外源硫化氢对盐胁迫下加工番茄幼苗光合参数及叶绿素荧光特性的影响

为探究外源硫化氢(H_2S)对盐胁迫下加工番茄幼苗光合作用和光合荧光参数的影响,以耐盐性不同的2个加工番茄KT-7(耐盐性强)和KT-32(耐盐性弱)为材料,采用分光光度法、CIRAS-3型光合仪和Imaging-PAM调制荧光成像系统分别测定光合色素含量、光合参数和叶绿素荧光参数。结果表明,外源H_2S提高了盐胁迫下加工番茄幼苗的生长及叶绿素a、叶绿素b、胡萝卜素含量、净光合速率(P_n)、气孔导度(G_s)、叶片蒸腾速率(Tr)、PSⅡ最大光化学效率(F_v/F_m)和PSⅡ实际光化学效率(ΦPSⅡ);降低了胞间CO_2浓度(Ci)、PSⅡ调节性能量耗散的量子产额[Y(NPQ)]和非光化学猝灭系数(NPQ);而PSⅡ非调节性能量耗散的量子产额[Y(NO)]稳定在较低水平。此外,外源H_2S对KT-32的缓解效应强于KT-7。综上所述,外源H_2S通过提高加工番茄幼苗叶片的光合色素量和光合电子传递效率,有效地缓解盐胁迫对加工番茄叶片PSⅡ的伤害。本研究结果为探究外源H_2S增强加工番茄耐盐性研究提供了科学依据。     

高温强光下Ca2+对西葫芦幼苗膜质过氧化、抗氧化酶系统及热耗散的影响

为探明不同浓度外源Ca2+对高温强光胁迫下西葫芦植株幼苗的影响,本试验选用西葫芦(Cucurbitapepo L.)品种"阿兰一代"为试验材料,通过外源喷施不同浓度CaCl2溶液,研究了Ca2+对高温强光胁迫下西葫芦幼苗叶绿素荧光特性、膜质过氧化及抗氧化酶系统的影响。结果表明,较低浓度Ca2+处理(5~20 mmol.L 1)可有效提高高温强光下西葫芦幼苗超氧化物歧化酶(SOD)、过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)和过氧化氢酶(CAT)活性,降低丙二醛(MDA)、过氧化氢(H2O2)、超氧阴离子自由基(O2&)含量和膜透性,还原型谷胱甘肽(GSH)含量升高;同时西葫芦叶片PSII的最大光化学效率(Fv/Fm)、PSⅡ实际光化学效率(ΦPSⅡ)和光化学猝灭系数(qP)较高,而非光化学猝灭系数(NPQ)较低。说明5~20 mmol.L 1Ca2+处理对高温强光胁迫具有明显的缓解作用,同时其热耗散较小。当Ca2+处理浓度超过40 mmol.L 1时对高温强光胁迫缓解效应不明显。     

外源NO对NaCl胁迫下山葡萄叶片叶绿素荧光和抗氧化酶活性的影响

为探究NO对山葡萄耐盐性影响的生理机制,以1年生双丰山葡萄扦插苗为试材,采用营养液栽培方法,研究了外源NO供体硝普钠(SNP)处理对50 mmol·L-1 NaCl胁迫下山葡萄叶片叶绿素含量、叶绿素荧光参数和抗氧化酶活性的影响.结果表明,外源NO能显著提升盐胁迫下山葡萄叶片超氧化物歧化酶(SOD)和抗坏血酸过氧化物酶(APX)活性,减少丙二醛(MDA)的产生和积累,保护光合机构免受活性氧伤害,从而提高叶片叶绿素含量;另一方面,外源NO使盐胁迫下山葡萄叶片的PSⅡ最大光化学效率(Fv/Fm)、PSⅡ实际光化学效率(ΦPSⅡ)、光化学淬灭系数(qP)和保护性热耗散(ΦNPQ)升高,而初始荧光(Fo)和非调节性能量耗散(ΦNO)显著下降,表明外源NO通过保护性热耗散机制缓解盐胁迫引起的光抑制,增强光合电子传递效率,进而维持PSⅡ的正常功能,最终提高了山葡萄耐盐性.     

