Vol 66, No 2 (2019)

Cytidine deaminase (CDA) belongs to the subfamily of cytidine deaminase-like family of proteins, which is involved in the nucleotide metabolism. As CDAs participate in stress response and disease resistance processes, especially as RNA editing enzymes, they are deemed to play vital roles in variety of biological processes. Considering that the reports of the exact functions of CDAs are obscure and rare, it is necessary to study the CDAs on evolution and bio-information levels. In this research, a genome-wide identification of the CDA subfamily in rice (Oryza sativa L.; OsCDAs) was performed, and the phylogeny, gene structure, and biological functions of the identified genes were investigated. The expression profiles of OsCDAs were also retrieved from public microarray databases, and some of OsCDAs expression patterns were further verified by qRT-PCR. The results of this comprehensive analysis suggested that the OsCDAs were highly conserved within species, but their gene structures were relatively divers. OsCDAs may play vital roles during plant development and participate in responses to different biotic and abiotic stresses. The data obtained from this research may provide important information for the functional characterization of CDAs and help to unravel their function in stress tolerance and disease resistance during plant growth and development.

This study was carried out to evaluate the effects of salinity stress on ion distribution in different alfalfa genotypes and its relation with stress tolerance indices. The experimental treatments consisted of two levels of salinity stress including 0 (control) and 200 mM of NaCl and 25 alfalfa (Medicago sativa L.) genotypes. These were arranged as factorial based on a Completely Randomized Design with three replications. There was an increase in sodium (Na⁺) content and decrease in potassium (K⁺) content in salinity stress compared to the control condition in the shoot and root of all genotypes. However, the tolerant genotypes showed lower shoot and root Na⁺ content and higher K⁺ content and therefore higher potassium/sodium ratio (K⁺/Na⁺). The results of this study showed that the relation between Na⁺ exclusion and tolerance indices is very close, but the positive characteristics of some genotypes did not directly correlate with these indices.

In this study, individual and combined effects of boron and sodium chloride salinity on growth, photosynthetic pigments (chlorophyll and carotenoids content), enzymatic activities (catalase and ascorbate peroxidase), hydrogen peroxide content, malondialdehyde content, proline accumulation, and some ion contents, such as B^–, Na⁺, Cl^–, K⁺, Ca²⁺, Mg²⁺ of purslane (Portulaca oleracea L.) were investigated. Five B levels (0, 4, 8, 16, 24, 40 mg/kg) and 100 mM NaCl were applied to the soil and mixed before sowing. Results showed that purslane growth was reduced significantly by higher B levels and salinity due to ion toxicity and osmotic stress. Also, content of photosynthetic pigments increased with both higher B levels and salinity, but they were decreased with combined effects of them. Tissue B^–, Na⁺, Cl^–, K⁺ and Ca²⁺ levels in shoot increased with applied NaCl, but B levels applied together with NaCl caused a decrease in B^– content due to antagonistic effects between B^– and Cl^– ions. The MDA content, proline accumulation, and H₂O₂ content increased with higher B levels, but salinity caused a decrease in MDA content. The catalase and ascorbate peroxidase activities increased with B and salinity combination, but did not change with salinity. Increasing B reduced the catalase activity. It is suggested that purslane has the potential to manage the amount of soluble boron and also it has a promising potential that can be grown in B-rich and saline soils.

