Eco‐physiological Characteristics of Alfalfa Seedlings in Response to Various Mixed Salt‐alkaline Stresses

Abstract

Soil salinization and alkalization frequently co-occur in nature, but little is known about the mixed effects of salt-alkaline stresses on plants. An experiment with mixed salts (NaCl, Na(2)SO(4), NaHCO(3) and Na(2)CO(3)) and 30 salt-alkaline combinations (salinity 24-120 mmol/L and pH 7.03-10.32) treating Medicago sativa seedlings was conducted. The results demonstrated that salinity and alkalinity significantly affected total biomass and biomass components of seedlings. There were interactive effects of salt composition and concentration on biomass (P<or= 0.001). The interactions between salinity and alkalinity stresses led to changes in the root activity along the salinity gradient (P<or= 0.001). The effects of alkalinity on seedling survival rate were more significant than those of salinity, and the seedlings demonstrated some physiological responses (leaf electrolyte leakage rate and proline content) in order to adapt to mixed salt-alkaline stresses. It was concluded that the mixed salt-alkaline stresses, which differ from either salt or alkali stress, emphasize the significant interaction between salt concentration (salinity) and salt component (alkalinity). Further, the effects of the interaction between high alkalinity and salinity are more severe than those of either salt or alkali stress, and such a cooperative interaction results in more sensitive responses of ecological and physiological characteristics in plants.

Physiological Responses of Alfalfa to High-level Salt Stress: Root Ion Flux and Stomatal Characteristics

“…Seedlings were treated as a randomly placed unit design wherein four salt treatments were employed as a series of NaCl concentrations of 0%, 0.3%, 0.9% and 1.5% (w/w) marked by the control, 50 mM, 150 mM and 250 mM NaCl treatments, respectively. As it is summarized in Table 1, the rate of 50 mM NaCl is widely adapted as the moderate stress dose in relevant studies, while the 150 mM rate is close to the highest level performed by Peng et al (2008) because it simulated the mean level of salt in Sanjiang Plains where alfalfa Gongnong No. 1 is distributed.…”

“…At present, almost half of world's irrigated lands and at least 20% of global cultivated lands are suffering from salinity (Qiao et al, 2014). In China, saline and alkaline soils occupy a large area of 6.7 × 10 6 ha, which accounts for approximately 7% of total cultivated lands (Peng et al, 2008). Furthermore, salt accumulation accompanied with water resource depletion caused by unsustainable irrigation aggravates spread of salinity in agricultural systems of arid and semiarid regions in recent years (Endo et al, 2014).…”

“…High-level salt concentration in soils has been an issue that cannot be evasive for crop production in saline regions. For example, mean salt concentration in grassland-soils of the Songnen Plains, one of the main forage centers in China, is more than 0.7%, equaling about ~120 mM NaCl in leaching liquors from local soils (Peng et al, 2008). With regard to the harmful impact of high-level salt stress on grass production, salt-stressed plant physiological performance is an important theoretical reference to cope with high-level salt stress (e.g., Anower et al, 2013;Bai et al, 2013;Wang et al, 2014).…”

“…Gongnong No. 1) is a fairly moderate salt-tolerant cultivar, but it was found to have some undesirable performance in response to high-level salt stress in saline regions of Songnen Plains, Northeast China (Peng et al, 2008). Additionally, many studies of salt effect on alfalfa were conducted in days or months (Table 1), quite limited evidence can be referred to for alfalfa at the species-specific level about their physiological response in a short term of the first 24 h after high-level salt stress.…”

The Role of Soil Beneficial Bacteria in Wheat Production: A Review

“…Proline is a known osmoprotectant, promoting the protection of the plant from drought, salt and other stresses [94]. Alternative to proline accumulation, another defence strategy is to increase total soluble sugar level in plants under salinity stress.…”