The role of Fe-nano particles in scarlet sage responses to heavy metals stress.

Despite the stabilized ornamental markets for scarlet sage (Salvia splendens), little is known about the stress resistance of heavy metals (HMs). Therefore, a hydroponic study was conducted to determine whether the addition of Fe nanoparticles (Fe NPs) at 0, 5, 10, 20 and 30 µM in Hoagland's nutrient solution reduce the toxicity caused by 100 µM of HMs (Cd, Cu, Ni, Cr and Pb). Exposure to HMs significantly reduced relative growth rate (RGR), chlorophyll content, chlorophyll fluorescence (Fv/Fm), total antioxidant activity (TAA), total phenol content (TPC) and antioxidant power assay (FRAP), while the malondialdehyde (MDA) accumulation, H2O2 generation and electrolyte leakage (EL) significantly increased. Fe NPs improved HMs toxicity by significant reduction in MDA content, H2O2 generation and EL while increase in the PGR, chlorophyll content, Fv/Fm, the TAA, TPC and FRAP. Exposure to HMs caused Fe deficiency-induced chlorosis while Fe NPs reduced the negative effects of HM by preventing further reduction of leaf Fe. The results highlighted that although using Fe NPs significantly improved plant growth and motivated the plant defense mechanisms in response to HMs toxicity, it had a negative effect on the phytoremediation properties of salvia splendens by reducing the accumulation of HMs in plant organs.

Grafting of watermelon (Citrullus lanatus cv. Mahbubi) onto different squash rootstocks as a means to minimize cadmium toxicity.

To test the possibility that using appropriate rootstocks could improve the tolerance of watermelon to cadmium (Cd) toxicity, a greenhouse experiment was conducted to determine growth and antioxidant activities of watermelons, either nongrafted or grafted onto summer squash and winter squash. We provided nutrient solutions having four levels (0, 50, 100, and 200 µM) of cadmium to treat the plants. Shoot and root biomass reduction were significantly lower in summer squash rootstock-grafted watermelon than winter squash rootstock-grafted and nongrafted watermelons. Cadmium induced a smaller decrease in leaf area index in grafted watermelons compared with nongrafted plants. The Cd- related reductions in chlorophyll content and efficiency of photosynthesis were more severe in nongrafted watermelons compared with dose grafted onto summer squash. Cd accumulation in shoot at the highest dose (200 µM) of CdCl2 was significantly lower (19.76 mg/kg) in summer squash rootstock-grafted watermelon compared with winter squash rootstock-grafted (37.58 mg/kg) and nongrafted watermelon (72.12 mg/kg). H2O2, MDA production and electrolyte leakage of summer squash rootstock-grafted watermelon showed less increase, which was associated with a significant increase in the activities of antioxidant. The improved crop performance of grafted watermelons was attributed to their strong capacity to inhibit Cd accumulation in the aerial parts.