In this study, the effect of freezing stress on expression of fatty acid desaturases (FAD2-2, FAD6 and FAD7) and beta-glucosidase (BGLC) genes was investigated in freezing- tolerant (“Fishomi”) and sensitive (“Zard”) olive (Olea europaea L.) cultivars. The olive cultivars were exposed to freezing stress (–10°C) at three different times points (1, 4 and 8 h), followed by a recovery stage. The degree of cell membrane damage was determined by measurement of leaves ion leakage of two olive cultivars both at freezing and recovery condition. The results indicated that ion leakage of cv. “Fishomi” was significantly lower than cv. “Zard” when exposed to the freezing stress and recovery condition. Furthermore, BGLC gene expression level in cv. “Zard” significantly suppressed 8 h after freezing stress. At the recovery period, its expression increased about three-fold at cv. “Fishomi”. However, it was suppressed in cv. “Zard” at recovery period. FAD genes expression pattern in cv. “Fishomi” was different from that in cv. “Zard”. FAD2 expression level in cv. “Fishomi” initially increased at the first 1 h and 4 h of freezing stress time and thereafter, decreased to control level over 8 h. Following recovery period, FAD2 gene expression level in cv. “Fishomi” increased up 5-fold. While, no expression detected in “Zard” at any time point or recovery period. The expression of FAD6 and FAD7 genes showed similar patterns at both cultivars. FAD6 and FAD7 genes expression significantly up-regulated 5- and 4.5-fold, respectively, following recovery period in “Fishomi”. Overall, the results suggested that FADs and BGLC could be involved in the increasing of freezing tolerance in olive cultivars, particularly in plants recovery from freezing stress.

During the evolutionary process, all living cells experience natural magnetic fields (geo-magnetic fields) as a usual part of their environment. Living organisms are adapted with natural fields, but magnetic waves derived from modern life may change the metabolism of cells. In this experiment, the effects of static magnetic fields (SMF) on total sugar, the contents of soluble proteins, proline, malondialdehyde (MDA), phenolic compounds and anthocyanin, as well as the activity of antioxidant enzymes and total antioxidant capacity, were studied in two species of Amygdalus i.e., Amygdalus scoparia Spach and Amygdalus eburnea Spach. Unique seeds of each species were treated with or without 10 mT SMF for four days, 5 h each day. A fresh weight of A. eburnea was reduced by SMFs. Exposure to SMFs also increased the contents of proline, phenolic compounds and anthocyanin, and improved the activity of ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and catalase (CAT). According to the results, it seemed that SMFs induce the production of free radicals. So almond seeds produce several antioxidants to be more resistant.

The C₃ species Аtriplex verrucifera M. Bieb and the C₄ species A. tatarica L. were compared in terms of their photosynthetic activities, plant growth rates, and the content of water, Na⁺, K⁺, and proline under water deficit and salinity conditions caused by polyethylene glycol (PEG) and NaCl solutions having equal osmotic potentials (–0.6 MPa). Nonstressed A. tatarica plants accumulated twofold larger biomass compared with A.verrucifera; they also featured a tenfold higher amount of proline and were superior in photosynthetic water use efficiency. Compared to A. tatarica, А. verrucifera plants were more resistant to osmotic stress: they exhibited normal growth rates at low osmotic potential of the medium, retained their water and K⁺ content in tissues, and preserved the rates of dark respiration and water use efficiency. Despite the attribution to C₄ plants, A. tatarica showed low resistance to PEG-induced osmotic stress and accumulated significant amounts of proline, whereas the C₃ species accumulated proline only under excess of Na⁺, i.e., under salinity. The principal component analysis of various parameters (content of proline, water, K⁺, Na⁺, and the K⁺/Na⁺ ratio) revealed the factors significant for adaptation of the examined plant species to water stress. In A. tatarica, the main role belongs to proline, Na⁺, and water, whereas this role is played by Na⁺ and proline in А. verrucifera. Potassium ions proved to be an indispensable component of adaptive mechanisms in both plant species. Under salt stress, the C₃ species accumulated proline, which served as an antioxidant and osmoprotector and also balanced the cell osmotic potential. The examined C₄ species accumulated the osmolyte proline under PEG-induced water stress. The results provide evidence that representatives of the genus Atriplex employ different strategies of adapting to water deficit and salinity.

