Iranian Journal of Plant Physiology
Volume:9 Issue: 3, Spring 2019

Cyanobacteria are an important source of natural products. In this article, we briefly review the responses of cyanobacteria to different stresses. Abiotic stresses (temperature, salt, heavy metals, metalloid and ultraviolet (UV) influence cell growth and metabolism in cyanobacteria. Salt stress is a major abiotic factor that decreases the growth of cyanobacteria and affects the different processes including photosynthesis, respiration, and metabolism. The basic mechanisms for salinity adaptation include the active extrusion of inorganic ions and the accumulation of compatible solutes such as sucrose, trehalose, glucosyl glycerol, and glycine betaine. Cyanobacteria have a complex antioxidative system including enzymatic and nonenzymatic antioxidants for mitigation of oxidative damage under salt stress. Cyanobacteria have some defense mechanisms for the decline of the direct and indirect destructive effects of UV. These mechanisms include avoidance, scavenging of reactive oxygen species (ROS), synthesis of UV-absorbing/screening compounds such as mycosporine-like amino acids and scytonemin, repair of UV-induced damage in DNA, and resynthesis of proteins. Metals are involved in key metabolic pathways as redox cofactors in proteins. High concentration of metals causes the generation of ROS and oxidative damage. Thus, the major role of metal homeostasis in maintaining the intracellular concentration of metal within a range compatible with cell viability becomes evident. The biosynthesis of metabolites can be triggered by a number of abiotic stresses because they affect metabolic pathways.

The study investigates the role of root glutathione (GSH) content and glutathione S-transferase (GST) activity in the response of hard wheat (Triticum durum Desf. variety Carioca) induced by different doses of phosphorus KH2PO4 and their relation to growth inhibition. Four doses were evaluated: control (0), 85, 170, and 340 mg/l. The experiment was carried out under in vitro culture conditions, during seven days. Results showed that P addition had a significant effect on growth parameters, root water content, and the amount of GSH and GST activity, but no significant changes were observed in chlorophyll contents. Treatment of seeds with KH2PO4 increased the GST activity from hard wheat roots and decreased GSH content. The GSH level in control was 2-fold greater than phosphorus 340 mg/l treatment. The highest induction of root GST activity compared to control was observed in 170 mg/l treatment. Phosphorus levels closely correlated with GSH (r²= -0.996***) and GST (r²= 0.991***).

Pot marigold (Calendula officinalis L.) is widely used due to its various biological activities to treat diseases as an analgesic, anti-diabetic, anti-ulcer and anti-inflammatory agent. To ameliorate the adverse effects of water stress on this medicinal plant, foliar application of glycine betaine (GB) and L-arginine (LA) was used. For this purpose, water stress was applied at three levels (100%, 70% , and 40% field capacity (FC)), and foliar application was used at five levels (control, 50 mM GB, 100 mM GB, 1.5 mM LA, and 3 mM LA) as factorial based on completely randomized  design. We measured phenol and flavonoid content, DPPH radical scavenging activity, superoxide dismutase (SOD) and phenylalanine ammonia-lyase (PAL) activity, and essential oil (EO) content and yield. Total phenol content in the interaction of 40% FC and GB 100 mM was higher than the other treatments. The highest and lowest total flavonoid content and DPPH radical scavenging activity were observed in the interaction of 40% FC and 100% FC, respectively. These variables at GB 100 mM were greater than the others. The highest SOD and PAL activity was found in the interaction of 40% FC and LA 3 mM/GB 100 mM. The content and yield of EO in the interaction of 70% FC and 100 mM GB were greater than other treatments. In sum, 70% of water stress did not significantly change the biochemical properties of C. officinalis, but 40% FC dramatically influenced the quality of the plant. GB 100 mM could stimulate the plant to activate its antioxidant systems under water stress and obtain the highest EO.

This research has been done to examine the effect of bio-priming on germination parameters related to seeds of canola cultivar (Hayola 401) under high salinity as factorial in seed laboratory of Shahed University based on a Completely Randomized Design (CRD) in three replications. Experimental factors included bio-priming with bacteria strains inoculation at three levels: seed inoculation with water as a control, inoculation of seed with Bacillus subtilis bacteria, inoculation of seed with Macrophomina phaseolina fungus, and combination of Bacillus subtilis bacteria and Macrophomina phaseolina fungus.  Salinity treatment was applied at four levels (0, 2.5 dS.m-1, 5 dS.m-1, and 7.5 dS.m-1). Results of variance analysis showed that the effect of priming and high salinity was meaningful for all characteristics. The highest length measurement for the radicle and relative content of leaf water was obtained in salinity 2.5 dS.m-1. The maximum root and seedling length and length matrix of seedling vigor was related to fungus priming in bacteria and high salinity as 7.5 dS.m-1. Seeds primed with fungi under high salinity 2.5 dS.m-1 produced the highest mean dry weight of seedlings, germination percentage, and the mean germination. Also, the results included the highest mean germination period, germination speed factor, and germination rate for bacteria priming in the salinity control. Generally, according to the results, using Bacillus subtilis bacteria and Macrophomina phaseolina fungus could improve germination index and modify the effects of salinity.

