菠萝叶片的稳定碳同位素比与PEP羧化酶及PEP羧激酶活性

STABLE CARBON ISOTOPE RATIO AND ACTIVITIES OF PEP CARBOXYLASE AND PEP CARBOXYKINASE IN PINEAPPLE LEAVES

专性景天酸代谢（ＣＡＭ）植物菠萝（Ａｎａｎａｓｃｏｍ ｏｓｕｓ （Ｌ．） Ｍｅｒｒ．）的下数第５ 到第３５ 位叶为材料，研究稳定性碳素同位素（δ１３Ｃ）值，磷酸稀醇式丙酮酸（ＰＥＰ）羧化酶和ＰＥＰ羧激酶活性的变化。１１ 个不同叶位叶片的δ１３Ｃ值平均为－ １２．９４‰，最大变幅相差－ ２．０６‰。两个酶的活性呈单峰形变化，第８—１１ 位叶的活性最高，低位叶的酶活下降。本试验条件下，ＰＥＰ羧激酶平均活性比ＰＥＰ羧化酶高３．４ 倍。结果表明，ＣＡＭ 植物的暗下羧化与光下脱羧之间具有一定的协调性。老叶虽然酶活较低，但总的看来，ＣＡＭ

Slight flutuation in carbon isotope values were found in counted from top dounward to the 35th in pineapple, Ananas comosus (L.) Merr., but more negative δ 13 C value (less heavier 13 C) was observed in lower position leaves. The average δ 13 C value was -12 94‰ in 11 leaves with maximum range of variation as -2 06‰. Similar single peak curves were found between PEPCase and PEP carboxykinase activities with leaves at various positions. Both enzymes reached the maximum activity in 8—11th leaves, then declined in others at lower positions. PEP carboxykinase activity was 3 4 folds higher than PEPCase activity under the present experimental condition (25—30℃). The results indicated that metabolic coordination evisted between dark carboxylation and light decarboxylation. For the obligate CAM plant, pineapple, though the carboxylation and decarxylation activities did occur in old leaves, the CAM level change did much, however.