The biology of flowering and structure of selected elements of Cornus alba L. flowers

The biology of flowering and the micromorphology of Cornus alba flowers were studied using light and scanning electron microscopy. The flowering of white dogwood in 2008 lasted 35 days, and the lifespan of a single flower was 3 days. The number of flowers per inflorescence was variable (on the average, it was 89). The largest group of insects visiting the flowers of C. alba comprised Hymenoptera (mainly bees and andrenids), then ants, dipterans and beetles. They foraged the dogwood flowers most intensively between 11.00 and 15.00. The inconspicuous four-petalled flowers of C. alba were characterised by the occurrence of T-shaped, two-armed non-glandular trichomes covering the receptacle as well as observed on the petals of the corolla, the style of the pistil and the anthers in a smaller number. The trichomes were covered by a thick cuticle with characteristic outgrowths. They contained a living protoplast, and plastids were observed in the cytoplasm of the trichome cells. In addition, anomocytic stomata were found in the epidermis of the receptacle and in the epidermis of the corolla petals. The stigma of the pistil and the adaxial epidermis of the petals were composed of very numerous conical papillae.