Influence of different methods for breaking seed dormancy of Ambrosia artemisiifolia, Abutilon theophrasti and Xanthium strumarium on emergence in field conditions

Seed dormancy is an important trait that contributes to the survival rate of weeds, helps to avoid the effects of herbicides and protects them against adverse environmental conditions. In order to determine which methods are effective in breaking seed dormancy of invasive weed species (Ambrosia artemisiifolia, Abutilon theophrasti, Xanthium strumarium), an experiment was set up in 2019 in a randomized block design, with three replications in the experimental field of the Institute of Field and Vegetable Crops (Novi Sad). The collected seeds of one population of A. artemisiifolia and A. theophrasti, were cleaned and stored in cold storage at 4°C until testing, while X. strumarium was stored at room temperature. Seed propagation was done in a weed science laboratory, using nine different methods for breaking seed dormancy. The seeds were exposed to different conditions of temperature, light and humidity over a certain period of time (24h or 48h). The dynamics of weed emergence were monitored daily, for a period of 31 days and expressed cumulatively in percentages. Based on the obtained results, the highest percentage of sprouted plants was determined in treatments where the seeds were propagated under light conditions, in water. An appropriate method of propagation can influence the breaking of seed dormancy and emergence in field conditions, which can have practical significance in the research of competitive relations between crops and tested weed species.

Fatty acids in wild hemp seeds (Cannabis sativa L. ssp. sativa var. spontanea Vavilov)

Wild hemp (Cannabis sativa L. ssp. sativa var. spontanea) is a special variety of industrial hemp (Cannabis sativa L. ssp. sativa), which is believed to have originated from the acclimatization of industrial hemp to the ruderal habitat conditions of Eastern Europe. In Serbia it is found along roads, on field edges, stubble fields, garbage dumps etc., but also as a weed in fields. Due to the great popularity of industrial hemp, which can be used for various purposes (as raw material in food and pharmaceutical industry, in the production of gluten-free flour, biodiesel, detergents, in folk medicine), many researchers have analyzed its seeds, including analysing their fatty acids content. However, even though this knowledge can be of chemotaxonomic, ecological, evolutionary and nutritional significance, there is no data on the presence and composition of fatty acids in wild hemp seeds For the analysis of fatty acids in wild hemp seeds, the seed material was collected from two locations. After the extraction with hexane, determination of fatty acid esters was performed by capillary gas chromatography. Chromatographic peaks in the samples were identified by comparing the retention times with the retention times of the fatty acid esters in the analytical standard of a mixture of 37 fatty acid esters. The fatty acid composition is expressed as the relative mass fraction of the total fatty acids. The analysis of fatty acids in wild hemp seeds reveales the presence of 15 different acids, with content of 17.5% (U1) and 14.7% (U2) in relation to the total seed weight. Linoleic (45.3 and 47.5%) and a-linoleic (13.6 and 15.5%) acids were the most dominant. Of the 15 detected fatty acids, only 4 are saturated, with a representation of about 12%. Unsaturated fatty acids are present in a significantly higher proportion (about 88%), which indicates the nutritional value of these seeds.

Distribution of economically important weed species in the riparian and roadside vegetation of Serbia

Transportation corridors such as waterways and road networks serve as an entranceway for invasive and economically important weed species. The unstable environment of riparian areas and nutrient enrichment of road verges promotes the establishment and spread of these species, which may have a negative effect on nearby arable land, leading to severe yield reductions. We aimed to register the presence and frequency of five selected weed species (Chenopodium album, Cirsium arvense, Convolvulus arvensis, Cynodon dactylon, and Lactuca serriola) within these linear corridors. Sites along waterways were visited during 2013-2016, and road networks during 2018-2019. At each site, studied weed species were registered along 100 m transects, resulting in 250 localities along waterways and 180 near road networks. The most frequent species is C. arvensis, followed by L. serriola and C. album, while less prevalent species are C. arvense and C. dactylon. The main characteristic of studied species is their preference for roadside habitats, except for Chenopodium album, which is more common in riparian areas.

