Ecological features of Ambrosia artemisiifolia L. flowers and characteristics of Ambrosia L. pollen seasons in the condition of Lublin (Poland) in the years 2001-2008

In the study, the biology of fl owering of Ambrosia artemisiifolia L. was investigated and the pattern of the Ambrosia pollen seasons in Lublin in the years 2001-2008 was characterised. The structure of male and female A. artemisiifolia flowers was observed in cultivated plants under controlled conditions in the 2000 vegetative season. The number of pollen grains produced by the stamen, flower, inflorescence and plant was determined. It was shown that in A. artemisiifolia flowers nonfunctional pistils occurred with a reduced ovary, performing the role of a pollen presenter. The pistils found in female flowers differed significantly in their morphological features from the pistils in male flowers. It was calculated that one stamrn produced an average of 3 375 pollen grains, whereas one flower 16 875. A plant which produces 20 racemes may release over 420 million pollen grains into the atmosphere. The Ambrosia pollen seasons in particular years had different patterns. In some years, the days of maximum concentration were in the second half of August, in other years in the first half of September. Over the 8-year period, the maximum daily concentration had a mean value of 116 pollen grains in m3 (31-311). Annual total concentrations of Ambrosia pollen grains ranged between 194 and 1200 grains, and it was 523 grains on the average. The pollen seasons were characterised by the occurrence of several-day-long interruptions in the presence of airborne pollen in the atmosphere of Lublin, which may indicate the long-distance transport of Ambrosia pollen