Salicylic acid attenuates salinity-induced growth inhibition in in vitro raised ginger (Zingiber officinale Roscoe) plantlets by regulating ionic balance and antioxidative system

Abstract

Ginger (Zingiber officinalis Roscoe) is valued as a spice and herbal plant with high economic importance, but its productivity is affected by soil salinity. In the present study, potential of salicylic acid (SA) to reduce salt stress was tested in ginger plantlets grown under in vitro conditions. NaCl stress at 150 mM concentration caused a significant decline in growth parameters and photosynthetic pigment contents and a rise in Na+, Cl−, H2O2, superoxide radical contents, activities of chlorophyllase, superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) enzymes. A foliar spray of 0.5 mM salicylic acid showed a remarkable improvement in the growth parameters (around 3-fold increase in shoot number and fresh weight) of stressed plantlets. SA treatment enhanced the contents of chlorophyll a (41%), chlorophyll b (51%), total chlorophyll (48.56%), carotenoids (36%) and reduced chlorophyllase activity (18%) under salt stress conditions. NaCl - induced activities of antioxidative enzymes were further increased by SA treatment. An increase of 71.22, 50.84 and 50.45 percent was recorded for SOD, CAT and POD, respectively. A reduction in H2O2 content (31.24%) and superoxide production rate (43%) in stressed plantlets was noted after SA application. This treatment also reversed the sodium ion toxicity as revealed by a decline in Na+and Cl− contents (90%) with a concomitant rise in K+ ion concentration (25.65%) in stressed plantlets. These results indicated that SA-mediated improvement in ionic balance and antioxidative defense system contributed to the acclimatization of plantlets under salinity. In conclusion, foliar application of 0.5 mM salicylic acid could help recover the reduced growth of stressed plantlets. Therefore, SA treatment could be suggested as a feasible approach to produce salt adapted ginger plantlets in vitro. Such plants can perform well on saline soils and could serve as a continuous source of raw material for ginger industry.