Lipid peroxidation, H2O2 content, and antioxidants during acclimatization of Abrus precatorius to ex vitro conditions

An efficient, rapid, and reproducible plant regeneration protocol was successfully developed for Abrus precatorius L. using mature nodal explants excised from a 5-year-old field grown plant. The highest shoot regeneration frequency (87 %) with maximum number of multiple shoots (15.0) and shoot length (4.8 cm) were recorded on Murashige and Skoog (MS) medium amended with 2.5 mu M thidiazuron, 120 mg dm(-3) polyvinylpyrrolidone, and 0.5 mu M alpha-naphthalene acetic acid. The best treatment for maximum root (4.0) induction was half strength MS medium supplemented with 1.5 mu M indole-3-butyric acid. The in vitro plantlets with well-developed shoots and roots were successfully transferred into plastic cups with Soilrite and acclimatized in a culture room under photon flux density (PFD) of 150 mu mol m(-2) s(-1), thereafter transferred to a greenhouse with PFD of 300 mu mol m(-2) s(-1), and finally to a field with 70 % survival rate. During the acclimatization period (0-49 d), leaf chlorophyll and carotenoid content increased whereas malondialdehyde and H2O2 content decreased probably due to increasing activities of antioxidant enzymes (catalase, superoxide dismutase, glutathione reductase, and ascorbate peroxidase). Our work suggests that micropropagated plants developed an antioxidant enzymatic protective system to avoid oxidative stress during establishment under ex vitro environment.