外源水杨酸、褪黑素对盐胁迫下大豆种子萌发和幼苗生长的影响

为研究外源水杨酸、褪黑素对盐胁迫下大豆种子萌发和幼苗生长的影响,筛选出效果较为明显的缓解剂。本试验以大豆吉育204为材料,对100 mmol/L NaCl胁迫下的大豆种子分别外源施加浓度为0.1、0.2和0.5 mmol/L的水杨酸或褪黑素,进行培养皿纸上发芽试验,对其发芽率、发芽势、发芽指数、活力指数、相对盐害率以及幼苗鲜重和苗长进行测定。结果表明,与CK0(空白对照、未经NaCl胁迫)相比,100 mmol/L NaCl胁迫下的大豆种子发芽率、发芽势、发芽指数、活力指数和幼苗鲜重、苗长分别下降了28.34%、21.67%、35.89%、47.79%、21.16%和47.82%,相对盐害率30.91%。0.1、0.2和0.5 mmol/L的水杨酸或褪黑素对盐胁迫下大豆种子发芽率、发芽势、发芽指数、活力指数和幼苗鲜重、苗长均有促进作用,并降低了相对盐害率。其中,与CK1(NaCl胁迫)相比较,0.2 mmol/L褪黑素处理的盐胁迫大豆种子的发芽率、发芽势、发芽指数、活力指数、幼苗鲜重和苗长分别提高23.00%、25.00%、43.43%、66.84%、20.19%和19.12%,并使相对盐害率降至23.48%。褪黑素对大豆盐胁迫的缓解效应整体上优于水杨酸,可作为大豆抵御盐胁迫的较优缓解剂。

大豆种子萌发影响因素研究进展

大豆种子萌发过程中除其自身的种子活力对种子萌发产生的影响之外,一些物理因素如温度、水分、浸种时间和次数、电场以及一些化学因素如化学气体、化学药剂、酸碱、金属离子、生物种衣剂、污灌、植物组织提取液、土壤有机化合物和土壤真菌等也可能对大豆种子萌发产生一定的促进或抑制作用。文章对近几年在影响大豆种子萌发方面的研究成果进行了综述,以期对大豆种子萌发影响因素的深入研究提供理论依据。

大豆种子萌发影响因素研究进展

大豆种子萌发除种子活力以外,还受到物理、化学等因素的影响。例如:温度、浸种时间、水分、电场、药剂、生物种衣剂、土壤有机化合物等。均会对大豆种子发芽率产生不同程度的影响。本文对大豆种子萌发影响因素方面的研究成果予以整理。

1,2,4-三氯苯胁迫对萌发大豆种子中活性氧的影响

以盆栽法研究了不同浓度 1,2 ,4 三氯苯 (TCB)胁迫对萌发大豆种子中活性氧代谢的影响 .结果表明 ,10 0～ 30 0 μg·g-1TCB胁迫初期 (1～ 3天 )促使萌发大豆种子呼吸强度升高及其峰值提前出现 ,超氧阴离子自由基 (O2 - )及过氧化氢 (H2 O2 )的积累显著增加 ,同时伴随丙二醛 (MDA)含量升高 ,显示发生膜脂质过氧化作用 .TCB胁迫 1～ 6天使活性氧清除酶功能紊乱 ,其中过氧化物酶 (POD)活性升高 ,超氧化物岐化酶 (SOD)活性开始上升后转为下降 .在萌发大豆种子受TCB胁迫伤害过程中 ,活性氧代谢失衡造成的膜脂质过氧化将起着重要作用 .

酸化土壤与镉对大豆萌发种子抗氧化保护酶的复合影响

为探索酸化土壤与镉对大豆萌发种子抗氧化保护酶的复合影响,采用种子常规萌发试验的方法,模拟pH=5.93和pH=2.5的酸化土壤,并用0.182mg·L^(-1)和20mg·L^(-1)的Cd^(2+)处理大豆种子,测定不同酸化土壤及镉浓度胁迫对大豆萌发种子过氧化物酶(POD)、过氧化氢酶(CAT)、丙二醛(MDA)和质膜透性的影响。结果表明,轻度酸化土壤(pH=5.93)或低质量浓度镉(0.182mg·L^(-1))可激活POD与CAT活性,降低MDA含量及质膜透性,且与胁时相关;复合处理上述效应更显著,但随胁时延长4指标变幅加大,膜系统恢复时间推后。重度酸化土壤(pH=2.5)与高质量浓度镉(20mg·L^(-1))胁迫下的POD与CAT活性随胁时延长而降低,MDA含量及质膜透性则随胁时延长而升高;低-高、高-高复合处理时,4指标随胁时延长变幅更大,7d时偏离CK更显著,且CAT、MDA和质膜透性峰值推后。由此可见,酸化土壤与镉复合污染可加剧对种子萌发的伤害,二者存在协同作用。

