外源多胺对低氧胁迫下黄瓜幼苗光合特性和膜脂过氧化的影响

以抗低氧能力不同的2个黄瓜(Cucumis sativus)品种为试材, 研究了外源多胺对黄瓜幼苗植株生长、光合特性和膜脂过氧化的影响。结果表明, 外源多胺能显著提高低氧胁迫下黄瓜幼苗叶片的净光合速率和水分利用率, 降低叶片中丙二醛含量和质膜透性, 使幼苗鲜重和干重明显增加。因此在低氧胁迫下, 外源喷施多胺能提高幼苗叶片的净光合速率, 促进植株生长, 缓解胁迫对黄瓜幼苗的伤害。此外, 与抗低氧能力较强的品种绿霸春4号相比, 外源多胺对抗低氧能力较弱的品种中农8号的影响更明显。     

D-精氨酸对低氧胁迫下黄瓜幼苗根系多胺含量和无氧呼吸代谢的影响

采用营养液水培法,研究了根际低氧胁迫下D-精氨酸（D-Arg）对两个抗低氧能力不同的黄瓜品种根系中多胺含量和无氧呼吸代谢的影响.结果表明,低氧处理下,黄瓜幼苗根系中多胺含量显著增加,无氧呼吸代谢能力提高;与抗低氧能力弱的‘中农八号’相比,抗低氧能力强的‘绿霸春四号’根系中乙醇发酵活性较高,乳酸发酵活性较低;低氧胁迫下,D-精氨酸能显著降低黄瓜幼苗根系中腐胺、亚精胺和精胺含量,根系中乙醇脱氢酶（ADH）和乳酸脱氢酶（LDH）活性增加,乙醇和乳酸含量升高,植株生长受到抑制,而外源腐胺能缓解D-精氨酸的这种作用.说明黄瓜幼苗根系中较高的多胺含量可能有利于缓解低氧胁迫对植株造成的伤害.     

外源多胺对低氧胁迫下黄瓜幼苗根系生长及H+-ATP酶和H+-焦磷酸酶活性的影响

采用营养液水培方式,研究了根际低氧胁迫下外源多胺对黄瓜幼苗植株根系生长,内源多胺含量与质膜H -ATP酶、液泡膜H -ATP酶和焦磷酸酶活性的影响.结果表明,根际低氧胁迫显著抑制黄瓜幼苗根系的生长,外源Put(腐胺)和Spd(亚精胺)可缓解低氧胁迫对根系的生长抑制,多胺主要以Spd的形式发挥促进性的生理作用,Put通过转化为Spd发挥作用;低氧胁迫下黄瓜根系内源多胺含量略有提高,外源多胺处理可增加内源多胺的含量;低氧胁迫下外源Put和Spd处理后质膜H -ATP酶活性显著提高,外源多胺对黄瓜根系液胞膜H -ATP酶和H -焦磷酸酶活性没有明显影响,说明低氧胁迫下外源多胺主要通过提高质膜H -ATP酶活性而发挥生理作用.     

外源亚精胺对根际低氧胁迫下黄瓜幼苗根系多胺含量和抗氧化酶活性的影响

采用营养液水培,研究了根际低氧胁迫下外源亚精胺对两个抗低氧能力不同的黄瓜(Cucumis sativus)品种(‘中农8号’和‘绿霸春4号’)根系中多胺含量和超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性的影响。结果表明,外源亚精胺能显著提高低氧胁迫下黄瓜幼苗根系中亚精胺和精胺含量,降低腐胺含量,同时,根系中SOD、POD、CAT活性也相应提高,使得幼苗鲜重和干重明显增加;单纯低氧处理及外源亚精胺的加入,抗低氧能力较强的品种‘绿霸春4号’较抗低氧能力较弱的品种‘中农8号’根系中抗氧化酶活性高。黄瓜幼苗根系中较高的亚精胺、精胺含量和较低的腐胺含量可能有利于提高抗氧化酶活性,增强幼苗的低氧逆境适应能力。     

