Characteristics of blooming and pollen in flowers of two Syringa species (f. Oleaceae)

Abstract

The observations were conducted in long-term sequence studies in the years 2006, 2009, 2013, in the Lublin area, Poland (51° 16' N, 22° 30' E). The flowering phenology, diurnal pattern of blooming, pollen production and insect visitation to the shrubs of Syringa oblata Lindl. var. dilatata (Nakai) Rehd. and S. meyeri 'Palibin' Schn. were examined. Syringa oblata var. dilatata and S. meyeri 'Palibin' bloomed from the mid May till mid June. The species are characteristic of early morning diurnal pattern of blooming, with approx. of 60% of daily instalment of flowers opened before 9.00 (GMT + 2h). Both species studied had the corolla tube 2-fold deeper during the pollen shedding phase compared to bud stage (mean = 14.9 mm ± 3.2 SD vs. 7.8 mm ± 2.8). No species effect was found for the size of anthers, for the mass of pollen produced in anthers and for the pollen viability. A constant number of 2 stamens in the flowers of Syringa species entailed the pollen yield was derivative mainly to the number of developed flowers. Therefore significant differences were noted for the pollen yield between individual shrubs (mean 0.9 kg for S. meyeri 'Palibin', and 8.1 kg/ha for S. oblata var. dilatata). The Syringa oblata var. dilatata and S. meyeri 'Palibin' due to their attractive flowering period, and the abundance of blooming are suitable for different ornamental designs in urban areas. Unfortunately, despite the entomophilous flower traits, the insect visitors appeared sporadically.