Effects of humic acid and titanium dioxide nanoparticles on some phytochemical properties and growth parameters in Withania coagulans (Stocks) Dunal

Withania coagulans (Stocks) Dunal from solanaceae family is a multi-purpose species that is distributed in Iran only in limited areas of natural habitats in Sistan and Baluchestan province. Different organs of this plant have antioxidant, antimicrobial, and anti-tumor biological effects. To investigate the effects of humic acid and titanium dioxide nanoparticles on the amount of phytochemical compounds and some growth parameters of this species, a pot factorial experiment was performed based on a randomized complete design with three replications. Experimental factors included humic acid at four levels (H0: 0, H1: 10, and H2: 30 g.kg-1 soil) and titanium dioxide nanoparticles at three levels (T0: 0, T1: 45, and T2: 90 mg.l-1). The results showed that the H2T2 treatment increased fresh weight, dry weight, number of lateral branches, height, phosphorus, potassium, and relative water content compared to the control, significantly. Increasing humic acid up to 30 g decreased the phenols content from 48.59 in H0 to 39.88 mg.g-1 fresh weight in H2. In T2, the phenols content increased by 2.37% compared to T0, which had a significant difference with the other treatments. Also, a similar trend was observed for the parameters like total flavonoids and proline. But increasing humic acid up to 30 g increased the amount of chlorophyll fluorescence by 70.79% compared to the control. Overall, the results indicated that the interaction of humic acid and titanium dioxide nanoparticles could improve the growth and plant yield parameters.