An Intermediate Category of Seed Storage Behaviour?: I. COFFEE

Seeds of four cultivars of arabica coffee (Coffea arabica L.)were tested for germination following hermetic storage for upto 12 months at several different combinations of temperaturesbetween –20 °C and 15 °C and moisture contentsbetween 5% and 10% (wet basis). Most of the seeds from one cultivarwithstood desiccation to between 5% and 6% moisture content,a seed water potential of approximately –250 MPa, butthose of the remaining three cultivars were much more sensitiveto desiccation damage. Moreover, in all four cultivars, seedlongevity at cool and sub-zero temperatures, and at low moisturecontents did not conform with orthodox seed storage behaviour:viability was lost more rapidly under these conditions thanat either warmer temperatures or higher moisture contents. Theresults confirm that coffee seeds fail to satisfy the definitionsof either typical orthodox or recalcitrant seed storage behaviour.These results, therefore, point to the possibility of a thirdcategory of storage behaviour intermediate between those oforthodox and recalcitrant seeds. One of the main features ofthis category is that dry seeds are injured by low temperatures. Key words: coffee, Coffea arabica L., seed storage, seed longevity, desiccation, temperature     

Logarithmic Relationship between Moisture Content and Longevity in Sesame Seeds

The relationship between seed moisture content and seed longevityin sesame (Sesamum indicum L.) in hermetic storage at 50 °Cis logarithmic. The logarithmic relationship is maintained from15 per cent down to 2 per cent – the lowest moisture contenttested — but above 15 per cent this ‘air-dry’relationship no longer holds since further increase in seedmoisture content does not reduce longevity. Tentative estimatesof constant values for the improved seed viability equationare provided, and implications for long-term storage are discussed. Sesame, Sesamum indicum L., seed storage, improved viability equation, seed moisture content, seed longevity prediction     

Seed Viability Constants for Groundnut

This research determined constants for a viability equationto predict the longevity of groundnut seeds and to improve themanagement of seedlot storage throughout the trading period.Seeds of the Brazilian cultivar ‘Tatu’ (Valenciabunch type) were tested. Nine moisture content levels (rangingfrom 2.4 to 12.8%) and three storage temperatures (40, 50 and65 °C) were used. Sub-samples for each moisture content-storagetemperature combination were sealed in laminated aluminium-foilpackets and stored in incubators until complete survival curveswere obtained. A reliable equation was obtained to predict groundnutseed longevity through the constantsK_E=6.177,C_W=3.426,C_H=0.0304andC_Q=0.000453.Copyright 1998 Annals of Botany Company Arachis hypogaeaL., seed longevity, seed storage, viability equation.     

The Dry Storage of Citrus Seeds

The survival of seeds of lemon (Citrus limon L.), lime [C. arantifolia(Christm.) Swing.] and sour orange (C. aurantium L.) was examinedunder a wide range of constant moisture contents and temperatures.Seed longevity was increased by decreasing the moisture contentand temperature of the storage environment. Maximum viabilitywas maintained in the combination of storage conditions includingthe lowest moisture content (5 per cent) and lowest temperature(–20 °C) investigated. The practicality of dry storageof citrus seed for genetic conservation is discussed. Citrus limon L., lemon, Citrus aurantifolia (Christm.), Swing, lime, Citrus aurantium L., sour orange, dry storage, moisture content, temperature, seed viability, seed longevity     

The Low-moisture-content Limit to the Negative Logarithmic Relation Between Seed Longevity and Moisture Content in Three Subspecies of Rice