In order to investigate the changes in fatty acids composition of rapeseed lines under Chitosan application, a factorial split-plot experiment was conducted based on RCBD in 3 replications during 2 years (2014-2016) in Karaj, Iran. Irrigation and Chitosan as main plots and cultivar in sub-plots were considered. In this study, treatments included irrigation at 2 levels (normal irrigation and cut off irrigation after flowering stage), Chitosan at 2 levels (pure water and foliar application of Chitosan 250 mg/l), and rapeseed cultivars (BAL104, DIE710/08, BAL101, BAL102, QUIE03/11, and OKAPI). The result of ANOVA showed irrigation and cultivar had a significant effect on fattiest acids. Results exhibited cut off irrigation after the flowering stage reduced the oleic acid content compared to normal irrigation. Results also indicated that erucic acid and grain glucosinolate contents were different among the mentioned varieties and they were influenced by irrigation regimes. Cut off irrigation at the flowering stage increased erucic acid and grain glucosinolate in all varieties. On the other hand, the lowest erucic acid and grain glucosinolate were observed in cv. Okapi under normal irrigation, and it might be considered useful rapeseed to include in the diet as it contains low specific glucosinolate and erucic acid. Moreover, var. DIE710/08 had the lowest erucic acid and grain glucosinolate under drought stress conditions.

In order to investigate the responses of potato plantlets under in vitro conditions to osmotic and temperature stresses, a factorial experiment was carried out in a completely randomized design with three replications. Each replicate contained a glass jar with 5 explants grown in it. The first factor was water deficit at four levels of osmotic stress caused by polyethylene glycol 6000 including control, -0.5,-0.1, and -1.5 MPa and the second factor was temperature at three levels of 15, 25 and 35° C.  Five potato cultivars, including 3 promising clones, 143, 301, and 306 as well as Marfona and Picasso cultivars were exposed to stresses in MS medium. Eight weeks after stress period, indicators such as fresh and dry weights of plantlets, electrolyte leakage, proline, catalase, phosphorus, and potassium concentrations were measured. The results of variance analysis indicated that the simple effects of factors as well as the interactions of the investigated factors at P≤0.01 had a significant effect on the study traits. Mean comparison showed that the temperature stress decreased the fresh and dry weights of plantlets and potassium concentration but increased electrolyte leakage, proline, catalase, and phosphorus concentration. On the other hand, osmotic stress reduced fresh and dry weight of plantlets, P and K, while proline, CAT, and electrolyte leakage increased. The combination of stresses lowered plantlets’ resistance to stresses because osmotic stress of -0.5 MPa and higher, in combination with 35° C caused the explants to dry. Finally, results showed that Marfona cultivar was more tolerant to stress conditions than other genotypes. This seems to be the result of accumulating more proline and high antioxidant activity. On the other hand, clone 306 was more susceptible to stress than other genotypes and the plantlets 306 experienced more damage and dried.

Hairy root induction in plants has affected by many factors including type, age of explant and bacterial strain. In the present study, the effects of bacterial strains (A4, C58, 15834 and GM), two concentrations (OD600= 0.5 and 1) and two explants (leaves and stems) in hairy root induction of C. blumei were investigated. According to the results of this study, the four strains showed different abilities to induce hairy root. The highest percent of induced roots (85%) was seen in explant treated with C58 strain, at OD600= 0.5 and the lowest induced roots (5%) by using of GM strain at OD600 = 1 and stem explants observed. The highest number of hairy roots per explant (12.94) has shown in leaf explant of leaf inoculated with C58 strain at (OD600 = 0.5) and the lowest number of hairy roots (1/1) was obtained from stem segments treated with GM strain at (OD600 = 1). According to the results of the analysis of variance, the effects of double reciprocal of strain in the concentration and strain in the explant was significant at a 1% probability level. Polymerase Chain Reaction (PCR) analysis using the role gene was performed for identification of the transformed hairy roots. In the lines of transgenic hairy roots, a sharp band of 304‑bp was amplified, but no such amplicon was observed in the untransformed root (negative control) sample. The results of this study indicated that the type of bacteria strain, explant type, and bacterial concentration are important factors in hairy roots induction.

Thyme is a valuable plant used in medicine, perfumery and food industry. Mineral deficiencies often limit the growth of plants. Nitrogen deficiency in agricultural soils is a problem throughout the world. The present study evaluated effects of applying Fe and Zn in absorption of some important nutrients of Thymus vulgaris L. under nitrogen deficiency. Potted experiments were designed to study effect of spraying some micronutrients on nutrient contents of thyme. Nitrogen deficiency applied whereas application of N decreased to half, 1/4 and zero. At the same time, foliar spraying of Fe2+ and Zn2+ in concentration of 1% and 2% was replicated each 15 days. Results showed that application of Zn 2% cause increase in NO3- content of thymus root and in shoots of deficient plants. Also foliar spraying of Zn and Fe cause increase in P and NO3- content of thymus plants under nitrogen deficiency conditions. There was significant correlation (P<0.05, r>0.9) among micronutrients, P and NO3- content under N deficiency. Analysis of variance showed that the difference in all nutrients content between nitrogen treatments, among spray of different micronutrients and nitrogen treatments × spray was significant in roots and shoots of plants and soil. Foliar application of iron and zinc significantly enhanced the absorption of other nutrients in thymus plants under deficiency conditions, but influence of zinc was higher. It seems that foliar fertilizer improves nutrition of plant in nitrogen deficiency conditions and decrease environmental hazard by decreasing the applying of chemical fertilizers in soils.