% metrizamide, resulting in an osmolality of approximately 0.400 Osm/kg, a high survival rate was obtained. Solutions at about 0.400 Osm/kg containing trehalose alone, trehalose + metrizamide, raffinose alone, and raffinose + metrizamide, were all effective for sperm freezing; frozen-thawed sperm could fertilize oocytes, and the resultant embryos could develop to live young after transfer. For freezing mouse spermatozoa, aqueous solutions at approximately 0.400 Osm/kg containing a disaccharide or a trisaccharide seem to be effective.     

Effects of starch additions on N turnover in Sitka spruce forest floor

Starch and carboxymethyl starch were added to forest floor samples collected from a sitka spruce stand near Aberdeen, Scotland. Samples were incubated for one month and were periodically analyzed for respiration, biomass-C, net and gross N-mineralization/immobilization. Gross mineralization/immobilization was measured by using a ¹⁵N-isotope pool dilution technique. Starch additions did not significantly affect respiration rates or biomass-C but caused net immobilization. The mechanism of this appeared to be inhibition of the decomposition of N-containing soil organic matter by the available starch-C, which resulted in decreased gross mineralization. Carboxymethyl starch acted as a biocide, probably as a result of an osmotic effect.     

Factors affecting the survival ofRhizoctonia bataticola in black soil

Summary Survival ofRhizoctonia bataticola was adversely affected at high soil moisturei.e. 60 and 80% MHC (moisture holding capacity); activity was good below 40% MHC. Half-life period was considerably reduced at 80% MHC. Variations in soil pH and addition of saltsviz Na₂SO₄, MgSO₄, CaCl₂ and NaCl did not affect the saprophytic activity of the fungus.     

Effect of mycorrhizal inocula on the growth of Sitka spruce seedlings in different soils

Summary Different mycorrhizal fungi were tested for their effectiveness in promoting growth of Sitka spruce seedlings, in two contrasting soils, in a glasshouse pot experiment. In nursery soil,Laccaria amethystina significantly improved growth of seedlings in comparison toL. laccata. Seedlings inoculated with a forest isolate ofThelephora terrestris were significantly larger than those inoculated with a nursery isolate when grown in forest soil. The effectiveness ofComplexipes moniliformis in forest soil was poor in comparison to other mycorrhizal fungi. Strains aswell as species of mycorrhizal fungi affect seedling growth differently. These effects are further influenced by soil type.     

低温20℃对意大利蜜蜂未受精卵发育的影响

【目的】蜜蜂是狭温性昆虫的代表,低温对意大利蜜蜂Apis mellifera ligustica未受精卵发育的影响尚不清楚。【方法】将0~66 h卵龄的意大利蜜蜂未受精卵放置在20℃下分别处理梯度时间。【结果】低温20℃导致意大利蜜蜂未受精卵的孵化率下降,发育历期延长。0、3、6、9 h卵龄的卵对低温极敏感,处理0.5 h孵化率下降,处理4.0 h,全部死亡;发育12、24 h的卵在低温中处理4.0 h不受影响(P>0.05),处理12.0 h,全部死亡;发育36 h以上的卵则较耐低温,处理12.0 h无影响(P>0.05),处理36.0 h,各卵龄没有全部死亡,其中最低的孵化率为25.4%。12~66 h的卵在低温20℃下的发育历期(y)与处理时间(x)呈现显著的线性回归关系,发育历期延长的时间约等于处理时间长。【结论】意大利蜜蜂未受精卵对低温20℃的敏感性与卵龄关系密切,低卵龄的意大利蜜蜂未受精卵比高卵龄更易受低温影响。这些结果为深入研究温度对蜜蜂胚胎发育影响的机制奠定基础,也为蜜蜂的科学饲养提供了理论依据。