The lower limit to the negative logarithmic relation betweenseed longevity and moisture content was determined in threesubspecies of rice (Oryza satwa L.) by storing seeds of fivecultivars at 65 °C with 11 different moisture contents (1.5–15.3%f. wt) for various periods up to 150 d and then testing forgermination. The estimates of the low-moisture-content limit(m_c) were 4.3% for subsp. indica, 4.4% for subsp. japonica,and 4.5% for subsp. javanica. These moisture contents were inequilibrium with 10.5—12.0% r.h. No significant effectof moisture content between 1.5% and m_c on longevity was detected(P > 0.05), while between m_c and 15.3% there were negativelogarithmic relations between longevity and moisture content.There were no significant differences in the relations betweenlongevity and moisture either above or below m_c between thetwo japonica cultivars or between the two javanica cultivars(P > 0.10). There was also no significant difference in theslope of the negative logarithmic relation between longevityand moisture above m_c among the three subspecies (P > 0.25).However, there were significant differences in the standarddeviation of the frequency distribution of seed deaths in timeat any one moisture content, both above and below m_c; this isa measure of seed longevity which is independent of pre-storageenvironment, and the differences observed show that there aregenetically determined differences in longevity among the threesubspecies (P < 0.005), indica being the longest and japonicathe shortest lived. The results provide no evidence for intra-specificvariation in m_c and support the view that the maximum seed storagemoisture content which provides the maximum longevity is thatwhich is in equilibrium with about 10–11% r.h. It is concludedthat while the seed viability constant C_w of the seed viabilityequation is species specific and therefore applies to most,if not all, cultivars of rice, variation in the value of K_Eis the source of the differences in potential longevity of thethree subspecies. Rice, Oryza sativa L, seed storage, seed longevity, seed moisture, viability equation     

The Effect of Temperature and Moisture Content on the Longevity of Seed of Ulmus carpinifolia and Terminalia brassii

Seeds of the Smooth-leafed Elm (Uimus carpinifolia) and of thetropical forest tree Terb (Terminalia brassii) were stored hermeticallyand sampled at intervals for periods of up to two years. Bothspecies possess ‘orthodox’ seed (increasing longevityis observed as either moisture content or temperature are reduced)within the temperature ranges from — 13 to 52°C (Elm)and from —4 to 42°C (Terb) and within the moisturecontent ranges from 3 to 19 per cent (Elm) and from 5 to 14per cent (Terb) on a fresh weight basis. Elm seed stored at—75°C showed the expected relationship between longevityand moisture content, but did not differ significantly in longevityfrom seed kept at — 13°C when moisture contents wereheld constant. Probit analysis of the relationship between germinationpercentage and time was performed for each storage environment,yielding a slope from which the standard deviation of the distributionof seed deaths over time () was calculated. Standard deviationvalues were used in turn to determine the values of constantsin a viability equation which had previously been applied toseed of barley, chickpea, cowpea and soybean. The equation,which gave a good fit to the results obtained, can be used topredict viability for seed in storage over a wide range of environmentalconditions. Some limitations to the applicability of the viability equationwere defined. At 22 per cent and higher moisture contents Elmseed survived longer than predicted. Furthermore, all Elm andTerb seed was killed quickly on placing in —75°C at22 and 20 per cent moisture content respectively, but high viabilitywas retained for several days at 19 and 17 per cent respectively.Practical implications of the results are discussed. Uimus carpinifolia Gleditsch, Smooth-leafed Elm, Terminalia brassii Exell, Terb, seed longevity, seed storage, moisture content, temperature     

Constant, Fluctuating and Effective Temperature and Seed Longevity: a Tomato (Lycopersicon esculentum Mill.) Exemplar

Tomato seeds with a moisture content of 16.4% were stored hermeticallyat one of five constant temperatures (10, 20, 30, 40, 50 °C)or in one of nine alternating temperature (24 h/24 h) regimes(10/30, 10/40, 10/50, 20/30, 20/40, 20/50, 30/40, 30/50, 40/50°C) for up to 224 d. In each regime, seed survival conformedto cumulative negative normal distributions and all 14 survivalcurves could be constrained to a common origin. Estimates ofthe constants C_Hand C_Qof the viability equation determined atconstant temperatures were 0.0346 (s.e. 0.0058) and 0.000401(s.e. 0.000096), respectively. The effective temperature forseed survival of each alternating temperature regime was alwaysmuch higher than the mean. Tomato seeds were also stored hermeticallyat 15.9% moisture content at 40 °C for 0, 7, 14, 21 or 28d before transfer to 50 °C. This investigation showed thatthe standard deviation of the subsequent survival curves at50 °C was unaffected by the duration of previous storageat 40 °C. The results of both investigations were consistentwith the hypothesis that loss in probit viability is solelya function of the current storage environment, with no effectof change in temperature per se. The application of the viabilityequation to seed survival in fluctuating environments was validatedagainst independent observations for rice in uncontrolled storageconditions. Copyright 2001 Annals of Botany Company Temperature, seed storage, longevity, moisture content, viability equation, tomato, rice     

