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

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

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

The distinctive features of floral nectaries facilitate identification of ecological and phylogenetic links between related taxa. The structure and functioning of nectaries determine the relationships between plants, pollinators, and the environment. The aim of the study was to determine and compare the micromorphology of the epidermis in the floral nectaries of six Rubus idaeus cultivars belonging to biennial (‘Glen Ample’, ‘Laszka’, ‘Radziejowa’) and repeated fruiting (‘Pokusa’, ‘Polana’, ‘Polka’) groups. Another objective was to characterize the cuticle ornamentation and stomatal morphology, the anatomy of the nectary epidermis, parenchyma, and sub-nectary parenchyma in the initial nectar secretion phase, as well as the ultrastructure of the nectary epidermis and parenchyma cells in the initial and full nectar secretion phases. The study was carried out using light, fluorescence, scanning and transmission-electron microscopy techniques. Semi-thin and ultrathin sections were used for the microscopic analyses. The cuticular ornamentation and stomatal morphology may be helpful elements in the identification of relatedness between Rubus species. The interaction of the extensive system of endoplasmic reticulum membranes, mitochondria, and Golgi apparatus indicates high metabolic activity, and the fusion of transport vesicles with the membrane suggests granulocrine nectar secretion. The results bring new data to the biology of plants

Nectar Abundance and Nectar Composition in Selected <i>Rubus idaeus</i> L. Varieties

The increasing commercial production of R. idaeus offers insects nectar and pollen rewards, thus increasing the chance of cross-pollination, which enhances fruit yields. The knowledge of nectar characteristics may help farmers/beekeepers to improve the quality of their products. Therefore, we determined and compared nectar weight, sugar concentration and weight, and the qualitative and quantitative composition of sugars and amino acids in the nectar of six raspberry cultivars: three biennial and three repeated fruiting cultivars. The nectary abundance in these cultivars ranged between 20.2 ± 3.84 mg (‘Polka’) and 26.4 ± 7.3 mg (‘Glen Ample’) of nectar per flower with a sugar concentration of 34.6 ± 5.61–47.3 ± 9.33%. The contents of glucose and fructose (g/100 g) were in the range from 42.96 ± 0.71 (‘Glen Ample’) to 46.94 ± 0.55 (‘Laszka’) and from 50.7 ± 1.43 (‘Polka’) to 54.2 ± 0.72 (‘Radziejowa’). Sucrose was detected only in ‘Glen Ample’ (5.6 ± 1.12 g/100 g) and ‘Polka’ (6.2 ± 0.95 g/100 g). Taking into account the increasing sugar weight in the nectar, the cultivars were ranked as follows: ‘Polka’ R. idaeus nectar for pollinators

<i>Rubi idaei fructus</i> as a Source of Bioactive Chemical Compounds with an Important Role in Human Health and Comparison of the Antioxidant Potential of Fruits and Juice of Three Repeat-Fruiting <i>Rubus idaeus</i> L. Cultivars

Rubi idaei fructus is a source of nutritionally important bioactive chemical compounds, mainly antioxidants, which strengthen the immune system and can be used in the prophylaxis and adjuvant therapies of many oxidative stress-induced diseases. There are no literature reports presenting a comprehensive comparative analysis of the antioxidant activity and nutritionally relevant metabolites contained in the fruits of repeat-fruiting raspberry cultivars, which are commonly grown in Europe. The aim of this study was to carry out a comparative analysis of the antioxidant potential (Folin–Ciocalteu, DPPH, FRAP), the content of selected primary and secondary metabolites, and the qualitative and quantitative composition of amino acids and fatty acids in the fruits of R. idaeus cv. ‘Pokusa’, ‘Polana’, and ‘Polka’. The fruits of the analyzed cultivars have a low caloric value (171–219 kcal/100 g); low content of available carbohydrates (6–6.6%) and total carbohydrates (3.4–4.8%); and high levels of dietary fiber (4.7–5.8%), vitamin C (22.8–27 mg/100 g), anthocyanins (25.1–29.6 mg/100 g), and flavonoids (0.5–2.6 mg/100 g). The fruits were found to contain valuable unsaturated fatty acids (35–60%), especially MUFAs with dominant oleic, elaidic, palmitic, and erucic acids and PUFAs (α-linolenic, eicosapentaenoic, and linoleic acids). MUFAs from the ω-9 group accounted for 12–18%, whereas the content of PUFAs from the ω-3 and ω-6 groups was in the range of 15–23 and 6–21%, respectively. Exogenous amino acids, accounting for 56–62%, were dominated by leucine, phenylalanine, and lysine. The following order of the total polyphenolic content was established in the fresh fruit juice from the analyzed cultivars: ‘Pokusa’ R. idaeus cultivars. This indicates that raspberry fruits can serve as a source of nutrients and can be used as a valuable supplement in a healthy human diet and a raw material in the pharmaceutical and cosmetic industries

Comparison of the Micromorphology and Ultrastructure of Pollen Grains of Selected Rubus idaeus L. Cultivars Grown in Commercial Plantation

The genus Rubus is one of the largest taxonomically diverse and complex genera in the family Rosaceae. Morphology of pollen grains (equatorial and polar axes length, shape and size, aperture position, exine sculpture, perforations) is regarded as one of its main diagnostic features for identification of species and varieties. An attempt was made to fill the gap concerning the pollen micromorphology and ultrastructure of R. idaeus L. using light, scanning, and electron transmission microscopy. This study is a comparative analysis of micromorphological and ultrastructural traits of pollen from six raspberry cultivars. The pollen grains were classified as small or medium of shape prolato-spheroids. The parallel striae in the equatorial view in the exine sculpture were sometimes branched dichotomously in &lsquo;Glen Ample&rsquo;, &lsquo;Polka&rsquo;, and &lsquo;Polana&rsquo;, arcuate in &lsquo;Laszka&rsquo; and &lsquo;Pokusa&rsquo;, or irregularly overlapping in &lsquo;Radziejowa&rsquo;. The width of exine striae of biennial fruiting cultivars was much larger than in repeated fruiting cultivars. In terms of the increasing number of perforations per unit area of the exine surface, the cultivars were ranked as follows: &lsquo;Pokusa&rsquo; &lt; &lsquo;Glen Ample&rsquo; &lt; &lsquo;Laszka&rsquo; &lt; &lsquo;Polka&rsquo; &lt; &lsquo;Polana&rsquo; &lt; &lsquo;Radziejowa&rsquo;. The thickest tectum, the highest and thickest columellae with the largest distances between them, and the thicker foot layer were demonstrated in &lsquo;Glen Ample&rsquo;. The ectoexine constituted on average ca. 78&ndash;90% of the exine thickness. The findings may constitute auxiliary traits i.a. for identification of related taxa, interpretation of phylogenetic relationships, and pollination biology