C3,C4和CAM植物的光呼吸及有关酶活性的比较研究

对4种C_3植物和4种C_4植物,6种CAM植物的光呼吸的研究表明:C_4和CAM植物象C_3植物一样表现出断光后CO_2的猝发;它们的乙醇酸氧化酶活性远低于C_3植物,而过氧化氢酶活性略低于C_3植物;光下有乙醇酸的合成。我们认为在C_4和CAM植物中也存在光呼吸乙醇酸循环。C_4植物表观光呼吸的大小可能与其叶的解剖特征有关,而CAM植物的表观光呼吸可能与其代谢的昼夜节律变化有关。我们还研究了CAM植物的乙醇酸循环在早晨和傍晚的变化规律,发现绝大多数CAM植物的乙醇酸氧化酶活性、过氧化氢酶活性和乙醇酸的合成量都一致表现为傍晚高于早晨。我们认为CAM植物体内乙醇酸循环的运转傍晚较早晨快。

COMPARATIVE STUDIES ON PHOTORESPIRATION AND THE ACTIVITIES OF PHOTORESPIRATION ENZYMES IN C1, C4AND CAM PLANTS

Studies on the photorespiration of four typical C3 and C4 plants and six CAM plants showed that C4 and CAM plants showed postilluminaiion CO2 burst (PICB) as did C3 plants. The activity of glycolate oxidase In C4 and CAM plants compared to that in the C plants was much lower and the activity of catalase slightly lower. Glycolate formation also existed in C4 and CAM plants. It was considered that there was a glycolate cycle in C4 and CAM plants. The rate of photorespiration In C, plants may be related to their anatomical features, and as to CAM plants it may be related to the diurnal rhythm of its metabolism. The variation of glycolate cycle in the morning and dusk in CAM plants was studied. It was found that most of the CAM plants showed higher activities both of glycolate oxidase and catalase and a larger quantity of glycolate formation at dusk than in the morning. The turnover of the glycolate cycle was postulated to be faster at nightfall than in the morning in CAM plants.