Improved Equations for the Prediction of Seed Longevity

Equations for predicting seed longevity in storage have beenimproved so that they now take into account variations withina species in initial seed quality—which is affected bygenotype and pre-storage environment—and so that theyare more accurate over a wider range of storage environmentsThese improvements have been incorporated into a seed viabilitynomograph for barley (Hordeum distichum L.) which may be usedto predict percentage viabihty of any seed lot after any timein any storage environment within the range –20 to 90°C and 5–25 per cent moisture content. Applicationsof the improved equations to seed drying and to long-term seedstorage for genetic conservation are discussed. Hordeum distichum L., barley, seed viability, seed longevity prediction, seed storage, seed drying, storage temperature, seed moisture content, genetic resources conservation     

Desiccation Tolerance and Potential Longevity of Developing Seeds of Rice (Oryza sativa L.)

The longevity and desiccation tolerance of samples of seedsof a japonica rice (Oryza sativa L.) harvested serially duringdevelopment from plants grown in two temperature regimes, viz28/20 °C and 32/24 °C (12/12 h) were determined. Massmaturity (defined as the end of the seed-filling phase) occurred19·7 and 18·3 d after 50% anthesis, respectively.Longevity (determined at 40 °C with 15% moisture contentand quantified by the value of the constant K_i of the seed viabilityequation) improved during seed development and maturation until17 and 14 d after mass maturity in the cooler and warmer regimes,respectively, but declined thereafter. Changes in K_i with timewere similar in the two environments until mass maturity, butthe increase in K_i values after mass maturity was much greaterin the cooler regime. Tolerance of desiccation to low (4%) moisturecontents improved until 22 and 14 d after mass maturity in thecooler and warmer regimes, respectively, when maturation dryinghad reduced seed moisture contents naturally to 24 and 32% moisturecontent, respectively. Further delays to seed harvest reduceddesiccation tolerance, particularly in the warmer environment.Comparison among 15 samples of seeds harvested at differenttimes in the two environments showed a strong correlation (r= 0·947, P < 0·01) between longevity (K_i) anddesiccation tolerance (to 4% moisture content). Hence, it issuggested that the regulation of desiccation tolerance to lowmoisture contents and potential air-dry longevity during seeddevelopment and maturation determined here may have a commoncause.Copyright 1994, 1999 Academic Press Oryza sativa L., rice, desiccation tolerance, genebanks, seed development, seed longevity, temperature     

Temperature and Seed Storage Longevity

Seed survival data for eight diverse species, namely the cerealbarley (Hordeum vulgare L.), the grain legumes chickpea (Cicerarietinum L.), cowpea [Vigna unguiculata (L.) Walp.] and soyabean [Glycine max (L.) Merr.], the timber trees elm (Ulmus carpinifoliaGleditsch.), mahogany (Swietenia humilis Zucc.), and terb (Terminaliabrassii Exell.), and the leaf vegetable lettuce (Lactuca sativaL.) were compared over a wide range of storage environments(temperatures from –13 °C to 90 °C, seed moisturecontents from 1.8 to 25% f. wt) using a viability equation developedpreviously. In accordance with that equation, the effect oftemperature on seed longevity was dependent upon the temperaturerange. The temperature coefficients of the viability equationdid not differ significantly (P > 0.05) among the eight speciesdespite their contrasting taxonomy. Thus the quantitative relationbetween seed longevity and temperature does not vary among diversespecies. The same conclusion was obtained for the coefficientsof a proposed alternative model of the relation between seedlongevity and temperature. The implications of the two temperaturemodels in the viability equation for extrapolations to low andvery low temperatures are discussed. Seed storage, seed longevity, seed moisture, temperature, viability equation, genetic resources conservation, Cicer arietinum L., Glycine max (L.) Merr., Hordeum vulgare L., Lactuca sativa L., Swietenia humilis Zucc., Terminalia brassii Exell., Ulmus carpinifolia Gleditsch., Vigna unguiculata (L.) Walp     

