Salicylic Acid Alleviates the Copper Toxicity in Zinnia elegans

Salicylic acid ( SA) plays a key role in plant disease resistance and hypersensitive cell death but is also implicated in hardening responses to abiotic stress. The aim of this study is to examine the effects of salicylic acid on the growth, eco-physiological and biochemical characteristics in Zinnia elegans plant exposed to copper stress. Effects of copper (Cu) on biomass, root length and shoot height and Cu uptake are also discussed. This experiment was arranged as a factorial experiment based on completely randomized design with four replications in greenhouse conditions. The experimental treatment consisted of four levels of Cu (0, 100, 200, and 400 mg/kg in potted soil) and three levels of salicylic acid (0, 1, 2 mM) as foliar spray and chelate to soil. Results showed that with increasing levels of copper, reductions in shoot and root growth, leaf area and leaf number were statistically significant (p < 0.01). Analysis of some biochemical indices (chlorophyll content) and eco-physiological indices such as primary florescence chlorophyll (Fo), ratio of variable chlorophyll to maximum (Fv/Fm) in treated plants were statistically significant (p < 0.01). The results showed that copper accumulation was higher in the roots than shoots. The Fluorescence measurements showed that primary florescence chlorophyll (Fo) was increased but maximum florescence chlorophyll (Fm) was decreased progressively with increasing Cu. Salicylic acid significantly increased root and shoot growth and chlorophyll content in copper stressed plants. SA applying as chelate 2 mM also showed an increased level of tolerance toward high Cu concentrations. The results support the conclusion that SA alleviates Cu toxicity.