Autoregulation and Nitrate Inhibition of Nodule Formation in Soybean cv. Enrei and its Nodulation Mutants

The regulation and nitrate inhibition of nodule formation insoybean, Glycine max (L.) Merr., was further examined usingthe nodulation mutants of cv. Enrei. The non-nodulating mutantsEn115, Enl282, and En1314 produced extremely few markedly-curledroot hairs which were all devoid of infection threads, and invariablyfailed to initiate sub-epidermal cell divisions (SCDs) in theroot cortex. A considerable number of arrested SCDs was foundbefore nodule emergence in Enrei, but not in En6500 which hadsignificantly more SCDs that progressively increased at moreadvanced stages of nodule ontogeny. These observations indicatethat autoregulation acts by blocking the developmental stagebefore nodule emergence. In both Enrei and En65OO, the maturationof emerged nodules was restricted by a late-acting nodulationcontrol mechanism that is apparently unrelated to autoregulation.Reciprocal wedge-grafts of plants inoculated at sowing showedthat the control of the supernodulating phenotype resides inthe shoot, while the non-nodulating phenotype is strictly root-controlled.The nodulation phenotype of the current non-nodulating mutantsresults not from an alteration of the autoregulatory mechanism,but from mutation that exerts a root-localized effect that blocksSCDs which trigger the autoregulatory mechanism. Reciprocalgrafting experiments on Enrei and En6500 seedlings grown undervarious nitrate levels suggest that nitrate inhibition of nodulation,like autoregulation, is shoot-controlled. Since these two processesare invariably expressed together, they are probably causallyrelated, acting synergistically to regulate nodule formationin soybean. These results indicate that the regulation and nitrateinhibition of nodulation in the nodulation mutants of cv. Enreiare similar to those of cv. Bragg nodulation mutants. Key words: Autoregulation, nitrate-tolerant symbosis, non-nodulating mutants, soybean, supernodulating mutant     

水分胁迫下山黧豆多胺代谢与β_N_草酰_L_α,β_二氨基丙酸积累相关性的研究

Seedlings of grass pea (Lathyrus sativus L.) were treated with polyethylene glycol (PEG), in addition with putrescine (Put) and α-difluoromethylarginine (DFMA) in order to study the relation between polyamine metabolism and accumulation of β-N-oxalyl-L-α, β-diaminopropionic acid (ODAP) under water stress. The results indicated that Put, spermidine (Spd) and spermine (Spm) contents of leaves gradually increased along with the extension of PEG-treatment time. Especially, the increase in Spm contents was significant together with a gradual increase of ODAP contents. Put and Spd contents of leaves markedly increased along with the extension of PEG+Put treatment time. There was little effect on Spm contents and ODAP contents in leaves with PEG+Put treatment. The accumulation of Put, Spd, Spm and ODAP in leaves was inhibited by PEG+DFMA treatment. The inhibition of DFMA for Put and Spd biosynthesis was partially overcome by adding exogenous Put, but little effect for the inhibition of DFMA on Spm biosynthesis by adding exogenous Put. The accumulation of ODAP was inhibited with PEG+DFMA+Put treatment in leaves. This indicated that there was a relationship between the increase of Spm contents and the accumulation of ODAP in leaves under water stress.     

Stress-dependent accumulation of spermidine and spermine in the halophyte Mesembryanthemum crystallinum under salinity conditions

We studied the effects of chloride salinity (300 and 500 mM NaCl) on the content of free polyamines (PAs) from putrescine (Put) family in Mesembryanthemum crystallinum L. leaves and roots. The contents of Put and spermidine (Spd) in leaves increased temporarily, achieving the highest values on the third day of salinity treatment; thereafter (by days 7–14), they dropped sharply. The content of spermine (Spm) increased gradually, and its high level was maintained until the end of experiment. The dynamics of Spm accumulation in leaves under salinity conditions resembled that of phosphoenolpyruvate carboxylase (PEPC), a key enzyme of the water-saving CAM pathway of photosynthesis. This indicates indirectly the involvement of Spm in the common ice plant adaptation to salinity. A decrease in the molar ratios of Spd to Spm in the leaves under salinity conditions could point to the acceleration of Spm biosynthesis (accumulation) during plant adaptation, whereas the levels of Spm precursors, Put and Spd, did not increase. This phenomenon could be explained by an accelerated conversion of Spd into Spm, an active liberation of free Spm from its conjugates, or changes in the rates of studied PA biosynthesis and degradation under salinity. At the same time, the intracellular concentration of ethylene rose under these conditions. It was supposed and then demonstrated, that the pathway of ethylene biosynthesis and that of the synthesis of Put family PAs compete under severe salinity conditions. This competition might be based on the disturbances in sulfur metabolism and a decrease in the methionine content, an immediate precursor of S-adenosyl-L-methionine.     

