Responses of Vegetable Seeds to Controlled Hydration

Leek, onion and carrot seeds were imbibed in water and in solutionsof polyethylene glycol (PEG) 6000 over the range –0.5to –4.0 MPa osmotic potential, for periods up to 28 dat 15 C. Seeds started to germinate after 7 and 14 d at –0.5MPa and –1.0 MPa PEG, respectively, but in the lattercase, germination did not exceed 5%. No germination occurredin solutions of lower (more negative) osmotic potential. Seedmoisture content increased with osmotic potential in all threespecies and the relationships were unaffected by the durationof imbibition in solutions of –1.0 to –4.0 MPa,though leek seeds had higher moisture contents than the otherspecies for any given osmotic potential. Linear relationships between response to priming (differencebetween mean germination times of primed and untreated seeds)and seed moisture content were obtained for each species, positiveresponses being obtained above 30–35% seed moisture contentwith optima at 46, 44.5 and 44% seed moisture contents in leek,onion and carrot, respectively. Priming had no effect on embryovolume or cell number per embryo in leek and onion. Carrot embryovolume increased by 43% and cell number per embryo doubled inprimed compared with untreated seeds, whereas seeds imbibedin water showed only a slight increase in cell number per embryoat the stage when radicles were beginning to penetrate the seedcoat. Allium cepa L. cv. Rijnsburger Robusta, onion, Allium porrum L. cv. Winterreuzen, leek, Daucus carota L. cv. Nantaise, carrot, germination, priming, polyethylene glycol, seed moisture, cell number, embryo volume     

Osmoconditioning as a Means of Counteracting the Ageing of Pepper Seeds during High-temperature Storage

Sweet pepper seeds were osmotically conditioned in 0.4 M mannitolsolution for 4 d (at 25 °C, in darkness) before or afterstorage at 35 °C for up to six months, and their germinationand viability was compared with that of untreated seeds storedunder the same conditions. Seeds that had been osmoconditionedprior to storage retained a high rate of germination and germinatedto a high final percentage (from 80 to 50 per cent) at both15 and 25 °C throughout the storage period. By contrast,both the rate and total level of germination of untreated pepperseeds declined rapidly at both germination temperatures, andby three months of storage the total level of seed viabilitywas already less than 10 per cent. Seeds that were first storedat 35 °C, and then osmoconditioned just prior to germination,showed a decline in germinability which when tested at 25 °Cwas the same as for untreated seeds, while tested at 15 °Coccurred at a slightly slower rate than for untreated seeds. It is evident that osmoconditioning prior to storage, in additionto the acceleration of germination, resulted in a dramatic delayof the ageing rate, thus increasing considerably the longevityof seeds. On the other hand, osmoconditioning after storagedid not seem to have any significant effect on seed viability,though it enhanced the germination rate. Capsicum annuum, sweet pepper, seed, germination, osmoconditioning, priming, storage, viability, ageing, longevity     

Physiological and enzymatic activity of pepper seeds (Capsicum annuum) during priming

Pepper ( Capsicum annuum L. cv. Keystone Resistance Giant 3) seeds were monitored during priming to determine if seed treatments which accelerate the rate of germination could be correlated with specific physiological changes within the seeds. Pepper seeds primed with −0.90 and −1.35 MPa NaCl solutions at 23°C for 18 days did not completely equilibrate with the osmotic potential of the priming solution. Seed respiratory rates indicated that priming extends the lag phase of germination following imbibition. Soluble protein levels increased 115% in primed seeds, and the uptake and incorporation of [¹⁴C(U)] labelled amino acids into the acid insoluble fraction increased throughout the priming treatments. Alcohol dehydrogenase (EC 1.1.1.1, anaerobic metabolism), glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (EC 1.1.1.44, pentose phosphate pathway) activities remained stable throughout the priming treatment, but were higher after 6 days. than the water-imbibed controls. Aldolase (EC 4.2.1.1. glycolysis) and isocitrate lyase (EC 4.1.3.1, glyoxylate cycle) activities increased with imbibition and were 61 and 56% (respectively) higher in primed seeds as compared to the water-imbibed controls after 12 days. Treatment with the −0.90 MPa NaCl solution was more effective than the −1.35 MPa solution in improving the rate of germination, yet there were no significant differences between the protein concentrations or enzyme activities of the two priming treatments. However, the incorporation of labelled amino acids into pepper seeds was significantly higher in the −0.90 MPa priming treatment.     