低氧胁迫下24-表油菜素内酯对黄瓜幼苗叶片光合特性及多胺含量的影响

采用1/2 Hoagland营养液培养,研究了低氧胁迫下24-表油菜素内酯(EBR)对黄瓜幼苗叶片光合特性及多胺含量的影响.结果表明：低氧胁迫下黄瓜幼苗的净光合速率(P_n)、气孔导度(g_s)、蒸腾速率(T_r)、胞间CO₂浓度(C_i)显著下降,而叶绿素含量显著提高,幼苗生长受抑;低氧胁迫显著提高了黄瓜幼苗叶片的腐胺(Put)、亚精胺(Spd)、精胺(Spm)、多胺(PAs)含量和Put/PAs,但降低了(Spd+Spm) /Put.低氧胁迫下,外源EBR不仅显著提高了黄瓜幼苗的P_n、g_s、T_r及叶绿素含量,也显著提高了黄瓜幼苗叶片的游离态Spm、结合态Spd、Spm及束缚态Put、Spd、Spm含量,促进了PAs的进一步积累,且降低了Put/PAs,提高了(Spd+Spm)/Put．可见,外源EBR调节了黄瓜幼苗内源多胺含量及形态的变化,维持了较高的光合性能,促进了叶面积和干物质量的显著增加,缓解了低氧胁迫对黄瓜幼苗的伤害.     

外源亚精胺对低氧胁迫下黄瓜根系多胺含量和呼吸代谢酶活性的影响

采用营养液水培,研究了根际低氧胁迫下外源亚精胺对2个抗低氧能力不同的黄瓜品种(‘中农八号’和‘绿霸春四号’)根系中多胺含量和呼吸代谢相关酶活性的影响.结果表明,单纯低氧处理下,黄瓜幼苗根系中腐胺、亚精胺和精胺含量显著提高,异柠檬酸脱氢酶(IDH)和琥珀酸脱氢酶(SDH)活性显著降低,乳酸脱氢酶(LDH)、乙醇脱氢酶(ADH)和丙酮酸脱羧酶(PDC)活性显著提高.同时,与抗低氧能力弱的‘中农八号’相比,抗低氧能力强的‘绿霸春四号’根系LDH活性增加幅度较低,ADH活性增加幅度较高,IDH和SDH活性降幅也较小;外源亚精胺能显著提高低氧胁迫下黄瓜幼苗根系中亚精胺和精胺含量,降低腐胺含量;根系中LDH、ADH和PDC活性降低,IDH和SDH活性升高,说明黄瓜幼苗根系中较高的亚精胺、精胺含量可能有利于提高根系有氧呼吸能力,缓解低氧胁迫对植株的伤害.     

外源亚精胺对盐胁迫下黄瓜(Cucumis sativus L.)叶绿体活性氧清除系统和结合态多胺含量的影响

采用营养液水培,研究了外源亚精胺(Spd)对NaCl胁迫下抗盐能力不同的两个黄瓜品种幼苗生长、叶绿体中活性氧清除系统、转谷酰胺酶(TGase)活性、结合态多胺含量及植株光合速率的影响.结果表明,外源Spd能提高NaCl胁迫下叶绿体中TGase活性、叶绿体结合态腐胺(Put)、Spd、精胺(Spm)及总多胺含量;提高超氧化物歧化酶(SOD)、抗坏血酸过氧化物酶(APX)和谷胱甘肽还原酶(GR)活性,提高抗坏血酸(AsA)、类胡萝卜素(Car)、还原型谷胱甘肽(GSH)含量及还原型谷胱甘肽/氧化型谷胱甘肽(GSH/ GSSG)比值,降低脱氢抗坏血酸/抗坏血酸(DAsA/AsA)比值;同时显著降低叶绿体过氧化氢(H2O2)和丙二醛(MDA)含量,提高植株净光合速率,缓解NaCl胁迫对幼苗生长的抑制.表明Spd对黄瓜盐害的缓解作用之一可能是通过提高叶绿体结合态多胺含量和叶绿体活性氧清除能力,从而缓解盐胁迫对叶绿体膜的伤害.     

