Background: In dry and semi-arid areas, salinity is the most serious hazard to agriculture, which can affect plant growth and development adversely. Over-accumulation of Na⁺in plant organs can cause an osmotic effect and an imbalance in nutrient uptake. However, its harmful impact can vary depending on genotype, period of exposure to stress, plant development stage, and concentration and content of salt. To overcome the unfavorable effect of salinity, plants have developed two kinds of tolerance strategies based on either minimizing the entrance of salts by the roots or administering their concentration and diffusion.Results: Having sufficient knowledge of Na⁺accumulation mechanisms and an understanding of the function of genes involved in transport activity will present a new option to enhance the salinity tolerance of vegetables related to food security in arid regions. Considerable improvements in tolerance mechanisms can be employed for breeding vegetables with boosted yield performance under salt stress. A conventional breeding method demands exhaustive research work in crops, while new techniques of molecular breeding, such as cutting-edge molecular tools and CRISPR technology are now available in economically important vegetables and give a fair chance for the development of genetically modified organisms.Conclusions: Therefore, this review highlights the molecular mechanisms of salinity tolerance, various molecular methods of breeding, and many sources of genetic variation for inducing tolerance to salinity stress.

Copper is an essential element for plants, but its higher concentration can make disruption in plant growth. The current study was conducted to determine the impact of excess copper (Control 0.2, 200 and 400 µM of copper sulfate) on growth, chlorophyll content, nutrient uptake and enzyme activity in lettuce. The results of this study highlighted that chlorophyll content, superoxide dismutase and ascorbate peroxidase activity were higher in the plants exposed to copper treatments. The peroxidase activity (POD) showed a different behavior depending upon the copper concentration; in this respect, 200 and 400 µM of copper sulfate increased POD activity by 59% and 32%, respectively in comparison to the untreated one. Copper application causes a decrease in leaf area (leaf expansion), root and shoot dry weight. Copper sulfate clearly decreased N, K, P, Si, Zn and Mg content in leaves and roots, whereas it increased B content in roots. Based on the outcomes of the current study, it can be concluded that lettuce showed tolerance to copper toxicity by alteration in mineral nutrition uptake, enzyme activity, chlorophyll content and leaf expansion.

Copper has many metabolic functions in the plants. However, it can be toxic to plants where it reaches the excess level. The aim of the present study was to evaluate the role of nitric oxide treatments on lettuce seed germination under copper stress. Thus a factorial laboratory experiment with a completely randomized design was carried out at the Ataturk University. Treatments include different doses of copper (0, 50, 100, 150 and 200 µM of copper sulfate)and nitric oxide (0, 50, 100, 150, 200 and 300 µM of sodium nitroprusside). The results of this study monitored that high concentration of copper (100, 200 and 300 µM) had a significant effect on the germination percentage, germination rate, mean period of ultimate germination, seed vigor index, seedling fresh weight and allometry coefficient, although the nitric oxide treatment (without copper) had not a significant effect on the seeds in comparing to the untreated ones. Copper treatment decreased the investigated parameters, but the simultaneous application of nitric oxide and copper had a positive impact. The results of this study suggested that nitric oxide treatments have been beneficial upon the seeds that treated with copper, but not upon the seeds that treated with water. In addition, the lower concentration of copper (50 µM) had a positive effect on the seed vigor index.