干旱对玉米幼苗PEP羧化酶活性的影响

Effect of Soil Drought on PEP Carboxylase Activity in Maize Seedlings

本文研究了土壤干旱过程中及复水后玉米幼苗ＰＥＰ羧化酶活性的变化。结果表明，当土壤含水量由２１．０％降至６．１％时，ＰＥＰ羧化酶活性由０．３５２μｍｏｌＣＯ２／ｍｇ·ｐｒｏ．ｍｉｎ降至０．０６３μｍｏｌＣＯ２／ｍｇ·ｐｒｏ·ｍｉｎ，复水后其活性恢复很慢，即使叶水势恢复到干旱前水平（－０．３ＭＰａ），此酶活性才恢复到０．１７μｍｏｌＣＯ２／ｍｇ·ｐｒｏ·ｍｉｎ，仅为干旱前的４７．４％。光合速率先升后降，叶绿素含量和叶片水势的变化与ＰＥＰ羧化酶相似，气孔阻力则随土壤干旱程度的加剧而逐渐升高。说明土壤干旱过程中玉米幼苗ＰＥＰ羧化酶活性的降低可能是光合作用下降的非气孔因素之一。

Changes in the activity of PEP carboxylase were studied in soil drought treatmentfollowed by rewatering.The results showed that PEP carboxylase activity declined from0.352umolCO2/mg·pro·min to 0.063 with the increase of intensity and duration of soildrought.Upon rewatering,the enzyme avtivity recovered slowly and finally remained lowerlevel(0.17umolCO2/mg·pro·min)even though the water potential of the leaf had returned to the initial water potential before drought(-0.3MPa).The leaf water potential and the content of chlorophyll decreased markedly,but the stomatal resistance increased with decreasing of soil water content.In the early period of soil drought the photosynthesis rate increased markedly and then decreased as water stress became more severe.Photosynthesis rate can not recovered completely after rewatering.Above-mentioned results lead to the assumption that the reduction of the PEP carboxylase activity resulted from a nonstomatal factor that limited leaf photosynthesis under drought stress.