The Effect of NaCl Stress on the Response of Lettuce (Lactuca sativa L.)

Abstract

In recent decades, increasing human pressure has caused the gradual deterioration of the physical and chemical properties of water and soil. Salinity is an important factor influencing the quality of water. The aim of this comprehensive research was to determine the effect of increasing concentrations of sodium chloride, which is a salinity inducer, on the yield, photosynthesis efficiency (expressed with chlorophyll fluorescence measurement) and content of selected nutrients in the leaves of hydroponically grown lettuce (Lactuca sativa L.). Experiments were conducted at the following concentrations of NaCl: 0 (control treatment), 10, 20, 40, and 60 mmol L−1. Studies were conducted in two independent seasons: spring and autumn. The plants exposed to NaCl stress modified their chemical composition by lowering the uptake of (for 60 mmol L−1 NaCl in relation to control): N (−11%), K (−35.7%), and Mg (−24.5%), while increasing the sodium content (+2400%). The Na:K ratio was significantly narrowed (from 76:1 to 2.6:1). The increase in the Cl level in the lettuce leaves may also have caused a decrease in the content of nitrates. As a result of disturbed ionic balance, the RWC was significantly reduced (−6.2%). As a result of these changes, the yield of the biomass of the aerial parts decreased (more than two-fold for the highest NaCl concentration in relation to control) whereas the dry matter content increased (+32%). The measurement of fluorescence showed significant changes at the PSII level. Salinity modified the energy flow rate (F0, FM, FV, FV/FM) as well as the specific energy flows through the reaction centre (ABS/RC, TR0/RC, ET0/RC, DI0/RC). The PSII functioning index, calculated on the basis of energy absorption (PIAbs), also changed. The salinity induced with NaCl significantly worsened the physiological reactions of the plants in the PSII, changed the ionic balance, which resulted in a significantly lower yield of the plants. Due to increasing water quality problems, it will be necessary to use, in agriculture on a much larger scale than before, saline water treatment systems (e.g., highly effective nanofiltration and/or reverse osmosis).

Modulation of Morpho-Physiological and Metabolic Profiles of Lettuce Subjected to Salt Stress and Treated with Two Vegetal-Derived Biostimulants

“…To adjust to the increased osmotic pressure due to media salinity, plants produce a variety of molecules such as proline and soluble sugars, deemed compatible solutes, which accumulate in tissues. In general, the combination of the production of such solutes and the accumulation of cell-wall-strengthening molecules such as lignin in salt stress results in increased plant dry weights [ 22 , 23 ], consistent with what has been recorded in our trial.…”

Salinity Tolerance of Different Silage Hybrids Maize Cultivars

“…Plant water content (pwc), dry matter ratio (%) (dw) and vigor index (vı) were calculated according to the following formulas, respectively: Plant water content (pwc) = (Fresh weight−Dry weight)/ Fresh weight×100 (Zheng et al, 2008) Dry matter (dm) ratio= (Dry weight/Fresh weight)*100 (Bres et al, 2022) Vigor index (vı) = (average root lenght +average hypocotyl length) x germination percentage (gp) (Abdul-…”

“…Multivariate analyzes such as principal component analysis (PCA) and cluster analysis have been widely used to screen for salt tolerance of different plant genotypes (Aslam et al, 2017;Kaya et al, 2019;Güngör et al, 2021;Bres et al, 2022) because using multiple parameters improves accuracy and provides a general tolerance level based on mean values generated from each stress level (Kaya et al, 2019). Chaum and Kirdmanee (2010) and Luo et al, (2017) showed that multivariate cluster analysis can be used to classify the salt tolerance of maize hybrids during seed germination and morphological parameters.…”

Salt Stress Affects the Photosynthetic and Chlorophyll Fluorescence Responses in Lettuce (<i>Lactuca sativa</i> L.)

“…Salt stress (SS) is one of the major ecological and abiotic estressors in food production. SS is one of the major factors for negative changes in the chemical and physical properties of soils, as well as crops in the hydroponic system, which is usually generated by natural and industrial sources [14]. It is of utmost concern that 7% of the total world area (930 million hectares) is affected worldwide and around 1.5 million of the productive land is affected every year by SS [15,16].…”

“…For this reason, growers are forced to irrigate crops with a relatively high concentration of water that contains mineral salts due to a scarcity of excellent quality water resources. Unfortunately, the negative impact on crop physiology and biochemical pathway could be generated by irrigation of crops with water with high EC levels containing high sodium chloride and other salts concentrations [14]. The occurrence of SS on the crop also leads to a series of changes in crop metabolic pathway and nutrient uptake including interruption in the uptake of mineral ions [17].…”