Moisture Content and the Longevity of Seeds of Phaseolus vulgaris

The lower limit to the negative logarithmic relation betweenseed longevity and moisture was determined in bean (Phaseolusvulgaris L.). Sub-lots of seed were hermetically stored at 65°C and 11 moisture contents (3.26–13.6% f. wt) forup to 80 d, tested for germination and the seedlings evaluated.In accordance with the seed viability equation, there was anegative logarithmic relation between moisture content (%, f.wt) and longevity. Two different criteria for estimating theslope constant of this relation gave similar values of 4.76(s.e. 0.26) and 4.82 (s.e. 0.24). The calculated lower moisturecontent limits to the relation were 5.7 and 5.6%, respectively,values at equilibrium with 10.6–10.8% relative humidity(rh). Further drying to 3.26% had little additional effect onlongevity, but initial germination was slightly reduced. Theresults are discussed in relation to water potential and comparedwith other crops. Arguments against transforming germinationvalues to disregard the seeds initially failing to germinateare emphasized. Common bean, Phaseolus vulgaris L. cv. Provider, seed storage, seed longevity, seed moisture, viability equation, water relations     

Wheat Viability at High Moisture Content under Hermetic and Aerobic Storage Conditions

Wheat seeds (Triticum durum) were stored under both hermeticand aerobic conditions at 25 °C with moisture contents from15 to 33 per cent. Under hermetic storage, seeds lost viabilitymore rapidly the higher the moisture content, whereas in aerobicstorage, seed longevity was enhanced as the moisture contentwas increased from 24 to 31 per cent, and over this range ofmoisture content the seeds survived longer under aerobic thanhermetic storage. On the contrary, an apparent reversal of thistrend occurred when moisture content was increased above 31per cent. The possibility that the changes in longevity occurring at highermoisture contents might be due to the activation of seed metabolismwas supported by the enhanced incorporation of [³H]leucine intoTCA insoluble material (indicating increased protein synthesis)and the reduced leakage of glucose (indicating increased membranerestitution) when seeds were allowed to achieve higher moisturecontents during the prehydration period. The highest level ofseed activation was found in seeds preconditioned to about 31per cent moisture content. Moreover, these seeds, when subsequentlystored under aerobic conditions, maintained a higher rate ofprotein synthesis and lower membrane permeability during thestorage period than seeds at lower water contents. It is suggested that seeds stored at a sufficient hydrationlevel in the presence of oxygen can sustain an effective metabolismduring extended storage, thus permitting the repair of cellulardamage. However, it might be possible that at about 33 per centmoisture content seed could suffer from an excessive advancementof metabolism. Triticum durum, seed storage, effects of high moisture content and oxygen     

Theoretical Basis of Protocols for Seed Storage III. Optimum Moisture Contents for Pea Seeds Stored at Different Temperatures

