植物中草酸积累与光呼吸乙醇酸代谢的关系

对几种C3 和C4 植物中草酸含量及相应的乙醇酸氧化酶活性测定结果表明 :叶片光呼吸强度及其关键酶活性大小与草酸积累量没有相关性 ;植物根中均能积累草酸 ,但未测出乙醇酸氧化酶活性。烟草根、叶中的草酸含量在不同生长时期差异明显 ,且二者呈极显著正相关 (y =2 .5 6 5lnx 2 .137,r =0 .749,P <0 .0 0 1) ,说明根中草酸可能来自叶片。氧化乙醇酸的酶的活性与氧化乙醛酸的酶的活性呈极显著线性正相关 (y =0 .2 41x 0 .0 0 6 ,r=0 .96 7,P <0 .0 0 0 1) ,进一步证实是乙醇酸氧化酶催化了两种底物的反应。烟草在不同生长期叶片中草酸总含量变化与相应的乙醇酸氧化酶活性变化亦没有相关性 ;低磷胁迫可显著诱导烟草根叶中的草酸形成和分泌 ,但并未影响乙醇酸氧化酶活性 ,进一步证明草酸积累与该酶活性大小无关

Relationship Between Oxalate Accumulation and Photorespiratory Glycolate Metabolism in Plants

Oxalate content and glycolate oxidase(GO) activity were measured in several C 3 and C 4 plants. The result showed that photorespiration intensity and the key enzyme activity were not correlated with oxalate accumulation in plant leaves, and that in roots oxalate was also of quantity but no GO activity could be detected there (Table 1). Leaf and root oxalate contents changed throughout the whole growth period (Fig.1), and both were positively correlated ( y = 2.565 ln x 2.137, r =0.749, P < 0.001 ), indicating that root oxalate may come from leaves(Fig.2). Glycolate oxidizing activity was highly correlated with glyoxylate oxidizng activity ( y =0.241 x 0.006, r =0.967, P < 0.0001 ), confirming that the same enzyme may catalyze oxidation of both glycolate and glyoxylate (Fig.3). By measuirng the enzyme activity in tobacco plant throughout the growth period, it was found that glycolate oxidase activity was also not correlated with oxalate content in both forms (Fig.4). Both oxalate secretion by roots and its accumulation in roots increased during phosphorus deficiency, but glycolate oxidase activity was little affected during the process (Table 2). This further verified that glycolate oxidase activity is not the limiting factor for oxalate accumulation in plants.