Activation of the Cell Cycle in Tomato (Lycopersicon esculentum Mill.) Seeds during Osmoconditioning as Related to Temperature and Oxygen

Using flow cytometric analyses of the nuclear DNA content, westudied the effects of various conditions of osmopriming onthe activation of the cell cycle in embryo root tips of tomato(Lycopersicon esculentum‘Elko’) seeds. In dry untreatedseeds, 90.7% of the nuclei revealed 2C signals. Priming of seedsin polyethylene glycol-8000 (PEG) improved the germination rateof seeds transferred onto water at 15 °C. This was associatedwith an increase in 4C signals when priming was carried outat -1.0 and -1.5 MPa. Priming at -2.0 MPa enhanced subsequentgermination but had no effect on DNA replication. For temperaturesduring priming up to 25 °C, a positive linear correlationexisted between the efficiency of the treatment, evaluated bythe reciprocal of time to obtain 50% germination at 15 °C,and the frequency of 4C nuclei or the 4C/2C values. Such a correlationdid not exist when priming was performed at higher temperatures.At least 5% oxygen in the atmosphere was required during primingfor the induction of DNA replication and for the enhancementof subsequent germination. In the presence of 5x10^-4M and 10^-3MNaN₃during priming, most of the cells were maintained with 2CDNA levels and the treatment had no stimulatory effect on germination.The results show a positive linear relationship between thefrequency of 4C DNA nuclei or the 4C/2C ratio and the improvingeffect of priming. However, in suboptimal conditions of priming(-2.0 MPa or temperatures higher than 25 °C), the improvementof seed germination was not associated with the onset of DNAreplication.Copyright 1999 Annals of Botany Company Cell cycle, germination, osmopriming, oxygen, temperature, Lycopersicon esculentum, tomato.     

beta]-Tubulin Accumulation and DNA Replication in Imbibing Tomato Seeds

The activation of the cell cycle in embryo root tips of imbibing tomato (Lycopersicon esculentum Mill. cv Lerica) seeds was studied by flow cytometric analyses of the nuclear DNA content and by immunodelection of [beta]-tubulin. With dry seeds, flow cytometric profiles indicated that the majority of the cells were arrested at the G1 phase of the cell cycle. In addition, [beta]-tubulin was not detectable on western blots. Upon imbibition of water, the number of cells in G2 started to increase after 24 h, and a 55-kD [beta]-tubulin signal was detected between 24 and 48 h. Two-dimensional immunoblots revealed at least three different [beta]-tubulin isotypes. Thus, [beta]-tubulin accumulation and DNA replication were induced during osmotic priming. These processes, as well as seed germination rate, were enhanced upon subsequent imbibition of water, compared with control seeds that imbibed but were not primed. By contrast, when aged seeds imbibed, DNA replication, [beta]-tubulin accumulation, and germination were delayed. In all cases studied, both DNA replication and [beta]-tubulin accumulation preceded visible germination. We suggest that activation of these cell-cycle-related processes is a prerequisite for tomato seed germination. Furthermore, [beta]-tubulin expression can be used as a parameter for following the initial processes that are activated during seed imbibition.     

Effects of mucilage on seed germination of the desert ephemeral plant Plantago minuta Pall. under osmotic stress and cycles of wet and dry conditions

To test the role of the seed mucilage of Plantago minuta Pall. in regulating germination under osmotic stress and cycles of hydration and dehydration, two experiments were carried out using seeds with intact mucilage and mucilage‐free seeds. In Experiment 1 seeds were immersed in a range of iso‐osmotic polyethylene glycol solutions (?1.15 to 0 MPa) for 14 days; any ungerminated seeds were transferred to deionized water to investigate the recovery germination. In Experiment 2 seeds were immersed in deionized water for 24 h, and were then incubated on filter paper for an additional 13 days to ensure complete desiccation before reimbibition to test the germination recovery percentage. Under mild osmotic stress (?0.73 to 0 MPa), the intact seeds with mucilage were shown to have higher germination rates than the mucilage‐free seeds, indicating that the mucilage led to a “fast sprouting” germination strategy under mild osmotic stress. However, when seeds were exposed to high osmotic stress (?1.15 MPa), the mucilage apparently slowed the germination rate, resulting in a “risk‐balancing” germination strategy. Extreme drought induced by polyethylene glycol solution and the desiccation pretreatment accelerated germination rates compared to non‐pretreated seeds; both germination potential and recovery percentage of the mucilage seeds were significantly higher than that of the mucilage‐free seeds. Our results revealed that the seed mucilage of P. minuta plays a crucial role in regulating seed germination rates and the germination strategies adopted by controlling seed water absorption when the seeds experience different osmotic stresses or alternating wet and dry conditions.     

