Alleviative effects of chitosan or humic acid on Vitex trifolia ‘Purpurea’ grown under salinity stress

Abstract

Pots experiment was conducted to investigate the effect of bio-stimulators chitosan (CHT) or humic acid (HA) on Vitex trifolia ‘Purpurea’ exposed to salinity stress. Salinity stress was imposed by irrigation with saline water at concentration of 1000, 2500 and 5000 ppm, in addition to control (280 ppm), plants exposed to salinity were sprayed every 4 weeks with either CHT at concentrations of 30, 60 and 90 ppm or HA at concentrations of 1000, 1500 and 2000 ppm, while control plants sprayed only with tap water. The results showed that, with increasing salinity stress all vegetative growth parameters were decreased and chemical constituents including total chlorophylls total carbohydrates, K+ %, Ca2+ % and K+/Na+ ratio were reduced. In contrast, elevating salinity stress increased contents of proline, total phenolic, Na+ %, Cl− %. On the other hand, foliar application of either CHT or HA had favorable impact on increasing vegetative traits and chemical compositions, meanwhile reducing accumulation of total phenolic, Na+ and Cl− % toxic ions in leaves, HA was generally more effective than CHT. Based on the results, it can be recommended that, CHT or HA at high concentration was the best effective treatments; however, HA was superior and economic treatment recommended for alleviating the adverse impact of salinity stress on Vitex trifolia ‘Purpurea’ plants irrigated with saline water at concentration up to 5000 ppm.