Photosynthetic Activities of Spinach Leaf Protoplasts 1

AUTOR(ES)

Nishimura, Mikio

RESUMO

Photosynthetic activities of protoplasts isolated from spinach leaf (Spinacia oleracea L.) were investigated. The protoplasts were stable up to 9 hr, without loss of the original activity of CO2 fixation (33-75 μmoles CO2/mg Chl·hr) and light-dependent O2 evolution (33-40 μmoles O2/mg Chl·hr), when stored in 0.8 m mannitol-0.05 m N-tris (hydroxymethyl)-methylglycine-NaOH buffer, pH 7, at 4 C in dark. The optimum pH of 8.5 for CO2 fixation reaction carried out in the present experimental condition employed is about the same as that reported for intact spinach chloroplasts. The CO2 concentration for half-maximal rate of CO2 fixation by protoplasts. “Km (CO2),” were determined to be 19.8 μm (pH 7) and 42 μm (pH 8.5) and are similar to those observed for intact spinach chloroplasts. Protoplasts showed postillumination CO2 fixation. Over-all results indicate that spinach protoplasts are as active as the intact plant leaf tissues in their photosynthetic activities.

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