铝胁迫对不同耐铝小麦品种根伸长生长影响的研究

为探讨铝胁迫抑制根生长的机理,以耐铝型小麦品种ET8和铝敏感型ES8为试验材料,研究了铝胁迫对小麦根相对伸长率,根尖细胞显微结构的影响以及细胞壁木质素含量及苯丙氨酸解氨酶(PAL)、肉桂醇脱氢酶(CAD)、过氧化物酶(POD)活性的变化。结果表明,ET8和ES8经50μmol/L铝胁迫6、122、4 h后,根相对伸长率随铝胁迫时间延长而变小。利用植物显微技术发现,ET8和ES8经50μmol/L胁迫24 h后,根尖伸长区皮层细胞变扁平,细胞间隙变小,细胞壁褶皱,并呈齿轮状交合;ES8细胞受伤害程度较ET8显著。经50μmol/L铝胁迫6、12、24 h后,ET8和ES8根尖细胞长度受铝胁迫的程度随时间延长而加强,根尖细胞相对长度与根相对伸长率呈显著正相关的关系(r=0.9911**)。50μmol/L铝胁迫24 h后,ET8和ES8根尖苯丙氨酸解氨酶(PAL)、肉桂醇脱氢酶(CAD)、过氧化物酶(POD)活性及细胞壁木质素合成显著增加。上述结果表明,铝胁迫通过增加苯丙氨酸解氨酶、肉桂醇脱氢酶、过氧化物酶活性,促进根尖细胞壁木质素合成,加快细胞的木质化,细胞壁延展性变小,从而抑制细胞的伸长,减小根的生长。由于铝胁迫下ES8中木质素合成显著高于ET8,且根尖细胞结构受破坏较ET8显著,造成铝胁迫下ES8根生长受抑制比ET8显著,是ET8较ES8耐铝胁迫的主要原因。

Effects of aluminum stress on root elongation of different aluminum tolerance wheat cultivars

A rapid inhibition of root elongation is the main character of plants under aluminum (Al) stress. Two near isogenic lines (NIL) wheat (Triticum aestivum L.) ET8 (Al-resistant) and ES8 (Al-sensitive) were selected to study the mechanism of Al induced inhibition of root elongation. Effects of Al treatments on relative root elongation, root tip cell structure, contents of lignin and activities of enzymes such as phenylalanine ammonialyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD) were investigated. The results show that the relative root elongation (RRE) of ET8 and ES8 are decreased after treated with 50 μmol/L Al for 6, 12 and 24 h. Longitudinal sections reveal that the cells in the elongation zone become flat, the cell wall is folded and ragged, intercellular space is decreased and occluded like gears after 50 μmol/L Al treated for 24 h. Damage to cell structure of ES8 is more serious than that of ET8. Both ET8 and ES8 showed an retardation of root cell elongation with the increase of treatment time (6, 12, 24 h) under 50 μmol/L Al, and there is a significant correlation between RRE and RCL (Relative Cell Length). The contents of lignin and the activities of PAL, CAD and POD are remarkably increased after the Al treatment (50 μmol/L 24 h). The above results indicate that Al-stress promotes the deposition of lignin by increasing the activities of PAL, CAD and POD, which accelerates the lignification of cell and leads to the decrease of cell wall extensibility and the inhibition of root growth. The content of lignin is higher in ES8 than that in ET8, and the damage to cell structure of ES8 is more serious than that of ET8, which induces the significant inhibition of root growth of ES8, and this might be the mechanism of ET8 could tolerate with Al-stress more than ES8.