Phenylurea-type Cytokinin ameliorates the performance of young pea plants under salt stress

Cytokinins are known to enhance stress tolerance in plants. The present study aimed to assess the possible protective effect of exogenous phenylurea-type cytokinin (4PU-30) on alleviating salt (NaCl) stress. Young pea (Pisum sativum L.) plants were sprayed with cytokinin 4PU-30 and were subsequently subjected to NaCl treatment. The effect of 4PU-30 on cell membrane stability was assessed based on electrolyte leakage from leaves of control and NaCl stressed plants. A previously established model system employing the kinetics of ion leakage served to evaluate the effect of the 4PU-30 application on plants response to salinity. Salt treatment caused a moderate decrease in leaf water content. Accumulation of proline, malondialdehyde (MDA), and hydrogen peroxide (H2O2) in the leaves of NaCl treated plants indicated the development of oxidative stress, which was significantly alleviated by pretreatment with phenylurea-type cytokinin 4PU-30. Foliar application of 4PU-30 reduced the damaging effect of NaCl, as evidenced by decreased electrolyte leakage. Distinct roles of cell walls and plasmalemma in the processes of ion efflux due to salt stress are discussed.

Variation in hip and sepal parameters of invasive Rosa rugosa between sites and years

Rosa rugosa is among the most invasive species in Europe, and it is considered a severe threat to the diversity and stability of coastal habitats. In Lithuania, it is a widespread invasive species occurring in coastal and inland areas. This research aimed to estimate the variation in R. rugosa hip and sepal parameters within and among sites from coastal and inland areas, and investigate the effects of environmental factors on the hip and sepal sizes. Field studies were performed at four coastal and three inland sites in 2008, and the studies were repeated in 2016. We collected 100 mature hips at each site and measured the hip width, hip length and sepal length. We analysed variation in hip and sepal parameters between the study years, and the effect of meteorological factors and agrochemical properties of the soil on hip and sepal sizes. This study revealed significant variation in R. rugosa hip width, hip length and sepal length among the studied sites. The largest hips and sepals were found in the coastal habitat at the Smeltė site, whereas the smallest hips and sepals were recorded in inland habitat at the Staviškės site, where R. rugosa occurred in woodland. The comparison of hip and sepal sizes at the same sites during two study years revealed irregular variation. Mean hip width and mean length of sepals in 2008 were significantly more prominent than in 2016, whereas no significant differences in hip length were found between the study years. The content of phosphorus in the soil negatively correlated, whereas the content of carbonates positively correlated with the sepal length. A strong negative relationship was found between the sunshine duration and hip length and width ratio. However, the revealed relationships of the hip and sepal parameters with the environmental factors could be a coincidence or a result of the cumulative effect of the multiple factors’ interaction and should be investigated separately.

Confirmed occurrence of the native plant species Eleocharis ovata (Cypera­ceae) in Lithuania

Information on the occurrence of Eleocharis ovata (Cyperaceae) in Lithuania for a long time had been based on misidentified specimens only. During the studies on the flora of South Lithuania in 2020, we discovered this species in Varėna district on the shores of Lake Pabezninkai. We performed field investigations on the distribution, size of population and habitats of E. ovata from August to October 2020 on the shores of Lake Pabezninkai and, searching for this species, surveyed potential habitats on the shores of eight other lakes in South Lithuania. A total of 63 individuals of E. ovata were found on the shores of Lake Pabezninkai, and they were widely dispersed on the northern and south-western shores of the lake. Most of the registered individuals of E. ovata were found growing on wet sand and mud in the communities of the Isoëto-Nanojuncetea class. Solitary individuals were also found in communities of the Phragmito-Magnocaricetea class. Assessment of E. ovata according to the IUCN criteria revealed that this species, currently occurring at a single locality in Lithuania, should be classified as critically endangered (CR). Conservation of E. ovata and other rare plant species recorded on the shores of Lake Pabezninkai should be organised by maintaining favourable habitat conditions.

New alien taxa of the genus Cornus (Cornaceae) recorded in Lithuania and Latvia

Plants of the genus Cornus are valued for their ornamental qualities, are often grown in gardens, parks, or other public plantings, and form various shelterbelts. This increases the likelihood that these bird-dispersed plants will escape from their sites. This paper provides information on the first record of C. mas in Lithuania in 2021 at two sites. This species is currently considered a casual alien species, but may become locally naturalised in the future. This study confirmed that C. sericea is widespread in Lithuania, and the oldest herbarium specimen of the species was collected in 1997. Cornus sericea, like C. alba, is naturalised and potentially invasive in Lithuania. The alien subspecies of C. sanguinea (C. sanguinea subsp. australis) was found for the first time in Lithuania and Latvia in 2018. Available data show that this subspecies is naturalised in both countries, and its abundance in some areas in Lithuania indicates that it may become an invasive plant. The paper discusses dispersal vectors, occupied habitats, and the potential for spreading three alien Cornus taxa.