NaCl胁迫对结荚期菜用大豆叶片游离态多胺水平的影响

采用蛭石栽培,在100mmol·L-1NaCl胁迫下,对耐盐性不同的2个菜用大豆[Glycinemax(L.)Merr.]品种结荚期干物质积累、单株产量及叶片游离态多胺(PAs)水平的变化进行了研究。结果表明:NaCl胁迫显著降低了菜用大豆植株干重及单株产量,但耐盐品种"绿领特早"的降幅低于盐敏感品种"理想高产95-1";与"理想高产95-1"相比,"绿领特早"叶片在整个NaCl胁迫期间均维持了相对较低的H2O2含量、游离态腐胺(Put)含量及较高的游离态亚精胺(Spd)含量,在胁迫6～15d期间维持了相对较高的游离态精胺(Spm)含量、(Spd+Spm)/Put值及较低的Put/PAs值。说明耐盐品种"绿领特早"叶片具有较强的由游离态Put向游离态Spd和Spm转化的能力,维持了较低的游离态Put含量和较高的游离态Spd及Spm含量,进而抑制了活性氧过量积累。     

水分胁迫对小麦幼苗叶片多胺含量的影响

水分胁迫下小麦幼苗叶片多胺含量变化的研究表明,聚乙二醇(PEG)的渗透胁迫明显提高了抗旱性强的周麦系列幼苗叶片游离态Put、Spd和Spm的含量和抗旱性弱的温麦6号的Put含量。外源Spd显著提高了水分胁迫下温麦6号的Spd的含量,对其抗性也有所改善。外源MGBG(Spd和Spm生物合成抑制剂)可提高水分胁迫下周麦12号Put的含量,但降低了Spd和Spm的含量和幼苗的抗性。     

水稻细胞质雄性不育系及其保持系幼穗发育过程中的多胺代谢

在幼穗发育过程中,不育系和保持系幼穗多胺含量先剧降后稳定或略回升,精氨酸脱羧酶活性快速下降,而二胶和多胺氧化酶活性缓慢下降。从雌雄蕊形成期到花粉母细胞形成期,不育系的多胺含量和精氨酸脱羧酶活性明显低于保持系;不过,两系二胺氧化酶和多胺氧化酶活性却差别不大。外施D-Arg抑制两系Put合成,也抑制以Put为前体的Spd的合成;外施MGBG抑制Spd和Spm的合成;同时,D-Arg或MGBG对不育系花粉育性影响不大,但明显降低保持系花粉育性,D-Arg＋MGBG对花粉育性的降低效应更强;Put和pd＋Spm可抵消（或部分抵消）D-Arg和MGBG的降低效应。且Put＋Spd＋Spm能使不育系花粉的育性得以轻度恢复。     

氯化钠胁迫对南瓜根系游离态多胺含量和活性氧水平的影响

以中国南瓜杂交种‘360.3×112.2’和黑籽南瓜为试验材料,在营养液栽培条件下研究了NaCl胁迫对两种南瓜植株生长、根系活性氧水平和游离态多胺含量的影响.结果表明,NaCl胁迫10 d后,与对照相比,两种南瓜植株生长都受到明显抑制,但中国南瓜杂交种比黑籽南瓜植株的耐盐性强.NaCl胁迫使南瓜根系O₂^-·产生速率和H₂O₂含量提高,且黑籽南瓜的O₂^-·产生速率和H₂O₂含量高于中国南瓜杂交种.两种南瓜根系中腐胺(Put)、亚精胺(Spd)、精胺(Spm)和多胺(PAs)含量及Put/PAs高于对照,并呈现先升后降的趋势;根系中（Spd+Spm）/Put低于对照,呈现先降后升的趋势.中国南瓜杂交种根系中Put含量和Put/PAs低于黑籽南瓜,而Spd、Spm含量和（Spd+Spm）/Put高于黑籽南瓜.表明两种南瓜根系中多胺含量的升高对减少或清除组织中的活性氧有积极作用,Put向Spd、Spm的转化有利于增强植株的耐盐性;中国南瓜杂交种‘360.3×112.2’的耐盐性高于黑籽南瓜与其根系中Put/PAs较低、（Spd+Spm）/Put和PAs含量较高,使其清除活性氧能力较强有关.     

