氯化钠胁迫对南瓜根系游离态多胺含量和活性氧水平的影响

以中国南瓜杂交种‘360.3×112.2’和黑籽南瓜为试验材料，在营养液栽培条件下研究了NaCl胁迫对两种南瓜植株生长、根系活性氧水平和游离态多胺含量的影响.结果表明，NaCl胁迫10 d后，与对照相比，两种南瓜植株生长都受到明显抑制，但中国南瓜杂交种比黑籽南瓜植株的耐盐性强.NaCl胁迫使南瓜根系O₂^-·产生速率和H₂O₂含量提高，且黑籽南瓜的O₂^-·产生速率和H₂O₂含量高于中国南瓜杂交种.两种南瓜根系中腐胺(Put)、亚精胺(Spd)、精胺(Spm)和多胺(PAs)含量及Put/PAs高于对照，并呈现先升后降的趋势；根系中（Spd+Spm）/Put低于对照，呈现先降后升的趋势.中国南瓜杂交种根系中Put含量和Put/PAs低于黑籽南瓜，而Spd、Spm含量和（Spd+Spm）/Put高于黑籽南瓜.表明两种南瓜根系中多胺含量的升高对减少或清除组织中的活性氧有积极作用，Put向Spd、Spm的转化有利于增强植株的耐盐性；中国南瓜杂交种‘360.3×112.2’的耐盐性高于黑籽南瓜与其根系中Put/PAs较低、（Spd+Spm）/Put和PAs含量较高，使其清除活性氧能力较强有关.

Effects of NaCl stress on free polyamines content and reactive oxygen species level in pumpkin roots.

Taking Cucurbita moschata Duch hybrid 360.3×112.2 and C. ficifolia Bouche as test materials, the effects of NaCl stress on their plant growth and the O₂^-· production rate and H₂O₂ and free polyamines (PAs) contents in their roots were studied with hydroponic culture. The results showed that after 10 d NaCl stress, the plant growth of the two pumpkin varieties was strongly inhibited, compared with the control, and C. ficifolia was more injured than hybrid 360.3×112.2. Under NaCl stress, the root O₂^-· production rate and H₂O₂ content of the two pumpkin varieties were increased, but their absolute values were lower in hybrid 360.3×112.2 than in C. ficifolia. The contents of PAs, putrescine (Put), spermidine (Spd) and spermine (Spm) and Put/PAs ratio in the roots of the two pumpkin varieties were always higher than the control and had a trend of increased first and decreased then; while the (Spd+Spm)/Put ratio was lower than the control and decreased first and increased then. Compared with C. ficifolia Bouche, hybrid 360.3×112.2 always had a lower Put/PAs ratio and a lower Put content in its roots, but the (Spd+Spm)/Put ratio and Spd and Spm contents were always higher. It was concluded that under NaCl stress, the increasing PAs content in the roots of test materials played an active role in decreasing or scavenging reactive oxygen species (ROS). The conversion of Put to Spd and Spm was advantageous to the increase of plant salt tolerance. The higher salt tolerance of hybrid 360.3×112.2 was closely related to the lower Put/PAs ratio and the higher (Spd+Spm)/Put ratio and PAs content in its roots, and thus, the stronger capacity to scavenge ROS.