一个种子特异的大豆AP2类转录因子参与调控种子萌发

植物种子的发育和萌发受严格的时空调控,其中转录因子起着重要的作用.本研究发现了一条在发育过程中的大豆种子里特异表达的表达序列标签(expressed sequence tag,EST).通过末端快速扩增技术(rapid amplification of cDNA end,RACE)得到该基因的全长序列并命名为GmSGR.序列分析表明该基因属于AP2/ERF类转录因子家族,其AP2结构域与拟南芥(Arabidopsis thaliana)中的AP2/ERF基因家族DREB亚家族中A-3组的AtABI4的AP2结构域同源性极高.在酵母系统中,未检测到GmSGR具有转录激活活性.将该基因在拟南芥中过量表达,在高浓度的脱落酸(abscisic acid,ABA)及葡萄糖的条件下,转基因植物种子的萌发率均高于对照组;而在高浓度的NaCl条件下,转基因植物种子的萌发率低于对照组.在转基因植物的幼苗中,AtEm6和AtRD29B的表达较野生型幼苗高.这些结果表明GmSGR可能通过调控AtEm6和AtRD29B的表达,从而导致转基因种子对ABA敏感度降低,对盐胁迫更敏感.

Allelopathic Potential of Some Crop Residues on the Germination and Growth of Soybean （Glycine max L,） Merrill

Allelopathic potentials of aqueous water extracts from residues of sorghum stem, maize inflorescence and rice husks on the germination of soybeans （Glycine max. L.） were investigated. The result showed that the extracts brought about a considerable inhibition in the germination of soybean seeds, reductions in the radicle and plumule lengths of soybean seedlings. Whereas, the extracts of maize inflorescence and rice husk had more inhibitory effects on the growth of soybean radicle, all the three extracts demonstrated pronounced inhibitory effects on the growth of the plumule. The retardation of soybean germination, radicle and plumule growths were concentration dependents as the degree of retardations increases with increase in the concentration of the extracts. Statistical analysis （ANOVA, P = 0.05） revealed that there were no significant differences in the germination, radicle and plumule growths at 24 and 48 h experimental time when compared to the control. However, statistical differences abound in the growth parameters at 72 and 144 h experimental time.

Effect of Water Stress Caused by PEG 6000 on Germination and Seedling Growth of Four Soybean Cultivars

Soybean [Glycine max （L.）] is one of the most important protein and oil seed crop. In attention to time consuming and effect of uncontrolled agents like soil elements and hemisphere, study of tolerance in soybean to water stress during germination was investigated. Four soybean cultivars ＇Williams, Linford, L 17 and M7＇ were screened for drought tolerance by treatment of PEG6000 concentration for induce osmotic potentials （0, -3, -6, -9 bar）. A factorial experiment based on completely randomized design with three replications was conducted. Germination percentage, radicle and hypocotyls length, fresh and dry weight of radicle, hypocotyl and seedling, TWC%, MDG, rate of daily germination and percentage of abnormal seedling were measured. Variance analysis of data indicated that difference between osmotic potential had significant effect on all parameters except germination percentage. A significant reduction in fresh weight of radicle and seedling, percentage of abnormal seedlings was observed for the genotypes as the concentration of PEG increased. In interaction between cultivars and water stress level, Linford and M7 with less damage had the highest yield in fresh and dry weight of radicle, respectively. Drought is one of the most important abiotic limited potential in germination and primary growth on these cultivars.

Influences of Temperature Regime on Germination of Seed of Wild Soybean(Glycine soja)

As an important plant species with high protein contents,wild soybean(Glycine soja),has drawn much attention and appeared to be useful for the genetic improvement of soybean germplasms.Since temperature is one of the numerous environmental factors affecting the germination of most plants,an experimental study was carried out to determine the effect of temperature on germination of wild soybean(G.soja)seeds.Germination test was conducted by setting up thirty-six constant and alternating temperature regimes,ranging from 5 to 40 ℃(16 h night/8 h day).Responses in germination rate to these temperature regimes were then used to construct a quadratic response surface,giving estimated germination rates with confidence intervals at P ≤ 0.05.The results showed that germination capacity was significantly greater while exposed to constant temperatures of 25 ℃,and under the alternating temperature regime the optimum temperature occurred at the 20/25,25/25,25/30 ℃ regime(16 h/8 h)with the amplitude widened from 0 to 5 ℃.Together with regional monthly climate data,these results could be used to improve and promote the cultivation of wild soybean(G.soja),making it available to develop the location-specific optimum seeding time and to apply weed-control treatments.

Effect of Mucuna Defatted Bran Extracted with Supercritical CO2 on Soybean Seed Germination

In the present work, we investigated the effect of Mucuna deeringiana defatted bran on seed germination of soybean （Glycine max L. Merrill）. For this, the defatted bran was obtained from different operational conditions using CO2 under pressurized conditions as solvent. Oil extractions were carried out in a laboratorial scale unit at temperatures ranging from 310 to 330 K, pressure from 15 to 25 MPa and solvent flow set in 3 mL min^-1. The experiment was conducted in a germination chamber （25℃, 12：12 h light：dark photoperiod）, and the germination rate and germination speed index （GSI） were evaluated for seven days. The results showed that the oil extraction with supercritical CO2 concentrates the allelochemical L-3,4-dihydroxyphenylalanine （L-DOPA） in bran with levels from 1.86% to 4.65%. Subsequent experiments revealed that the rate of soybean seed germination was not affected by defatted bran whereas the GSI increased significantly after treatment. In brief, we concluded that the extraction process with supercritical CO2 is efficient to obtain L-DOPA of Mucuna, which influences the soybean seed germination.