Ageing and Osmotic Priming in Wheat Seeds: Effects Upon Certain Components of Seed Quality

Deteriorated wheat seed lots were osmotically primed and surface-dried,dried-back, then aged for two more weeks Osmotic priming didnot affect the final germination in any of the aged seed lots,but mean germination time was decreased The response of unagedseed lot to treatments was studied in the following the timecourses of germination, as well as L-[4, 5-²H]leucine and [6-³H]thymidineincorporation (as a measure of protein and DNA synthesis, respectively)into dissected embryos during the early hours of germinationIt was found that the variation in mean germination time andthe rate of synthetic reactions were related The greatest improvementin the components of seed lot quality was achieved after primingand surface drying The beneficial effects of priming were apparenteven after dehydration followed by two further weeks of ageingCumulative correlations between mean germination time and variousbiochemical tests in variously treated aged seed lots were highlysignificant The physiological processes involved in deteriorationand recovery and the potential application of biochemical testsin detecting vigour changes are discussed Triticum durum, seed, ageing, osmotic priming, mean germination time, protein DNA synthesis     

The Effects of Priming and Ageing on Seed Vigour in Tomato

A comparison was made of the effects of seed priming or ageingtreatments on the performance of tomato (Lycopersicon esculentumMill. cv. UC204C) seeds according to a number of indices ofseed vigour. A single lot of tomato seeds was primed in 120mol m^–3 K2HPO4 + 150 mol m^–3 KNO₃ for 5 d at 20?C, or aged at 13% moisture content (dry weight basis) and 50?C for 6 d. Germination percentage (>98%) was unaffectedby priming and reduced to 85% by ageing. X-ray photographs andlongitudinal sections revealed the formation of free space surroundingthe embryo in dry primed seeds, which was not evident in controlor aged seeds. Priming increased the rate of germination atall temperatures above the base temperature (T_b), while ageingdecreased it. T_b was unaffected by priming and only slightlyincreased by ageing. The variation in individual times to germinationwas approximately doubled in both primed and aged seed comparedto the control, based upon the slopes of probit germinationpercentage versus log thermal time curves. Root growth aftergermination tests and seedling growth in both greenhouse andfield tests were not influenced by either priming or ageing.The conductivity test was found to be unreliable as a vigourtest for tomato seeds. The results identify several indiceswhich can be used to quantify seed vigour in tomato. They alsoillustrate that seed priming can enhance seed performance accordingto some criteria, while having no effect or decreasing qualityaccording to other criteria. Seed vigour can apparently be separatedinto various components which can be independently influencedby seed enhancement treatments. Key words: Tomato, seed germination rate, seed priming, seed vigour     

The Effects of Priming and Ageing on Resistance to Deterioration of Tomato Seeds

The influence of seed priming and ageing treatments on viabilityand rate of germination of tomato (Lycopersicon esculentum Mill.)seeds was examined under both long-term and controlled-deteriorationstorage conditions. Seeds of a single lot of tomato were eitherprimed or aged to increase or decrease the rate of germination(Argerich and Bradford, 1989). They were then stored at 6% moisturecontent (dry weight basis) at either 4 ?C or 30 ?C for 1 year.Both viability and germination rate were unaffected by eitherstorage temperature in control seeds, or by 4 ?C storage inprimed or aged seeds. At 30 ?C, however, viability and germinationrate of primed and aged seeds was markedly reduced after 6 monthsof storage. The temperature dependence of the germination rateand the spread of germination times within the population wasalso adversely affected by high temperature storage, particularlyfor primed seeds. Under controlled deterioration conditions(13.5% moisture content and 50 ?C), the rate of loss of viabilitywas greater for primed seed than for control or aged seeds.The relationship between seed viability and the mean germinationrate, however, was not influenced by the seed treatments. Thesedata are analysed in relation to current models of seed deteriorationduring storage and seed repair during priming. The results indicatethat enhancement of seed germination rates by priming treatmentssimultaneously lowers the resistance of seeds to deterioration.Primed tomato seeds must, therefore, be considered to be vigorousseeds with a reduced storage life. Key words: Tomato, controlled deterioration, seed germination rate, seed viability     

