Seed Survival Curves Research Articles

Seed Longevity Potential Predicted by Radicle Emergence (RE) Vigor Test in Watermelon Seed Cultivars

The study was conducted to test whether radicle emergence (RE) would correlate with the storage potential of ten seed lots of watermelon (Citrullus lanatus (Thunb.) Matsum. and Nakai) hybrid cultivars (>98% normal germination). The RE test was performed by frequent counting radicle emergence (2 mm) percentage between 34 h and 60 h after germination was set up at 25 °C in the dark. Seed longevity was hermetically determined by artificial storage of seeds (air and waterproof) at 17 ± 0.3% of seed moisture and at 35 ± 2 °C over 63 days. Twelve seed samples were taken out during aging, and seed survival curves were constructed based on normal germination percentages conducted at 25 °C for seven days in the dark. The seed longevity criterion was P50 (time for the germination to fall to 50%), which was determined through probit analysis by using survival curves. Correlation analysis showed that RE counts at 42 h during germination were highly correlated (p < 0.01) with initial seed quality, Ki (r = 0.7538), and the half-viability period, P50 (r = 0.7936). Pre-storage normal germination percentages of seed lots were not related to longevity. Results showed that the RE vigor test has the potential to predict longevity in highly germinating hybrid watermelon seed lots.

Estimation of Seed Longevity in Onion Seed Lots by a Vigor Test of Radicle Emergence Test in Artificial Ageing Conditions

The study was conducted to test whether a vigor test of a single count of radicle emergence (RE test) would correlate with the storage potential of 10 seed lots of onion (Allium cepa L.) cultivars in artificial storage conditions. The RE test was performed by counting radicle emergence (2 mm) percentage at 80 h after germination was set up at 20 °C. Seed longevity was determined by storage at 75% relative humidity, obtained by saturated NaCl, at 35 °C over 60 days. Twelve seed samples were taken out during ageing, and seed survival curves were constructed based on normal germination percentages conducted at 20 °C for 12 days in the dark. The seed longevity criterion was P50 (time for the viability to fall to 50%), which was determined through probit analysis by using survival curves. Correlation analysis showed that RE counts at 80 h during germination were highly correlated (p < 0.001) with initial seed quality, Ki (R2 = 0.888) and the half-viability period, P50 (R2 = 0.823). Non-aged pre-storage final normal germination percentages of seed lots were also significantly related to longevity (Ki, R2 = 0.808, p < 0.001, P50, R2 = 0.750, p <0.01), while the level of significance was lower. It can be concluded that the RE test can be used as a fast vigor test to estimate the longevity in onion seed lots.

The radicle emergence test and storage longevity of cucurbit rootstock seed lots

A study was carried out to test whether a single count of radicle emergence (RE test) would correlate with the storage potential of seed lots of cucurbit (C. maxima × C. moschata) rootstock cultivars. The RE test was performed by counting radicle emergence percentage between 26 and 100 hours of germination. Seed longevity was determined by storage at 75% relative humidity at 35°C over 100 days, with seed survival curves constructed based on normal germination percentages. Ki (estimated initial viability in probits), σ (standard deviation of the normal distribution of seed death in time) and p50 (time for viability to fall to 50%) were determined through probit analysis. Correlation analysis showed that RE counts particularly between 30 and 34 hours were highly (P < 0.01) correlated with normal germination percentage, Ki and p50. It can be concluded that RE tests can be used as an indicator of subsequent seed lot longevity in cucurbit rootstock seed cultivars.

Seed longevity of two nutrient-dense vegetables (Amaranthus spp.)

For many traditional vegetables, seed longevity is unknown, limiting proper seed bank management. In this study, the comparative seed longevity of two nutrient-dense leafy vegetables, blood amaranth (Amaranthus cruentus) and edible amaranth (A. tricolor), was compared together with two reference crops, crookneck squash (Cucurbita moschata) and soya bean (Glycine max). Seed lots of four genebank accessions of the corresponding vegetable species were treated under accelerated ageing (AA) conditions with an average of 41.1°C and an average of 89.9% relative humidity for 33 days to generate single seed survival curves and calculate the time taken for seed viability to fall to 50% (p50). The seed survival curves of all four species had values of goodness to fit (R2) values between 0.43 and 0.85. Seeds of the A. cruentus and A. tricolor accessions had high p50 values of 19.5 and 32.8 days, respectively, compared with the C. moschata and G. max accessions, which returned p50 values of 8.2 and 4.9, respectively. This means that these leafy amaranths have a long seed longevity compared with other vegetable crops. This suggests that properly dried seeds of amaranth crops can be stored for long periods of time at 5°C in aluminium foils.

