Biochemical changes in embryogenic and non-embryogenic callus of Bambusa nutans Wall. during somatic embryogenesis

Key message1. This investigation provides insight into the physiological and biochemical changes during SE and factors contributing to it.2. GSA has a strong correlation with SE and can be a potential biochemical marker for the process.3. Peroxidase activity and expression of its isozymes denote a chaotic situation rather than a marker of SE. Bambusa nutans Wall. is a clump-forming, evergreen bamboo species that is most often found in Southeast Asian forests. Comparative activities of nitrate reductase (NR), glutamine synthetase (GS) and peroxidase (POX) as well as expression of peroxidase isozymes during somatic embryogenesis (SE) were investigated in the segregated embryogenic callus (EC) and non-embryogenic callus (NEC) from the same genotype (CPC-648) of B. nutans Wall. The EC was compact, with large prominent nuclei and dense cytoplasm, while the NEC was fragile, with rudimentary nuclei and hyaline cytoplasm. SE in EC encompassed induction, maturation and germination stages each of 30 days on MS medium supplemented with ascorbic acid 50 mg L- 1, citric acid 25 mg L- 1, cysteine 25 mg L(- 1)and glutamine 100 mg L- 1 + 2, 4-D 2 mg L- 1 + coconut water 10%. EC exhibited dedifferentiation and growth leading to SE, while NEC remained amorphous loose lump throughout. EC had lower NR and POX activities and less number of peroxidase isozymes but higher GS activity than NEC during three stages of SE. NR activity in EC followed a trend as induction > germination > maturation; GS activity, maturation > germination > induction and POX activity. EC exhibited less peroxidase isozymes than NEC. SE is an epigenetically regulated process that leads to the expression of enzymes involved in primary metabolism in EC and secondary metabolism in NEC. GS activity corresponding to SE process may be developed as biochemical marker. Peroxidase activity and isozyme expression in NEC express a disorderly oxidative stress scenario.