Biochemical Changes During Osmopriming of Leek Seeds

Osmotic priming treatments reduced both the mean time to germinationand the spread of germination for two leek seed-lots of highviability but differing vigour. In addition the differencesin germination performance between these two seed-lots was abolishedby the priming treatments. In the unprimed seed-lots, differencesin germination performance were reflected in differences inrates of protein biosynthesis in leek embryo tissue during germination.Osmopriming treatments abolished these differences upon subsequentgermination of osmotically primed seed and furthermore inducedhigh levels of protein biosynthesis in embryo tissue. DNA synthesiswas detectable in leek embryos during the priming period inthe absence of any cell division and was followed by a five-foldincrease in the rate of DNA synthesis in embryo tissue upongermination following priming at which time the rates of DNAsynthesis in these leek embryos was significantly greater thanthat found at any time over the first 4 d of germination inembryos of unprimed leek seeds. The increases in rates of bothprotein and DNA synthesis observed upon germination of primedseed occurred only after a 6–12 h lag period during whichtime there is little increase in these rates above those foundat the end of priming Analysis of nucleotide and nucleotide sugar levels in leek embryosboth during and after priming showed that only traces of GTPand CTP and low levels of ATP and UTP were present in embryosduring priming. After a 6 h lag period following the end ofpriming these levels increased sharply, probably via de novosynthesis. A similar pattern was found for UDP glucose levelsduring priming and subsequent germination. These results indicatethat there is considerable biochemical activity during primingand that the significant benefits in germination performanceof primed leek seeds is accompanied by marked increases in protein,DNA and nucleotide biosynthesis after a lag period of 6–12h following the end of the priming period Allium porrum, leek, seed, osmopriming, germination, protein synthesis, nucleic acids, nucleotides, nucleotide sugars     

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     

Effects of osmotic priming and ageing on the germination and emergence of carrot and leek seed

Carrot and leek seed was osmotically primed in polyethylene glycol solution (273 g/kg water and 342 g/kg water respectively) for 10, 14 or 17 days before accelerated ageing for 0, 24, 48, 72 or 96 h. Priming reduced the germination time compared with non-primed seed. Accelerated ageing increased germination and emergence times and decreased percentage germination and emergence to a greater extent for the primed seeds than for non-primed seeds in both species. Primed and dried but non-aged seed from both species was stored at 10°C for 12 months. There was no loss of viability and improvements in germination time due to priming were maintained throughout the storage period for all the priming treatments in leek, and for the 10 and 14 day priming treatments in carrot. Carrot seed primed for 17 days lost some viability after 12 months storage compared with non-stored seed.     

Effects of osmotic priming and ageing on onion seed germination

Onion seeds were osmotically primed in polyethylene glycol solution (342 g/kg water) either for 14 days before accelerated ageing at 40°C. 18% m.c. for 0, 24, 48, 72 or 96 h, or for 10, 14 or 17 days after ageing. Priming improved the rate of germination compared with non-primed seed. Priming before ageing delayed the loss of viability due to ageing, but priming after ageing had no effect on viability. Primed and dried onion seed was stored for 18 months at 10°C, 9% m.c. with no effect on viability; improvements in germination rate due to priming were maintained over the storage period. Conductivity measurements of seed leachates were not a consistently reliable indicator of germination performance.     

Inter-nucleosomal DNA fragmentation and loss of RNA integrity during seed ageing

The germination of viable seeds is the basis for new plant growth and development. Seeds lose viability during storage, but the biochemical mechanisms of seed death are not fully understood. This study aimed to investigate degradation patterns of nucleic acids during seed ageing and subsequent water uptake. Seeds of Pisum sativum L. were artificially aged at 50°C and 12% seed water content (WC). Nucleic acids degradation was studied during ageing and during imbibition of four seed lots with differential viability from highly viable to dead. As seeds lost viability during ageing, DNA was gradually degraded into internucleosomal fragments, resulting in ‘DNA laddering’, in conjunction with disintegration of 18S and 28S rRNA bands. During imbibition, non-aged controls had high levels of DNA and RNA integrity through to radicle protrusion. In an aged seed lot with 85% total germination (TG) DNA fragmentation decreased upon imbibition probably due to nucleosome degradation, while rRNA integrity did not improve. In an aged seed lot with 44% TG, neither DNA nor rRNA integrity improved upon imbibition. Dead seeds showed DNA degradation as laddering throughout imbibition along with extensive degradation of rRNA. We present a model in which interlinked programmed and non-programmed events contribute to seed ageing, and suggest that protection of nucleic acids during ageing is key to seed longevity.     

