Environmental Factors Affecting Airborne Pollen Concentration in Anemophilous Species of Plantago

Abstract

Pollination of Plantago species in the Extremadura Region (SW of the Iberian Peninsula) was studied using three volumetric traps located in the cities of Badajoz, Mérida and Cáceres between 1994 and 1999. Variations in atmospheric concentration of Plantago pollen were analysed between locations, and annual, daily, and hourly variations recorded for each location. The highest concentrations of pollen were recorded at Cáceres, while the Mérida and Badajoz values were similar. This is explained by the nature of the surroundings of each city. Interannual variations in pollination levels were significantly correlated with autumn rains, which determine the extent of development of the populations. The hourly patterns of pollen capture were well-defined and similar for all three study sites. Maximum levels were reached between 1000 and 1200h. Nocturnal concentrations were very low. Furthermore, this pattern was maintained throughout the flowering period, impling a very close link with the patterns of anthesis of the species. The three stations showed similar patterns of daily variation, which were significantly correlated with certain meteorological parameters. Pollen concentrations were affected positively by temperature, but negatively by relative humidity. The influence of wind direction also seemed to be explicable in these terms since the easterly winds, which are dry and hot in this region, had a positive influence, and the westerly winds which are moist and cool had a negative effect. The most relevant factor influencing levels ofPlantago pollen in the atmosphere was wind speed, which was negatively correlated with pollen levels.