In previous work, we demonstrated that there was an optimummoisture level for seed storage at a given temperature (Vertucciand Roos, 1990), and suggested, using thermodynamic considerations,that the optimum moisture content increased as the storage temperaturedecreased (Vertucci and Roos, 1993b). In this paper, we presentdata from a two year study of aging rates in pea (Pisum sativum)seeds supporting the hypothesis that the optimum moisture contentfor storage varies with temperature. Seed viability and vigourwere monitored during storage under dark or lighted conditionsat relative humidities between 1 and 90%, and temperatures between-5 and 65°C. The optimum moisture content varied from 0·015g H₂O g^-1 d.wt at 65°C to 0·101 g H₂O g^-1 d.wt at15°C under dark conditions and from 0·057 at 35°Cto 0·092 g H₂O g^-1 d.wt at -5°C under lighted conditions.Our results suggest that optimum moisture contents cannot beconsidered independently of temperature. This conclusion hasimportant implications for 'ultra-dry' and cryopreservationtechnologies.Copyright 1994, 1999 Academic Press Seed storage, seed aging, seed longevity, water content, temperature, glass, desiccation damage, ultradry, Pisum sativum L., pea, cryopreservation     

The Survival of Germinating Orthodox Seeds after Desiccation and Hermetic Storage

Seeds of barley (Hordeum vulgare L.) and mung bean (Vigna radiata(L.) Wilczek), with orthodox seed storage behaviour, were imbibedfor between 8 h and 96 h at 15 °C and 25 °C, respectively,while barley seeds were also maintained in moist aerated storageat 15 °C for 14 d. These seeds and seedlings, together withcontrols, were then dried to various moisture contents between3% and 16% (wet basis) and hermetically stored for six monthsat —20°C, 0°C or 15°C. In both species, neitherdesiccation nor subsequent hermetic storage of the control lotsresulted in loss in viability. The results for barley seedsimbibed for 24 h were similar to the control, but desiccationsensitivity increased progressively with duration of imbibitionbeyond 24 h in barley or 8 h in mung bean; these treatmentsalso reduced the longevity of the surviving seeds in air-drystorage. Loss in viability in barley imbibed for 48 h was mostrapid at the two extreme seed storage moisture contents of 3·6%and 14·3%, and in both these cases was more rapid at15 °C than at cooler temperatures. Similarly, for mung beanimbibed for 8 h, loss in viability was most rapid at the lowest(4·3%) moisture content, but in this case it was morerapid at –20 °C than at warmer temperatures. Thus,these results for the storage of previously imbibed orthodoxseeds conform with the main features of intermediate seed storagebehaviour Key words: Barley, Hordeum vulgare L., mung bean, Vigna radiata (L.) Wilczek, desiccation sensitivity, seed longevity, seed storage behaviour     

Low Moisture Content Limits to Relations Between Seed Longevity and Moisture

Discontinuities at low moisture contents in the otherwise logarithmicrelations between seed longevity and seed moisture content (%,f. wt basis) in hermetic storage at 65 °C were detectedat 2–0% in groundnut (Arachis hypogaea L.), 3·5%in onion (Allium cepa L.), 4·5% in sugar beet (Beta vulgarisL.), 4·6% in barley (Hordeum vulgare L.), 5·3%in chickpea (Cicer arietinum L.) and wheat (Triticum aestinumL.), and 5·6% in cowpea [Vigna unguiculata (L.) Walp.].In contrast, the equilibrium relative humidity of seeds at thesevalues was similar, varying between 9·9% (onion and sugarbeet) and 11·5% (wheat). The mean value was 10·5%r.h. (s.e. 0.2). There was no significant (P > 0·05)effect of further reduction in seed moisture content below thesecritical values on longevity, except in wheat (P < 0·005),in which there was a further increase in longevity. In soyabean [Glycine max (L) Merrill], the logarithmic relation continueddown to the lowest moisture content investigated, 3·3%(11·4% equilibrium relative humidity). Above the criticalvalue, seed longevity in groundnut showed the least sensitivityto increase in percentage moisture content, while barley showedthe greatest, the values of the viability constant C_w (slopeof the negative logarithmic relation between longevity and moisture)being 4·089 (s.e. 0·278) and 5·966 (s.e.0·325), respectively. These differences in the valueof C_w among the eight crops were significant P < 0·005),whereas the relative sensitivity of seed longevity to changein equilibrium relative humidity above the critical moisturecontent did not differ significantly among the eight (P >0·10) and was equivalent to a doubling of longevity foreach 8·7% reduction in equilibrium relative humidity.Accordingly it is concluded that the relative effect of waterpotential on seed longevity can be considered to be the samefor these and probably also for many other orthodox species. Barley, chickpea, cowpea, groundnut, onion, soya bean, sugar beet, wheat, seed storage, seed longevity, seed moisture content, viability equation, water relations     