Ambrosia trifida L.: Giant ragweed

Ambrosia trifida L. (AMBTR, fam. Asteraceae/Compositae) is native to North America. It was introduced accidentally to Europe at the end of the 19th century, with contaminated animal feed and seeds for planting. Today A. trifida is present in ruderal and agricultural habitats of many European countries (France, Italy, Germany, Russia, Spain, Romania, Slovakia, Czech Republic, Poland, Serbia, Bulgaria, etc.). Giant ragweed was detected for the first time in 1981 in Serbia (site Čoka). Over the following period it disappeared from this site, but was recorded again in 2006 in another site (central Bačka: Despotovo, Kucura, Savino Selo, Ravno Selo, Ruski Krstur). Currently in Serbia it has the status of an alien naturalized weed species. This summer annual plant can grow up to 6 m in height and exhibits a high degree of morphological and reproductive plasticity in response to encroachment by neighboring plants. It is present in disturbed habitats, such as agriculture fields, where it plays the role of the dominant species throughout the entire growing season. In most cases, leaves are opposite and always simple and generally have 3 distinct lobes but can also have as many as 5. It is a diploid (2n = 24), meso-hygrophilic species, preferring wet habitatse and can tolerate a wide variety of soil types. Also, this is a monoecious plant, where male and female flowers are separated on the same individual. A. trifida can hybridise with A. artemisiifolia (A. x helenae Rouleau, with 2n= 27 and 2n= 33), but this hybrid has been described as sterile. Compared to other summer annual species, A. trifida is among the first to emerge in early spring, at optimal temperatures from 10-24°C. Under optimal environmental conditions, giant ragweed produces around 1,800 (max 5,100) seeds plant-1. It flowers and bears fruit from July to September (October).The pollen of this species has allergenic potential. Additionally, in the USA and Canada giant ragweed populations have developed resistance to acetolactate synthase inhibitor herbicides and glyphosate. Giant ragweed can be a problematic weed in row crops (corn, soybean, sunflower, sugerbeet) and vegetables. In A. trifida the control measures should prevent further spread, and existing populations should be controlled by integrated weed management practices. Furthermore, A. trifida has a relatively low fecundity, a transient soil seedbank and a high percentage of non-viable or low-survivorship seeds, which are features that may have constrained its establishment and spread in the current environmental conditions in Serbia.

Investigation of SPAD values and morphometric characteristics of leaves in wild blackberry populations on Stara Planina Mt.

Natural populations of Rubus hirtus Waldst. & Kit. were studied at three locations along the Gabrovnica river on Stara Planina mountain, to assess the inter-population differences in ecophysiological and ecomorphological parameters. The content of total chlorophyll in leaves, estimated by the SPAD method, as well as leaf width and leaf width/length ratio had the highest values in population A, which inhabits a forest community dominated by hornbeam and sessile oak and grows in vegetative shade. Populations B (which is also located within the forest complex) and C (which is located in a relatively open habitat) had lower values for the examined parameters. Inter-population differences in the examined parameters can be partially interpreted as an adaptation to habitat light conditions (significant differences between individuals from populations A and C). However, the values of parameters in population B cannot be explained by light conditions, indicating the need to consider complex environmental conditions at that site, primarily heavy metal contamination of soil and groundwater.

Relative sensitivity of conventional soybean to three dicamba based herbicides at different growth stages

Widespread use of dicamba-based herbicides such as Clarity® (dicamba diglycolamine salt, 480 g l-1), Engenia® (dicamba N,N-Bis-[3-aminopropyl] methylamine salt, 600 g l-1) and XtendiMax® (dicamba diglycolamine salt, 350 g l-1)with Vapor-Grip Technology for weed control in dicamba-tolerant (DT) crops have resulted in UN-intended drifts, partly due to windy and common temperature inversions in many parts of United States. It is unclear if the dicamba-based herbicides made of different formulations or technologies have differential impact on sensitive soybeans including a conventional variety. Thus, field studies were conducted in 2016 and 2017 to evaluate the relative sensitivity of a conventional soybean to micro-rates of three dicamba-based herbicide products (Clarity®, Engenia® and XtendiMax® ) applied at second trifoliate (V2), seventh trifoliate/beginning of flowering (V7/R1), and full flowering (R2) stages of soybean. The dicamba micro-rates were 0, 0.56, 1.12, 5.6, 11.2, and 56 g ae ha-1; equivalent to 0, 1/1000, 1/500, 1/100, 1/50, 1/10 of the standard rate (560 g ae ha-1) respectively. The experimental design was a randomized complete block design in a split-split-plot arrangement with 4 replications. There was no significant difference in visual injury, growth or yield response of the conventional soybean to the three dicamba herbicides. The dicamba micro rates caused 40-80% visual injury and 0-97% yield loss depending on the growth stage of application. The estimated effective doses (ED values) suggested that conventional soybeans exposed to dicamba micro-rates at V7/R1 growth stage were more sensitive than those exposed at V2 and R2 growth stages. Based on the ED values, about 0.1% of dicamba standard rate was enough to cause 10% soybean yield loss when applied at V7/R1 stage; while about 1% of dicamba standard rate was required to cause the same level of yield loss when applied at V2 or R2 stage. By implication, dicamba drift on sensitive soybean plants should be avoided to prevent yield loss.

