耐低钾玉米自交系延缓叶片衰老的生理特性

以典型的耐低钾玉米自交系90-21-3和低钾敏感玉米自交系D937为试材，采用大田试验，研究了生育后期低钾胁迫对不同自交系叶片持绿性、叶绿素含量、光合特性及叶绿素荧光参数、烯醇式丙酮酸羧化酶(PEPC)和NAD激酶(NADK)活性、保护酶活性的影响，探讨耐低钾玉米延缓叶片衰老的生理特性。结果表明，低钾胁迫持续到生育后期，90-21-3与D937相比，叶片持绿时间长，叶绿素含量下降缓慢，叶片净光合速率(P_n)高；胞间CO₂浓度(C_i)和气孔限制值(L_S)上升幅度小；F_PSII、F_v、F_m高，而F_o明显低；PEPC和NADK活性高；MDA含量上升缓慢且维持较低水平；抗氧化酶SOD、POD和CAT活性相对较高。低钾胁迫下，90-21-3自交系延缓叶片衰老的原因可能为持绿性较好，延长了叶片功能期；光合能力强，受光抑制程度较轻；NADK活性稳定，为光反应提供电子受体NADP，同时PEPC活性较高，暗反应又能固定相对较多的CO₂，从而保证了CO₂的供应；光反应和暗反应的协同，使90-21-3自交系具有相对较高的光合速率，同时抗氧化酶又具有较高的活性，可有效清除活性氧。

Physiological Characteristics of Delaying Leaf Senescence in Maize Inbred Lines Tolerant to Potassium Deficiency

A field experiment was conducted using two maize inbred lines with significant difference in potassium sensitivity to investigate the effects of low potassium stress at grain filling stage on leaf stay-green,chlorophyll contents,photosynthetic gas exchange and chlorophyll fluorescence parameters,and various antioxidant enzymes activities related with senescence.The results showed that,under low potassium stress,the characteristics of leaf stay-green of 90-21-3 were better than that of D937.In addition to changes in stay-green,it was found that decreased more strongly in D937,the photosynthetic pigment level in 90-21-3 was remained nearly normal under K deficiency conditions.Moreover,compared with D937,90-21-3 showed a lower stomatal restriction and a higher electronic transition capacity after accelerated ageing by K deficiency.FPSII,Fv,Fm in 90-21-3 were higher than in D937,while Fo was lower than those in D937.In addition,under low potassium stress,activities of PEPC and NADK were less decreased and photo system was less damaged in 90-21-3.And the content of malondialdehyde(MDA)was lower in 90-21-3 than in D937 under low potassium stress.The activities of superoxide dismutase(SOD),peroxidase(POD),and catalase(CAT)in ear leaf of 90-21-3 were obviously higher than those of D937 under low potassium stress,indicating that the antioxidant enzymes could eliminate reactive oxygen species,inhibit the membrane lipid peroxidation and decrease the content of MDA more efficiently in 90-21-3.Therefore,compared with D937,the leaf senescence of 90-21-3 was relatively slower,which could prolong the functional period of leaves.The activity of NADK could provide NADP as electronic receptors for photoreaction,at the same time the increased activity of PEPC led to more effective fixation of CO2,and the synergistic effect of light and dark reactions contributed to the higher photosynthetic rate and yield in 90-21-3.