水杨酸对菊芋耐高氯酸盐胁迫的影响

为探究ClO_4~-胁迫下外源水杨酸(salicylic acid, SA)对菊芋(Helianthus tuberosus L.)的生理调节作用,以徐州、潍坊和南京3个不同产地耐盐菊芋为试材,进行液培处理,研究NaClO_4胁迫条件下(50 mmol/L),SA不同时间间隔喷施处理对菊芋幼苗的形态学指标、根系活力和光合作用及抗氧化能力的影响。结果表明,ClO_4~-对菊芋幼苗的生长发育可产生不同程度的毒害作用,喷施SA可有效减轻其对植株的胁迫损伤,且不同产地菊芋的变化趋势相似,植物鲜重、叶面积、株高和根长明显改善,叶片中叶绿素含量及荧光参数显著升高,且每天喷施缓解效果最大;而根系活力在间隔1天喷施效果最佳。同时,H_2O_2含量呈现出随SA喷施频率的增加而上升趋势,当喷施间隔为2天时,平均增加47.69%,喷施间隔为1天时平均增量为50.93%,每天喷施时平均增幅达到最大值56.80%;且超氧化物岐化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)的活力得到提高,丙二醛(MDA)及游离脯氨酸含量显著降低(P0.05)。表明SA可通过诱导H_2O_2作为信号分子增强植株耐受ClO_4~-的能力。通过灰色关联度分析可知,喷施SA对ClO_4~-胁迫下叶绿素荧光参数和根系活力影响最大。综上所述,叶面喷施50μmmol/L SA主要是通过影响菊芋叶片和根系,激发H_2O_2调控抗氧化酶活性的变化,参与体内渗透调节来保护植株光合系统和根系活力,降低ClO_4~-胁迫对菊芋的伤害,且每天喷施处理的缓解效果最佳,这为菊芋在ClO_4~-污染土壤中的栽培提供理论指导。     

外源NO对酸枣幼苗抗盐性的影响

探讨外施NO减轻NaCl逆境对酸枣植株伤害的生理生态效应,旨在为深入认识NO增强植株的抗逆性及其在酸枣绿色栽培生产上的应用提供科学依据。采用营养液培养方法,设置对照(T1)、0.1mmol/L SNP(T2)、100mmol/L NaCl(T3)、0.1mmol/L SNP+100mmol/L NaCl(T4)4个处理组,研究外施NO对NaCl盐害下酸枣(Zizyphus jujuba Mill)多胺、谷胱甘肽抗氧化酶系统及叶绿素荧光特性的作用。结果表明:100mmol/L NaCl盐害处理抑制了酸枣植株的长势,施加NO明显缓解了NaCl逆境对酸枣植株生长的毒害,外源NO使腐胺(Put)、多胺(PAs)、精胺(Spm)、亚精胺(Spd)含量呈持续上升趋势,提高了叶片还原型谷胱甘肽(GSH)含量、谷胱甘肽还原酶(GR)活性及GSH/GSSG比值,而氧化型谷胱甘肽(GSSG)总量略有下降,谷胱甘肽-S-转移酶(GST)的活性、抗坏血酸(ASA)的总量以及抗坏血酸过氧化物酶(APX)的活性均上升。同时,NO处理亦显著增强了酸枣植株的PSⅡ最大光化学效率(Fv/Fm)、PSⅡ潜在活性(Fv/Fo)、表观光合电子传递速率(ETR)、实际光化学效率(ΦPSⅡ)和光化学荧光猝灭系数(qP),而非光化学荧光猝灭系数(qN)出现下降。施用外源NO通过提高NaCl逆境下幼苗游离态多胺含量,同时增强抗氧化酶活性和非酶抗氧化物质含量,减少光抑制现象,保证摄入光能的合理利用,进而减轻NaCl逆境对酸枣幼苗生长的毒害,提高植株的耐盐性。     