Changes in RNA and Protein Metabolism Associated with Alterations in the Germination Efficiency of Sunflower Seeds

Precise knowledge of seed quality after harvest and during storageis of particular importance for seed producers. We analyseddifferent sunflower seed lots (Helianthus annuusL.) characterizedby extremes of germination ability. We used RNA analysis tostudy possible changes in gene expression in seeds unable togerminate. Total RNA content was very small in dry seeds showinga low germination ability. Capacity for total RNA synthesisat the onset of imbibition was also reduced in these seeds.In addition, correlations were found between these parametersand germination ability at 19 °C. We demonstrated a highcorrelation between the amount of total RNA in the dry seed,the capacity of RNA synthesis at the onset of imbibition andthe seed moisture content at the time of the harvest. The abilityof dry seed mRNAs to be translatedin vitrowas also reduced andseven polypeptides, from stored mRNAs, were characteristic ofthe cotyledons from high germinability seeds. Germination canthus be affected at several levels including membrane, enzymaticand nucleic acid deteriorations. Gene expression; germination ability; Helianthus annuusL.; marker; protein; RNA; seed; sunflower     

Proteolytic Activities in x Haynaldoticum sardoum Seeds of Different Ages

Carboxypeptidase, aminopeptidase and proteinase activities weremeasured in endosperms from dry and germinating x Haynaldoticumsardoum naturally aged seeds. Carboxypeptidase activity, presentin dry seeds, decreased slightly during germination and remainednearly unchanged during the storage period. Aminopeptidase activityincreased during germination in younger seeds, but decreasedin non-viable seeds. Proteinase activity was absent in dry seeds,increased during germination in younger seeds and disappearedin the older ones. Proteinase activity was not recovered in old endosperms followingtransplantation of young embryos, and was recovered only toa very small extent in young endosperms following transplantationof old embryos. Young endosperms onto which young embryos hadbeen transplanted gave maximum recovery of enzyme activity,although this was lower than in young intact seeds. These results suggest that the reduced or delayed availabilityof nutrients to the embryo axis is not the only factor causingthe failure of seeds to germinate, the ageing process beinga progressive phenomenon affecting both embryo and endosperm. x Haynaldoticum sardoum, Denti de cani, seed ageing, proteolytic activities, embryo-transplantation     

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     

Catalase is a key enzyme in seed recovery from ageing during priming

Ageing induces seed deterioration expressed as the loss of seed vigour and/or viability. Priming treatment, which consists in soaking of seeds in a solution of low water potential, has been shown to reinvigorate aged seeds. We investigate the importance of catalase in oxidation protection during accelerated ageing and repair during subsequent priming treatment of sunflower (Helianthus annuus L.) seeds. Seeds equilibrated to 0.29 g H₂O g⁻¹ dry matter (DM) were aged at 35 °C for different durations and then primed by incubation for 7 days at 15 °C in a solution of polyethylene glycol 8000 at −2 MPa. Accelerated ageing affected seed germination and priming treatment reversed partially the ageing effect. The inhibition of catalase by the addition of aminotriazol during priming treatment reduced seed repair indicating that catalase plays a key role in protection and repair systems during ageing. Ageing was associated with H₂O₂ accumulation as showed by biochemical quantification and CeCl₃ staining. Catalase was reduced at the level of gene expression, protein content and affinity. Interestingly, priming induced catalase synthesis by activating expression and translation of the enzyme. Immunocytolocalization of catalase showed that the enzyme co-localized with H₂O₂ in the cytosol. These results clearly indicate that priming induce the synthesis of catalase which is involved in seed recovery during priming.     

Interactions between seed priming treatments and nine seed lots of carrot, celery and onion. I. Laboratory germination

Samples of three seed lots of each of three cultivars of carrot, celery and onion were primed in polyethylene glycol solution for 2 weeks at 15 °C. Priming reduced the mean germination times (recorded at 15 °C) of all seed lots (compared to the untreated control) by 3–4 days in carrot, 6–10 days in celery and 3–5 days in onion. The largest reductions in mean germination time occurred in the slowest-germinating seed lots. There were highly significant interactions between priming and cultivars, and between priming and seed lots within cultivars for each species. Drying back the primed seeds at 15 °C increased the mean germination times (compared to primed seed which had not been dried) by 0·6 day in carrot and 1·4 days in celery, and there was no interaction with cultivars or seed lots. The corresponding increase for onion was either 1·0 or 1·8 days, according to the cultivar, but this variation was largely attributable to differences in time taken for the dried seeds to re-imbibe. Seeds dried back at 30 °C germinated 0·2·0·7 day (depending on the species) later than those dried at 15 °C. Percentage germination was not affected by either priming or drying back. Priming reduced the spread of germination times in all cultivars. For primed and dried-back seed, the spread of germination times was larger than that of primed seed in certain cultivars, but was always smaller than that of untreated seeds.     

