Phenology and pollen production of Parietaria judaica L. in Catalonia (NE Spain)

Variability of phenology and pollen production of three geographically distant (20-60 km) populations of Parietaria judaica L. in Catalonia (Spain) was analysed together with their relationships to airborne pollen dynamic curves. Parietaria judaica L. is a perennial herb, with individual plants consisting of many shoots emerging from a common rootstock, most of them flowering copiously in Spring. Flowers are hermaphrodite or female, and pollination is anemophilous. From November 1999 to October 2000 pollen production was estimated from periodical records in three permanent plots per zone. Moreover, records of airborne Urticaceae pollen were obtained daily by means of Hirst spore traps operating in each zone. Parietaria judaica grows vegetatively and reproductively throughout the year, but intensity of these phenological phases peaks in Spring. The number of pollen grains per anther range from 35 744 to 86 333, and average pollen production is 2 350 × 106 pollen grains per square meter, both varying significantly between months and zones. Urticaceae pollen is present in the atmosphere year round, and concentration values of airborne pollen are highest in Spring. Correlation between airborne pollen values and pollen production is significant in the three study areas.