A rapid and sensitive method to assess seed longevity through accelerated aging in an invasive plant species

BackgroundSeed longevity and vigor assessment is crucial for efficient ex situ biodiversity conservation in genebanks but may also have potential applications for the understanding of ecological processes and in situ biodiversity conservation. In fact, one of the factors determining the persistence of invasive species, a main threat to global biodiversity, is the generation of soil seed banks where seeds may remain viable for several years. Artificial seed aging tests using high temperatures and high relative humidity have been described for seed longevity estimation but have been mainly optimized for species with commercial interest. Thus, the aim of the study is to define a rapid and sensitive method to assess seed longevity and vigor through accelerated aging in the worldwide distributed invasive species Carpobrotus edulis to provide tools to biodiversity managers to evaluate invasive potential and develop effective post-eradication plans.ResultsSlow seed deterioration rate was obtained when C. edulis seeds were subjected to common accelerated aging temperatures (43–45 °C). This contrasts with the rapid viability decay between 24–72 h when seeds were subjected to temperatures superior to 55 °C, a strong inflection point for this species’ thermosensitivity. Relative humidity also played a role in defining seed survival curves, but only at high temperatures, speeding up the deterioration process. The selected aging conditions, 55 °C at 87% relative humidity were tested over two C. edulis populations and three measures were proposed to parametrize the differential sigmoidal seed survival curves, defining the seed resistance to deterioration (L5, aging time where 95% of seeds maintain their viability), medium longevity (L50, 50% of seeds lose their viability) and lethal aging time (L95, 95% of viability loss).ConclusionsAn accelerated aging test at 55 °C and 87% relative humidity constitutes a rapid and sensitive method that can be performed within a working week, allowing managers to easily test seed vigor and longevity. This test may contribute to assess invasive potential, design effective monitoring programs and soil seed bank eradication treatments.

Effect of simulated flooding during rice seed development and maturation on subsequent seed quality

AbstractThe resilience of seed quality in rice (Oryza sativaL.) to flooding was investigated. Pot-grown plants of thejaponicacv. Gleva, theindicacv. IR64, and the introgressed line IR64-Sub1 were submerged in water, to simulate flooding, for 3‒5 days at different stages of seed development and maturation. Mean seed weight, pre-harvest sprouting, ability to germinate, and subsequent longevity in air-dry storage were assessed. Whereas seed quality in both IR64 and IR64-Sub1 was resilient to submergence, in Gleva the longer the duration of submergence and the later in development when plants were submerged the greater the pre-harvest sprouting. Thousand seed dry weight was reduced more by submergence in Gleva than IR64 or IR64-Sub1. At harvest maturity, few pre-harvest sprouted seeds were able to germinate upon rehydration after desiccation to 11‒12% moisture content. Seed longevity of the non-sprouted seed fraction in air-dry hermetic storage (40°C, 15% moisture content) was not affected greatly by submergence, but longevity of thejaponicarice was less than that of theindicarices due to the former's steeper seed survival curves. Longevity of the twoindicarices was predicted well by the seed viability equation and previously published estimates of viability constants for rice. The greater dormancy of IR64 and IR64-Sub1, compared with Gleva, enhanced resilience to pre-harvest sprouting and reduced thousand seed dry weight from plant submergence. There was little or no effect of plant submergence on subsequent air-dry storage longevity of non-sprouted seeds in any genotype.

A continental-scale study of seed lifespan in experimental storage examining seed, plant, and environmental traits associated with longevity

Management of seed banks conserving the biodiversity of phylogenetically diverse species requires insight into seed longevity. This study determined the seed longevity of 172 species sourced from across the mega-diverse flora of the Australia continent. Seeds were aged via a controlled ageing experiment through storage at 45 °C and 60 % RH, or 60 °C and 60 % RH, and regularly tested for germination. Relative seed longevity between species was determined by comparing the time to 50 % viability loss (p 50), calculated via probit analysis of seed survival curves. Seed, plant, and environmental traits were examined for associations with longevity. The p 50 values varied between species from 3.0 to 588.6 days. Serotinous species, and woody trees and shrubs, had significantly longer-lived seeds than geosporous species, and species of herbaceous habit. Seeds that possess physical dormancy, and seeds with large embryos with little endosperm, were also long-lived. There was a weak, but significant, positive correlation between seed mass and longevity. Seeds sourced from regions of higher mean annual temperature and rainfall were significantly longer-lived than seeds from cooler and drier regions, although both environmental factors were weakly associated with longevity. Compared with species from other regions of the world, prolonged longevity is a feature of many Australian species. Nevertheless, seed life-spans vary substantially between species and close consideration of seed traits along with biotic and abiotic components of the plants and their environment can assist to differentiate between potentially long- and short-lived seeds.

