When they were subjected to a range of physical and chemical treatments, spores of Pasteuria penetrans showed properties similar to those of other endospore‐forming bacteria. The spores did not take up some stains, were resistant to desiccation and sonication and showed extrusion of spore contents (‘spore popping’) on prolonged exposure to 0.1% KMnO4 in 0.3 n HNO3. Calcium and dipicolinic acid (DPA) were present at concentrations of 0.28% and 0.96% of the spore dry weight respectively, giving a Ca: DPA molar ratio of 1.2. The infectivity of P. penetrans spores was reduced to a low level after heating at 100°C for 5 min, but spore attachment was not markedly affected by heating at 100°C for 15 min. Evidence for the presence of catalase in P. penetrans spores was equivocal because the low levels of catalase activity observed in spore suspensions may have been due to contamination from catalase‐positive nematode tissue. When P. penetrans spores were exposed to a range of substances known to act as germinants for spores of Bacillus spp., germination or loss of refractility was not observed by phase microscopy. In vitro culture of P. penetrans was attempted by inoculating either spores or vegetative mycelial bodies onto a diverse range of simple and complex media and incubating them in aerobic, reduced oxygen, anaerobic and increased CO2 environments. Signs of spore germination or growth of vegetative stages were never observed.
The efficiency of a pollen trap in trapping kiwifruit (Actinidia deliciosa) pollen pellets was investigated. The trap had an average daily efficiency of 16.5 and 16.7% on 2 consecutive days. Hourly efficiencies varied between 0 and 25% with the highest efficiency in the middle of the day which coincided with periods of maximum honey bee (A pis melifera) foraging activity. The amount of staminate pollen in foragers' corbiculae was closely related to the proportion of staminate pollen on their body indicating that pellets can be used as a measure of pollination efficiency.
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