Marina Mačukanović-Jocić

Flower morphophysiology of selected Lamiaceae species in relation to pollinator attraction

Summary The floral biology and attractiveness of five Lamiaceae species, namely Hyssopus officinalis, Lavandula officinalis, Melissa officinalis, Salvia officinalis and Salvia sclarea, were studied by correlating morphological characteristics of flower and nectar production with pollinator visits, especially with reference to honey bee forage preferences. Although these species are cultivated for medicinal purposes, they also represent a significant source of pollen and nectar for honey production, so the investigation aimed to estimate their melliferousness and significance for bee pasture. Pollinator observation indicated the visitation of seven species of Hymenoptera, three species of Diptera and two species of day flying Lepidoptera. The honey bee (Apis mellifera) was the most abundant pollinator, and the major elements of attractiveness were flower scent and colour, followed by the shape and size of the corolla and to a lesser extent nectar abundance. Corolla tube length and number of open flowers per whorl were of little significance. According to all analyzed flower characteristics and observation of pollinator behaviour and visits, the most attractive plants were H. officinalis, S. officinalis and L. officinalis, whilst M. officinalis was the least attractive and S. sclarea completely unattractive to all recorded pollinators except for Xylocopa violacea.

Nectar secretion in basil (Ocimum basilicum L.) grown in different soil conditions

The fragrant basil flower (Ocimum basilicum L.) is enthomophylic, with nectar storage at a depth suitable for the proboscis length of the honey bee. Owing to the position of stamens, pollen can be easily collected by the ventral side of the bees body. Despite the fact that basil is acknowledged to be a good melliferous plant, predominantly visited by honey bees, there is little information about its nectar production. The quality and quantity of nectar secretion is influenced by numerous endogenous and external factors (Farkas and Orosz-Kovács, 2003). Species specific endogenous factors include the size, shape, position and age of a flower, as well as the duration of flowering. Nectar production is also strongly affected by environmental factors, such as microclimate, soil properties, day length and general site conditions, including altitude and latitude. The complex interaction between these factors strongly affects a plants capacity for nectar secretion (Vogel, 1983). This study was conducted to analyse the influence of diverse soil conditions on diurnal and seasonal dynamics of nectar secretion in basil, aiming to estimate its melliferous potential. Ten basil seedlings at the two leaf stage were transplanted into experimental pots (46.5 x 19 x 14.5 cm) filled with three different soils (eutric cambisol, fluvisol and humoglay) taken from the basin of the Sava river situated in the northern part of Serbia. Three pots of each soil were used. The experiment was conducted during the flowering period of 2003, in the experimental field of the Faculty of Agriculture in Belgrade. The physical (texture) and chemical properties (pH, total carbon, humus and carbonates) of the soils were determined by standard methods. The texture of fluvisol was estimated as a sandy loam (63.88 % sand), and it contained 5.82% CaCO3, 3.07% humus, 1.78% total carbon, and was slightly alkaline (pH 7.85). The eutric cambisol exhibited a loam structure, was slightly acid (pH 6.16), was slightly carbonated (CaCO3: 1.49%), rich in humus (5.15%) and rich in total carbon (C: 2.98%). The texture of the humoglay varied from sandy loam to clayey loam and clay, and it was slightly alkaline (pH 7.62), and it contained 1.28% carbonates, 2.52% humus and 1.46% total carbon. Nectar secretion was measured directly by the microcapillary method (McKenna and Thomson, 1988) using 0.5-0.6 mm diameter microcapillaries. Inflorescences were covered with fine mesh (20 x 20 cm) for 12 hours prior to nectar removal (from the evening of the previous day) and between daily measurements, to prevent access by flower visitors. Individual flowers were marked at the bud stage and the nectar was collected in the second day of flower life. Nectar was taken from five randomly chosen plants of each pot, and the length of the nectar column was measured immediately in the field. The nectar volume expressed in μl per flower (n = 15, per soil type) was calculated as:-

The Melliferous Potential of Forest and Meadow Plant Communities on Mount Tara (Serbia)