外源水杨酸和一氧化氮对盐胁迫番茄幼苗光系统Ⅱ功能及激发能分配利用的影响

【目的】 为了探明外源水杨酸 (SA) 和一氧化氮 (NO) 协同缓解番茄幼苗盐渍伤害的光合生理机制。 【方法】 以番茄品种‘秦丰保冠’为试材,在水培条件下,研究单独和复配施用外源SA、NO供体硝普钠 (SNP) 对100 mmol/L NaCl胁迫下番茄幼苗气体交换、光系统Ⅱ (PSⅡ) 光化学效率、激发能分配和天线色素吸收光能利用的影响。 【结果】 SA、SNP单独和复配处理均能有效缓解NaCl胁迫对PSⅡ的损伤,其中以SA和SNP复配处理效果最好,3～7 d番茄叶片净光合速率 (P_n)、PSⅡ最大光化学效率 (F_v/F_m)、天线转化效率 (F_v′/F_m′)、光化学荧光猝灭系数 (qP)、吸收光能用于进行光化学反应的份额 (P) 和叶绿素荧光衰减率 (R_fd) 分别较胁迫处理显著提高了25.5%～94.9%、9.5%～15.3%、25.7%～34.6%、38.8%～121.9%、74.2%～198.6%和22.2%～25.5%;初始荧光 (F_o)、PSⅡ非光化学荧光猝灭系数 (NPQ)、激发能压力 (1-qP)、反应中心非光化学耗散的份额 (E_x)、天线热耗散的份额 (D) 和双光系统间激发能分配不平衡偏离系数 (β/α-1) 分别较胁迫处理不同程度降低了19.8%～23.5%、22.8%～23.4%、32.5%～39.9%、15.1%～19.1%、27.8%～31.4%和51.8%～72.8%。 【结论】 外源SA和NO在保护PSⅡ及光合电传递链免受盐害损伤,提高番茄幼苗耐盐性方面具有协同增效作用。      

强光胁迫下外源NO对霍山石斛叶绿素荧光的影响

以兼性景天酸代谢CAM植物霍山石斛为材料,研究了强光胁迫条件下,外源一氧化氮(NO)对霍山石斛叶绿素荧光参数的影响。结果表明:在强光胁迫下,0.1mmol/L硝普钠(SNP,NO供体)处理显著缓解强光对霍山石斛光合系统Ⅱ(PSⅡ)的抑制,霍山石斛PSⅡ荧光参数潜在光化学效率(Fv/Fm)、实际光化学效率(ΦPSⅡ)、光化学猝灭系数qL、非光化学猝灭系数NPQ和ΦNPQ下降缓慢,且非光化学猝灭系数ΦNO值较低,PSⅡ反应中心恢复较快,说明该处理缓解了光抑制的发生,保护了光合机构免受强光胁迫的伤害,而经0.5mmol/L SNP处理后,霍山石斛的Fv/Fm、ΦpsⅡ、qL、NPQ和ΦNPQ下降程度增加,ΦNO也较高,恢复较慢,表明该处理加剧了PSⅡ反应中心光抑制的发生。可见,高浓度(0.5mmol/L)SNP处理可加剧光抑制的发生,而低浓度(0.1mmol/L)SNP处理可缓解强光对石斛的胁迫作用。     

外源NO对Ca(NO_3)_2胁迫下番茄幼苗PSII功能及光能分配利用的影响

为探讨外源NO缓解番茄幼苗次生盐渍伤害的光合生理机制,以秦丰保冠番茄幼苗为试材,在水培条件下,利用叶绿素荧光动力学技术研究喷施NO供体硝普钠(SNP)对80 mmol·L-1Ca(NO_3)_2胁迫下番茄幼苗PSII光化学效率、激发能分配和天线色素吸收光能利用的影响。结果表明,喷施SNP有效缓解了Ca(NO_3)_2胁迫对PSII的损伤,使第15天番茄幼苗叶片的PSII最大光化学效率(F_v/F_m)、天线转化效率(F_v'/F_m')、实际光化学效率(ΦPSII)、光化学荧光猝灭系数(q P)及吸收光能用于进行光化学反应(P)和非光化学耗散(Ex)的份额分别较胁迫处理显著提高了4.93%、39.31%、92.84%、39.00%、92.83%和10.33%;初始荧光(Fo)、非光化学荧光猝灭系数(NPQ)、双光系统间激发能分配不平衡偏离系数(β/α-1)和天线热耗散的份额(D)分别较胁迫处理显著降低了7.20%、13.22%、43.09%和24.70%。综上,外源NO能通过改善PSII光化学活性和增强PSII反应中心的非光化学耗散减轻Ca(NO_3)_2胁迫造成的光抑制,进而提高番茄幼苗的耐盐能力。本研究结果为利用外源NO缓解蔬菜设施生产的次生盐渍障碍提供了理论和技术依据。     

