ISHS Acta Horticulturae 636: XXVI International Horticultural Congress: Key Processes in the Growth and Cropping of Deciduous Fruit and Nut Trees
PRIMARY AND SECONDARY ATTRACTANTS OF FLOWERS IN PEAR PYRUS BETULIFOLIA |
| Authors: | A. Farkas, ZS. Orosz-Kovács |
| Keywords: | autogamy, homogamy, insect attraction, nectar, periodicity, pollen, pollination |
| Abstract:
The insect attraction of Pyrus betulifolia, a drought-resistant pear species was studied in a Hungarian pear collection between 1998-2002. A detailed floral morphological description was made, including size, shape and colour of flower (secondary attractants). Flowers were homogamous, since both stigma receptivity and anther dehiscence began at the balloon stage, and continued synchronously afterwards. Dynamics of nectar and pollen production (primary attractants) were studied hourly. Nectar secretion could be detected from early morning to noon, the most intensive anther dehiscence was observed in the noon hours, coinciding with maximal nectar secretion in two of the years. The percentage of viable pollen grains was above 50% each year, which should be sufficient for successful pollination and attractive enough for bees. Flowers isolated for 12 hours produced very small amounts of nectar (1.6-2.7 μl/flower), with relatively high refraction values (13-17%). The nectar of P. betulifolia is hexose-rich, but also contains sucrose, in contrast with the majority of pears, which produce only glucose and fructose. The structural basis of floral nectar production is the receptaculo-ovarial nectary, being automorphic both at the apical and the basal part, stretching also along the style. The nectary epidermal cells are palisad-like, with meso- or xeromorphic stomata among them. The thick glandular tissue, which can be well distinguished from the parenchymatous tissue, consists of 3-8 cell rows. P. betulifolia proved to be highly attractive for bees, most probably due to its ample pollen offer and sucrose-containing nectar, and was accordingly visited by a large number of bees each year. | |
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