Structure of Anther Epidermis and Endothecium, Production of Pollen, and Content of Selected Nutrients in Pollen Grains from Six Rubus idaeus L. Cultivars

Abstract

Poland is the largest European Union producer of Rubus idaeus. This species provides insects with nectar and pollen from June to September. The rationale behind the present research is the increasing commercial production and the use of food attractants for pollinators increasing fruit yields. The intensive search for phytochemicals applicable in industry and phytotherapy together with the unavailability of data on anther epidermis and endothecium structure justify undertaking these investigations. The pollen mass, the content of elements, protein, and fat, as well as the composition of amino acids and fatty acids in the pollen of six R. idaeus cultivars were compared. In terms of pollen production, the cultivars ranked as follows: ’Pokusa’ < ‘Polana’ < ‘Glen Ample’ < ‘Polka’ < ‘Radziejowa’ < ‘Laszka’. The protein content (26–31%) in the pollen indicates its good quality and high attractiveness. Exogenous amino acids, including those with dietary importance, constituted a substantial proportion (33–39%). The content of MUFAs and PUFAs was 32–47% and 3.7–9.1%, respectively. The presence of elements that determine the nutritional value and proper development of pollen was detected in the mineral composition of the exine. The data on the epidermis and endothecium structure provide new information about the micromorphology, anatomy, ultrastructure of and generative organs and auxiliary criteria in the taxonomy of related species.

Pollen Development and Stainability in Vicia faba L. and Lupinus angustifolius L.

“…Another interesting feature concerned endothecium-a tissue that plays a crucial role in anther dehiscence and the release of pollen grains [57]. Lignification of endothecium walls is accompanied by the disappearance of the middle layer and tapetal cells as well as the formation of characteristic thickening [58], which was clearly observable in our study in both tested species. The endothecium cells were substantially larger than the epidermal cells.…”

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

“…There are also no data on nectar abundance and nectar transport processes at the cellular level in common raspberry varieties cultivated in commercial production in Poland, i.e., 'Glen Ample', 'Laszka', 'Radziejowa', 'Pokusa', 'Polana', and 'Polka'. The present study is a continuation of previous research [16,36].…”

Nectar Abundance and Nectar Composition in Selected Rubus idaeus L. Varieties

“…The constantly increasing area of R. idaeus cultivation in Poland, Europe, and the world and the abundant and long flowering (from May to August) of the plants offers a continuous nectar and pollen supply [16][17][18]. Data on the R. idaeus pollen reward were presented by Kostryco et al [19] and Kostryco and Chwil [20]. Nectar secretion increases the frequency of cross pollination in raspberry plantations, contributing to higher yields and quality of Rubus fruits [21][22][23][24].…”

“…Overall, pollination of crops by honeybees, wild bees, and flies generates revenues of around $577 billion annually and is an important factor in agricultural economy [28]. The increasing commercial R. idaeus production ensures an adequate pollen and nectar supply to pollinators [20,29,30]. Poland is one of the main raspberry fruit producers in the European Union in terms of acreage, and the share of global production in the world has been estimated at 13% with a sale value of approximately 930,100 EUR (euro) in 2019 [11,31].…”

“…These values indicate that, due to the production of nectar and pollen, R. idaeus plays not only an important role in the production of fruit but also a key role in the ecology of pollination. The increasing commercial production of these shrubs guarantees high supplies of this reward [20,117]. In turn, the pollination process increases fruit yields [20,29,30,118].…”