外源腐胺对根际低氧胁迫下黄瓜幼苗多胺和抗氧化系统的影响

采用营养液栽培,研究了外源腐胺(Put)对根际低氧胁迫下黄瓜幼苗体内多胺含量和抗氧化系统的影响.结果显示,低氧胁迫显著刺激了黄瓜幼苗体内活性氧(ROS)和内源多胺含量的增加,提高了抗氧化酶活性;外源Put进一步提高了低氧胁迫下黄瓜幼苗体内多胺的含量和抗氧化酶活性,降低了ROS含量,从而缓解了低氧胁迫的伤害作用;Put合成抑制剂D-精氨酸(D-Arg)不仅显著抑制黄瓜幼苗体内多胺的合成,而且抑制抗氧化酶活性,同时ROS大量积累,进一步抑制黄瓜幼苗的生长;而外源Put可缓解D-Arg的抑制作用;Put转化抑制剂甲基乙二醛-双(脒基腙)(MGBG)和Put降解抑制剂氨基胍(AG)的混合施用造成游离态Put的过量积累,以及亚精胺(Spd)、精胺(Spm)含量和抗氧化酶活性的显著降低,造成ROS大量积累,进一步加重了低氧胁迫对植株的伤害.结果表明,低氧胁迫下外源Put可提高黄瓜幼苗体内游离态Put含量,促进游离态Put向Spd和Spm转化,Spd、Spm含量的增加以及(free-Spd free-Spm)/free-Put比值的升高有利于提高植株抗氧化酶活性,增强清除ROS的能力,降低膜脂过氧化的伤害,从而增强植株的低氧胁迫耐性.     

Ca2+对低氧胁迫下黄瓜幼苗生长和根系无氧呼吸酶的影响

采用营养液水培,以抗低氧能力不同的2个黄瓜品种为试材,研究了Ca2+对黄瓜幼苗植株生长和根系无氧呼吸酶活性的影响.结果表明,在低氧胁迫下,LDH、PDC和ADH活性提高程度与幼苗的抗低氧性和Ca2+浓度密切相关.与抗低氧性较弱的"中农8号"相比,抗低氧性强的"绿霸春4号"幼苗根系LDH活性增加缓慢,而PDC和ADH活性增加幅度较大,因此增强了植株对低氧胁迫的抗性.低氧胁迫下,营养液中8 mmol·L-1 Ca2+处理能显著提高根系ADH活性,降低LDH和PDC活性,0 mmol·L-1 Ca2+处理表现出相反的规律.由此可以说明,低氧胁迫下,Ca2+能够提高ADH活性,降低LDH和PDC活性,可增强黄瓜植株对低氧胁迫的抗性.     

24-表油菜素内酯对低氧胁迫下黄瓜根系抗氧化系统及无氧呼吸酶活性的影响

用营养液水培,研究了根际低氧胁迫下24-表油菜素内酯(EBR)对2个抗低氧能力不同的黄瓜品种根系中抗氧化系统及无氧呼吸酶活性的影响。结果表明,在低氧胁迫下,EBR处理显著提高了低氧胁迫下2品种黄瓜幼苗根系SOD、POD及ADH活性,降低了O2-·、H2O2和MDA含量、LDH活性及‘中农八号’根系PDC活性,而对‘绿霸春四号’根系PDC及2个品种CAT活性无明显影响,表明外源EBR处理通过促进低氧胁迫下根系中抗氧化酶和ADH活性的提高,降低LDH活性及ROS含量,增强植株抗低氧胁迫的能力。     

Exogenous calcium affects nitrogen metabolism in root-zone hypoxia-stressed muskmelon roots and enhances short-term hypoxia tolerance