ABSTRACT The apiflora of 34 forest and meadow plant communities in Tara National Park was studied with the aim of assessing their melliferous potential and their contribution to bee pasture during the vegetation period. The melliferous plants were analyzed individually from the aspect of their flowering phenology, abundance, and the intensity of nectar and pollen production, as well as the production of honeydew. The melliferous potential of each investigated plant community was theoretically assessed on the basis of the coenotic coefficient of melliferousness incorporating a phytocoenotic analysis, the coenotic coefficients of nectar and pollen production, and the percentage of melliferous species in relation to the total number of species that characterize the association. The highest percentage of the melliferous species was noted in the meadow association Petasitetum hybridi (70%) and the forest association Piceetum-Abietis serpentinicum (63.6%). The highest values of the coenotic coefficient of melliferousness were established for the forest association Querco-Carpinetum iliricum, and the meadow association Rhinantho-Cynosuretum cristati. Trees notable for their honeydew production in good quantities were Pinus nigra Arnold, Picea sp. Fagus sylvatica Linnaeus, Populus tremula Linnaeus, and Quercus cerris Linnaeus. Because, the vegetation in the study area is forest dominated, forest bee pasture including early flowering herbaceous and woody plants, is of the greatest significance for the honey bee, both in the early spring because of pollen and nectar production, and in the autumn as a source of honeydew.

Preliminary investigation of mineral content of pollen collected from different Serbian maize hybrids - is there any potential nutritional value?

BACKGROUND Bee pollen has already proved to be a good supplement rich in iron and zinc. Studies on the application of flower pollen in the food industry and medicine have begun. Bearing in mind the prevalence of maize as a crop culture, its pollen will be easily available. The mineral composition of pollen of seven Serbian maize hybrids was analyzed in order to establish its nutritional value and the benefits of its implementation in the human diet using the inductively coupled plasma method. RESULTS The presence of twenty four different macro- (nine) and micronutrients (fifteen) was detected. The most common minerals were phosphorus and potassium, while arsenic, cobalt, lead, nickel and molybdenum were found in some samples. CONCLUSION Comparing the results obtained with recommended or tolerable dietary intake references for adults, it was found that maize pollen can be used as a very good source of zinc, iron, chromium and manganese for humans. With regard to selenium content, pollen samples proved to be moderately good source of this important micronutrient. Contents of some elements (Fe, Zn, Mn, Cr, Se, Al and V) showed significant differences depending on hybrid type. In some samples increased concentrations of aluminum and vanadium were recorded, which may pose a potential problem due to their toxicity.

Pollen morphology and the flower visitors of Chaerophyllum coloratum L. (Apiaceae)

Abstract The pollen features of Chaerophyllum coloratum L., endemic to the Dinaric Alps, have been examined by both light microscopy and scanning electron microscopy in order to contribute to a better understanding of the taxonomic status of the species. Flower visitors have also been observed and analyzed with the aim of clarifying certain pollination aspects of the species including flower attractiveness especially to honeybees, and also in order to ascertain its contribution to the bee pasture. The pollen grains of C. coloratum are isopolar, radially symmetrical and medium sized. Polar axis (P) is 26.83±1.77 μm length, and equatorial diameter (E) is 9.17±0.57 μm length. P/E ratio amounts 2.90±0.10 indicating a perprolate shape. In an equatorial view, the grains are constricted in the equatorial region (bone-shaped), with obtuse polar caps. In polar view, they are triangular with obtuse angles and furrows in the sides of the triangle (interangular). The grains are tricolporate with three straight ectocolpi arranged regularly meridionally, of mean length 14.43±2.17 μm, each of which has one endopore. The characteristic internal thickenings around the protruding, clearly visible endopores (costae) in the constricted equatorial region are obvious in light microscopy. The ornamentation is psilate, irregularly rugulate (“cerebroid”), the exine surface is rather undulating. With regard to the observed flower visitors, the following pollination types occurred: melittophily, myophily, sapromyophily, cantharophily, and phalaenophily, and the most frequent pollinator was the honeybee.

Palynomorphological study of primrose (Primula vulgaris Huds.) grown in natural reserve Obedska bara (Serbia)

The pollen morphology of primrose (Primula vulgaris, fam. Primulaceae) has been investigated using light and scanning electron microscopy to contribute to melissopalynological studies of honeys originating from the native apiflora. Palynomorphological investigation included the examination of pollen symmetry, polarity, ornamentation, aperturation, shape and size. The pollen grains are isopolar, radially symmetric and shed as monads. The exine ornamentation is reticulate. Analysis of pollen morphometric characteristics revealed that grains are small to medium size and prolate in shape. Given the aperturation, the number of colpi was mostly variable among individuals with a different type of flower ranging from 6 to 9.