A quick microtechnique for inspection of potato periderm or wound periderm formation

Summary A method for a quick inspection of wound periderm formation is described. Sections are freehand cut into a stain solution, and microscopic examination is accomplished with an epiplanatic lens.     

Advancing growth vigor of seed potatoes by a haulm application of gibberellic acid and storage temperature regimes

Seed tubers that are planted soon after their harvest give low yields because of dormancy and low growth vigor. In the research reported in this paper, we investigated the advancing effect of a haulm application of gibberellic acid (750 g GA/ha) 6 days before haulm pulling and its interaction with storage temperature regimes on the growth vigor of immaturely harvested seed tubers of three cultivars. The effects on tuber yield were also examined in one experiment. The storage regimes were: 18 C continuously, hot pre-treatments of different duration (different periods at 28 C and subsequently 18 C) and a cold pre-treatment (20 days at 2 C and subsequently 18 C). Both a foliar spray with GA and storage at 28 C enhanced physiological aging of the tubers and greatly advanced the growth vigor, without negative effects on the morphology of the plants. There was a clear interaction between the GA treatment and the storage temperature regime. At early planting, the effect of the treatments on tuber yield were small for Diamant (short dormancy), but strongly positive for Désirée and Draga (long dormancy).     

Relationships between numbers of main stems and yield components of potato (Solanum tuberosum L. cv. Erntestolz) as influenced by different daylengths

Summary The relationshops between numbers of main stems and some measures of growth and yield, as well as total tuber yield, were examined for potatoes grown under different daylengths. Leaf area, tuber number and tuber yield per plant increased significantly with increasing daylength and number of main stems. Numbers of main stems and leaf area were correlated positively with tuber number and tuber yield and negatively with average tuber weight. The correlations were stronger with stem number than with leaf area and were differently affected by daylength. Standard regression coefficients indicated that stem number has strong positive and negative relationships with tuber number and average tuber weight, respectively. Since tuber number was a better determinant of yeild than average tuber weight, the final relationship between the numbers of main stems and tuber yield remained positive for all daylengths. Determinants that will best explain variation in tuber total yield, tuber number, and average tuber weight are suggested.     

Gaseous Nitrogen Emission from Soil Aggregates as Affected by Clay Mineralogy and Repeated Urine Applications

Urine-treated soils make a significant contribution to gaseous N losses to the atmosphere. Our goal was to investigate the influence of clay type and content on ammonia (NH₃) and nitrous oxide (N₂O) emissions from urine under different wetting–drying soil conditions and to relate these results to urine-N transformation processes in soil. Three types of silt loam soils and synthetic sand–clay aggregates with three different clay-dominated materials (kaolinite, montmorillonite and vermiculite) were used in this laboratory study. Bulk soil, 4–4.75 mm and 9.5–11.2 mm aggregates were incubated with synthetic urine at 50% and 75% saturation under aerobic conditions. Repeated urine application affected the properties of the aggregates depending on the type of clay present. Greater clay content increased aggregate stability and reduced NH₃ volatilization. The variation in clay ammonium (NH₄ ⁺) fixation capacities was reflected in NH₃ volatilization as well as in the onset of N₂O emissions, occurring first from kaolinite-dominated and last from vermiculite-dominated soils. Nitrous oxide production was greater in aggregates than in bulk soil, a difference that consistently increased with repeated urine applications for kaolinitic and vermiculitic treatments. A dual-peak N₂O emission pattern was found, with the second maximum increasing with the number of urine applications. Emission of ¹⁵N-labeled N₂ was found at 75% saturation in kaolinite and vermiculite-dominated samples. Anaerobic conditions were less pronounced with montmorillonite-dominated samples because shrink–swell action caused aggregate breakage.     

A Lactobacillus sp. from diseased female rainbow trout, Salmo gairdneri Richardson, in Newfoundland, Canada

Abstract. Post-spawning mortalities of 2- to 3-year old female rainbow trout, Salmo gairdneri Richardson, at a Newfoundland hatchery were studied. The fish were found to have a mixed bacterial infection involving primarily a Lactobacillus sp. (a Gram-positive, chain-forming coccobacillus) and to a lesser degree Enterobacteriaceae, Aeromonas hydrophila and Pseudomonas fluorescens. The bacteria were isolated from the visceral organs, kidney, and ascitic fluid present in the coelomic cavity. The fish had extensive degeneration and necrosis of the liver, spleen and kidney, and sloughing of intestinal epithelium, but whether these were caused directly by the bacterial infection was not established because the fish appeared to have received substantial stress from the mechanical stripping and from the retention of dead, unshed eggs in the coelomic cavity. Tissue sections suggested that substantial growth of the Lactobacillus sp. was occurring within these unshed eggs. The present study describes this unusual observation and compares the Lactobacillus sp. to two other Lactobacillus isolates from cultured trout.     

Improved techniques for the induction and isolation of polyploids in the genus Fragaria

Summary The sensitivity of Fragaria seedlings to colchicine is dependent on the plant organ that is treated. Complete immersion of seedlings in a 1.5% colchicine solution results in total lethality, whereas the survival rates were more than 75% even at concentrations of 3.0% when only shoot apices were treated. High proportions of polyploids were isolated by treating shoot apices of seedlings with a 2.0% colchicine solution for 24–28 h. The dropper method is preferred to the tube method as it involves a minimum of manipulation and requires simple equipment. A differential response to colchicine was observed within and between different diploid species, diploid and tetraploid hybrids.