Development and characterization of a photoautotrophic cell line of pak-bung hairy roots

A cell line of photoautotrophic pak-bung hairy roots was established from p hotomixotrophic ones by acclimation cultivations with a stepwise change of sucrose concentration in a medium with 3.0% CO2-enriched air supplied under continuous light irradiation. The derived photoautotrophic hairy roots had high chlorophyll content and activity of 1,5-ribulose-bisphosphate carboxy lase/oxygenase, the values of which were 4.1- and 2.0-fold more than those of the parent photomixotroph, respectively. Electron microscopic observatio n revealed that the photoautotrophic hairy root cells possessed well-develo ped chloroplasts. The activities of ascorbate peroxidase and guaiacoal pero xidase found in the hairy roots were comparable to those found in the leave s and roots of parent plants of pak-bung, respectively. The elongation rate of growing points of the hairy roots was maximum at 5.0% CO2 concentration in gas phase and an incident light intensity of 10 W/m(2) under the photoa utotrophic conditions examined. Although light was indispensable for ensuri ng photoautotrophy of the hairy roots, it was found that exposure of the ro ots to strong light resulted in the reduction in the number of viable growi ng points governing the overall growth rate of the hairy roots.