Prehydration and Priming Treatments that Advance Germination also Increase the Rate of Deterioration of Lettuce Seeds

The influence of prehydration in water or priming in –1.5 MPa polyethylene glycol 8000 solution for various periods,followed by redrying, on germination rate and longevity of lettuce(Lactuca sativa L.) seeds (achenes) was determined during controlleddeterioration at 10% moisture content (fresh weight basis) and40°C. Short prehydration treatments (up to 1 h) had littleeffect on either germination rate or longevity, but significantlyimproved root growth rates. Increasing durations of prehydrationor priming reduced the mean time to germination by up to 61%relative to untreated seeds, but also reduced mean seed longevityby as much as 84% Prehydration and priming altered the relationshipsbetween germination rate and viability and between normal andabnormal seedlings during ageing. Prehydration in abscisic acidor at a temperature inhibitory to germination did not preventthe reduction in longevity under controlled deterioration conditions.While prehydration or priming treatments effectively acceleratesubsequent germination rates of lettuce seeds, the redried seedsare nonetheless highly susceptible to deterioration in storage. Key words: Lettuce, Lactuca sativa L., seed priming, seed deterioration, germination rate     

Organization of lipid reserves in cotyledons of primed and aged sunflower seeds

Imbibing sunflower (Helianthus annuus L., cv. Briosol) seeds at water potentials between –2 MPa and –5 MPa leads to faster (priming) or slower (accelerated ageing) germination depending on the temperature and duration of treatment. Mobilization of food reserves may be associated with the changes in seed vigor. To study this, morphological, biochemical and phase properties of lipid, the major food reserve in sunflower, were compared in freshly harvested (i.e., control), primed and aged sunflower cotyledons using electron microscopy, biochemical analyses and differential scanning calorimetry, respectively. Lipid bodies became smaller and more dispersed throughout the cytoplasm during priming and ageing. Despite ultrastructural changes, there were few measured changes in biochemistry of the neutral lipid component; lipid content, proportion of saturated and unsaturated fatty acids and level of free fatty acids were unchanged in primed and slightly aged seeds, with only severely aged seeds showing a net decrease in polyunsaturated fatty acids and an increase in free fatty acids. Subtle changes in the calorimetric behavior of lipids within sunflower cotyledons were observed. Sunflower lipids exhibited polymorphic crystalline and amorphous solid phases when cooled to <–100°C, but priming decreased the rate of crystallization in vivo and ageing increased the rate of crystallization, but decreased percentage crystallinity. The observed changes in thermal behavior in vivo are consistent with losses and gains, respectively, of interacting non-lipid moieties in the triacylglycerol matrix.     

A comparison of two large-scale seed priming techniques

Leek seed lots of high (91%) and low (82%) viability were primed in aerated polyethylene glycol (PEG) solutions in Bubble-columns and by a non-osmotic priming technique in both 1987 and 1988 and the seeds were then sown in the field. Both methods of priming established a similar seed moisture content during treatment and, in the laboratory, produced seeds with more rapid and uniform germination than untreated seeds, with a greater advantage for Drum compared with Bubble-column priming in PEG. In the field, both priming techniques gave seedling emergence responses similar to those from priming in PEG by the laboratory-scale technique on filter paper. Both large-scale priming methods gave earlier and more uniform emergence than untreated seeds and gave similar or slightly higher levels of seedling emergence, except on one sowing occasion when seeds were stored before sowing followed by sowing into a drying seedbed.     

Free radical scavenging as affected by accelerated ageing and subsequent priming in sunflower seeds

Lipid peroxidation resulting from loss of free radical scavenging is thought to be involved in deterioration of sunflower (Helianthus annuus L.) seeds during accelerated ageing. In other respects, presoaking of seeds in a solution of low water potential (osmopriming) has been demonstrated to reinvigorate aged seeds. The aim of the present work was to study the effect of osmopriming on the germination of aged sunflower seeds and to investigate whether this effect was associated with the restoration of antioxidant defence systems. Seeds were aged for 5 days at 45°C and 100% relative humidity and then primed for various durations up to 7 days at 15°C in a solution of polyethylene glycol 6000 at ?2 MPa. Lipid peroxidation was estimated by measuring malondialdehyde (MDA) and conjugated diene contents, and the activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR) were measured throughout the treatments. Accelerated ageing resulted in a marked decrease in the germination rate, and was associated with an increase in the levels of MDA and conjugated dienes, thus indicating lipid peroxidation. Ageing was also characterized by a decrease in the activities of CAT and GR. The activities of SOD and DHAR were much less altered. No APX activity was detected whatever the seed treatment. Priming of aged seeds progressively restored the initial germinative ability and resulted in a marked decrease in the levels of MDA and conjugated dienes, indicating a fall in lipid peroxidation processes. These effects of priming were also well correlated to the recovery of SOD, CAT and GR activities. Priming treatment for 7 days led to full restoration of the cell detoxifying mechanisms which were strongly altered during ageing. Glutathione content showed the same changes as GR activity. There existed a clear-cut relationship between seed germinative energy, expressed as the germination rate, and the efficiency of free radical scavenging systems, in particular CAT and GR activities and glutathione content. The results suggest that the antioxidant defence systems might play a key role in seed vigour.     