Abscisic acid promotes accumulation of toxin ODAP in relation to free spermine level in grass pea seedlings (Lathyrus sativus L.).

Interrelationship among abscisic acid (ABA) content, accumulation of free polyamines and biosynthesis of beta-N-oxalyl-l-alpha,beta-diaminopropionic acid (ODAP) was studied in grass pea (Lathyrus sativus L.) seedlings under drought stress induced by 10% polyethylene glycol (PEG6000). Increase of ABA content occurred prior to that of ODAP and polyamine contents, and was found significantly positive correlation between ABA content and ODAP content. Addition of exogenous ABA increased ODAP content in leaves. On the other hand, pretreatment with alpha-difluoromethylarginine (DFMA), a polyamine biosynthesis inhibitor, significantly suppressed the accumulation of free putrescine (Put), free spermidine (Spd) and free spermine (Spm), which in turn inhibited biosynthesis of ODAP in well-watered leaves. Meanwhile, addition of exogenous Put alleviated DFMA-induced inhibition on the biosynthesis of Put and Spd, but did not affect the biosynthesis of Spm and ODAP in well-watered leaves. Same result was also achieved in drought-stressed leaves. Increasing accumulation of ODAP was significantly correlated with increasing Spm content (R=0.7957**) but not with that of Spd and Put. Therefore, it can be argued that ABA stimulated the biosynthesis of ODAP simultaneously with increasing the level of free Spm under drought stress condition.     

Effects of exogenous polyamines on nitrate tolerance in cucumber

Putrescine (Put), spermidine (Spd), and spermine (Spm) are the major polyamines (PAs) in plant, which are not only involved in the regulation of plant developmental and physiological processes, but also play key roles in modulating the defense response of plants to diverse environmental stresses. In this study, Cucumis sativus L. seedlings were cultivated in nutrient solution and sprayed with three kinds of PAs (Put, Spd, and Spm). The effects of PAs were investigated on excess nitrate stress tolerance of C. sativus by measuring growth and nitrogen (N) metabolism parameters. The contents of NO_3-^?N, NH_4-⁺N, proline and soluble protein in leaves were increased; while plant height, leaf area, shoot fresh and dry weight, root fresh weight were decreased under 140 mM NO₃^? treatment for 7 d. In addition, the activities of nitrate reductase (NR), glutamate synthase (GOGAT), and glutamate dehydrogenase (GDH) were significantly inhibited under 140 mM NO₃^? treatment for 7 d. With foliar treatment by 1 mM Spd or Spm under stress treatment, the contents of Spm, Put, and Spd in leaves increased significantly, except that Spm content decreased under Spd treatment. The activities of NR, glutamine synthetase (GS), GOGAT and GDH and plant height, leaf area, shoot fresh and dry weights were significantly increased. The contents of proline and soluble protein in leaves were significantly enhanced. In contrast, the accumulation of NO_3-^?N and NH_4-⁺N were significantly decreased. However, there were minor differences in activities of N metabolism enzymes and the content of osmotic adjustment substances under 1 mM Put treatment. These findings suggest that 1 mM exogenous Spm or Spd could enhance the capacity of N metabolism, promote growth and increase resistance to high concentrations of NO₃^?. The ameliorating effect of Spd was the best, and that of Put the worst.     

