Dragana Rančić

The application of various anatomical techniques for studying the hydraulic network in tomato fruit pedicels.

The abscission zone in fruit pedicels plays an important role in affecting not only water uptake in the developing fruit, but also in the transport of chemical signals from root to shoot. In order to characterize the hydraulic network of tomato fruit pedicels, we applied various techniques, including light, fluorescence microscopy, electron microscopy, maceration, tissue clearing, and X-ray computed tomography. Because of significant changes in xylem anatomy, the abscission zone in tomato fruit pedicels is illustrated to show a clear reduction in hydraulic conductance. Based on anatomical measurements, the theoretical axial xylem conductance was calculated via the Hagen–Poiseuille law, suggesting that the hydraulic resistance of the abscission zone increases at least two orders of magnitude compared to the pedicel zone near the stem. The advantages and shortcomings of the microscope techniques applied are discussed.

Anatomical injury induced by the eriophyid mite Aceria anthocoptes on the leaves of Cirsium arvense

Anatomical injury of the leaves of the invasive species, Cirsium arvense (L.) Scop., caused by the eriophyid mite Aceria anthocoptes (Nal.), which is the only eriophyid mite that has been recorded on C. arvense worldwide, is described. The injury induced by the mite feeding on the leaves of C. arvense results in visible russeting and bronzing of the leaves. Other conspicuous deformations are folding and distortion of the leaf blade and curling of leaf edge, as well as gradual drying of leaves. The anatomical injury of the mature leaves of field-collected plants was limited to the epidermis of the lower leaf surface. However, on young leaves of experimentally infested plants, rust mite injuries extend to epidermal cells on both leaf surfaces and to those of deeper mesophyll layers. On these leaves, lesions on the lower leaf surface even affected the phloem of the vascular bundles. Leaf damage induced by A. anthocoptes is discussed with regard to the mite’s potential as a biological control agent of C. arvense.

Comparison of light and fluorescence microscopy for xylem analysis in tomato pedicels during fruit development

The xylem hydraulic connection between shoot and fruits has previously been investigated, but contradictory conclusions were drawn about the presence of a flow resistance barrier in the pedicel. In this paper we were studying effect of the drought on the functional xylem vessels in the pedicels of tomato fruit. Commercial tomato genotype was grown in cabinet conditions under two watering regimes (full and deficit irrigation). An aqueous solution of eosin Y were used to visualize the path of water movement through tomato fruit pedicel and fluorescence microscopy observations were done on transversal and longitudinal sections. Dye uptake studies suggested that in well watered plants and in plants exposed to drought, a large majority of xylem vessels are not functional in water transport. Reduced‐irrigation treatment significantly altered number and width of functional xylem elements in the fruit pedicel, especially in the abscission zone. This indicates that drought modifies xylem architecture and, thus, environmentally produced change in the hydraulic property of pedicel may affect fruit development.

Eriophyid mite Aceria artemisiifoliae sp.nov. (Acari: Eriophyoidea) potential biological control agent of invasive common ragweed, Ambrosia artemisiifolia L. (Asteraceae) in Serbia

Abstract Common ragweed, Ambrosia artemisiifolia L. (Asterales: Asteraceae), is an annual harmful weed of North American origin, now widely distributed in Central and Southern Europe, Asia and Australia. It is an agricultural weed, but it represents a serious risk for human health because its pollen can cause severe allergies. Recently, in the framework of the EU-COST Action ‘SMARTER’, an European program was started with the aim to develop sustainable management strategies for ragweed in Europe, with a special emphasis in the search and selection of biological control agents. Among them, the record of a new eriophyid mite Aceria species in Serbia has been considered as potential important biological control candidate. This paper describes the species following both morphological and bio-molecular approaches, and is giving some preliminary data on the geographical distribution and on the biology of the eriophyid mite on its host plant.

Genetic analysis of water loss of excised leaves associated with drought tolerance in wheat

Background Wheat is widely affected by drought. Low excised-leaf water loss (ELWL) has frequently been associated with improved grain yield under drought. This study dissected the genetic control of ELWL in wheat, associated physiological, morphological and anatomical leaf traits, and compared these with yield QTLs. Methods Ninety-four hexaploid wheat (Triticum aestivum L.) doubled haploids, mapped with over 700 markers, were tested for three years for ELWL from detached leaf 4 of glasshouse-grown plants. In one experiment, stomata per unit area and leaf thickness parameters from leaf cross-sections were measured. QTLs were identified using QTLCartographer. Results ELWL was significantly negatively correlated with leaf length, width, area and thickness. Major QTLs for ELWL during 0–3 h and 3–6 h were coincident across trials on 3A, 3B, 4B, 5B, 5D, 6B, 7A, 7B, 7D and frequently coincident (inversely) with leaf size QTLs. Yield in other trials was sometimes associated with ELWL and leaf size phenotypically and genotypically, but more frequently under non-droughted than droughted conditions. QTL coincidence showed only ELWL to be associated with drought/control yield ratio. Discussion Our results demonstrated that measures of ELWL and leaf size were equally effective predictors of yield, and both were more useful for selecting under favourable than stressed conditions.

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.