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. پرونده مقاله

Salinity of soil is a major abiotic stress limiting the crop production and growth of safflower. To mitigate stress, the effects of penconazole (PEN) on the growth of safflower were studied to understand the underlying mechanisms of salt tolerance. PEN, a triazole derivative, which has both fungicidal and plant growth regulator properties, protects plants from several types of abiotic stresses. The purpose of this work is to assess the effect of sodium chloride (0, 100, and 200 mM) and PEN (15 mg/L) on some biochemical responses of safflower. Results revealed that salicylic acid (SA) content increased under salinity however, indol-3-acetic acid (IAA) and gibberellic acid (GA) contents decreased. Further, in terms of fatty acids, palmitic and oleic acids contents decreased, while stearic, linoleic and linolenic acids content increased under salinity. Exogenous PEN had a positive effect on SA and GA contents, as well as palmitic and stearic acids content, but decreased IAA, linoleic acid and linolenic acid contents in safflower plants. Safflower is a viable alternative for use in rotations where saline irrigation water limits productivity of non-tolerant crops. Our data provide new insights to mechanisms that help regulate salinity resistance in safflower. PEN may be considered as a foliar application to ameliorate salinity effects, due to its low price and availability. پرونده مقاله

Acclimation of plants to stress conditions depends upon activation of cascade of signaling networks involved in stress perception. Regulation of antioxidative system to maintain a balance between the overproduction of reactive oxygen species and their scavenging to keep them at signaling level has been previously documented. Recently, role of triazolic compounds like penconazole, paclobutrazole, triadimefon, and hexaconazole in the regulation of metabolic network under stress conditions has emerged through crosstalk between chemical signaling pathways. Thus, stress signaling and metabolic balance is an important area with respect to increase crop yield in adverse environmental conditions. This review outlines the recent advances on improvement in stress resistance by various triazolic compounds, aiming to identify new mechanisms of stress tolerance, and therefore, to contribute sustainable crop yield under stress to bring some potential practical utilization in the future. Researches have revealed that triazolic compounds, to some extent, help plants to cope with adverse environmental conditions. Therefore, these compounds could be used for improvement of plant growth and productivity in such severe conditions. پرونده مقاله