Assessment of different salt concentrations on the growth and phytochemical change of the ice plants

Abstract

The ice plant (Mesembryanthemum crystallinum L.) has become a halophyte model to study the plant photosynthetic responses C3 photosynthesis to crassulacean acid metabolism (CAM), which is accelerated by salt stress. However, this adaptive mechanism improves water use efficiency, and water stress tolerance is still poorly known. This study examined the effect of individual and mixture of NaCl and CaCl2 concentrations on morphological parameters and bioactive component contents of ice plants in a plant factory system. Eight salt treatments individually and a combination of sodium chloride (NaCl) and calcium chloride (CaCl2), and Hoagland solutions were applied after the transplanting of ice plants. Morphological parameters like the number of leaves and lateral stems, leaf chlorophyll content (SPAD value), fresh weight, and dry weight of shoots and roots were measured at the adult stage. Concurrently, in the juvenile phase, the area of a canopy was evaluated using an image processing technique in HSV (hue, saturation, value) colour space. Correspondingly, ice plant secondary metabolites such as cations, anions, and radical scavenging activity were assayed in the adult phase correlated to the salt stress. The effects of salt stress on the growth of ice plants and secondary metabolite production were analysed using completely randomized block designs through the variance by one-way ANOVA with a significance level of p < 0.05. This study demonstrated that 400 mM CaCl2 (T4) enhanced the biomass and high sodium (Na+) and calcium (Ca2+) accumulations, and 200 mM CaCl2 (T3) accelerated the potassium (K+), magnesium (Mg2+), phosphate (PO43−), and sulfate (SO42−) accumulations. Moreover, NaCl 400 mM (T1) and combination of 100 mM NaCl and 300 mM CaCl2 (T5) positively influenced the chloride (Cl−) deposition and combination of 200 mM NaCl and 200 mM CaCl2 (T6) improved nitrate (NO3–) accretion. Furthermore, 100 mM CaCl2 (T2) exhibited the highest antioxidant activity in ice plants grown under the plant factory system.