茭白肉质茎膨大期间的氧化胁迫

OXIDATIVE STRESS DURING STEM ENLARGMENT OF Zizania latifolia Turcz.

以"雄茭"为参照,研究了茭白肉质茎膨大期间的氧化胁迫状况。肉质茎膨大开始后,茎中H2O2和MDA含量快速上升,并分别在6和8d达到最大,约为膨大前的6.5倍和3.7倍,此后降至膨大初期水平。抗坏血酸(AsA)在肉质茎即将膨大前上升约30%,但膨大后快速下降处于较低水平,为0d的25%～30%。氧化型抗坏血酸比例在膨大开始时较低,随后则处于较高水平。GSH含量变化与AsA类似,也呈现先升后降的趋势。"雄茭"茎顶端组织的MDA、H2O2、AsA及GSH含量与膨大前的肉质茎相近或更低,而同样没有菰黑粉菌侵入的成熟叶片中,MDA和GSH水平在植株孕茭期间的相对变化幅度都较小。因此,茭白肉质茎膨大期间菰黑粉菌的活动造成肉质茎组织中氧化胁迫程度逐渐加重,抗氧化剂AsA和GSH不能有效清除肉质茎膨大期间产生的活性氧。

Enlargement of succulent stem of Zizania latifolia Turcz.was accompanied by proliferation of smut fungus（Ustilago esculenta P.Henn.） and hyperplastic growth of the first 3 to 5 nodes beneath the apical meristem.This process was found to be preceded by rapid increase of H2O2 and MDA contents,reaching maxima at 6d and 8d,respectively,and followed by decline to their initial levels.Ascorbate（AsA） content was raised by ～30% before enlargement but dropped quickly to a lower level afterwards（about 25～30% of 0d,whereas the ratio of dehydroascorbate in total ascorbate maintained at a high level during enlargement.GSH content took a similar time course as that of AsA.The uppermost part of non-enlargingstems of the plant,the so-called ＂Xiongjiao＂,contained similar or lower levels of MDA,H2O2,AsA and GSH,as compared to those in the pre-enlargement state of succulent stem.Similar to the non-enlarging stems,mature leaves were also not infected by U.esculenta and relatively small fluctuations occurred in MDA and GSH levels during period of stem enlargement taking place in the same tiller.These results showed that the systematic smut fungus caused a progressive oxidative stress in the succulent stem,and antioxidants such as AsA and GSH probably contribute little to the scavenging of ROS during stem enlargement of Z.latifolia.