Abstract
The date palm is a commercially important woody crop and is a good target plant for improving agricultural yields in extreme environments. However, salinity has been the primary abiotic stress complicating its cultivation and damaging its production worldwide. This study investigated the effect of alleviating salt stress on date palm growth and development by using arbuscular mycorrhizal fungi (AMF) and/or compost. The experiment was arranged in a completely randomized design with eight treatments. The treatments comprised control without inoculation or amendment and application of compost (made from green waste) and AMF (an autochthonous consortium) individually or in combination under non-saline (0 mM NaCl) or saline (240 mM NaCl) conditions. Growth, physiological characteristics, nutrient uptake, chlorophyll content, oxidative stress markers, and antioxidant enzyme activities were assessed. Salt stress increased sodium (Na+) and chlorine (Cl-) content, lipid peroxidation and proline, soluble sugar, and H2O2 content. However, it reduced growth parameters, AMF colonization, leaf water potential, nitrogen (N), phosphorus (P), potassium (K+), calcium (Ca2+), and chlorophyll content. The application of AMF and compost separately or in combination mitigated the deleterious effects induced by salinity. AMF inoculation contributed to plant salt tolerance through strategies such as increased nutrient uptake (particularly P and Ca2+), chlorophyll content, relative water content, stomatal conductance, antioxidant enzymatic activities (superoxide dismutase, ascorbate peroxidase, catalase) and by decreasing lipid peroxidation and H2O2 content. Plants grown in soil amended with compost under salt stress showed an improvement particularly in K+ and proline content and a decrease in H2O2 concentration compared to controls under the saline condition. In the presence of NaCl stress, the dual application of the compost and AMF consortium maximized plant growth, stomatal conductance, leaf water potential, all antioxidant enzyme activities and P, K+, N, and Ca2+ uptake as well as proline and soluble sugar content. However, it reduced Na+ and Cl- uptake and oxidative stress marker content. In conclusion, our study suggests that the application of AMF with compost has the potential to improve the tolerance of date palm seedlings to salt stress more than AMF or compost applied separately.
Highlights
Climate change causes perturbations to the surrounding environment and significantly induces soil salinization
Root dry matter was reduced by 42% while shoot dry weight was reduced by 34% compared with nonstressed plants
The dual application of AMF and compost significantly mitigated the effects of salt stress on all growth parameters followed by the AMF treatment, which in turn was better than the compost treatment
Summary
Climate change causes perturbations to the surrounding environment and significantly induces soil salinization. The increase in soil salinity results in osmotic as well as specific ion effects, which induce secondary stress in plants known as oxidative stress (Evelin et al, 2019; Abdel Latef et al, 2020). Salt stress causes adverse effects on physiological and biochemical activities such as mineral homeostasis, seed germination, osmotic balance, photosynthesis, and respiration processes (Porcel et al, 2012; Ben Laouane et al, 2019). Oxidative salt-induced stress leads to the production of reactive oxygen species (ROS) that induce deleterious effects on normal metabolism and growth (Gill and Tuteja, 2010). Plants can tolerate both osmotic and oxidative stress caused by soil salinity through several mechanisms (Evelin et al, 2019). Enzymatic antioxidants, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR) have been previously reported as the main antioxidant enzymes under salinity stress (Abdel Latef and Chaoxing, 2014; Foyer, 2018; Evelin et al, 2019)
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