A model of the effects of water stress on seed advancement and germination

A model of seed germination is proposed which uses a variable with the units of an osmotic potential (virtual osmotic potential) to integrate the effect of a constant or a varying water potential. This differs from existing models that describe the effects of fixed water potentials on germination, or the effects of fixed priming water potentials on the subsequent germination at a fixed water potential. When a seed is sown, the virtual osmotic potential is assumed to fall at a rate that depends on the ambient water potential, and on the difference between its current and a minimum value. Radicle growth is assumed to initiate when the difference between the ambient water potential and the virtual osmotic potential exceeds a threshold. The germination of carrot and onion seeds at various fixed potentials below 0 MPa was well described by the virtual osmotic potential model. The model was also used to simulate the results of experiments in which seeds were given a single step change in water potential.     

脱落酸引发对夜香紫罗兰种子萌发的效应

研究脱落酸引发及其与植物生长调节剂的复合处理对夜香紫罗兰(Matthiola bicornis)种子萌发的效应.结果表明,将夜香紫罗兰种子于20℃下在2.5×10-5 mol/L脱落酸(ABA)溶液中引发7 d,能显著缩短种子平均萌发时间,增加种子萌发指数.在ABA溶液中加入吲哚乙酸(NAA)未能进一步改善夜香紫罗兰种子萌发,但其他复合处理均显著提高正常幼苗百分率.ABA和细胞分裂素(KT)及NAA复合处理进一步增加种子萌发指数,不仅比单独用ABA引发的效果好,而且也比用聚乙二醇(PEG)引发的效果好.ABA引发和PEG引发的夜香紫罗兰种子相对吸水量显著不同.对ABA引发机理和应用潜力进行了讨论.     

云锦杜鹃种子萌发及对干旱胁迫的响应

以不同渗透势的PEG-6000溶液模拟干旱胁迫条件, 研究云锦杜鹃种子的萌发、幼苗生长和累积吸水率对干旱胁迫的响应。结果显示：种子于第14 d开始萌发,萌发期为8 d,总萌发率为45.5%±1.7%。在渗透势为-0.3～-0.6 MPa的溶液中, 种子的累计吸水率在第5 d就超过对照(蒸馏水中), 种子的萌发和幼苗的生长也优于对照, 说明云锦杜鹃种子不适合过于湿润的土壤环境中萌发。但溶液的渗透势≥-0.9 MPa时, 种子的吸水减缓、萌发率下降, 同时幼苗的生长也慢, 而当渗透势≥-1.8 MPa时, 种子不能充分吸涨、萌发, 说明云锦杜鹃种子对干旱胁迫比较敏感。另外, 经PEG溶液浸种2天后移入蒸馏水中,萌发率均有一定程度的提高, 其中经-0.3～-1.5 MPa的PEG溶液浸种后, 萌发率显著高于对照。提示用一定浓度范围的PEG溶液浸种可使休眠种子活化, 提高种子繁育的效率。     

Effect of Salinity on Germination and Seedling Growth of twoAtriplexspecies (Chenopodiaceae)

Salinity is one of the environmental factors that has a criticalinfluence on the germination of halophyte seeds and plant establishment.Salinity affects imbibition, germination and root elongation.However, the way in which NaCl exerts its influence on thesevital processes, whether it is through an osmotic effect ora specific ion toxicity, is still not resolved. Dimorphic seedsof the halophytesAtriplex prostrataandA. patulawere treatedwith various iso-osmotic solutions of NaCl and polyethyleneglycol (PEG). For each treatment, imbibition, germination rate,percent germination, germination recovery and nuclear area ofroot tip cells were compared. Higher concentrations of NaCl(-1.0 MPa) were more inhibitory to imbibition, germination andseedling root elongation than iso-osmotic PEG solutions. Allseeds recovered from a pre-treatment with -2.0 MPa NaCl andPEG solutions, except large seeds ofA. prostratawhich failedto germinate following transfer from -2.0 MPa NaCl. NaCl causeda greater increase in nuclear volume than iso-osmotic PEG solutions.These data suggest that the influence of NaCl is a combinationof an osmotic effect and a specific ion effect.Copyright 1998Annals of Botany Company Atriplex patula,Atriplex prostrata,cytophotometry, osmotic potential, salinity, seed germination.     