Evaluation of seed quality: from physiology to international standardization

Seed quality standards enable seed users to achieve their objectives in the establishment of uniform seedlings to a high and reliable level for a range of agricultural and horticultural crops, growing systems and market outlets. Quality standards of commercial seed lots are determined by their positions on the seed survival curves and the shape of their germination progress curves. Although comparative descriptions of germination curves can be achieved by the calculation of the mean germination time (MGT; delay to radicle emergence), single early counts of radicle emergence provide a convenient means of predicting MGT and differences between seed lots. Evidence is presented for an ageing and metabolic repair hypothesis as the overall physiological basis to explain the principles behind the standard germination and vigour tests (ageing, electrolyte leakage, cold test, germination rate and seedling size). The work of the International Seed Testing Association (ISTA) in developing convenient, inexpensive and internationally repeatable tests is illustrated.

Longevity equation for tomato seeds

The objective of this research was to equate the standard deviation of the frequency of distribution of tomato seed deaths (σ) in the probit model using a small number of storage conditions and a relatively short storage period. Four accessions of tomato seeds were taken from the vegetable germoplasm bank of the Federal University of Vicosa, Brazil and were used to obtain data of seed longevity under constant conditions of temperature and moisture content. Seed samples with moisture contents of 10, 12, and 14% on wet basis were sealed in aluminum foil polyethylene storage packets and stored at 31, 41, and 51°C over 208 days. Percentage germination values obtained during storage were transformed into probit and used in multiple linear regressions for determination of the coefficients of the longevity equation. The equation obtained to express the logarithm of σ presented an adjusted linear coefficient of determination of 0.924 and a standard error of 0.14. All equation coefficients were significant at a 0.001% probability level. The viability model presented an adjusted linear coefficient of determination of 0.707 and a standard error of 10.2% for all data points and seed survival curves.

Variation in seed longevity among different populations, species and genera found in collections from wild Australian plants

Natural variation in longevity among populations of the same species, and between species and genera was investigated to inform seed-collection strategies. Seed longevity for 30 wild Australian populations was measured with a controlled ageing test. The populations were represented by eight species from three genera, namely Minuria (Asteraceae), Wahlenbergia (Campanulaceae) and Plantago (Plantaginaceae), each collected from up to eight different locations. Seed-survival curves were fitted by using the equation v = Ki + p/σ, which allowed comparison of the initial population viability (Ki), the population distribution of seed life spans (σ), and mean seed longevity (P50, calculated as Ki × σ). At a genus level, the average P50 indicated that M. integerrima (DC) Benth. is the longest-lived, Wahlenbergia is intermediate and Plantago is the shortest-lived. However, there was also variation in P50 values among populations of most species. Some species had the same σ value for all populations, e.g. all eight populations of W. communis Carolin had the same σ value, with the differences in Ki causing the variation in P50. This consistency in σ existed even though seedlots were collected from diverse locations, with mean annual rainfall ranging from 180 to 840 mm. In comparison, for the six seedlots of W. gracilis (G.Forst.) A.DC., a large difference in σ as well as Ki led to the variability in P50, with some indication of a possible correlation between annual rainfall and P50 or σ in some species. A relationship between variation in σ and the breeding system is proposed for Wahlenbergia. The data show that it can be risky to expect accurate prediction of seed longevity for a wild species on the basis of survival data from a single collection.

