Unraveling the impact of sodium nitroprusside on morphogenesis, selected phytochemical profiling, and antioxidant activities of in vitro–raised plantlets of Citrus indica Yu. Tanaka

The objective of this study was to assess the effect of sodium nitroprusside (SNP) on the morphology, physiology, and biochemistry of Citrus indica Yu. Tanaka, which is considered a native and endangered species in northeast India. Moreover, C. indica seeds do not germinate well in their natural habitat, and the species does not have a good commercial standing in terms of valuable metabolite synthesis. Therefore, an efficient quick-growth method with improved phytochemical synthesis has been accomplished. For mass production employing micropropagation with embryos as explants, Murashige and Skoog (MS) medium was supplemented with 0.2 µM, 0.4 µM, and 0.6 µM of SNP, 3.0 µM of 6-benzylaminopurines (BAP), and 4.0 µM of thidiazuron (TDZ). The results showed that 0.4 µM of SNP alone or in conjunction with 3.0 µM of BAP was sufficient to improve morphological characteristics. In addition, established clones were examined for membrane stability by measuring electrolyte leakage (EL) and malondialdehyde (MDA), as well as photosynthetic pigment and carotenoids. In almost all the cases, high values were recorded when 0.4 µM of SNP was used, either singly or in conjunction with 3.0 µM of BAP in the MS medium. Clonally produced plantlets were also subjected to phytochemical screening and antioxidant activities, such as hydrogen peroxide (HO), superoxide anion, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, wherein these tests also revealed incorporation of SNP exhibited enhanced phytochemical concentrations and antioxidant activities. This research can thus be used to mass produce in vitro plantlets with considerably higher quantities of secondary metabolites, which may make them more resistant to environmental challenges than their natural counterparts without treatment.