外源NO对盐胁迫下黑麦草幼苗活性氧代谢、多胺含量和光合作用的影响

采用溶液培养法研究了外源一氧化氮(nitric oxide,NO)供体硝普钠(sodium nitroprusside,SNP)对100 mmol·L^-1 NaCl胁迫下黑麦草幼苗生长、活性氧代谢、多胺含量和光合作用的影响。结果表明，50 μmol·L^-1 SNP显著提高盐胁迫下黑麦草幼苗叶片的超氧化物歧化酶(SOD)、过氧化物酶(POD)和抗坏血酸过氧化物酶(APX)活性及谷胱甘肽(GSH)、精胺(Spm)、亚精胺(Spd)含量和(Spm+Spd)/Put比值，降低了腐胺(Put)、超氧阴离子(O^—·₂)、H₂O₂和丙二醛(MDA)含量，使幼苗叶片叶绿素和类胡萝卜素含量、净光合速率(P_n)和气孔导度(G_s)升高，胞间CO₂浓度(C_i)下降，相对生长量增加。叶绿素荧光动力学资料显示，SNP处理降低盐胁迫下黑麦草叶片的初始荧光(F₀)，表明它对光合膜系统具有保护效应。SNP处理不仅提高了盐胁迫下叶片的最大荧光(F_m)、PSⅡ潜在光化学效率(F_v/F₀)和PSⅡ最大光化学效率(F_v/F_m)，而且提高了PSⅡ实际光化学效率(Φ_PSⅡ)、光化学荧光猝灭系数(q_P)、表观光合电子传递速率(ETR)和光化学速率(PCR)，降低了非光化学荧光猝灭系数(NPQ)和天线热耗散(D)，而1 mmol·L^-1 NO清除剂PTIO和0.5 μmol·L^-1 NaNO₂处理(对照)则无此效应。由此表明，外源NO可能通过提高植株的抗氧化能力及光能的捕获与转换而增强盐胁迫下黑麦草叶片的光合能力，从而缓解盐胁迫对幼苗生长的抑制作用。

Effects of Exogenous Nitric Oxide on Active Oxygen Metabolism,Polyamine Content and Photosynthesis of Ryegrass(Lolium perenne L.) Seedlings Under Salt Stress

In a solution culture experiment, the effects of exogenous sodium nitroprusside (SNP) as nitric oxide (NO) donor on ryegrass(Lolium perenne L.) seedlings in growth, active oxygen metabolism, polyamine content and photosynthesis under the stress resulting from 100 mmol·L^-1 NaCl were studied, and the results showed that 50 μmol·L^-1 SNP significantly increased the activities of superoxide dismutase(SOD), peroxidase (POD) and ascorbate peroxidase (APX) and the contents of glutathione(GSH), spermine (Spm) and spermidine (Spd), and (Spm+Spd)/Put ratio, decreased the contents of putrescence(Put), O^—·₂, H₂O₂ and malondiadehyde (MDA) in ryegrass seedling leaves under NaCl stress, SNP also increased the contents of chlorophyll and carotene, net photosynthetic rate (P_n), stomatal conductance(G_s), reduced intercellular carbon dioxide concentration (C_i) and increased relative dry weight of seedlings. The kinetic data of chlorophyll fluorescence revealed that SNP reduced the minimal fluorescence (F₀) of ryegrass seedling leaves under NaCl stress, which indicated that SNP has certain protecting effect on photosynthetic membrane system. SNP could not only significantly raised the maximum fluorescence (F_m), PSⅡ potential fluorescence efficiency (F_v/F₀) and PSⅡ maximum fluorescence efficiency (F_v/F_m) of ryegrass seedling leaves under NaCl stress but also increased the actual photochemical efficiency of PSⅡ (Φ_PSⅡ), photochemical quenching (q_P), electron transport rate (ETR) and photochemical rate (PCR), reduced non photochemical quenching (NPQ) and antennae heat dissipation (D), but were ineffective treated with 1 mmol·L^-1 PTIO(2-phenel-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, a NO scavenger) and 0.5 μmol·L^-1 NaNO₂ (as control). These results suggested that the alleviation of salt damage by exogenous NO may be because of increasing the capacity of antioxidation and the capture and conversion of solar energy help enhance the photosynthetic capacities of ryegrass suffering salt stress.