Effect of temperature and humidity on the longevity of Orobanche seeds

The effects of moisture and temperature on seed longevity were studied over periods of up to 426 days in three species of Orobanche. Saturated salt solutions were used to achieve equilibrium relative humidities (e.r.h.) between 11% and 85% at temperatures of 20–60 °C. The viability equation describing loss of viability in these conditions applied to the three species such that the lower the temperature and lower the equilibrium relative humidity the greater the longevity. The initial viability differed between species with the seed lot of Orobanche crenata having the lowest viability. However, the relative effect of temperature on longevity and the relative sensitivity of seed longevity to changes in equilibrium relative humidity were the same in all species. Longevity, estimated by the standard deviation of the seed survival curves was greater in Orobanche aegyptiaca and O. crenata than in Orobanche minor, being for example about 100, 103 and 49 days, respectively, at 40 °C, 50% e.r.h. Accurate prediction of longevity is necessary to understand and quantify the population dynamics of weeds and will help the farmer to optimize control measures such as solarization. Taken in conjunction with published data on loss of viability of imbibed seeds, the annual loss of viability on a typical Eritrean farm is predicted to be about 38%.

Prediction of seed longevity: a modification of the shape of the Ellis and Roberts seed survival curves

AbstractThe prediction of the viability of stored seeds is important both for the management of germplasm collections and for the management of commercial seed production and storage. The Ellis and Roberts model for seed viability during storage is examined, and an inadequacy of the model highlighted. A modification is proposed, based on the ‘control mortality’ probit model developed for insecticide bioassays, to take proper account of variation in initial viability. This new ‘control viability’ model, relating seed viability to storage time, is fitted to data from a carrot seed storage experiment and found to fit well for a range of storage environments. A relationship, similar to that proposed by Ellis and Roberts for the effects of storage conditions on the rate of loss of viability, is fitted to the estimated rates from this new model. Data from a second carrot seed storage experiment are used to validate this relationship.

The effect of temperature and CO2on seed quality development in wheat (Triticum aestivumL.)

Winter wheat (Triticum aestivum L.) cv. Hereward was grown in the field in two double-walled polyethylene-covered tunnels within each of which a temperature gradient was superimposed on diurnal and seasonal fluctuations in temperature. The mean temperature between anthesis and harvest maturity varied from 14.3 to 18.4°C among plots within these tunnels. The CO 2 concentration was controlled at different values in each tunnel ; seasonal mean concentrations were 380 and 684 μmol CO 2 mol -1 air. Crops were also grown outside the tunnels at ambient temperatures and CO 2 . Samples of seeds were harvested sequentially from each plot between anthesis and harvest maturity. Seed germination and seed survival during subsequent air-dry storage were determined for each sample. The onset of both ability to germinate and desiccation tolerance (ability to germinate after rapid desiccation to 10-15% moisture content and subsequent rehydration) coincided in all environments. Full germination capacity (>97%, determined at 10°C) was reached 4-18 d before the end of the seed-filling phase (mass maturity) in most cases. There was little or no decline in germination capacity during subsequent seed development and maturation. Differences in seed quality were evident, however, throughout seed development and maturation when seed survival curves during subsequent storage were compared. Potential longevity in air-dry storage (assessed by the value K i of the seed viability equation) improved consistently both before and after mass maturity. There was a significant positive relation between the rate of increase in potential longevity (dK i /dt) and temperature (the minimum temperature for seed quality development was 4.8°C), but neither CO 2 concentration nor production within the polyethylene tunnels affected this relation.

Seed development and maturation inPhaseolus vulgarisII. Post-harvest longevity in air-dry storage

Changes in seed quality were monitored during the development and maturation of seeds of bean (Phaseolus vulgaris L.) in different environments by determining the subsequent survival of seeds in airdry storage. The seed survival curves (percentage normal germination plotted against period of storage) conformed to negative cumulative normal distributions, and the same seed storage environment (40 °C with 14% moisture content) provided the same estimate of the standard deviation of the frequency distribution of seed deaths in time for all the seed lots harvested at different times during development in the different environments (21.3 d and 20.9 d in 1993 and 1994, respectively). The potential longevity of developing seeds (quantified by the value of the seed lot constant of the seed viablity equation) continued to increase after mass maturity (end of the seed-filling phase). Maximum potential longevity was attained 23 d (30/24 °C, 1993), 13 d (30/24 °C, 1994), or 34 d (27/21 °C, 1994) after mass maturity, by which time seeds had dried naturally to 17% (30/24 °C, 1993), 18% (30/24 °C, 1994), and 16% (27/21 °C, 1994) moisture content. Seed quality was greater in the cooler temperature seed production regime because of an increased duration of seed quality improvement. The results show that maximum seed quality is not attained until some time after the end of the seed-filling phase in bean, and confirm that the slow desiccation that occurs after ovule abscission during natural maturation drying is beneficial to the development of seed quality in bean.

