【作者】 徐文静；

【导师】 王政权；

【作者基本信息】 东北林业大学 ， 森林培育， 2005， 硕士

【摘要】 本研究以水曲柳(Fraxinus mandshurica)苗木细根为材料,用温室土培的方法,测定遮荫条件下一系列反映植物根系衰老的指标,分析了遮荫条件下细根衰老过程中生理代谢、酶活性以及DNA的降解变化,揭示了C控制对细根衰老的影响,以及各级根序间的衰老顺序,得出水曲柳细根衰老的结果如下: 1.在C停止供应条件下,根尖活力、可溶性糖以及可溶性蛋白含量随着遮荫时间的延长,不断降低,并且随根序上升而下降,MDA含量和膜透性逐渐升高。这在生理水平上说明在C向根系分配减少时,树木根系的衰老具有顺序性,即按根序从低向高逐渐衰老。 2.C供应的停止,使根细胞内的保护酶SOD、POD、CAT活性随之改变,但在遮荫处理的前期,根系内活性氧的产生和清除系统保持平衡。但随着遮荫时间的推移,根细胞内保护酶SOD、POD、CAT活性比例失调,使根系内活性氧的产生和清除系统失衡,根系生理代谢紊乱,导致根系衰老和死亡。结果表明在酶水平上,树木根系的衰老随根序上升而下降。 3.遮荫使根系渐趋衰老,在衰老后期出现DNA降解现象,处理根系的根尖和1级根出现DNA降解的现象,尽管电泳结果变得弥散。而其它根序的的细根没有出现同样的现象。这在一定程度上证明了细根的衰老是从根尖开始的,随后是1级根。 试验结果表明,遮荫控制C向细根的分配对细根的生理功能产生了很大的影响,促使细根衰老。不同根序的细根,衰老程度明显不同。根尖首先呈现衰老的特征,随之是1级根和2级根,与之相比3级根衰老程度最小。这些结果表明在遮荫条件下,水曲柳细根衰老不是随机发生的,而是随着根系级别的增加而减少,与根系发育顺序相反。进一步解释了细根周转过程中1级根的寿命较短,周转迅速的原因。更多还原

【Abstract】 Fine root senescence was an important question on the study of fine root longevity and turnover. The physiological metabolism, enzyme activity and DNA fragment of fine roots were studied for understanding principle of fine root senescence of Manchurian ash (Fraxinus mandshurica) seedlings under the stress of shading treatment in greenhouse, and some parameters were applied for assessing degrees of fine root senescence. The objective of this study was to explain how C allocation affected on fine roots senescence and their senescence sequence. The main conclusions of investigation as follows:1 The results showed that reduced C allocation to fine roots, the root vigor, soluble sugar, and soluble proteins decreased with increasing root order, and MDA and membrane penetration increased, comparing with control. Those suggested that fine root senescence in physiological view was affected by C allocation and had a sequence from root tips, first order to the third order roots.2 When C allocation to fine roots was stopped, activities of protective enzymes, such as SOD, POD, and CAT, were changed with increased root order. The data under shading treatment indicated that fine root could keep the balance between production and scavenging of active oxygen by heightening activities of the enzymes at the early treatment. In contrast to the early treatment time, activities of the enzymes, such as SOD, POD, and CAT, were broken and disproported in middle or long time C stress. These enzyme systems changed which suggested that the balance of production and scavenging systems of active oxygen were broken, and fine root senesced and died off. These results also indicated that protective enzymes were correlated with root order, and fine root senescence, at protective enzyme level, had a sequence from root tips, first order to the third order roots.3 The most important indicator of fine root senescence was DNA fragmentation in latter shading treatment, DNA fragmentation was found in cell of root tip and the first order root although DNA fragmentation pattern becoming smear bands in agarose gel. In the second and third order roots, DNA had not been observed any fragmentation on electrophoresis map. However, the beginning of fine root senescence had been proved in root tip, and subsequently the first order roots in this experiment.These results suggested that reduced C allocation to fine roots caused by leaf shading had great impacts on physiological functions of fine roots and stimulated senescence. With the different root branching order, difference of root senescence was larger significantly. Root tips firstly exhibited senescence, and subsequently the first and second-orders, the third-order roots had the slight senescence comparing with root tip and the first two orders in this experiment. These results indicated that fine roots had the senescence sequence which explained why fine roots of the first-order at the distal ends of a root system had a short life-span and rapid turnover.更多还原