Allochthonous plant species in the vegetation of the Great War Island

The main aim of the conducted research was to determine the presence of allochthonous plants in the area of the protected natural reserve - The Great War Island. The research was conducted during the vegetation season of 2020. Thirty four allochthonous plant species were recorded and classified into 19 families. Asteraceae (8 species), Fabaceae Poaceae and Sapindaceae (3 species each) had the highest species diversity. Phytogeographic analysis of their primary distribution areas has shown that most belong to the category of floral elements of the "adventitious" areal type. The chorological spectrum is dominated by species of North American origin (58.8%), while in the biological spectrum the most common are therophytes (38.2%). Chronological spectrum analysis has shown the highest prevalence of neophytes (64.7%). Seventeen species have the status of invasive, 16 naturalized, while one species (Morus alba) is characterized as ephemerophyte. The most frequent neophytes on the Great War Island are Acer negundo, Ailanthus altissima, Amorpha fruticosa, Fraxinus pennsylvanica, while among neotophytes, Echinocystis lobata and Symphyotrichum lanceolatus stand out in terms of frequency of occurrence. The geographical position of the Great War Island, due to which it is exposed to periodic floods, high levels of groundwater, strong influence of anthropogenic factors and the biological characteristics of allochthonous species are the main factors enabling them to inhabit this area. Results of this research should be the basis for the development of a strategy for monitoring the condition and planning control measures for the unwanted plant species, in order to protect the indigenous flora. Only careful and responsible management of landscapes of outstanding features such as The Great War Island and taking appropriate preventive measures can prevent the settlement, domestification and further spread of allochthonous plants.

Plants causing dermatosis in humans

Many plants cause dermatosis in the human population, thus presenting an everyday problem for dermatologists and allergologists around the world. To this day it is still not known how common are plant-induced dermatosis. It is estimated that around 334 million people worldwide, or 3.5% of the world population, is affected by dermatosis each year. The onset of dermatitis is most common in the early childhood. Around 20% of children in Great Britain and 10% in the USA are affected by different types of dermatosis. It is believed that around 10,000 plant species can cause dermatosis in humans. Phytodermatosis are dermatosis caused by plants. They are usually induced by direct contact with a plant, but can also occur without a direct contact or be activated by the sun. Dermatosis which occur without a direct contact with the plant are observed in those cases where certain perfumes, cremes or other cosmetic products are used. Some cosmetic products contain substances such as eugenol, isoeugenol, cinnamaldehyde, colophonium, turpentines and other substances which originate from plants. Similarly, lichens, which are not plants, but organisms resulting from a fungi and algae symbiosis, produce usnic acids, which are most commonly used in sun protection products.

Lawns along the Belgrade roads: Taxonomic and phytogeographical analysis

This study was done with the aim to comparatively analyze the taxonomic and phytogeographical spectrum of lawns along the Belgrade roads. The analysis was done using the results of a floristic research done in 2001, combined with results of the field research conducted in 2019. A comparative analysis of the obtained results has shown that a lower heterogeneity of the floral elements and plant taxa was recorded in the studied lawns in 2019, when compared to the previous research period. Such a reduction in heterogeneity is the result of more intensive measures of lawn care, and of a stronger anthropogenic influence, which has led to a homogenization of the lawn flora.

Critical time for weed removal in dicamba tolerant soybean as influenced by pre emergence herbicides

Field experiment was conducted in 2019 at Haskell Agriculture Laboratory, Concord, NE, USA. Goal of the study was to test the influence of PRE-EM herbicides on the Critical Time for Weed Removal (CTWR) in dicamba-tolerant soybean. The study was arranged in a split-plot design which consisted of four herbicide regimes as main plot treatments and seven weed removal timings as subplot treatments, with four replications. The herbicide regimes included: (1) no PRE and glyphosate, (2) acetochlor and dicamba as PRE and glyphosate as POST, (3) acetochlor and dicamba as PRE and glyphosate and dicamba as POST, and (4) acetochlor and fomesafen as PRE and acetochlor, glyphosate and dicamba as POST. The five weed removal times included the V1, V3, V6, R2 and R5, and there were also weedy and weed-free season long plots. By utilizing herbicide regimes, the CTWR was delayed to 632 GDD (until V4 soybean growth stage, 28 days after emergence) for acetochlor and dicamba as PRE and glyphosate as POST, 861 GDD (until V6 soybean growth stage, 32 days after emergence) for acetochlor and dicamba as PRE and glyphosate and dicamba as POST, and 1060 GDD (until R1 soybean growth stage, 42 days after emergence) for acetochlor and fomesafen as PRE and acetochlor, glyphosate and dicamba as POST.