Comparative seed longevity testing is a useful tool for setting appropriate germination test intervals for viability monitoring of ex situ conservation collections. A reduced seed number comparative longevity protocol, designed to screen for short-lived species and which uses only 150 seeds sampled at just four intervals during controlled ageing, at 2, 10, 15 and 30 days, was compared with the standard comparative longevity protocol of nine or ten sampling intervals using a total of either 450 or 500 seeds, respectively. Reduced seed number longevity test survival curves differed significantly (P < 0.05) from standard longevity test survival curves in only one of the 30 collections tested. Estimates of p(50) for reduced seed number longevity tests were not significantly different from standard longevity tests. Adoption of this reduced seed number longevity test as a routine procedure in genebank management will identify conservation collections with potentially short-lived seeds and thereby reduce the risk of undetected viability loss. The reduced seed number longevity test will also reduce staff time and costs and use fewer seeds compared with standard seed longevity testing, thus enabling more effective management of conservation collections.

BACKGROUND AND AIMS Seed longevity, a fundamental plant trait for ex situ conservation and persistence in the soil of many species, varies across populations and generations that experience different climates. This study investigates the extent to which differences in seed longevity are due to genetic differences and/or modified by adaptive responses to environmental changes. METHODS Seeds of two wild populations of Silene vulgaris from alpine (wA) and lowland (wL) locations and seeds originating from their cultivation in a lowland common garden for two generations (cA1, cL1, cA2 and cL2) were exposed to controlled ageing at 45 °C, 60 % relative humidity and regularly sampled for germination and relative mRNA quantification (SvHSP17.4 and SvNRPD12). KEY RESULTS The parental plant growth environment affected the longevity of seeds with high plasticity. Seeds of wL were significantly longer lived than those of wA. However, when alpine plants were grown in the common garden, longevity doubled for the first generation of seeds produced (cA1). Conversely, longevity was similar in all lowland seed lots and did not increase in the second generation of seeds produced from alpine plants grown in the common garden (cA2). Analysis of parental effects on mRNA seed provisioning indicated that the accumulation of gene transcripts involved in tolerance to heat stress was highest in wL, cL1 and cL2, followed by cA1, cA2 and wA. CONCLUSIONS Seed longevity has a genetic basis, but may show strong adaptive responses, which are associated with differential accumulation of mRNA via parental effects. Adaptive adjustments of seed longevity due to transgenerational plasticity may play a fundamental role in the survival and persistence of the species in the face of future environmental challenges. The results suggest that regeneration location may have important implications for the conservation of alpine plants held in seed banks.

Germination requirements and suitability for ex situ conservation were investigated for seeds from the only population of Ranunculus peltatus Schrank subsp. baudotii (Godron) Meikle ex C.D.K. Cook (Ranunculaceae) from the Tuscan Archipelago (Italy). A 2 x 2 x 3 factorial experiment investigated the interactive effects of light, alternating temperatures and mean temperature on the germination of seeds sown on agar. Logistic regression analysis showed significant effects of both temperature (P < 0.0001) and light (P < 0.05). Alternating temperatures improved germination but only at mean temperatures of 20 and 15 degrees C. The results indicate that seeds of R. baudotii exhibit morphological dormancy and a phenological adaptation to seasonal ponds. Drying led to a significant reduction in germination in seeds collected in both 2009 and 2010 (P < 0.05); the reduction was larger for 2009. The better quality of the 2010 seed was probably due to a post-harvest treatment that enabled continued maturation of the seeds. Storage of seeds for one year under seed bank conditions (-20 degrees C) did not reduce viability. Seeds of R. baudotii possess orthodox storage behaviour and are therefore suited to ex situ conservation in seed banks; however, further research is needed to confirm their long term storage prospects.

BACKGROUND AND AIMS:Serotiny is common in the genus Banksia, so any seed collection is likely to be comprised of seeds that were produced in many different years. This study aimed to determine the impact of cone age and degree of serotiny on longevity in ex situ storage.METHODS:Cones of identifiable age classes were collected from three species of Banksia. Seeds were extracted from cones and the degree of serotiny calculated. An estimate of initial viability (K(i)), the time for viability to fall by one probit (σ) and the relative longevity of seeds (p(50)) for each species and cone age class was determined using a comparative longevity test (50 °C, 63 % relative humidity).KEY RESULTS:The degree of serotiny ranged from moderate (7·9) for Banksia attenuata to strong (40·4) for B. hookeriana. Survival curves for all seed age classes within each species could be described by regressions with a common slope (1/σ), but with different values for K(i). The time taken for viability to fall by one probit (σ) could be described by a common value (29·1 d) for all three species.CONCLUSIONS:Differences in seed longevity between cone age classes and species was related to variation in initial viability (K(i)) rather than to differences in σ. While targeting the youngest mature seed cohort on a plant will maximize the viability of seeds collected, a wide range of age classes should be collected (but stored as separate cohorts if possible) for quality conservation/restoration seed collections where genetic diversity is important.

