低磷和铝毒耦合胁迫对杉木叶片抗坏血酸——谷胱甘肽循环的影响

为揭示抗坏血酸-谷胱甘肽(As A-GSH)循环在杉木适应低磷和铝毒胁迫中的作用,以耐低磷和铝毒胁迫的杉木家系YX3及对低磷和铝毒胁迫敏感的杉木家系YX12为试验材料,研究不同处理下对照处理(CK)、低磷处理(-P)、铝处理(Al)和低磷加铝处理(-P+Al)]2个杉木家系叶片中As A-GSH循环代谢关键酶的变化规律。结果表明:不同胁迫处理下(-P、Al和-P+Al),2个杉木家系的丙二醛(MDA)含量均显著高于各自对照(-P处理下YX12叶片MDA含量除外),而且在Al和-P+Al处理下,耐性杉木家系YX3叶片中MDA含量均小于敏感型杉木家系YX12。进一步分析表明,与各自对照相比,不同胁迫处理增加了2个杉木家系叶片中的As A和DHA含量,同时提高了其叶片中抗坏血酸过氧化物酶(APX)、单脱氢抗坏血酸还原酶(MDHAR)、脱氢抗坏血酸还原酶(DHAR)、谷胱甘肽还原酶(GR)的活性,而且除DHA含量外,在-P、Al和-P+Al处理下耐性杉木家系YX3叶片中APX、GR、MDHAR、DHAR和As A含量均高于敏感型杉木家系YX12。此外,耐性杉木家系YX3叶片中还原型谷胱甘肽(GSH)含量以及As A/DHA值和GSH/GSSG值均高于敏感型家系YX12。因此,上述结果表明在不同胁迫条件下,杉木幼苗通过提高叶片抗氧化物质含量和As A-GSH循环关键酶活性来清除过量的活性氧,减轻胁迫诱导的氧化损伤;不同胁迫处理下,2个杉木家系叶片抗氧化物质含量及As A-GSH循环中关键酶活性响应的差异表明耐性杉木家系YX3具有较高的As A—GSH循环效率和抗氧化物质再生能力,从而有效抑制胁迫诱导的氧化损伤,这可能是其具有较强耐性的重要原因之一。

Effects of Low Phosphorus and Aluminum Toxicity Coupled Stress on Ascorbate-glutathione Cycle in Leaves of Cunninghamia lanceolata

In order to elucidate the role of AsA-GSH in adaptation to low phosphorus and aluminum toxicity in Cunninghamia lanceolata (C. lanceolata), the dynamic changes of key enzymes in AsA-GSH cycle were studied in the leaves of C. lanceolata under low phosphorus and aluminum toxicity stresses using low phosphorus and aluminum toxicity tolerant and sensitive families YX3 and YX12, and different treatments were set based on Hoagland nutrient solution namely, CK: the Hoagland nutrient solution, -P: the nutrient solution with 1 μmol/L phosphorus concentration, +Al: the nutrient solutions with 1 mmol/L Al, and –P+Al: the nutrient solutions with 1 μmol/L phosphorus concentration and 1 mmol/L Al concentration. The results showed that the malondialdehyde (MDA) content in both families were significantly higher than their controls under each stress condition (except for the MDA content in leaves of YX12 under –P treatment),  and the MDA content in the leaves of the tolerant families (YX3) was less than that in sensitive ones (YX12) under both +Al and –P+Al treatments. The antioxidants content and key enzymes in AsA-GSH cycle were further analyzed, and indicating that the contents of ascorbic acid (AsA) and dehydrogenated ascorbic acid (DHA) as well as the enzymes activities in AsAGSH cycle including ascorbate peroxidase (APX), dehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) increased compared with the controls. Moreover, we also found that the enzymes activities of APX, GR, MDHAR, DHAR and AsA content were higher in the leaves of the tolerant families YX3 compared with the sensitive ones, except for DHA content. Additionally, the contents of reduced glutathione (GSH), as well as AsA/DHA and GSH / GSSG in the YX3 leaves were higher than those in YX12. Taken together, the above results suggested that under different stress conditions the seedlings of C. lanceolata alleviated stress-induced oxidative damage by increasing  the antioxidants content (AsA) and enzymes activities in AsA-GSH cycle. The stress responses differed in the antioxidants content and enzymes activities between two C. lanceolata families suggested that higher efficiency of AsA-GSH cycle and its higher regeneration capacities of nonenzymatic antioxidant in the leaves of C. lanceolata tolerant family YX3 may be one of the important reasons for its good performance under stress conditions.