Category Archives: Salinity STRESS

Physiological, transcriptional and metabolomic evidence for arbuscular mycorrhizal fungi and Lactobacillus plantarum in peanut resistance to salinity stress

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Abstract

Arbuscular mycorrhizal fungi (AMF) and Lactobacillus plantarum (LP) play pivotal roles in plant salinity resistance; however, difficulties are still exist in ascertaining their synergistic effects in counteracting legume soil salinity. Here, two peanut cultivars (salt-tolerant and salt-sensitive) were subjected to salinity stress, and the alleviation effects of combined microbial agent (CMA, inoculation with AMF + application with LP) on peanut salinity tolerance have been comprehensively characterized. CMA significantly enhanced the biomass production, leaf relative water content, increased the net photosynthetic rate, the maximal photochemical efficiency of photosystem II (PSII) and strengthened the antioxidant system, while dramatically decreased the reactive oxygen species (ROS) accumulation, lipid peroxidation and relative electrolyte conductivity under salinity conditions. Moreover, transcriptional and metabolomic evidence advocated that a subset of stress-responsive pathways involved in plant growth (e.g. sucrose and starch), photosystem, antioxidant response, signal transduction (e.g. phytohormone and MAPK), osmotic homeostasis (e.g. total soluble sugar and amino acids) and root metabolism (e.g. asparagine and phenylpropanoid) have been regulated by CMA. Taken together, the physiological, transcriptional and metabolomic results indicate that CMA could induce peanut salinity tolerance through increasing plant growth performance, maintaining photosynthetic apparatus integrity, enhancing antioxidant system and regulating root metabolism. This study provides a promising CMA product and would be important for deepening the knowledge of the mechanisms regarding bacterial–fungal interactions.

Saline stress affects the growth of Saccharum complex genotypes

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Abstract

Soil salinity affects plant growth, compromising sugarcane cultivation in regions with great production potential. Saccharum complex genotypes that respond positively to growth under saline environment can be used in the diversification of sugarcane cultivars to obtain greater economic returns. The objective of this study was to evaluate growth-related traits of Saccharum genotypes grown under the presence and absence of salinity. The experiment was carried out in a 32 × 2 factorial scheme in a randomized block design with three replicates. The first factor consisted of 32 genotypes of the Saccharum complex and the second factor consisted of the presence and absence of salinity. The salinity provided higher mean values than the environment without salinity for plant height in the genotypes G9, G11, G13, G22 and G28, leaf number for G9 and G24, leaf area index for G9 and stem diameter for G1, G11 and G24. Among the genotypes tested, G1, G9, G11, G13, G22, G24 and G28 were the most promising genotypes and could be used for breeding new sugarcane cultivars of enhanced salinity tolerance.

Salinity effects on the activities of ROS scavenging enzymes in leaves of two sweet potato clones

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Abstract

Sweet potato production, particularly in coastal areas is often prone to salinity. Salt-tolerant clones will be needed to maintain production, but to date, little is known about salt tolerance traits in sweet potato. Salt stress may result in excessive uptake of unwanted ions into plant tissues leading to the formation of reactive oxygen species (ROS), which in turn may destroy membranes and reduce photosynthesis and growth. Antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), glutathione reductase (GR) and ascorbate peroxidase (APX) scavenge ROS and early changes in the activities of such enzymes could be used to identify salinity tolerant genotypes. Therefore, cuttings of two contrasting cultivars of sweet potato, BARI SP 8 (tolerant) and BARI SP 4 (sensitive) were greenhouse-cultivated in nutrient solution for 21 days and then exposed to 100 mmol NaCl for 7 days. Three, five and seven days after salt application the youngest leaves were sampled individually and enzyme activities, potassium (K) and sodium (Na) concentrations, and SPAD (as a proxy for chlorophyll content) were determined. In both varieties leaf growth was not affected by salinity and young leaves grown under salinity had higher SPAD values than older leaves. Na concentration increased over time, particularly in earlier and in older leaves, whereas K was reduced in younger leaves. In general, enzyme activities were strongly affected by leaf age and leaf position. SOD and APX showed varietal but no salinity effects, CAT increased under salinity in both varieties, whereas POX was strongly reduced and GR was strongly increased under salinity in BARI SP 8 with no effect in BARI SP 4. Enzyme activities were not correlated to leaf Na, neither in relation to leaf age, nor leaf number or duration of salt stress in both varieties. However, varietal differences were observed regarding leaf K. Activities of SOD were highly positive and of CAT highly negatively correlated with leaf K under salinity in BARI SP 8 but not in BARI SP 4, whereas activities of GR and POX were strongly positively correlated with leaf K in BARI SP 4 under salinity but not in BARI SP 8. We conclude that potassium may have a strong regulating role on leaf stress levels and therefore on the activities of antioxidant enzymes. Varieties may differ in their tolerance strategy and we have shown that salinity does not generally increase levels of ROS-scavenging enzymes in sweet potato leaves under salt stress. Confounding factors such as leaf age and leaf position as well as maintaining high leaf level K concentrations need to be considered when evaluating metabolic traits for salinity tolerance traits.