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Effect of CO 2 concentration on photorespiration, sucrose synthesis, and carbon transport in C 3 and C 4 plants

1980; Taylor & Francis; Volume: 26; Issue: 2 Linguagem: Inglês

10.1080/00380768.1980.10431203

1747-0765

Minoru Yamauchi, Yoshio Yamada,

Light effects on plants

Abstract The synthesis of sucrose from the glycolate pathway was investigated in relation to the carbon transportation at different CO2 concentrations in the air. Tomato and maize plants were fed with 14CO2 in the light in an assimilation chamber containing 90, 220, 840, and 2,290 ppm of CO2. The distribution of 14C in the leaf extract with 80% ethanol, the leaf residue, and the root and stem was determined at 30 and 60 min. l-U-14C-serine was supplied to tomato leaves through their cut bases in the light in the air containing 10, 340, and 1,700 ppm of CO2, and the radioactive compounds formed from serine were analyzed. The following results were obtained. 1. The proportion of 14C transported from the leaves decreased in maize but not in tomato at lower CO2 concentration.2. The proportion of 14C in glycine, serine, and malic acid in the leaf extracts increased corresponding to the decrease of that in starch at lower CO2 concentration in tomato at 30 min. At 60 min, the proportion of 14C in glycine and serine decreased and that in starch increased at lower CO2 concentration. On the other hand, the influence of CO2 concentration on the proportion of 14C in the metabolites was small for maize.3. The amounts of 14C in the leaf extract and residue significantly increased in tomato with an increase in photosynthesis, but that in the leaf residue in maize was constant regardless of the photosynthesis and CO2 concentration.4. From l-U-14C-serine, the incorporation of 14C into the CO2 evolved and the intermediates of glycolate pathway increased and that into starch decreased at lower CO2 concentration in tomato. From these results it was considered that sucrose is synthesized mainly from the intermediates of glycolate pathway at lower CO2 concentration and from the intermediates of Calvin cycle at higher CO2 concentration in tomato and only from the latter in maize. One of the roles of photorespiration was thought to be the maintenance of the carbon transport in C3 plants. Additional Index Words: glycolate pathwaysucrose synthesistomatomaize