低钾胁迫对烟草幼苗活性氧及抗氧化酶系统的影响

作物对养分胁迫的响应机制已成为新的研究热点，而在低钾胁迫下，烟草苗期体内活性氧（ROS）及抗氧化酶系统的响应机制需要进一步的深入研究。采用控制水培试验，以不同耐低钾型烟草品种（耐低钾基因型烟草品种NC89和不耐低钾烟草品种云烟1号）为材料，研究了低钾胁迫对不同耐低钾型烟草品种苗期生长及内源活性氧清除系统的影响。研究表明:与正常供钾处理相比，在低钾胁迫处理下不同钾基因型烟草品种的根系生物量、总根长和根系总体积均显著下降，而不耐低钾烟草品种云烟1号降幅均大于耐低钾型烟草品种NC89；与正常供钾相比，在低钾胁迫处理下不耐低钾烟草品种云烟1号显著增加了根系中丙二醛（MDA）和超氧阴离子（O₂-）产生速率，增幅分别为30.32%和18.78%，而耐低钾型烟草品种NC89差异不显著；同时，低钾胁迫显著增加了不同钾耐性烟草品种过氧化氢酶（CAT）活性，在低钾处理条件下NC89地上部和根系中超氧化物歧化酶（SOD）和过氧化物酶（POD）的含量均显著增加，而云烟1号地上部POD和根系SOD显著增加。因此，在低钾胁迫条件下，耐低钾型烟草品种体内抗氧化酶活性更强，能更有效的清除ROS，更好的抵御低钾胁迫带来的氧化损伤。 

Effects of potassium deficiency stress on active oxygen and antioxidant enzyme system in tobacco seedlings

Response mechanism of crop to nutrient stress has become a new research hotspot. Effect of active oxygen (ROS) and antioxidant enzyme system in tobacco seedlings under potassium deficiency stress needed to be examined. Solution culture experiments were carried out to study the effect of potassium deficiency stress on biological characteristics and active oxygen scavenging system of tobacco varieties with different potassium sensitivities at seedling stage. Results showed that dry weight, total length and volume of roots in tobacco seedlings decreased significantly under potassium deficiency treatment compared to normal nutrient. Malondialdehyde (MDA) content and superoxide anion radical (O₂-) production rate in roots of potassium-sensitive tobacco were increased by 30.32% and 18.78% respectively, while there was no significant difference in the increased scope of potassium-tolerant tobacco. Compared with normal nutrient, the protective enzyme activities increased in two tobacco varieties under potassium deficiency stress except catalase (CAT) activities in shoots and roots of potassium-sensitive tobacco. The relative expression levels of protective enzyme activities such as superoxide dismutase (SOD), peroxidase (POD) and CAT of potassium-tolerant tobacco were higher than potassium-sensitive tobacco, especially in roots. It was indicated that under potassium deficiency stress, potassium-tolerant tobacco had high protective enzyme expression to protect tobacco seedlings from harm of excess O₂- and H₂O₂, thus increasing adaptability to potassium deficiency.