Accelerated ageing and subsequent imbibition affect seed viability and the efficiency of antioxidant system in macaw palm seeds

Accelerated ageing is an accurate test indicator of seed vigor and storability that helps to understand the mechanisms of cellular and biochemical deterioration that occur during seed ageing. This study was carried out to elucidate the mechanisms of ageing in macaw palm embryos. Seeds were artificially aged during 4, 8 and 12 days at 45 °C and 100% relative humidity. After ageing, seeds were tested for viability (tetrazolium), electrical conductivity, lipid peroxidation (MDA) and hydrogen peroxide (H₂O₂) content. Part of the aged seeds was imbibed for 8 days and then determined the hydrogen peroxide content and the activity of antioxidant system enzymes (superoxide dismutase, catalase and glutathione reductase). Ageing reduced the embryo viability from 8 days of treatment and increased malondialdehyde content (MDA) and solute leakage. Hence, membrane permeability correlated with both loss of viability and lipid peroxidation. Imbibition after ageing significantly increased H₂O₂ content along with superoxide dismutase activity. Catalase activity was significantly higher than control in embryos aged from 8 days and imbibed, and glutathione reductase activity did not change. Our results suggest that macaw palm seed deterioration during accelerated ageing is closely related to lipid peroxidation, and that enzymatic antioxidant system is not completely efficient in reducing reactive oxygen species after imbibition, a critical phase to germination. Moreover, accelerated ageing test can be used as a reliable model to understand the mechanisms involved in palm seeds deterioration.     

The use of an ELISA to quantitate the extent of 11S globulin mobilization in untreated and primed sugar beet seed lots

Seed priming (controlled imbibition) is a widely used technique for improving crop establishment, because it allows a reduction of the time to radicle emergence following seed imbibition and synchronization of individual seeds within seed lots with respect to germination timing. The major problem encountered in seed priming is the control of seed imbibition to a level permitting pre-germinative processes to proceed but that blocks radicle emergence. If not, the consequence of drying back the seeds to initial moisture content for storage purposes could be a total loss of the treated batch. This is because, as long as radicle growth has not begun, seeds may be re-dried without any permanent deleterious effects upon subsequent germination or growth. Recently, we reported the discovery of a molecular marker of sugar beet seed priming, corresponding to the basic B-subunit of the seed storage protein 11S globulin. An ELISA based upon this molecular marker has been used to analyse how different sugar beet seed lots respond to a priming treatment. The results demonstrate that this ELISA allows us to readily distinguish between the primed seeds and the corresponding untreated seeds.     

Beneficial Effects of Moist Chilling on the Seeds of Black Spruce (Picea mariana [Mill.] B.S.P.)

Moist chilling (cold stratification) is well-known as a simpleand effective means of overcoming physiological seed dormancyand enhancing germination of many temperate tree and shrub species.However, the apparent activation of intracellular repair mechanismsin non-dormant black spruce (Picea mariana) seeds followingmoist chilling, has not previously been reported. The presentcontribution records the beneficial effects of moist chillingafter accelerated ageing (40°C/98% relative humidity) for3–10 d of black spruce seeds. This treatment was maximallyeffective after 7 d of accelerated ageing, increasing germinationfrom 43 to 61%. Ultrastructural examination of embryo cellsindicated that intracellular activation occurred during moistchilling even when seeds had not been subjected to acceleratedageing, and that the increasing levels of damage accumulatingover the 3–7 d period of ageing were substantially reversedduring subsequent moist chilling. The results of cold stratificationof non-dormant seeds are discussed in terms of the value ofthis practice in nursery seedling production from seeds thatare of less than the highest quality.Copyright 2000 Annals ofBotany Company Accelerated ageing, black spruce, cold stratification, embryonic axes, germination, moist chilling, Picea mariana, repair mechanisms, ultrastructure