We investigated the effects of short-term root-zone hypoxic stress and exogenous calcium application or deficiency in an anoxic nutrient solution on nitrogen metabolism in the roots of the muskmelon cultivar Xiyu No. 1. Seedlings grown in the nutrient solution under hypoxic stress for 6 d displayed significantly reduced plant growth and soluble protein concentrations. However, NO₃⁻ uptake rate and activities of nitrate reductase and glutamate synthase were significantly increased. We also found higher amounts of nitrate, ammonium, amino acids, heat-stable proteins, polyamines, H₂O₂, as well as higher polyamine oxidase activity in the roots. In comparison to the reactions seen under hypoxic stress, exogenous calcium application led to a marked increase in plant weights, photosynthesis parameters, NO₃⁻ uptake rate and contents of nitrate, ammonium, amino acids (e.g., glutamic acid, proline, glycine, cystine, γ-aminobutyric acid), soluble and heat-stable proteins, free spermine, and insoluble bound polyamines. Meanwhile, exogenous calcium application resulted in significantly increased activities for nitrate reductase, glutamine synthetase, and glutamate synthase but decreased activities for diamine and polyamine oxidase, as well as lower H₂O₂ content in roots during exposure to hypoxia. However, calcium deficiency in the nutrient solution decreased plant weight, photosynthesis parameters, NO₃⁻ reduction, amino acids (e.g., alanine, aspartic acid, glutamic acid, γ-aminobutyric acid), protein, all polyamines except for free putrescine, and the activities of glutamate synthase and glutamine synthetase. Additionally, there was an increase in the NO₃⁻ uptake rate, polyamine oxidase activity and H₂O₂ contents under hypoxia-Ca. Simultaneously, exogenous calcium had little effect on nitrate absorption and transformation, photosynthetic parameters, and plant growth under normoxic conditions. These results suggest that calcium confers short-term hypoxia tolerance in muskmelon, most likely by promoting nitrate uptake and accelerating its transformation into amino acids, heat-stable proteins or polyamines, as well as by decreasing polyamine degradation in muskmelon seedlings.     

外源亚精胺对盐胁迫下黄瓜幼苗游离态多胺含量和多胺合成酶基因表达的影响

以黄瓜品种‘津春2号’（Cucumis sativusL.cv.Jinchun No.2）为材料,采用营养液栽培,研究了外源亚精胺（Spd）对NaCl胁迫下黄瓜幼苗叶片游离态多胺含量和多胺合成酶基因表达的影响。结果表明,75 mmol/LNaCl胁迫下,幼苗株高、茎粗和干鲜重显著降低,外源喷施1 mmol/L Spd处理可明显缓解盐胁迫对幼苗生长的抑制。盐胁迫下叶片游离态多胺含量显著增加,外源Spd进一步促进了游离态Spd和精胺（Spm）的积累,降低了游离态腐胺（Put）的积累。多胺合成酶基因表达分析表明,盐胁迫上调了adc、odc、samdc和spds基因的表达,施用外源Spd后进一步上调了samdc基因,下调了adc、odc、spds基因的表达。表明外源Spd参与了黄瓜幼苗体内多胺代谢的调节,通过下调盐胁迫下adc、odc基因的表达,抑制游离态Put的积累,上调samdc基因的表达促进游离态Spd和Spm的积累,进而缓解盐胁迫对植物生长的抑制。     

γ-氨基丁酸对低氧胁迫下甜瓜幼苗多胺代谢的影响

以‘西域一号’甜瓜为试验材料,采用营养液水培法,研究了低氧胁迫下外源添加γ-氨基丁酸(GABA)对甜瓜幼苗多胺代谢的影响.结果表明：与通气对照相比,低氧胁迫处理的甜瓜幼苗谷氨酸脱羧酶(GAD)活性和GABA含量显著提高,同时多胺合成酶活性提高诱导多胺含量显著增加,但二胺氧化酶(DAO)和多胺氧化酶(PAO)活性也显著提高;根系精氨酸脱羧酶(ADC)活性提高幅度较大,导致根系游离态腐胺含量较高,而叶片鸟氨酸脱羧酶(ODC)和S-腺苷甲硫氨酸脱羧酶(SAMDC)活性提高幅度较大,导致叶片游离态亚精胺(Spd)含量较高;根系游离态DAO和PAO活性显著低于叶片,其细胞壁结合态PAO活性显著高于叶片.与低氧胁迫处理相比,低氧胁迫下外源添加GABA处理的甜瓜幼苗叶片和根系中GABA和谷氨酸含量均显著提高,而GAD活性显著降低;精氨酸、鸟氨酸、甲硫氨酸含量的提高促使多胺合成酶活性显著提高,从而诱导多胺含量显著增加,DAO和PAO活性显著降低.     