外源一氧化氮对NaCl胁迫下番茄幼苗叶绿素荧光特性的影响

通过水培试验, 研究了外源NO供体硝普钠(SNP)处理对100 mmol·L-1 NaCl胁迫下番茄幼苗叶绿素荧光特性的影响.结果表明, 外源NO提高了盐胁迫下番茄幼苗叶片的最大荧光(Fm)、PSⅡ最大光化学效率(Fv/Fm)、PSⅡ潜在活性(Fv/Fo)、表观光合电子传递速率(ETR)、实际光化学效率(ΦPSⅡ)、光化学荧光猝灭系数(qP)和光化学速率(Prate), 降低了初始荧光(Fo)、非光化学荧光猝灭系数(qN)、天线热耗散速率(Drate)和PSⅡ激发能压力(1-qP), 同时降低了激发能在两个光系统间的分配不平衡性.表明外源NO通过减少过剩激发能的耗散, 提高光合电子传递效率, 可有效缓解盐胁迫对番茄PSⅡ系统的伤害, 进而在缓解盐胁迫中发挥重要作用.     

土壤相对含水量对不同茬口番茄叶片PSⅡ光化学活性和光能分配影响

为探明不同茬口番茄光合特性对土壤水分响应机制,采用盆栽方式研究50%、65%和80%土壤水分处理对冬春两茬番茄叶片PSⅡ光化学活性和光能分配的影响。结果表明,随着土壤相对含水量减少,春茬番茄叶片的叶绿素含量下降,电解质渗透率增加,叶片最大光化学效率(F_v/F_m)、实际光化学效率(ΦPSⅡ)、电子传递速率(ETR)、光化学猝灭系数(q P)和吸收光能用于进行光化学反应份额(P)降低,非光化学猝灭(NPQ)、双光系统间激发能分配不平衡偏离系数(β/α-1)、天线热耗散份额(D)和非光化学猝灭量子产量[Y(NO)]显著升高,表明叶片用于PSⅡ反应中心的光化学活性降低,用于非化学反应的能量增加,叶片发生光抑制和光损伤程度增加,且与水分亏缺程度呈显著正相关,春茬番茄以80%土壤含水量表现较好。冬茬番茄以50%水分处理的F_v/F_m、ΦPSⅡ、ETR、q P和P较低,但生长中后期时,65%水分处理的F_v/F_m、ΦPSⅡ、ETR、q P和P却显著高于80%处理,与充足供水相比,轻度水分胁迫下的番茄叶片的光抑制发生程度较轻。综上可知,春茬番茄以80%水分处理的叶片光化学活性较高,而冬茬番茄以65%水分处理表现较好。本研究结果为不同茬口番茄生产的合理灌溉提供了理论依据。     

碳酸氧镧改性生物炭材料的合成及对磷酸盐去除性能

为高效去除废水中过量的磷酸盐为目的，该研究将研究利用艾草生物质与镧溶液共生共热的方法制成具有大量纳米级碳酸氧镧突起的镧基复合生物炭材料，研究了材料投加量、初始磷酸盐浓度、吸附时间、初始溶液pH值和共存离子对其吸附磷酸盐性能的影响及饱和磷吸附镧基复合生物炭材料（La-CB2-P）对生菜种子发芽率的试验。试验结果表明：La-CB2最佳投加量为1 g/L，最佳吸附温度为25 ℃，对磷酸盐的吸附主要为多分子层吸附，Langmuir模型模拟最大吸附容量为126.82 mg/g，并在12h内达到吸附平衡，酸性至中性水环境中La-CB2吸附性能更优，并对碱性水环境的pH值具有缓冲作用，在pH值为3时La³⁺浸出率为7.66%，其他pH值条件下仅为0.029%左右，在磷吸附过程中La-CB2的DOC溶出量随着初始溶液pH值的升高呈先增后减的趋势，在多种共存阴离子中对磷酸盐具有很强的选择性吸附，水体中的腐殖酸会大幅度降低La-CB2对磷酸盐的吸附性能。饱和磷吸附镧基复合生物炭材料（La-CB2-P）能够作为磷缓释肥显著促进生菜发芽，对La-CB2在富营养水体的磷吸附及资源回收提供了大量的理论基础。     