The Effect of Chilling and Moisture Status on the Germination, Desiccation Tolerance and Longevity ofAesculus hippocastanumL. Seed

Effects of 2 °C chilling on the threshold moisture contentsand water potentials for various physiological processes wereestimated forAesculus hippocastanumL. seed. Seed harvested atthe time of maximum seed fall exhibited a dual response to drying:partial drying from near 50% to 32–40% moisture contentprogressively increased germination percentage (at 16 °C)up to various peak values; further desiccation was detrimental,confirming that the seeds are ‘recalcitrant’. Themoisture content for optimum germination was increased by atleast 10% as the chilling period was raised from 0 to 9 weeks.A negative linear relationship was found between log₁₀mean timeto germinate and probit final germination, regardless of pre-treatment,indicating that partial desiccation and chilling are interchangeablein promoting germination of hydrated seed. For nearly fullyhydrated seeds, increasing the chilling period from 6 to 26weeks increased the viability-loss onset point for desiccationinjury from near 40% to about 48% moisture content without alteringthe drying rates of seed tissues. Extending moist chilling invarious seed lots from 0 to 26 weeks decreased subsequent longevityat 16 °C. For 26-week-chilled seeds longevity (the periodto lose one probit of germination) differed above and belowa threshold moisture content of 48%. It remained constant inthe moisture-content range 48–38%, but increased progressivelyas moisture content was raised above 48%. This threshold moisturecontent coincided with the value above which chilled seed pre-germinatedin storage. The results indicate that post-harvest desiccationand chilling alter the water relations of various physiologicalprocesses and a schematic summary is presented which relatesthe results to an axis water sorption isotherm.Copyright 1998Annals of Botany Company Aesculus hippocastanumL., horse chestnut, chilling, moisture content, water potential, desiccation tolerance, longevity, recalcitrant seed, embryo axis, maturation, germination.     

Alternating Temperatures and Rate of Seed Germination in Lentil

The effect of alternating temperatures on the times taken byseeds of lentil (Lens culinaris Medikus) to germinate was investigatedusing a two-way temperature-gradient plate. Between 5 and 25°C,warmer temperatures increased the rate of germination. Variationamong the individual seeds in the times required for germinationat different constant temperatures within this range were describedwell by a log-normal distribution of thermal times, accumulatedabove a base temperature of 1·5°C. Even with amplitudesas great as 20°C, no effect of alternation per se on thethermal time required for germination was detected—whetherthe cool temperature was applied for 8 or 16 h d^-1. Similarly,in alternating temperature regimes where the minimum temperatureof the diurnal cycle was between 0°C and the base temperature,the thermal times required for germination (where no thermaltime accrued during the periods when temperature was below T_b)were in close agreement with those values provided by the modeldetermined at warmer constant temperatures. However, where theminimum temperature applied was < 0°C the germinationof all but the earliest germinators was delayed beyond modelpredictions, and more so where the sub-zero minimum temperaturewas applied for 16 rather than 8 h d^-1. The results, therefore,contradict the view that alternation in temperature per se reducesthe thermal time required for seed germination. Rather, rateof germination responds instantaneously to current temperature,but prolonged exposure to sub-zero temperatures can result indamage sufficient to delay germination when seeds are returnedto regimes warmer than the base temperature.Copyright 1994,1999 Academic Press Lens culinaris Medikus, lentil, seed germination, alternating temperatures, thermal time, temperature-gradient plate     

The Effect of Desiccation on the Longevity of Seeds of Araucaria hunsteinii and A. cunninghamii

