Effect of some symbiotic fungi and iron nanoparticles on morphological and physiological traits of purslane (Portulaca oleracea L.) under cadmium stress

Nowadays, the soil contamination by heavy metals including cadmium (Cd) is one of the environmental problems which not only damage the animal and plant species but also diminish plant function, enters the food chain and endanger human health and other organisms (Sheoran et al., 2016). Phytoremediation is one of the most important methods that have been developed in the last two decades to address soil contamination, including heavy metals in various countries where planting of suitable plants is used to clean and absorb pollutants from the soil (Shahgholi et al., 2012). On the other hand, many studies have shown that the use of beneficial microorganisms such as fungi can significantly reduce the toxicity of heavy metals by bonding metals to their cell walls and consequently their immobilization (Akhtar et al., 2007). The aim of the research was to investigate the effect of application of some symbiotic fungi and iron nanoparticles on morphological and physiological traits of purslane (Portulaca oleracea L.) under cadmium stress.

The factorial experiment was conducted in a completely randomized design with three replications. The experimental factors included cadmium chloride in four levels (0, 25, 50 and 75 mg/kg soil from cadmium chloride source), four levels of fungal symbiosis (uninoculated and inoculated with fungi Chaetomium subaffine (SF), Trichoderma atroviride (SN) and Trichoderma longibrachiatum) and foliar spraying  of iron nanoparticles in three levels (0, 0.15 and 0.3 g/l).

The results showed that the plant height and stem diameter  linearly decreased (with 69.6 and 56.6%, respectively) when the cadmium levels incresed. Leaf area increased at zero cadmium level in plants inoculated with T. longibrachiatum, 18.4% as compared to the uninoculated control . When 25 mg/kg of Cd was added to the soil, purslane plants which inoculated with Chaetomium subaffine (SF) showed 11.4% more leaf area than those uninoculated plants. At all foliar concentrations of iron nanoparticles, the highest content of chlorophyll a+b was obtained at 25 mg/kg soil cadmium.

Overall, the interaction of symbiotic fungi and foliar spraying of iron nanoparticles (especially at a concentration of 0.15 g/l) showed  a synergistic effect, hence some  growth parameters and chlorophyll concentrations markedly increased in the purslane plants.