Primary and Secondary Attractants of Flowers in Pear Pyrus Betulifolia

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 µ µ µ 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.

Nectar Secretion, Morphology, Anatomy and Ultrastructure of Floral Nectary in Selected Rubus idaeus L. Varieties

“…These values were higher than those reported in Prunus cerasus and P. avium (0.41-0.57) and lower than in Prunus armeniaca and P. domestica (0.9-3.3 µm), P. avium (1.5-6.0 µm), Prunus laurocerasus (1.21-1.30 µm), and Pyrus sp. (1.26-2.58 µm) [20,21,60,78,79]. In the present study, the evenly distributed cuticle comprised lamellar and reticulate layers and cellulose microfibrils.…”

“…In turn, nectary cells in several species of the genus Malus formed from 14 to 31 layers and the gland was from 203 to 430 µm thick [25]. The nectaries of Cydonia oblonga, Cotoneaster betulifolia, and Pyrus betulifolia were composed of 8-15, 3-4, and 3-8 layers, respectively [21,27]. The subnectary parenchyma in the raspberry cultivars analyzed in the presented study was composed of 5-8 layers and its thickness was in the range of 145-199 µm.…”

“…Nectaries in the Rosaceae family represent the receptacular type. They are composed of three layers: nectary epidermis, nectary parenchyma, and subnectary parenchyma [20,21]. The structure of floral nectaries in the Rubus genus has not been studied.…”

“…produce epimorphic, transitional, or automorphic nectaries [25]. Other authors have described receptaculo-ovarial nectaries in the flowers of Cydonia and Pyrus [21,26,27]. In turn, Farkas [28] has distinguished xeromorphic, mesomorphic, and hygromorphic nectaries.…”

Pollen morphology and viability of some Indian mangroves

“…Pollen grains viability test with 1% aceto-orcein shows that all the investigated taxa produced more than 90% viable pollens under in situ condition that ultimately lead to successful participation in pollination mechanism and seed production. Farkas and Orosz-Kovacs (2004) conducted an experiment on pollen grain viability in pear (Pyrus betulifolia) and obtained above 50% viable pollen grains. He concluded that this percentage is sufficient for successful pollination and enough to attract bees.…”