PLANTS AND MAXIMUM PERMISSIBLE CONCENTRATIONS OF HEAVY METALS IN SOIL

The tentative permissible concentrations and the maximum permissible concentration of heavy metals do not always give a complete adequate assessment of the effect on plants. Plant growth inhibition can be at concentrations below the maximum permissible concentrations and tentative permissible concentrations. We studied the effect of copper, zinc, cadmium, and lead concentrations on plants. The object of the research is the lawn grass, the Agrostis stolonifera used in urban greening. According to the data obtained, Agrostis stolonifera showed a low degree of resistance to copper, lower than the tentative permissible concentration and the maximum permissible concentration. Consequently, the tentative permissible concentration and the maximum permissible concentration do not fully reflect the real phytotoxicity of copper. Plants of Agrostis stolonifera demonstrated a relatively high sensitivity to zinc in comparison with the maximum permissible concentration and the tentative permissible concentration. The content of cadmium and lead corresponding to the tentative permissible concentrations did not have a significant effect on the plants.

Occurrence of the Lance Nematode Hoplolaimus stephanus Infecting Bentgrass Agrostis stolonifera in Georgia, USA

A high population of lance nematodes Hoplolaimus spp. were found associated with creeping bentgrass (Agrostis stolonifera L.) in May 2019 in Georgia, USA. The nematode was pathogenic to bentgrass as its population increased by over 3-fold 180 days after inoculation under greenhouse conditions. Morphological measurements of body and stylet lengths of both mature females and males were similar to a grass population of H. stephanus from South Carolina. DNA sequence analyses of the D1-D3 expansion segments of the 28s gene identified the nematode as H. stephanus. The DNA sequence of the nematode was 99.7% identical to a H. stephanus isolate from South Carolina. Also, the PCR method using a species-specific primer set confirmed the identity of H. stephanus. To the best of our knowledge, this is the first report of H. stephanus Sher, 1963, infecting creeping bentgrass in Georgia.

Fungus-originated glucanase and monooxygenase genes in creeping bent grass (Agrostis stolonifera L.)

Recent studies have revealed presence of fungus-originated genes in genomes of cool-season grasses, suggesting occurrence of multiple ancestral gene transfer events between the two distant lineages. The current article describes identification of glucanase-like and monooxygenase-like genes from creeping bent grass, as lateral gene transfer candidates. An in silico analysis suggested presence of the glucanase-like gene in Agrostis, Deyeuxia, and Polypogon genera, but not in other species belonging to the clade 1 of the Poeae tribe. Similarly, the monooxygenase-like gene was confined to Agrostis and Deyeuxia genera. A consistent result was obtained from PCR-based screening. The glucanase-like gene was revealed to be ubiquitously expressed in young seedlings of creeping bent grass. Although expression of the monooxygenase-like gene was suggested in plant tissues, the levels were considerably lower than those of the glucanase-like gene. A phylogenetic analysis revealed close relationships of the two genes between the corresponding genes in fungal endophyte species of the Epichloë genus, suggesting that the genes originated from the Epichloë lineage.

Synthesis of novel pyrazoline-thiazolidin-4-one hybrids and evaluation their biological activity

In the present work, the synthesis of pyrazoline-thiazolidin-4-one hybrids and their pharmacological properties are described. The structure of compounds is characterized using 1H, 13C NMR, and LC-MS spectra. The antioxidant (DPPH assay), antimicrobial (Gram-positive bacterium Lactobacillus plantarum, Gram-negative bacterium Escherichia coli, and yeasts Candida albicans, MIC determination), redox (cyclic voltammetry) as well as herbicidal activity (against grass species Agrostis stolonifera) of compounds have been studied. All derivatives have demonstrated radical scavenging activity with IC50 values in the range from 4.67-7.12 mM in the DPPH test. The tested compounds presented very low antimicrobial and herbicidal activity and no redox peaks were observed in the cyclic voltammetry studies.

Leachates from plants recently infected by root-feeding nematodes cause increased biomass allocation to roots in neighbouring plants

Plants can adjust defence strategies in response to signals from neighbouring plants attacked by aboveground herbivores. Whether similar responses exist to belowground herbivory remains less studied, particularly regarding the spatiotemporal dynamics of such belowground signalling. We grew the grass Agrostis stolonifera with or without root-feeding nematodes (Meloidogyne minor). Leachates were extracted at different distances from these plants and at different times after inoculation. The leachates were applied to receiver A. stolonifera plants, of which root, shoot, and total biomass, root/shoot ratio, shoot height, shoot branch number, maximum rooting depth and root number were measured 3 weeks after leachate application. Receiver plants allocated significantly more biomass to roots when treated with leachates from nematode-inoculated plants at early infection stages. However, receiver plants’ root/shoot ratio was similar when receiving leachates collected at later stages from nematode-infected or control plants. Overall, early-collected leachates reduced growth of receiver plants significantly. Plants recently infected by root-feeding nematodes can thus induce increased root proliferation of neighbouring plants through root-derived compounds. Possible explanations for this response include a better tolerance of anticipated root damage by nematodes or the ability to grow roots away from the nematode-infected soil. Further investigations are still needed to identify the exact mechanisms.

MiR396 is involved in plant response to vernalization and flower development in Agrostis stolonifera

MicroRNA396 (miR396) has been demonstrated to regulate flower development by targeting growth-regulating factors (GRFs) in annual species. However, its role in perennial grasses and its potential involvement in flowering time control remain unexplored. Here we report that overexpression of miR396 in a perennial species, creeping bentgrass (Agrostis stolonifera L.), alters flower development. Most significantly, transgenic (TG) plants bypass the vernalization requirement for flowering. Gene expression analysis reveals that miR396 is induced by long-day (LD) photoperiod and vernalization. Further study identifies VRN1, VRN2, and VRN3 homologs whose expression patterns in wild-type (WT) plants are similar to those observed in wheat and barley during transition from short-day (SD) to LD, and SD to cold conditions. However, compared to WT controls, TG plants overexpressing miR396 exhibit significantly enhanced VRN1 and VRN3 expression, but repressed VRN2 expression under SD to LD conditions without vernalization, which might be associated with modified expression of methyltransferase genes. Collectively, our results unveil a potentially novel mechanism by which miR396 suppresses the vernalization requirement for flowering which might be related to the epigenetic regulation of VRN genes and provide important new insight into critical roles of a miRNA in regulating vernalization-mediated transition from vegetative to reproductive growth in monocots.