The rapid isolation of photosynthetically active mesophyll cells from Asparagus cladophylls

Abstract

Mesophyll cells were isolated rapidly from the cladophylls of Asparagus sprengeri Regel, by gentle grinding of the tissue by hand. About 60 to 65% of the leaf cells on a chlorophyll basis were released, of which 85 to 90% were cells with an intact plasmalemma. The isolated cells had photosynthetic rates of 50 to 80 μmol O₂ per milligram chlorophyll per hour at pH 7.2 and 25 °C although rates of 90 to 105 μmol O₂ per milligram chlorophyll per hour were recorded. The apparent K_m of photosynthetic bicarbonate uptake at pH 7.2 was 176 μM in air and 104 μM under nitrogen, which corresponds to apparent K_m's of CO₂ fixation of 23 μM and 13.5 μM respectively. The isolated cells maintained high photosynthetic rates for 50 h when stored in the light at 4 °C and for over 160 h after storage in the dark at 4 °C.