In the present study, in vitro mutagenesis techniques were applied to investigate the effects of gamma irradiation at 0, 10, 20, 30, 40, 50 and 60 Gy on physiological changes in callus of Gerbera jamesonii Bolus ex. Hook f. Biochemical changes in chlorophyll and soluble protein content of pre- and post- irradiated Gerbera callus were studied. Non-irradiated callus demonstrated the highest amount of chlorophyll content as compared to callus irradiated at 10, 20, 30, 40, 50 and 60 Gy. In addition, the amount of chlorophyll b was relatively higher than chlorophyll a in both the irradiated and non-irradiated callus, except for callus irradiated at 10 Gy. Biochemical differentiation based on total soluble protein content revealed gradual reduction after day 9 of exposure to gamma irradiation. Reduction of soluble protein content was observed in all the treatments as the increase of incubation period.

O presente trabalho foi realizado para estudar os efeitos da radiação gama no crescimento in vitro de explantes de calos, e a formação de brotos e mudas. A irradiação é conhecida por induzir ou inibir a diferenciação de células e o crescimento das plantas in vitro, o que ajuda na produção de novas variedades vegetais. Radiação gama é um dos agentes mutagenicos que são amplamente utilizados para o melhoramento através da mutação. Um declínio gradual foi observado no número de brotos regenerados a partir de explantes de pecíolos irradiados comparado com o controle. O número de brotações regeneradas de explantes de pecíolos irradiados, cultivados em meio Murashige & Skoog, suplementado com 2,0 mg L-1 BAP e 0,5 mg L-1 ANA, foi reduzido de 7,5±0,4 (controle) para 6,6±0,9, quando explantes foram expostos a 20 Gray de irradiação. Observação semelhante foi relatada sobre os efeitos da radiação gama em plântulas propagadas in vitro. Um declínio gradual foi observado com base na altura da planta com o aumento da dose de radiação gama. Um declínio significativo foi observado no peso fresco de calos irradiados em relação ao controle. Neste caso, as respostas de crescimento de calos foram fortemente influenciados pela dose de radiação. O peso fresco de calos foi reduzido para 76,4±2,2% em comparação com 89,7±0,5% (controle) quando calos foram expostas a 20 Gy.

The present work was carried out to study the effects of gamma irradiation on in vitro growth of explants, callus and the formation of shoots and plantlets. Irradiation is known to exhibit or inhibit the differentiation of cells and growth of plants in vitro, which helps in producing new plant varieties. Gamma irradiation is one of the physical mutagens that are widely used for mutation breeding. A gradual decline was observed in the number of shoots regenerated from irradiated petiole explants compared to control. Numbers of shoots regenerated from irradiated petiole explant cultured on Murashige & Skoog medium supplemented with 2.0 mg L-1 BAP and 0.5 mg L-1 NAA was reduced to 6.6±0.9 from 7.5±0.4 (control) when explants were exposed to 20 Gray of irradiation dose. Similar observation was reported on effects of gamma irradiation on in vitro propagated plantlets. Gradual decline was observed based on plant height as the dose of gamma irradiation increased. A significant decline was observed in the fresh weight of irradiated callus compared to control. In this case, growth responses of callus were strongly influenced by the radiation dose. The fresh weight of callus was reduced to 76.4±2.2% compared to 89.7±0.5% of control when callus tissues were exposed to 20 Gy.