LAUSR

Abstract Excess of fluoride (F) in irrigation water is a serious threat inducing variety of deleterious impacts in plants via over-production of active oxygen species (AOS), modifying antioxidant enzymes and nucleic acid. Present study was aimed to monitor protective functions of glycinebetaine (GB) against F-toxicity in Cajanus cajan L. GB is an osmolyte, serves as quencher of AOS and stabilizes membranes and proteins in stressed tissues. Seeds of C. cajan L. were exposed to F (75 ppm of NaF), and its combination with GB (50 μM), for five days. The results indicated that F caused inhibited growth, membrane stability index (MSI) and protein content, which were inversely related with the AOS levels and F sequestered. Moreover, few other stress markers viz. ; malondialdehyde (MDA), 4-hydroxy-2-nonenal (4-HNE), lipoxygenase (LOX), and DNA polymorphism were found to be enhanced significantly, with a little of proline, in response to F. On the other hand, exogenous addition of GB exhibited improved growth, MSI, genomic template stability, protein and proline accumulations with lower levels of AOS, MDA, 4-HNE, LOX and DNA polymorphism in stressed tissue. Additionally, alterations in the activities/isoforms of superoxide dismutase, catalase, guaiacol peroxidase and ascorbate peroxidase were examined in F-stressed samples, and were found to be up-regulated by GB. This study concludes that GB counteracts F-toxicity strongly via restricting accumulation of F, AOS operated membrane deterioration and injury symptoms, and improving proline accumulation, defensive function and genomic template stability. Conducted study for the first time provides evidence that support the protective function of GB against F-toxicity.