The Effects of Biochar and Salicylic Acid on Alleviation of Pb Stress in Salvia (Salvia afficinalis L.)

Amending soil with biochar (BC) and foliar application of salicylic acid (SA) are two new methods for reducing the effects of heavy metals on plant growth. To evaluate the effects of SA and BC made from rapeseed wastes on alleviation of lead (Pb) stress in salvia (Salvia afficinalis L.), a factorial experiment was conducted in a complete randomized design with three replications in the greenhouse. The factors included Pb concentration at three levels (0, 150 and 300 mg/kg as Pb(NO3)2), BC at three levels (0, 1 and 3% by weight) and SA at three levels (0, 150, and 300 μM). The results showed that Pb stress reduced all growth characteristics of salvia, but the treatments interactions on the proline content, soluble sugars and Pb concentration and the most growth characteristics such as leaf area ad root volume were significant (p < 0.01). The highest proline content (25.7 mmol/g) and Pb concentration (4.36 mg/kg) were obtained at 300 μg/kg of Pb, and BC and SA controls. Also, the highest concentration of soluble sugars (0.41 mg/kg) was found at 300 mg/kg of Pb, 300 μM SA and BC control. In general, although Pb stress had a decreasing effect on most morphological characteristics of salvia, but simultaneous application of BC and SA, as a simple and low-cost strategy, could reduce the negative effects of Pb by increasing proline and soluble sugars in the plant.