Biological pollution of the flora of Volyn’ Polissya in Ukraine by alien plants

This study aimed to analyse biological pollution of the native flora of Volyn’ Polissya in Ukraine by alien plant species. According to the research results, 364 alien plants belonging to 228 genera and 68 families were identified in the spontaneous flora of Volyn’ Polissya. The spectrum of the most species-rich families of the alien fraction of the region’s flora includes Asteraceae, Brassicaceae, Poaceae, Rosaceae, Chenopodiaceae, Fabaceae, Lamiaceae, Solanaceae, Caryophyllaceae. As a result of the phytopollution, at least 16 families were included in the region’s flora. Four species currently in a stage of expansion were identified (Reynoutria japonica, Impatiens parviflora, Echinocystis lobata, Bidens frondosa). By origin, the species of the alien fraction of the region’s flora are dominated by the immigrants from the Mediterranean, Iranian-Turan and Atlantic-North American floristic regions. Over the past 30–50 years, at least 80 new species of alien plants have been introduced into the territory of Volyn’ Polissya. Over the past 5–7 years, the speed of the spread and naturalisation rate of species such as Quercus rubra, Asclepias syriaca, Parthenocissus quinquefolia, Prunus cerasifera, Hippophae rhamnoides, Oenothera biennis has increased. These species intensively invade the native plant communities. Phytopollution of Volyn’ Polissya is promoted by the migration of alien species from agricultural lands and escaping from cultivation. This process is also facilitated by urbanisation and the development of transport infrastructure.

Comparison of sand burial-dependent growth responses of two Tragopogon species from different habitats

Wind-driven sand movement leading to sand burial is an essential environmental factor in coastal sand dunes; therefore, plants native to sand dunes need to possess specific adaptations. The present study aimed to compare responses to variable sand burial intensity of Tragopogon heterospermus, rare plant species native to coastal dunes, and Tragopogon pratensis taxonomically related grassland species. Plants in culture were established from seeds collected in natural habitats, cultivated in an automated greenhouse, and individuals of different age were buried by sand in the different depths. Both plants had basic sand burial tolerance, seen as an elongation of adult plants’ leaf bases under moderate sand burial conditions. However, only dune-adapted T. heterospermus plants exhibited efficient resource allocation from roots to shoots with increased sand accretion intensity. T. heterospermus plants had pronounced age dependence of burial tolerance, with higher sensitivity to sand burial at an earlier stage due to small shoot height and, possibly, certain physiological factors.

Revision of the characeae (Charales, Charophyceae) species and their distribution in Lithuania

The current inventory was mainly based on revising herbarium specimens collected since the 19th century and confirmed twenty-one Characeae species in Lithuania. They are representatives of five genera: Chara (12 species), Nitella (5), Tolypella (2), Lychnothamnus and Nitellopsis (by one species each). Thirteen species mentioned in references or labels of herbarium specimens were not confirmed. The occurrence of the Characeae species was recorded in 251 map grid cells (42% of the total number 593). Herbarium specimens were collected from 693 water bodies, mainly lakes. Chara globularis was the most common species, recorded in 150 map grid cells and more than 250 water bodies. Ten species (C. aspera, C. contraria, C. filiformis, C. subspinosa, C. tomentosa, C. virgata, C. vulgaris, Nitella mucronata, N. flexilis, Nitellopsis obtusa) were recorded in the interval from 100 to 50 grid cells and also belong to the group of common species. Chara papillosa and C. strigosa were recorded less than in 50 grid cells and should be considered quite common. Eight species (C. baltica, C. canescens, Lychnothamnus barbatus, Nitella confervacea, N. gracilis, N. syncarpa, Tolypella nidifica, T. prolifera) were recorded in ten or fewer grid cells and belong to the group of rare or very rare species. The occurrence of species that have not been confirmed by the herbarium specimens was discussed.

Comparison of physiological effects of osmotic stress on two wheat genotypes

Revealing stress tolerance mechanisms in plants would contribute to the selection of crop varieties with a higher capacity for surviving in unfavourable environments. In this regard, it is essential to identify possible physiological features that might be beneficial for increasing plant resistance to stress. Two contrasting common wheat (Triticum aestivum L.) cultivars with different drought tolerance were subjected to 48 h treatment with 20% polyethylene glycol 8000, which provoked an extra degree of osmotic and oxidative stress as well as distinct physiological responses. Better water retention capacity in leaves and lesser extent of membrane injury found in cultivar ‘Guinness’ compared to cultivar ‘Niki’ correlated with increased osmotic adjustment by accumulating higher amounts of proline and higher antioxidant scavenging capacity in the former. Compared to soluble sugars and total free amino acids, proline contributed to a greater extent to preserving leaf water. It was speculated that such a combination of features would set a genotypic advantage for this cultivar, which could also determine better performance under drought conditions in the field.

Effect of abiotic stresses on germination behaviour of Ruta chalepensis

This work aims to highlight the optimal temperature for the seed germination of Ruta chalepensis, an important threatened ethnomedicinal shrub, and assess its germination tolerance against salinity and water stresses as well. For this, the seeds were incubated firstly under different temperatures (5 to 30°C). After that, at 20°C, germination tests were performed under different sodium chloride (NaCl) concentrations (0 to 273.9 mM) and various polyethylene glycol solutions (PEG6000) (0 to -2.20 bar). Final germination percentage, velocity coefficient and latency time were subsequently the germination patterns determined and analysed. The optimum temperature for germination was 15°C, in which the maximum final germination percentage (85%) was noticed; germination fell steadily, however, above and below this temperature and completely ceased at 30°C. Germination behaviour of R. chalepensis seeds under osmotic stress conditions showed a significant effect of both NaCl and PEG6000. Germination decreased whether sodium chloride or polyethylene glycol was increased in the medium (p < 0.05). Moreover, the salinity tolerance threshold was 205.4 mM, equivalent to 16 g L-1 NaCl, while water stress was -1.16 bar, corresponding to 80 g L-1 PEG6000. Beyond these thresholds, germination stopped. Dropping in velocity coefficient and postponing in latency time with increasing both stresses were recorded either. The sensitivity of R. chalepensis seeds to environmental stresses should be taken into account for successful conservation programmes, which should be implemented by sowing seeds and planting seedlings in fresh habitats with sufficient annual rainfall.