Abstract
Soil salinity is one of the major factors that affect plant growth and decrease agricultural productivity worldwide. Chitosan (CTS) has been shown to promote plant growth and increase the abiotic stress tolerance of plants. However, it still remains unknown whether the application of exogenous CTS can mitigate the deleterious effects of salt stress on lettuce plants. Therefore, the current study investigated the effect of foliar application of exogenous CTS to lettuce plants grown under 100 mM NaCl saline conditions. The results showed that exogenous CTS increased the lettuce total leaf area, shoot fresh weight, and shoot and root dry weight, increased leaf chlorophyll a, proline, and soluble sugar contents, enhanced peroxidase and catalase activities, and alleviated membrane lipid peroxidation, in comparison with untreated plants, in response to salt stress. Furthermore, the application of exogenous CTS increased the accumulation of K+ in lettuce but showed no significant effect on the K+/Na+ ratio, as compared with that of plants treated with NaCl alone. These results suggested that exogenous CTS might mitigate the adverse effects of salt stress on plant growth and biomass by modulating the intracellular ion concentration, controlling osmotic adjustment, and increasing antioxidant enzymatic activity in lettuce leaves.
Highlights
Accepted: 22 September 2021Saline stress is a harmful form of abiotic stress that restricts the growth and function of plants and can cause a 10%–25% decrease in the yield of many agricultural crops [1].More than 20% of global farmland is affected by various degrees of salinity, and the farmland area affected by salinity is increasing each year, which severely limits agricultural productivity [2,3]
Compared with the control plants, the lettuce plants exposed to NaCl stress exhibited considerably inhibited plant growth in terms of a lower total leaf area, shoot fresh weight (FW), and shoot
The total leaf area, shoot FW, root FW, shoot dry weight (DW), and root DW of the NaCl group were 67.3%, 60.3%, 73.8%, 66.5%, and 51.6% lower, respectively, than those of the control group (Table 1)
Summary
Accepted: 22 September 2021Saline stress is a harmful form of abiotic stress that restricts the growth and function of plants and can cause a 10%–25% decrease in the yield of many agricultural crops [1].More than 20% of global farmland is affected by various degrees of salinity, and the farmland area (approximately 20,000 km per year) affected by salinity is increasing each year, which severely limits agricultural productivity [2,3]. Salinity in soils can occur naturally or as a result of human activities. Irrigation water with a high salt concentration, excessive chemical fertilization, and poor soil management are the main reasons for an increase in the area of saline–alkali land [4,5]. In some semi-arid and arid areas (e.g., Sahara in North Africa, Saudi Arabia, large parts of Iran and Iraq, parts of Asia, California in the USA, South Africa, and most of Australia), high temperatures and uneven distribution of rainfall result in higher evapotranspiration rates than the size of the leaching fraction, which causes an accumulation of soluble salts in the plough layer [6]. To increase the output of salinized agricultural land, the salt tolerance of plants must be increased and the conditions of saline–alkali land must be improved
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