Characteristics of blooming, floral nectaries and nectar of Malus sargentii Rehd.

Abstract

In the years 2007-2008, the flowering biology of Malus sargentii, an ornamental apple tree native to Japan, was studied in the conditions of Lublin (Poland). The daily rate of flower opening, flowering duration and flower visitation by insects were determined. The amount of nectar produced per flower and sugar content in the nectar were investigated. The size of nectaries and the micromorphology of their surface were examined using light and scanning electron microscopy. It was found that the greatest amount of flowers opened between 11.00 and 13.00. During this time, the largest number of insects was observed in the flowers. Bees (90%) were predominant among the insects, with a much smaller number of bumblebees (6%) and butterflies (4%). The flower life span was 5 days. Over this period, the flower produced, on the average, 0.71 mg of nectar with an average sugar content of 32%. The nectaries of Malus sargentii are orange-yellow coloured and they represent the hypanthial type. Due to the protrusion of the nectariferous tissue, they are classified as automorphic nectaries. The surface of the epidermal cells of the nectary was distinguished by distinct cuticle folds. A small number of stomata were located only in the basal part of the nectary. At the beginning of flowering, all stomata were closed, but secretion traces were observed near well-developed outer cuticular ledges.