小麦旗叶自然衰老过程中清除活性氧能力的变化

野生一粒小麦(Triticum boeoticum Boiss)、栽培小麦“扬麦五号”(T.aestivum L.)的旗叶自然衰老过程中,活性氧清除系统中各部分的清除能力下降是不均衡的。在光合速率高值持续期(叶绿素含量缓降期),SOD的活力略有下降,过氧化氢酶(CAT)活力却迅速下降,同时抗坏血酸过氧化物酶(ASP)活力呈现先上升后下降的趋势,上述SOD、CAT、ASP活力变化的不均衡,最终导致H_2O_2的迅速累积,从而使叶片迅速进入衰老(叶绿素含量速降期),于是SOD活力迅速下降。野生一粒小麦活性氧清除系统中各部分清除能力失衡过快,可能是其早衰的原因之一。H_2O_2的迅速累积与叶片衰老的启动密切相关。

CHANGES OF ABILITY OF SCAVENGING ACTIVE OXYGEN DURING NATURAL SENESCENCE OF WHEAT FLAG LEAVES

During the natural senescence of wheat flag leaves in Triticum boeoticum Boiss and "Yangmai No.5" ( T. aestivum L.), the decrease of their ability of scavenging active oxygen was an unbalanced process. During photosynthetic active duration (relative steady phase of chlorophyll content) , the activity of SOD decreased slightly, but that of catalase (CAT) decreased rapidly, while the activity of ascorbate peroxidase (ASP) increased at first and then decreased. The changing disparity among the SOD, CAT, ASP activities during natural senescence of wheat leaves consequently lead to the accumulation of hydrogen peroxide, which was associated with the rapid senescence of the leaf (sharp fall phase of chlorophyll content). Finally,SOD activity decreased remarkably.That the system of scavenging active oxygen appeared earlier in an unbalanced state could be one of the causes of early senescence in T. boeoticum as compared with "Yangmai No.5" . The rapid accumulation of hydrogen peroxide in wheat leaves was closely related to the priming of senescence.