The formation of pollen in male flowers and yearly atmospheric pollen counts of Cryptomeria japonica in the following year

Prediction of yearly atmospheric pollen counts is a very important component in the prevention of allergenic symptoms. We investigated the relationship between atomspheric pollen counts and the formation of male flowers of Cryptomeriajaponica D. Don (C. japonica). An atmospheric pollen survey of C. japonica was conducted from 1983 to 1996 using a Durham’s sampler. A regression analysis was performed between the total pollen count and July temperature in previous years. The atmospheric pollen counts of C. japonica had a high positive correlation with the mean temperature in July of the previous year. However, the predicted using average mean July temperature records of the previous year were insufficient, especially in years following high pollen count. In experimental conditions, using 60 C. japonica trees in pots, the formation of male flowers was shown to increase with a rise in incubation temperature. In a forest of C. japonica, our results showed that the length and weight of new needle growth from old needles, which produced many flowers in the previous year, were shorter and lighter, respectively. These aerobiological and plant physiological studies provide evidence that a smaller number of pollen counts are a common result in a year following one in which many male flowers are produced, even if the mean July temperature of that year was high

Male flowering index can predict the annual airborne pollen count of Cryptomeria japonica at different altitudes

Cryptomeria japonica D. Don (the so-called Sugi or Japanese cedar) is one of the most important coniferous afforestation species. Its afforestation area today has reached 4.5 million hectares, making up 45% of the afforestation area in Japan. Cryptomeria japonica pollinosis was first reported in 1964. The prevalence of this disease has increased yearly and now affects over 10% of the Japanease population. In order to establish an accurate prediction method of airborne pollen counts for C. japonica, research into the relationship between the amount of airborne pollen, the distribution of C. japonica forests and flowering conditions has become very important. In order to clarify differences in airborne pollen counts at different altitudes, four gravity samplers (Durham's type) were set up at four observation points that were located from the coast to the side of a mountain up to 780 m altitude in Toyama Prefecture, Japan. The male flowering index and distribution of C. japonica forests were determined in order to evaluate the quantity of male flowers. The relationship between airborne pollen counts, the distribution of C. japonica forests and the male flowering index at each observation point was examined. There was a high positive correlation between the male flowering index of C. japonica and airborne pollen counts. The male flowering indices, as well as the distribution of C. japonica forests at different altitudes, were closely associated with airborne pollen counts at different altitudinal observation points. The flowering index and the distribution of C. japonica forests are useful indicators for the accurate prediction airborne pollen counts of C. japonica

Observations of airborne Cryptomeria japonica pollen in the summer

ABSTRACTBackground: Airborne Cryptomeria japonica pollen has been detected from July to September, after the main pollen dispersal season (during florescence), in Toyama and Niigata prefectures, Japan.Methods: To identify the source of the pollen, two possible pathways were investigated: (i) secondary pollen dispersal from the ground; and (ii) release from male flowers remaining on the tree crown in C. japonica forests.Results: Secondary pollen dispersal from the ground ceased just after the main pollen dispersal season ended. However, male flowers remained on the crown until the end of September and released significant amounts of pollen, which contained as much allergenic Cry j 1 as normal pollen dispersed during the spring. There is a significant positive correlation between airborne pollen counts in the spring (February-May) and summer (June-September).Conclusions: These results indicate that the main sources of airborne pollen grains during the summer are male flowers remaining on the tree crown after their florescence