Polyamine metabolism of potato seed-tubers during long-term storage and early sprout development

Growth potential of potato (Solanum tuberosum L.) plants is influenced by seed-tuber age. After 24 days of growth, single-eye seedcores from 7-month-old seed-tubers produced 64% more foliar dry matter than those from 19-month-old seed-tubers, reflecting a higher growth rate. This study was initiated to determine if differences in polyamine (PA) metabolism are associated with aging and age-reduced vigor of potato seed-tubers. As tubers aged in storage, putrescine (Put) increased 2.2-fold, while spermidine (Spd) and spermine (Spm) decreased 33% and 38%, respectively. Ethylene content of the tuber tissue also increased with advancing age, suggesting that during the aging process S-adenosylmethionine was directed toward ethylene biosynthesis at the expense of the PAs. Single-eye cores from 7- and 19-month-old tubers were sown and PA levels in core and shoot tissues were monitored during plant development. Put titer of younger cores increased 8.8-fold by 12 days. In contrast, the increase in Put over the initial titer in older cores was 2.9-fold. The reduced ability of older cores to synthesize Put during plant establishment is probably due to a 45% decline in ornithine decarboxylase activity between 12 and 16 days after planting. Lack of available Put substrate limited the biosynthesis of Spd and Spm, and thus their concentrations remained lower in older cores than in younger cores. Lower PA titer in older cores during plant establishment is thus coincident with reduced growth potential. Concentrations of Put and Spd were higher in shoots developing from older cores throughout the study, but there was no age-related difference in Spm content. In contrast, activities of arginine and S-adenosylmethionine decarboxylases were higher in shoots from younger cores during establishment. The results indicate that aging affects PA metabolism in both tuber and developing plant tissues, and this may relate to loss of growth potential with advancing seed-tuber age.     

氯化钠胁迫对嫁接黄瓜叶片多胺含量的影响

以日本耐盐品种‘帝王新土佐’南瓜为砧木,以’新泰密刺’黄瓜为接穗,在100 mmol·L^-1 NaCl胁迫下,对黄瓜嫁接和自根植株不同时期叶片中不同形态多胺含量的变化进行了研究.结果表明：NaCl胁迫下黄瓜嫁接植株游离态腐胺（Put）含量在胁迫2 d时与自根植株无显著差异,其余时间均显著高于自根植株;游离态亚精胺（Spd）和游离态精胺（Spm）含量在整个胁迫期间均显著高于自根植株;游离态多胺总量（PAs）在胁迫第4天出现峰值;嫁接植株游离态Put/PAs值在胁迫4 d时与自根植株无显著差异,其余胁迫时间均显著低于自根植株,而(Spd+Spm)/Put值在整个胁迫期间均显著高于自根植株;嫁接植株结合态和束缚态Put、Spd和Spm含量在整个胁迫期间均显著高于自根植株,结合态和束缚态PAs在胁迫第6天出现峰值;结合态多胺的Put/PAs值和(Spd+Spm)/Put值变化趋势与游离态多胺一致;嫁接植株束缚态Put/PAs值在胁迫6 d时与自根植株无显著差异,其余时间均显著低于自根植株,而(Spd+Spm)/Put值在整个胁迫期间均显著高于自根植株.表明黄瓜嫁接植株表现出较强的耐盐特征.     

Involvement of polyamines in the drought resistance of rice

This study investigated whether and how polyamines (PAs) in rice (Oryza sativa L.) plants are involved in drought resistance. Six rice cultivars differing in drought resistance were used and subjected to well-watered and water-stressed treatments during their reproductive period. The activities of arginine decarboxylase, S-adenosyl-L-methionine decarboxylase, and spermidine (Spd) synthase in the leaves were significantly enhanced by water stress, in good agreement with the increase in putrescine (Put), Spd, and spermine (Spm) contents there. The increased contents of free Spd, free Spm, and insoluble-conjugated Put under water stress were significantly correlated with the yield maintenance ratio (the ratio of grain yield under water-stressed conditions to grain yield under well-watered conditions) of the cultivars. Free Put at an early stage of water stress positively, whereas at a later stage negatively, correlated with the yield maintenance ratio. No significant differences were observed in soluble-conjugated PAs and insoluble-conjugated Spd and Spm among the cultivars. Free PAs showed significant accumulation when leaf water potentials reached -0.51 MPa to -0.62 MPa for the drought-resistant cultivars and -0.70 MPa to -0.84 MPa for the drought-susceptible ones. The results suggest that rice has a large capacity to enhance PA biosynthesis in leaves in response to water stress. The role of PAs in plant defence to water stress varies with PA forms and stress stages. In adapting to drought it would be good for rice to have the physiological traits of higher levels of free Spd/free Spm and insoluble-conjugated Put, as well as early accumulation of free PAs, under water stress.     