Priming and accelerated ageing affect L-isoaspartyl methyltransferase activity in tomato (Lycopersicon esculentum Mill.) seed

Damage and degradation of cellular proteins is observed duringage-induced seed deterioration. L-Isoaspartyl protein methyltransferase(EC 2.1.1.77 [EC] ) is an enzyme hypothesized to play a role in limitingand repairing age-induced damage to proteins. Tomato (Lycopersiconesculentum Mill. ‘New Yorker’) seeds were assayedfor changes in L-isoaspartyl methyl-transferase activity duringaccelerated ageing and after osmotic priming. Accelerated ageingof seeds for 1–4 d at 45C and 100% relative humidityreduced germination from 94% to 71%, increased the mean timeof germination (MTG) from 2.4 to 5.8 d, and was accompaniedby a correlative decrease in L-isoaspartyl methyltransferaseactivity (r²=0.90). Aged and untreated seeds were primed for7 d at 20C in darkness using aerated solutions of 3% KNO₃ orpolyethylene glycol 8000 (PEG) with equivalent osmotic potential(–1.25 MPa). Priming with KNO₃ decreased the MTG, butdid not improve germination percentage for untreated seeds.Priming did not affect L-isoaspartyl methyltransferase activityin untreated seeds, but restored activity in aged seeds primedin KNO₃ to levels near that of untreated seeds. Priming withPEG did not effectively improve the MTG or increase L-isoaspartylmethyltransferase activity. During germination, L-isoaspartylmethyltransferase activity remained constant for 48 h post-imbibitionand then declined, suggesting that the enzyme was developmentallyregulated and inactivated or degraded as radicle emergence occurred. Key words: L-Isoaspartyl methyltransferase, protein repair, seed priming, accelerated ageing, Lycopersicon esculentum     

种子引发提高小麦抗渗透胁迫能力的效应

种子经渗透势-0.8 MPa或-1.2 MPa PEG—6000处理后,抗旱性不同小麦(Triticum aesttvum L．)“晋麦33”和“84G6”种子萌发率均有提高,种子电解质外渗率明显降低,种子萌发适应渗透胁迫能力提高,种子可溶蛋白质含量、PAL和POD活性显著增加,“晋麦33”种子CAT活性增加,两品种幼苗PAL、POD和CAT活性也均有提高,但“84G6”种子CAT活性下降。     

Water Relations of Seed Development and Germination in Muskmelon (Cucumis melo L.): VI. INFLUENCE OF PRIMING ON GERMINATION RESPONSES TO TEMPERATURE AND WATER POTENTIAL DURING SEED DEVELOPMENT

Seed priming (imbibition in water or osmotic solutions followedby redrying) generally accelerates germination rates upon subsequentre-imbibition, but the response to priming treatments can varyboth within and among seed lots. Seed maturity could influenceresponsiveness to priming, perhaps explaining variable primingeffects among developmentally heterogeneous seed lots. In thecurrent study, muskmelon (Cucumis melo L.) seeds at two stagesof development, maturing (40 d after anthesis (DAA)) and fullymature (60 DAA), were primed in 0?3 M KNO₃ for 48 h at 30 ?C,dried, and imbibed in polyethylene glycol 8000 solutions of0 to –1?2 MPa at 15, 20, 25, and 30 ?C. Germination sensitivitiesto temperature and water potential () were quantified as indicatorsof the influence of seed maturity and priming on seed vigour.Germination percentages of 40 and 60 DAA control seeds weresimilar in water at 30 ?C, but the mean germination rate (inverseof time to germination) of 40 DAA seeds was 50% less than thatof 60 DAA seeds. Germination percentages and rates of both 40and 60 DAA seeds decreased at temperatures below 25 ?C. Reductionsin also delayed and inhibited germination, with the 40 DAAseeds being more sensitive to low than the 60 DAA seeds. Primingsignificantly improved the performance of 40 DAA seeds at lowtemperatures and reduced , but had less effect on 60 DAA seeds.Priming lowered both the minimum temperature (T_b) and the minimum (_b) at which germination occurred. Overall, priming of 40 DAAseeds improved their germination performance under stress conditionsto equal or exceed that of control 60 DAA seeds, while 60 DAAseeds exhibited only modest improvements due to priming. Asthe osmotic environment inside mature fruits approximates thatof a priming solution, muskmelon seeds may be ‘primed’in situ during the late stage of development after maximum dryweight accumulation. Key words: Cucumis melo L., seed priming, germination, vigour, development, temperature     