Seed Maturity and the Effects of Different Drying Conditions on Desiccation Tolerance and Seed Longevity in Foxglove (Digitalis purpurea L.)

The effects of different drying methods on desiccation tolerance and longevity in seeds of foxglove (Digitalis purpurea L.) were assessed from just prior to mass maturity (when seeds have attained maximum dry weight), and at intervals during the post-abscission phase of development. Tolerance of drying under seed conservation conditions (15% relative humidity, RH, and 15 °C), was acquired close to mass maturity at 36 d after flowering (DAF). Increases in desiccation tolerance were induced when drying was delayed for 4 d by placing seeds in a near-saturated atmosphere (approx. 100% RH), or if seeds were pre-dried for 7 d at either approx. 32% or approx. 73% RH.Irrespective of the drying treatment, seed longevity increased throughout the sampling period, i.e. beyond the point of mass maturity and throughout the post-abscission phase, up to the point of incipient natural dispersal. At each developmental stage, delayed drying or pre-drying led to an increase in seed longevity under controlled ageing conditions compared with seeds dried directly under seed conservation conditions. Increases in longevity were apparent as increases in the estimates for the intercept of transformed seed survival curves (Ki) and for the standard deviation of the normal distribution of seed lifespans, and also in the mean time to death of individuals in storage, consistent with a continuation of ripening events.The results are discussed in relation to the assessment of seed longevity and to current post-harvest drying practices for seeds intended for long-term ex-situ conservation.

Response of Seed Longevity to Moisture Content in Three Genotypes of Soyabean (GLYCINE MAX)

SummaryReports that an Indonesian soyabean (Glycine max) line (TGm737p) shows greater seed storage longevity than an American cultivar (Bossier), and that the cross between them (TG×536–02D) is intermediate between the two parents in this regard, were investigated by growing all three genotypes under identical conditions (30°C/20°C, 12 h d-1 photoperiod) in a plastics house. Seeds were harvested when moisture content had declined naturally to 14–15% (wet basis), and then stored hermetically at five different moisture contents at 40°C. Analyses of the resultant seed survival curves revealed that the seed lot constant Ki (a measure of potential longevity) was greatest in TGm737p and least in cv. Bossier, the cross being much closer to the American parent in this regard. The negative logarithmic relation between σ (standard deviation of the frequency distribution of seed deaths in time) and moisture content did not differ (p > 0.10) among the three genotypes. Moreover, this relation was close to that predicted by earlier results for four different genotypes. Similarly, there was no significant difference (p > 0.25) among genotypes in the negative semi-logarithmic relation between σ and seed equilibrium relative humidity (rh): the regression slope was equivalent to a doubling of longevity for each 8.0% reduction in rh. Finally, comparison of the negative logarithmic relation between absolute longevity (50% viability period) and seed moisture content confirmed that TGm737p showed greatest longevity (p > 0.005), but failed to show a difference in absolute longevity between cv. Bossier and the cross (p > 0.25). The results confirm that the seed viability equation of Ellis and Roberts (1980a, b) provides a framework within which the seed longevity of different genotypes can be compared. They suggest too that there is considerable doubt as to whether or not the greater potential longevity of the Indonesian line TGm737p has been incorporated successfully into the cross TG×536–02D.Longevidad de la semilla de soja

Models and sampling for studying weed seed survival with wild mustard (Sinapis arvensis) as a case study

Most studies of seed survival over time are not repeated in different years because they are long-term efforts. Methodological research reported in this paper shows that the shape of seed survival curves can differ for the same species for seed produced in different years. Consequently, seed survival of wild mustard could not be described by a single type of seed survivorship curve. Wild mustard seed survival was a negative exponential function of time in one 4-yr-long trial [Y = a + b*exp(−X)], but decreased as a negative linear function of time in a second trial (Y = a + b*X), where Y is percent seed survival, X is time in years, and a, b, and c are coefficients. However, both data sets could be adequately described by a mixed negative exponential model [Y = a + b*X + c*exp(−X)]. The negative hyperbolic model [Y = a/(X + b)] did not describe both trials as well as did the mixed negative exponential model. Sample sizes of four groups of 100 seed each, harvested each year for four years, provided acceptable nonlinear regression models for seed survival data. It was not advantageous to increase sample size more than this because r2 was not greatly increased and the residual mean square error (RMSE) was not decreased. Key words: Model, seed persistence, seed survival, wild mustard, Sinapis arvensis