γ-氨基丁酸对低氧胁迫下甜瓜幼苗多胺代谢的影响

以‘西域一号’甜瓜为试验材料,采用营养液水培法,研究了低氧胁迫下外源添加γ-氨基丁酸(GABA)对甜瓜幼苗多胺代谢的影响.结果表明:与通气对照相比,低氧胁迫处理的甜瓜幼苗谷氨酸脱羧酶(GAD)活性和GABA含量显著提高,同时多胺合成酶活性提高诱导多胺含量显著增加,但二胺氧化酶(DAO)和多胺氧化酶(PAO)活性也显著提高;根系精氨酸脱羧酶(ADC)活性提高幅度较大,导致根系游离态腐胺含量较高,而叶片乌氨酸脱羧酶(ODC)和S-腺苷甲硫氨酸脱羧酶(SAMDC)活性提高幅度较大,导致叶片游离态亚精胺(Spd)含量较高;根系游离态DAO和PAO活性显著低于叶片,其细胞壁结合态PAO活性显著高于叶片.与低氧胁迫处理相比,低氧胁迫下外源添加GABA处理的甜瓜幼苗叶片和根系中GABA和谷氨酸含量均显著提高,而GAD活性显著降低;精氨酸、鸟氨酸、甲硫氨酸含量的提高促使多胺合成酶活性显著提高,从而诱导多胺含量显著增加,DAO和PAO活性显著降低.     

Uptake and excretion of polyamines from baby hamster kidney cells (BHK-21/C13) the effect of serum on confluent cell cultures

In confluent cultures of BHK-21/C13 cells there was little uptake oxogenous polyamines and only a low level of polyamine biosynthesis. These cultures continously excreted polyamines into the extracellular medium. Spermidine, in both the free and bound form, was the predominant excretion product, whereas the major intracellular polyamine was spermine implying that excretion of polyamines was specific. Reinitiation of growth by the addition of fresh serum immediately increased the uptake of exogenous putrescine, increased the biosynthesis of polyamines and decreased the excretion of polyamines. Thus, polyamine transport into and out of the cell appears to be regulated by the growth status of that cell.     

Regulation of thyroid ornithine decarboxylase by the polyamines. Induction of a protein inhibitor of ornithine decarboxylase by the end-products of the reaction

When spermidine, putrescine or 1,3-diaminopropane was injected (12.5 mumol/100 g body weight) into rats 1 h before thyrotropin, ornithine decarboxylase activity was increased by 75--150% over control levels. However, when greater than or equal to 75 mumol polyamine/100 g body weight was injected, thyrotropin-activated activity was inhibited by 70--95%. Multiple polyamine injections inhibited goitrogen-induced activity and gland weight increase by approx 35%. The polyamines also inhibited thyrotropin-activated rat thyroid ornithine decarboxylase in vitro in a dose-related fashion, with 50% inhibition occurring at 2--5 . 10(-4)M. The inhibition was not due to a direct effect on the enzyme. No stimulation was seen with low concentrations of polyamine. The polyamines had no effect on in vitro thyroid protein/RNA synthesis or glucose oxidation but had a biphasic effect on plasma membrane adenylate cyclase activity. A protein inhibitor to thyroid ornithine decarboxylase was generated in vivo by multiple injections of the polyamines into rats and in vitro by incubating bovine thyroid slices with 2--10 mM polyamine. The inhibitor was non-dialyzable, destroyed by boiling, and its formation was blocked in a dose-related fashion by cycloheximide. We conclude that: (1) thyroid ornithine decarboxylase is subject not only to positive control, but is also negatively regulated by its end-products, the polyamines, which induce a protein inhibitor to ornithine decarboxylase; (2) since gland growth is also inhibited under these conditions, the polyamine effect on thyroid ornithine decarboxylase may be biologically significant.