Source–sink relations in the “leaf–stem–root” system at the time of cambial growth were studied in two forms of silver birch: common birch (Betula pendula Roth var. pendula) and Karelian birch (B.pendula var. carelica (Merckl.) Hämet-Ahti). As compared with common birch, reduced sucrose content in the leaves of elongated (auxiblasts) and short (brachyblasts) twigs of Karelian birch is associated with the accumulation of starch. In common birch, a pronounced sucrose gradient between the phloem (responsible for sucrose delivery to sink tissues) and xylem (the main acceptor of sucrose flowing from the leaves) points to an active consumption of the disaccharide in the production of structural elements of wood. As compared with common birch, in the phloem of Karelian birch where apoplast invertase activity is high, the content of sucrose decreases and the level of starch rises. Formation of anomalous patterned wood is associated with a suppression of sucrose synthase pathway and activation of the apoplastic pathway of sucrose utilization. At the same time, the content of cellulose in the tissues decreases and the level of starch increases. Sucrose gradient between the phloem and xylem in the anomalous areas is less pronounced. We suppose that, as a result of metabolism transformation in Karelian birch, the sink power of trunk tissues increases, which shows itself in structural and functional peculiarities of the source of photoassimilates—the leaves of brachyblasts that are larger in size in Karelian birch.

Absolute content and composition of fatty acids (FAs) in total lipids from the buds of white birch (Betula pubescens Ehrh.), silver birch (B. pendula Roth), and its subspecies B. pendula var. carelica Merckl. were investigated. The examined birches differed in these characteristics calculated per gram of dry weight. The buds of Karelian birch contained reliably greater content of FAs in total lipids as compared with the buds of two other birches. Detected differences in the content of total lipid FAs in two species and one variety of birch reflect peculiarities of biosynthesis of lipid compounds and may serve as an indicator for identification of plants from the genus Betula L.

Early in the 20th century, disparate human developmental processes culminate excess artificial light during night time and distort the phenological, physiological and ecological responses, which are sustained in the plants, animals and microorganism from millions of years. Earlier studies regarding artificial light (AL) during the night predominantly covered the drastic effects on animal systems. Although, drastic effects of AL during night time are enormous; therefore, the present topic is focused on the physiological and ecological consequences of artificial night light pollution (ANLP) on plant systems. In these consequences, most of the plant processes under ANLP are affected intensely and cause compelling changes in plant life cycle from germination to maturity. However, severe effects were observed in the case of pollination, photoreceptor signalling, flowering and microhabitats of plants. Along with drastic effects on ecology and environments, its relevance to human developmental processes cannot be avoided. Therefore, we need to equipoise between sustainable environment and steadily human development processes. Further, selection of plant/crop species, which are more responsive to ANLP, can minimize the ecological consequences of night light pollution. Likewise, changing artificial nightscape with the implication of new LEDs (Light Emitting Diodes) lightening policies like UJALA (www.ujala.gov.in), which are low cost, more durable, eco-friendly and less emitter of CO₂, have potential to overcome the biodiversity threats, which arise due to old artificial lightening technology from decades. Hence, adopting new advance artificial lightening technology and understanding its impact on plant ecosystem will be a future challenge for plant biologist.

The work dealt with the influence of free L-histidine on nickel (Ni) translocation into the shoots of the hyperaccumulator plants Alyssum murale, A. fallacinum, A. corsicum, A. tenium, A. lesbiacum, A. bertolonii, A. pintodasilvae, and A. obovatum and of the closely related non-hyperaccumulator Aurinia saxatilis (formerly Alyssum saxatile). The Ni concentration in the xylem sap was determined by graphite furnace or flame atomic absorption spectrophotometry. If plants were not treated with L-histidine or L-alanine, the highest Ni concentration was found in the xylem sap of A. murale and A. corsicum. When the plants were pretreated with L‑histidine, the Ni loading into the xylem vessels increased in only two hyperaccumulator species, A. pintodasilvae and A. obovatum, and in the non-hyperaccumulator A. saxatilis. The plant pretreatment with L-alanine did not increase the Ni level in the xylem sap. This indicates that the stimulation of Ni xylem loading is histidine-specific and not characteristic of any amino acid. Therefore, the role of histidine in the selective nickel accumulation in the shoots may considerably differ even in closely related plant species of one genus. This may presumably be accounted for by both different contents of endogenous histidine in the roots and specific patterns of the metal transport and distribution in different species.