Seeds of Araucaria hunsteinii K. Schum. dried quicker at 29°Cthan at 19°C and quicker with the seed-coat removed thanwhen intact; seeds enclosed in polyethylene bags increased inmoisture content. At 15°C, seeds in a flow of air driedquicker than seeds in a box with silica gel, which in turn driedquicker than seeds in a box with no desiccant. No loss of germinationability occurred on drying fresh seed from 53 to about 32 percent moisture content (fresh weight basis); during further desiccationthe percentage germination was related to percentage moisturecontent in the form of a sigmoid curve, culminating in a completefailure to germinate at approximately 14 per cent moisture content.A consistent relationship was observed for all treatments andthe mean critical moisture content for seed death (failure togerminate) was near 23 per cent. Excised embryos grew on 1 percent agar but died if previously subjected to 14 h of desiccationat 15°C. In contrast, no relationship was found between germination andmoisture content of A. cunninghamii D. Don on desiccation from21 to 7 per cent moisture content. Possible causes for the observeddifference in response to desiccation are discussed and methodsfor seed storage are considered. Araucaria hunsteinii, Klinkii pine, Araucaria cunninghamii, Hoop pine, desiccation, seed longevity, storage of seeds     

The effect of temperature and CO2 on seed quality development in wheat (Triticum aestivum L.)

Winter wheat (Triticum aestivum L.) cv. Hereward was grown inthe field in two double-walled polyethylene-covered tunnelswithin each of which a temperature gradient was superimposedon diurnal and seasonal fluctuations in temperature. The meantemperature between anthesis and harvest maturity varied from14.3 to 18.4C among plots within these tunnels. The CO₂ concentrationwas controlled at different values in each tunnel; seasonalmean concentrations were 380 and 684 µmol CO₂ mol^–1air. Crops were also grown outside the tunnels at ambient temperaturesand CO₂. Samples of seeds were harvested sequentially from eachplot between anthesis and harvest maturity. Seed germinationand seed survival during subsequent air-dry storage were determinedfor each sample. The onset of both ability to germinate anddesiccation tolerance (ability to germinate after rapid desiccationto 10–15% moisture content and subsequent rehydration)coincided in all environments. Full germination capacity (>97%, determined at 10C) was reached 4–18 d before theend of the seed-filling phase (mass maturity) in most cases.There was little or no decline in germination capacity duringsubsequent seed development and maturation. Differences in seedquality were evident, however, throughout seed development andmaturation when seed survival curves during subsequent storagewere compared. Potential longevity in air-dry storage (assessedby the value K₁ of the seed viability equation) improved consistentlyboth before and after mass maturity. There was a significantpositive relation between the rate of increase in potentiallongevity (dK₁Idt) and temperature (the minimum temperaturefor seed quality development was 4.8 C), but neither CO₂ concentrationnor production within the polyethylene tunnels affected thisrelation. Key words: Wheat, Triticum aestivum L., seed development, seed longevity, carbon dioxide, temperature     

The Influence of Temperature and Moisture on Seed Viability Period in Barley (Hordeum distichum L.)

Storage experiments were carried out on barley seed (Hordeumdistichum L.) lasting from 1 min to 926 days, including 52 hermeticstorage environments covering a range of temperatures from 3to 90 °C and 5·5 per cent to 24·6 per centmoisture content (f. wt basis). Over the entire range of conditionssurvival curves conformed to negative cumulative normal distributionsand, for any given measure of longevity, e.g. half-viabilityperiod, longevity was roughly proportional to the negative exponentof both temperature and moisture content. Although previouslyreported viability equations were adequate to describe theserelationships over restricted ranges of environments, over theextended range of conditions tested here it was shown that therelationship between log seed viability and temperature is infact slightly convex, whilst that between log seed viabilityand moisture content is slightly concave. An improved viabilityequation was applied which takes into account those curvaturesand, at the same time takes into account the initial viabilityof a seed lot which reflects pre-storage deterioration. Thefit was excellent and thus it is now possible to predict percentageviability of any lot of barley seed after any storage periodunder a very wide range of conditions. Hordeum distichum L., barley viability, seed longevity, seed storage, moisture content of barley seed, temperature, influence of seed viability