NaCl胁迫对菜用大豆种子多胺代谢的影响

采用蛭石栽培,在100 mmol·L-1NaCl胁迫下,对耐盐性不同的两个品种菜用大豆种子的丙二醛(MDA)含量和多胺(PAs)代谢进行了研究.结果表明:NaCl胁迫显著增加了菜用大豆种子的MDA含量,但耐盐品种‘绿领特早’(LL)的增幅低于盐敏感品种‘理想高产95-1’(LX).与LX相比,LL种子在整个NaCl胁迫期间均维持了相对较高的游离态精胺(Spm)、结合态Spm、结合态亚精胺(Spd)、束缚态Spd和束缚态腐胺(Put)含量,较高的(Spd +Spm )/Put 和(cPAs+bPAs)/fPAs值及较低的Put/PAs值,在胁迫中、后期(9～15 d)维持了相对较高的游离态Spd含量;胁迫期间,LL的精胺酸脱羧酶(ADC)长时期(6～15 d)保持相对较高的活性,而多胺氧化酶(PAO)则长时期(6～15 d)维持相对较低的活性.综上,LL具有较强的多胺合成能力及较强的Put向Spd和Spm以及游离态多胺向结合态和束缚态多胺转化的能力,进而有效抑制了细胞的膜脂过氧化,这可能是其耐盐性较强的重要原因之一.     

Exogenous polyamines enhance copper tolerance of Nymphoides peltatum

The protective effects of polyamines (PAs) against copper (Cu) toxicity were investigated in the leaves of Nymphoides peltatum. Cu treatment increased the putrescine (Put) level and lowered spermidine (Spd) and spermine (Spm) levels, thereby reducing the (Spd+Spm)/Put ratio in leaves. Exogenous application of Spd or Spm markedly reversed these Cu-induced effects for all three PAs and partially restored the (Spd+Spm)/Put ratio in leaves. It also significantly enhanced the level of proline, retarded the loss of soluble protein, decreased the rate of O2*- generation and H2O2 content, and prevented Cu-induced lipid peroxidation. Furthermore, exogenous Spd and Spm reduced the accumulation of Cu and effectively maintained the balance of nutrient elements in plant leaves under Cu stress. These results suggest that exogenous application of Spd or Spm can enhance the tolerance of N. peltatum to Cu by increasing the levels of endogenous Spd and Spm as well as the (Spd+Spm)/Put ratio.     

‘神马’菊花花芽分化与内源多胺的关系

用薄层层析-荧光法测定菊花'神马'花芽分化期间顶芽和叶片中多胺的动态变化,分析了菊花花芽分化与多胺的关系.结果表明,花芽分化起始期顶芽中的腐胺(Put)含量急剧下降,此后在低水平上波动;叶片内Put则于总苞鳞片分化初期大幅上升,其后各阶段处于较低的水平.顶芽中精胺(Spm)与亚精胺(Spd)含量呈平行波动上升趋势,顶芽中Spin在小花原基分化初期直到花冠分化中期处于优势地位,而顶芽中Spd并无明显变化.顶芽、叶片中的Spin变化趋势相反,顶芽中Spm、Spd的含量变化趋势十分相似,但叶片中却呈交替性变化.结果显示,菊花花芽分化过程中,Put含量的降低有利于启动菊花花芽分化,后期Spm的增加有利于小花的分化,叶片可能向顶芽提供Spm,顶芽和叶片中的Spd与小花原基分化有密切关系.     

外源多胺对铜胁迫下水鳖叶片多胺代谢、抗氧化系统和矿质营养元素的影响

采用营养液水培的方法,研究了外源亚精胺(Spd)和精胺(Spm)对Cu胁迫下水鳖叶片3种形态多胺(PAs)、抗氧化系统及营养元素的影响。结果表明:(1)Cu胁迫使水鳖叶片腐胺(Put)急剧积累,Spd和Spm明显下降,从而使(Spd+Spm)/Put比值也随之下降。外源Spd和Spm显著或极显著逆转Cu诱导的PAs变化,抑制Put的积累,缓解Spd和Spm的下降,从而提高了(Spd+Spm)/Put比值。(2)外源Spd和Spm抑制了Cu胁迫诱导的多胺氧化酶(PAO)的增加,缓解了二胺氧化酶(DAO)的下降。(3)与单一Cu胁迫相比,Spd和Spm显著或极显著提高了超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)和谷胱甘肽还原酶(GR)活性和抗坏血酸(AsA)、谷胱甘肽(GSH)、游离脯氨酸(Pro)含量,从而降低了超氧阴离子(O2.-)产生速率和过氧化氢(H2O2)含量,极显著降低了丙二醛(MDA)含量,缓解了Cu诱导的氧化胁迫。(4)外源Spd和Spm显著或极显著缓解了Cu胁迫下矿质营养元素吸收平衡的紊乱。以上结果均说明了外施Spd和Spm可增加水鳖对Cu胁迫的耐受性。     