Flow Cytometric Determination of Nuclear Replication Stages in Tomato Seeds during Priming and Germination

Flow cytometric determination of DNA levels in embryos of fullymatured dry tomato (Lycopersicon esculenium) seeds revealedlarge amounts of 2C DNA signals, indicating that most cellshad arrested in the cell cycle at the presynthetic G₁ phaseof nuclear division. After imbibition in water, an augmentationof the 4C signal in the embryonic root tip region was found.This increase could be ascribed to cells entering the syntheticphase of nuclear division leading towards the doubling of chromosomalmaterial. In the root tip cells, 4C:2C ratios increased I dafter imbibition in water though radicle emergence started 2d later. Apparently, DNA synthesis preceded germination. Onlya small increase in the number of cells with 4C DNA levels wasfound in the rest of the embryonic tissues. In whole dry seeds,DNA histograms revealed both a 2C signal and a considerable6C peak, the latter originating from the endoreduplicated endosperm. A priming period of 14 d in PEG-6000 considerably enhanced therate and uniformity of germination. In the ungerminated seeds,the 4C DNA signal of root tip cells started to increase after3 d incubation in PEG. The ratio of 4C:2C steadily increasedduring the 14 d priming period, though did not reach the levelobtained after hydration in water. Upon priming, the 4C:2C ratiowas constant after redrying the seeds towards the original moisturecontent, indicating that the chromosomal material in the rootcells had stably ceased cell cycle activity at the G² phase.The present results indicate that the beneficial effects ofpriming on seedling performance are associated with the actionof replicative DNA synthetic processes prior to germination. Lycopersicon esculeniumMill, tomato, DNA content, flow cytometry, priming, seed, nuclear replication stage, C levels     

种子引发提高小麦抗渗透胁迫能力的效应

种子经渗透势－０．８ＭＰａ或－１．２ＭＰａＰＥＧ－６０００处理后,抗旱性不同小麦（ＴｒｉｔｉｃｕｍａｅｓｔｉｖｕｍＬ．）“晋麦３３”和“８４Ｇ６”种子萌发率均有提高,种子电解质外渗率明显降低,种子萌发适应渗透胁迫能力提高,种子可溶蛋白质含量、ＰＡＬ和ＰＯＤ活性显著增加,“晋麦３３”种子ＣＡＴ活性增加,两品种幼苗ＰＡＬ、ＰＯＤ和ＣＡＴ活性也均有提高,但“８４Ｇ６”种子ＣＡＴ活性下降。     

Seed Treatment with Auxins Modulates Growth and Ion Partitioning in Salt-stressed Wheat Plants

Experiments were performed to determine whether seed priming with different concentrations （100, 150, and 200 mg/L） of auxins （indoleacetic acid （IAA）, indolebutyric acid （IBA）, or their precursor tryptophane （Trp）） could alter salinity induced perturbances in salicylic acid and ion concentrations and, hence, growth in wheat （Triticum aestivum L.） cultivars, namely M.H.-97 （salt intolerant） and tnqtab-91 （salt tolerant）. Primed and non-primed seeds were sown in Petri dishes in a growth room, as well as in a field treated with 15 dS/m NaCl salinity. All priming agents, except IBA, increased the final germination percentage in both cultivars. The seedlings of either cultivar raised from Trp-treated seeds had greater dry biomass when under salt stress. In field experiments, Trp priming was much more effective in mediating the increase in grain yield, irrespective of the cultivar, under salt stress. The alleviatory effect of Trp was found to be associated with reduced uptake of Na^＋ in the roots and subsequent translocation to the shoots, as well as increased partitioning of Ca^＋ in the roots of salt-stressed wheat plants. Plants of both cultivars raised from Trp-and IAA-treated seeds accumulated free salicylic acid in their leaves when under salt stress. Overall, the Trp priming-induced improvement in germination and the subsequent growth of wheat plants could be related to ion homeostasis when under salt stress. The possible involvement of salicylic acid in the Trp priming-induced better growth under Conditions of salt stress is discussed.     

