Effects of light intensity on photosynthesis and toxic O-2 scavenging enzymes during acclimatization of micropropagated Calathea

Directly after transplantation, micropropagated Calathea louisae GAGNEP. `Maui Queen' plantlets did not show any positive net photosynthetic activity (= heterotrophic metabolism), and photoinhibition exacerbated with increasing light intensity as was shown by the decrease in F-v/F-m. Recovery from light stress was observed during the second week after transfer, when plants became fully autotrophic. An inverse relation between light intensity and the total chlorophyll over carotenoid ratio was found. Also changes in activities of antioxidative enzymes were observed. Catalase and glutathione reductase increased during the first three weeks of acclimatization, while an increase in guaiacol peroxidase and ascorbate peroxidase was observed later on in the acclimatization. Both superoxide dismutase and guaiacol peroxidase activities increased with increasing light intensity, while catalase activity was reduced. The results suggest an adaptive response of the plants to stress conditions generated by changes in climatic conditions at transplantation.