模拟干旱和盐碱胁迫对碱蓬、盐地碱蓬种子萌发的影响

为研究干旱和盐碱胁迫对碱蓬(Suaeda glauca)、盐地碱蓬(Suaeda salsa)种子萌发的影响,比较碱蓬和盐地碱蓬逆境生理特性的异同,本研究利用PEG6000、NaCl和Na_2CO_3分别模拟干旱、盐和碱胁迫,配制相同渗透势的PEG6000、NaCl、Na_2CO_3处理液,以蒸馏水处理为对照,对碱蓬、盐地碱蓬种子的萌发与胚的生长进行比较研究。结果表明:1)低渗处理(-0.46 MPa)对碱蓬、盐地碱蓬种子的萌发无显著影响;高渗处理(-1.38MPa、-1.84 MPa)抑制碱蓬、盐地碱蓬种子的萌发。2)当溶液渗透势相等时,NaCl处理下碱蓬种子的萌发率显著大于PEG、Na_2CO_3处理;而等渗PEG、NaCl、Na_2CO_3处理对盐地碱蓬种子萌发率的影响无显著差异。3)PEG、NaCl、Na_2CO_3处理组碱蓬、盐地碱蓬种子的最终萌发率与对照无显著差异。4)在幼苗形成阶段,PEG、Na_2CO_3处理对碱蓬、盐地碱蓬胚的抑制作用显著大于等渗NaCl处理。5)碱蓬、盐地碱蓬胚的生长对NaCl、Na_2CO_3胁迫的响应存在差异。-0.92 MPa NaCl处理抑制碱蓬胚的生长,却对盐地碱蓬产生促进作用;-0.46 MPa Na_2CO_3处理对碱蓬胚的抑制作用小于盐地碱蓬。综合分析表明:碱蓬、盐地碱蓬均具有很强的抗盐性。在种子萌发阶段,碱蓬种子的抗旱、抗碱能力低于盐地碱蓬;在幼苗形成阶段,碱蓬胚的抗盐性小于盐地碱蓬,但对轻度碱胁迫的抗性高于盐地碱蓬。     

土壤团聚体N_2O释放与反硝化微生物丰度和组成的关系

不同粒径团聚体的物理化学和生物学特性差异可能影响N2O的产生与释放,但目前有关团聚体N2O释放的微生物学机制少有研究。本研究从菜地土壤中分筛出粒径为1 mm、2~4 mm和4~8 mm的团聚体并开展培养试验,通过实时荧光定量PCR(Quantitative Polymerase Chain Reaction,q PCR)与末端限制性片段长度多态性分析(Terminal-Restricted Fragment Length Polymorphism,T-RFLP)技术的结合,研究了不同粒径团聚体反硝化微生物群落数量与组成的变化规律及其与N2O释放的相互关系。结果表明,不同粒径团聚体N2O释放速率表现为:粒径小于1 mm团聚体2~4 mm团聚体4~8 mm团聚体;硝酸还原酶基因(nar G)和氧化亚氮还原酶基因(nos Z)的丰度也表现为小粒径团聚体最高,随团聚体粒径增加而显著下降。然而,不同粒径团聚体间含nar G和nos Z基因的群落组成并没表现出显著差异。因此,不同粒径团聚体N2O释放速率差异与反硝化功能微生物丰度密切相关,而与它们的组成没有显著相关性。     

CO2浓度升高对三江平原湿地小叶章碳氮含量的影响

利用开顶箱薰气室(open-top chamber),设置正常大气CO2浓度和高CO2浓度(700 μmol/mol)2个水平和不施氮(NN,0 g/m2)、常氮(MN,5 g/m2)和高氮(HN,15 g/m2)3个氮素水平,研究CO2浓度升高对三江平原草甸小叶章碳氮积累的影响.结果表明,CO2浓度升高条件下小叶章植株总固碳量增加,不同氮水平下小叶章总固碳量分别增加19.3％(NN),24.4％(MN)和24.6％(HN),且根固定碳量占植株总体碳库比例均有不同程度的提高.CO2浓度升高降低了小叶章各器官氮含量,其中叶、茎氮含量以抽穗期降幅最大(14.4％和19.5％),根氮含量以腊熟期降幅最大(17.4％).小叶章各器官N含量的降低是由于CO2浓度升高条件下植株生长加快引起的稀释效应所致.     