Seed Treatment with Auxins Modulates Growth and Ion Partitioning in Salt-stressed Wheat Plants

Experiments were performed to determine whether seed priming with different concentrations (100, 150, and 200 mg/L) ofauxins (indoleacetic acid (IAA), indolebutyric acid (IBA), or their precursor tryptophane (Trp)) could alter salinity inducedperturbances in salicylic acid and ion concentrations and, hence, growth in wheat (Triticum aestivum L.) cultivars, namelyM. H.-97 (salt intolerant) and Inqlab-91 (salt tolerant). Primed and non-primed seeds were sown in Petri dishes in a growthroom, as well as in a field treated with 15 dS/m NaCl salinity. All priming agents, except IBA, increased the final germinationpercentage in both cultivars. The seedlings of either cultivar raised from Trp-treated seeds had greater dry biomass whenunder salt stress. In field experiments, Trp priming was much more effective in mediating the increase in grain yield,irrespective of the cultivar, under salt stress. The alleviatory effect of Trp was found to be associated with reduced uptakeof Na~ in the roots and subsequent translocation to the shoots, as well as increased partitioning of Ca~(2 )in the roots ofsalt-stressed wheat plants. Plants of both cultivars raised from Trp-and IAA-treated seeds accumulated free salicylic acidin their leaves when under salt stress. Overall, the Trp priming-induced improvement in germination and the subsequentgrowth of wheat plants could be related to ion homeostasis when under salt stress. The possible involvement of salicylicacid in the Trp priming-induced better growth under conditions of salt stress is discussed.     

温度对干旱、盐胁迫下两种黄芪属种子萌发和幼苗生长的影响

为探讨温度对干旱、盐胁迫下黄芪属种子萌发和幼苗生长特性的影响,以黄芪属蒙古黄芪和扁茎黄芪2种种子为研究对象,纯净水处理为对照组,NaCl、PEG处理为实验组,设置4个渗透势水平(0、-0.1、-0.3、-0.5 MPa),置于5种不同的温度(10、15、20、25、30 ℃)下,每日观察并记录两种种子萌发和幼苗生长情况。结果表明：旱盐胁迫下蒙古黄芪和扁茎黄芪种子萌发最适宜的温度分别为25和20 ℃左右;蒙古黄芪耐高温不耐低温,而扁茎黄芪恰恰相反;但25和20 ℃均适宜两种幼苗生长,包括胚根、胚轴和子叶的生长。蒙古黄芪各处理组(除未发芽的种子)的平均发芽时间都比扁茎黄芪长;NaCl胁迫程度的增加使得两种种子的最终发芽率降低,但蒙古黄芪的耐盐性高于扁茎黄芪;随着PEG胁迫程度的增加,二者的发芽均受到抑制,甚至会出现完全不萌发,但扁茎黄芪的耐旱性高于蒙古黄芪;在相同的渗透势时,尤其是-0.5 MPa,PEG比NaCl对两种种子的影响大;交互胁迫作用下,随着渗透势的增加两种幼苗的鲜重、干重以及胚根、胚轴、子叶的长和宽变化较大;利用Design Expert软件预测发现：温度25 ℃、NaCl渗透势为-0.1 MPa,温度24 ℃、PEG渗透势为-0.04 MPa的处理是蒙古黄芪种子萌发和幼苗生长达到最优化的组合;而扁茎黄芪最优化的组合则为23 ℃下NaCl渗透势为-0.07 MPa的处理,20 ℃下PEG渗透势为-0.13 MPa的处理。     

Establishing the large scale osmotic priming of onion seeds by using enriched air

Onion seeds were primed in polyethylene glycol solutions (PEG) (-1.5 MPa) for 14 days at 15°C on filter paper and in bubble columns containing 50 g seed litre^-1 PEG using air or enriched air (75% O₂/25% N₂) to aerate and suspend the seeds. Compared with untreated seeds, priming seeds in bubble columns using enriched air increased the percentage seed germination but it did not when air was used, or when seeds were primed on filter paper. Mean germination times (t_m) were significantly reduced in all cases but the reduction was greatest using enriched air and least using air. The spread of germination times was significantly reduced only for seeds primed in enriched air. Drying seeds following priming reduced the percentage germination compared with untreated seeds, but only significantly for those primed in bubble columns using air. Drying also increased the mean germination times by 1.5 to 1.8 days (relative to primed seed which had not been dried). Seeds primed in enriched air were least affected. This increased time is that typically required for water re-imbibition after drying. Priming with enriched air followed by drying gave the same number of normal seedlings as untreated seeds.