Issue Archive

Effect of hypotonic swelling on photosynthesis in spinach intact chloroplasts

Ye Jiyu, Li Deyao, Shen Yungang

Shanghai Institute of Plant Physiology, Chinese Academy of Sciences. Shanghai 200032

Abstract

When the osmotic pressure of the medium was decreased by lowering sorbitol concentration from 0.33 mol/L to 0.17 mol/L, the percentage of intact chloroplasts remained unchanged until a critical osmotic pressure of about 0.5 MPa was reached. Below 0.4MPa the chloroplast envolope rupture occurred and CO_(2)fixation capacity lost. In slightly hypotonic conditions, the CO_(2)-dependent O_(2) evolution was inhibited, though the chloroplasts were still intact(Fig.1). Between 0.9 MPa and 0.5MPa, the inhibition of PGA reduction in hypotonically swollen chloroplasts could be overcome by adding sorbitol to normal concentration (0.33 mol/L)(Fig.3). Light-dependent changes of ATP and NADPH levels in intact chloroplasts were measured. By using different penetrable electron acceptors NO~(-)_(2), PGA and OAA, it was found that swelling of chloroplasts had no effect on nitrite reduction which used reduced ferredoxin as electron donor. On the other hand, PGA or OAA reduction which required NADPH as electron donor was significantly inhibited by hypotonic swelling(Fig.5).

Key words: Hypotonic swelling;Intact chloroplast;CO_(2)-dependent O_(2) evolution

Received: 　　Accepted:

Corresponding author: 　　E-mail:

Citing This Article：

Ye Jiyu, Li Deyao, Shen Yungang. Effect of hypotonic swelling on photosynthesis in spinach intact chloroplasts. Acta Physiol Sin 1995; 47 (1): (in Chinese with English abstract).