Elevated CO2 concentration and nitrogen fertilisation effects on N2O and CH4 fluxes and biomass production of Phleum pratense on farmed peat soil

The effects of elevated CO₂ supply on N₂O and CH₄ fluxes and biomass production of Phleum pratense were studied in a greenhouse experiment. Three sets of 12 farmed peat soil mesocosms (10 cm dia, 47 cm long) sown with P. pratense and equally distributed in four thermo-controlled greenhouses were fertilised with a commercial fertiliser in order to add 2, 6 or 10 g N m⁻². In two of the greenhouses, CO₂ concentration was kept at atmospheric concentration (360 μmol mol⁻¹) and in the other two at doubled concentration (720 μmol mol⁻¹). Soil temperature was kept at 15 °C and air temperature at 20 °C. Natural lighting was supported by artificial light and deionized water was used to regulate soil moisture. Forage was harvested and the plants fertilised three times during the basic experiment, followed by an extra fertilisations and harvests. At the end of the experiment CH₄ production and CH₄ oxidation potentials were determined; roots were collected and the biomass was determined. From the three first harvests the amount of total N in the aboveground biomass was determined. N₂O and CH₄ exchange was monitored using a closed chamber technique and a gas chromatograph. The highest N₂O fluxes (on average, 255 μg N₂O m⁻² h⁻¹ during period IV) occurred just after fertilisation at high water contents, and especially at the beginning of the growing season (on average, 490 μg N₂O m⁻² h⁻¹ during period I) when the competition of vegetation for N was low. CH₄ fluxes were negligible throughout the experiment, and for all treatments the production and oxidation potentials of CH₄ were inconsequential. Especially at the highest rates of fertilisation, the elevated supply of CO₂ increased above- and below-ground biomass production, but both at the highest and lowest rates of fertilisation, decreased the total amount of N in the aboveground dry biomass. N₂O fluxes tended to be higher under doubled CO₂ concentrations, indicating that increasing atmospheric CO₂ concentration may affect N and C dynamics in farmed peat soil.     

Elevated CO2 stimulates N2O emissions in permanent grassland

To evaluate climate forcing under increasing atmospheric CO₂ concentrations, feedback effects on greenhouse gases such as nitrous oxide (N₂O) with a high global warming potential should be taken into account. This requires long-term N₂O flux measurements because responses to elevated CO₂ may vary throughout annual courses. Here, we present an almost 9 year long continuous N₂O flux data set from a free air carbon dioxide enrichment (FACE) study on an old, N-limited temperate grassland. Prior to the FACE start, N₂O emissions were not different between plots that were later under ambient (A) and elevated (E) CO₂ treatments, respectively. However, over the entire experimental period (May 1998–December 2006), N₂O emissions more than doubled under elevated CO₂ (0.90 vs. 2.07 kg N₂O-N ha⁻¹ y⁻¹ under A and E, respectively). The strongest stimulation occurred during vegetative growth periods in the summer when soil mineral N concentrations were low. This was surprising because based on literature we had expected the highest stimulation of N₂O emissions due to elevated CO₂ when mineral N concentrations were above background values (e.g. shortly after N application in spring). N₂O emissions under elevated CO₂ were moderately stimulated during late autumn–winter, including freeze–thaw cycles which occurred in the 8th winter of the experiment. Averaged over the entire experiment, the additional N₂O emissions caused by elevated CO₂ equaled 4738 kg CO₂-equivalents ha⁻¹, corresponding to more than half a ton (546 kg) of CO₂ ha⁻¹ which has to be sequestered annually to balance the CO₂-induced N₂O emissions. Without a concomitant increase in C sequestration under rising atmospheric CO₂ concentrations, temperate grasslands may be converted into greenhouse gas sources by a positive feedback on N₂O emissions. Our results underline the need to include continuous N₂O flux measurements in ecosystem-scale CO₂ enrichment experiments.     