Polyamines and cellular metabolism in plants: transgenic approaches reveal different responses to diamine putrescine versus higher polyamines spermidine and spermine

Distribution of biogenic amines—the diamine putrescine (Put), triamine spermidine (Spd), and tetraamine spermine (Spm)—differs between species with Put and Spd being particularly abundant and Spm the least abundant in plant cells. These amines are important for cell viability and their intracellular levels are tightly regulated, which have made it difficult to characterize individual effects of Put, Spd and Spm on plant growth and developmental processes. The recent transgenic intervention and mutational genetics have made it possible to stably alter levels of naturally occurring polyamines and study their biological effects. We bring together an analysis of certain metabolic changes, particularly in amino acids, to infer the responsive regulation brought about by increased diamine or polyamine levels in actively growing poplar cell cultures (transformed with mouse ornithine decarboxylase gene to accumulate high Put levels) and ripening tomato pericarp (transformed with yeast S-adenosylmethionine decarboxylase gene to accumulate high Spd and Spm levels at the cost of Put). Our analysis indicates that increased Put has little effect on increasing the levels of Spd and Spm, while Spd and Spm levels are inter-dependent. Further, Put levels were positively associated with Ala (α and β), Ile and GABA and negatively correlated with Gln and Glu in both actively growing poplar cell cultures and non-dividing tomato pericarp tissue. Most amino acids showed positive correlations with Spd and Spm levels in actively growing cells. Collectively these results suggest that Put is a negative regulator while Spd–Spm are positive regulators of cellular amino acid metabolism.     

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.     

Exogenously added polyamines recover browning tissues into normal callus cultures and improve plant regeneration in pine

Polyamines are known to influence a variety of growth and developmental processes in higher plants. Tissue browning seriously reduces in vitro plant regeneration in pine species by decreasing the levels of antioxidant enzymes and polyamines in tissue cultures. In the present investigation, the effect of exogenously added polyamines on recovering browning tissues into normal callus cultures and on improving plant regeneration was examined in Virginia pine ( Pinus virginiana Mill.). Among the polyamines administered, 1.5 m M putrescine (Put), 1.5 m M spermidine (Spd), or 1.5 m M spermine (Spm) alone resulted in a 19.55%, 18.92%, and 1.45%, respectively, recovering of browning tissues into normal callus cultures in 5 weeks. A combination of Put with Spd or Spm did not result in an increase of recovering rate, compared to the Put or Spd alone. Exogenously added 1.5 m M Put, 1.5 m M Spd, 1.5 m M Put + 1.5 m M Spd, or 1.5 m M Put + 1.5 m M Spm recovers browning tissues into normal callus cultures by increasing the activity of antioxidant enzymes ascorbate peroxidase (APOX), glutathione reductase (GR) and superoxide dismutase (SOD) and by decreasing lipid peroxidation. Exogenously added 1.5 m M Put, 1.5 m M Spd, 1.5 m M Put + 1.5 m M Spd, or 1.5 m M Put + 1.5 m M Spm significantly improve the growth rate of callus cultures, shoot formation, and rooting adventitious shoots. These results demonstrated that exogenously added polyamines recover browning tissues into normal callus cultures by decreasing oxidative damage and improving plant regeneration by acting as plant growth substances.     

多胺及其合成抑制剂MGBC对稀脉萍成花反应的影响

腐胺、亚精胺和精胺对稀脉萍的成花均有一定的抑制作用,这种作用随多肢的浓度增加而增强。多胺合成抑制剂MGBG强烈抑制稀脉萍群体的增殖速率,并使稀脉萍群体在非诱导光周期下开花。这种由MGBG引起的增殖速率的降低及成花诱导作用均可被多胺逆转。稀脉萍成花诱导过程中,内源腐胺含量显著升高,亚精胺则下降。