不同参数超临界CO2处理对乳酸菌活性的影响

为了研究超临界CO₂作为非水相介质在生化反应工程中的作用，有必要考察超临界CO₂处理对微生物活性的影响。本文以乳酸杆菌为试验菌种，进行了该菌在不同参数超临界CO₂处理对菌体生长曲线、耐渗透压能力、耐酸能力、抑菌能力、降解胆固醇能力等活性指标影响的研究。结果表明：当提高超临界CO₂压强或延长超临界CO₂处理时间，乳酸杆菌的活性指标会发生如下变化：生长曲线的最大菌体浓度降低，但菌体的生长速率差异不大；菌体的耐渗透能力、耐酸能力降低；所得的抑菌圈比较明显，但抑菌圈直径减小；平均胆固醇降解率降低，而且长时间处理对降解效果的影响比高压强处理的明显。因此，在工程应用中需要研究一定的弥补措施。     

A new technique to measure soil CO2 efflux at constant CO2 concentration

A new principle for measuring soil CO₂ efflux at constant ambient concentration is introduced. The measuring principle relies on the continuous absorption of CO₂ within the system to achieve a constant CO₂ concentration inside the soil chamber at ambient level, thus balancing the amount of CO₂ entering the soil chamber by diffusion from the soil. We report results that show reliable soil CO₂ efflux measurements with the new system. The novel measuring principle does not disturb the natural gradient of CO₂ within the soil, while allowing for continuous capture of the CO₂ released from the soil. It therefore holds great potential for application in simultaneous measurements of soil CO₂ efflux and its δ¹³C, since both variables show sensitivity to a distortion of the soil CO₂ profile commonly found in conventional chamber techniques.     

Relationship between soil CO2 concentrations and forest-floor CO2 effluxes

To better understand the biotic and abiotic factors that control soil CO₂ efflux, we compared seasonal and diurnal variations in simultaneously measured forest-floor CO₂ effluxes and soil CO₂ concentration profiles in a 54-year-old Douglas fir forest on the east coast of Vancouver Island. We used small solid-state infrared CO₂ sensors for long-term continuous real-time measurement of CO₂ concentrations at different depths, and measured half-hourly soil CO₂ effluxes with an automated non-steady-state chamber. We describe a simple steady-state method to measure CO₂ diffusivity in undisturbed soil cores. The method accounts for the CO₂ production in the soil and uses an analytical solution to the diffusion equation. The diffusivity was related to air-filled porosity by a power law function, which was independent of soil depth. CO₂ concentration at all depths increased with increase in soil temperature, likely due to a rise in CO₂ production, and with increase in soil water content due to decreased diffusivity or increased CO₂ production or both. It also increased with soil depth reaching almost 10 mmol mol⁻¹ at the 50-cm depth. Annually, soil CO₂ efflux was best described by an exponential function of soil temperature at the 5-cm depth, with the reference efflux at 10 °C (F₁₀) of 2.6 μmol m⁻² s⁻¹ and the Q₁₀ of 3.7. No evidence of displacement of CO₂-rich soil air with rain was observed.Effluxes calculated from soil CO₂ concentration gradients near the surface closely agreed with the measured effluxes. Calculations indicated that more than 75% of the soil CO₂ efflux originated in the top 20 cm soil. Calculated CO₂ production varied with soil temperature, soil water content and season, and when scaled to 10 °C also showed some diurnal variation. Soil CO₂ efflux and concentrations as well as soil temperature at the 5-cm depth varied in phase. Changes in CO₂ storage in the 0–50 cm soil layer were an order of magnitude smaller than measured effluxes. Soil CO₂ efflux was proportional to CO₂ concentration at the 50-cm depth with the slope determined by soil water content, which was consistent with a simple steady-state analytical model of diffusive transport of CO₂ in the soil. The latter proved successful in calculating effluxes during 2004.