Seeds from six Kenyan Euphorbia species were placed into experimental storage under open conditions (i.e. not hermetically scaled) over a range of relative humidities (between 25 and 75%) at 45 degrees C. Viability during storage was assessed at pre-determined intervals and seed viability equation constants estimated. The constants Cw, which quantifies the relative effect of change of moisture content on longevity, and K(E). which quantifies inherent longevity were variant between species. Similarly the constants describing the relative effect of change in rh on longevity differed between species. The highest estimate of K(E) was 10.2 for E. quinquecostata followed by 10.1 for E. pseudoburuana, 8.9 for E. heterochroma, 7.4 for E. heterophylla and 7.3 for E. bussei. The reverse order of the species was observed in the estimates for C(w) which ranged from 3.96 for E. bussei to 8.09 for E. quinquecostata. These viability constants were used to predict seed longevity following recommended Seed Banking protocols. Longevity was also predicted for seeds stored under ambient conditions at two Kenyan cities., Nairobi and Kisumu. with and without refrigeration at 5 degrees C. These predictions show how even basic refrigeration can improve the longevity of seed stocks destined for short-term storage, for example those required to Support academic teaching in universities. Seed stocks destined for long-term conservation should be dried and stored at conditions prevailing in standard gene bank facilities.

Summary Weed seed persistence is strongly influenced by individual seeds and seed populations interacting with soil factors such as temperature, moisture content, nutrient status and micro-organism activity. The complexity of the interactions means that persistence of seeds in a particular environment is often difficult to quickly and accurately predict (Bekker et al. 2003). Field trials, although accurate in their context, are time-consuming and expensive to conduct for individual species. Laboratory-based life expectancy tests do exist, but these fail to simulate the environmental complexity of the field and it has been questioned whether or not tests, such as the accelerated ageing test, are useful indicators of field persistence. This study aims to test the suitability of the accelerated ageing test (seed ageing at 45°C and 60% RH) for predicting field persistence. It is motivated by a comparison of the field persistence of north-west European species with their longevity as measured using the accelerated ageing test, which demonstrated a significant positive correlation and thus a role for the simple test in estimating field persistence. Three southern Queensland weed species: Gomphocarpus physocarpus E.Mey. ( balloon cotton bush); Avena sterilis ssp. ludoviciana L. ( wild oat); and Ligustrum lucidum L. ( broadleaf privet), were buried for 15 months in three contrasting soils, as well as aged in the laboratory using the accelerated ageing test. Results from this study support a correlation between laboratory seed ageing with field longevity and the theory that there is an underlying genetic basis to seed persistence. In laboratory-based accelerated ageing tests, the viability of L. lucidum followed a typical sigmoidal decline to zero in approximately 20 days. For G. physocarpus, zero viability was reached in approximately 40 days, whilst for A. sterilis ageing to 243 days only reduced viability to approximately 50%. Thus L. lucidum was shortest-lived and A. sterilis is clearly the longest-lived in this test. To date, three retrievals of G. physocarpus, A. sterilis and L. lucidum field samples have been conducted. The black organic soil aged seeds of all three species most quickly, as no filled seeds were recovered after burial for 12 months. L. lucidum appeared to be the shortest-lived species, as no filled seeds were recovered in any soil type following 12 months ageing. Germination of A. sterilis and G. physocarpus remained above 80% after 12 months ageing in the red clay and sandy loam soils, although some variability was observed in G. physocarpus germination, indicating that it may be losing vigour. Thus, early indications suggest that seed ageing in the field follows the same order as in the accelerated ageing test. Subsequent work will refine the current accelerated ageing test to further improve its applicability to field ageing scenarios.

O desaparecimento de especies vegetais de relevante importância socioeconomica pela acao do homem, exige, com urgencia, o estabelecimento de eficazes tecnologias voltadas para a conservacao de genes para as futuras geracoes. O objetivo deste trabalho foi o de fornecer subsidios basicos sobre o comportamento fisiologico das sementes de aroeira (Myracrodruon urundeuva Fr.All. syn. Astronium urundeuva (Fr. All.) Engl.), especie madeireira e medicinal, visando sua conservacao a longo prazo, em bancos de germoplasma. Especificamente, buscou-se o estudo da viabilidade das sementes de M. urundeuva, quando submetidas a secagem (5,9% e 6,0% de umidade, base umida), reidratacao (12,2% e 13,6%, base umida), baixa (2°C e ?13°C) e ultra-baixa temperaturas (-20°C; -30°C; -70°C e -196°C), e definir o seu comportamento fisiologico e forma de conservacao. As pesquisas foram realizadas em 1994 no Laboratorio Jodrell do Royal Botanic Gardens, Inglaterra. Foram utilizadas câmaras de secagem a 15°C±3°C/15%±5%UR para desidratacao e solucao salina saturada de NH4Cl, para a reidratacao das sementes. As sementes foram armazenadas em câmaras frias, ?freezers? e botijoes com nitrogenio liquido. Os experimentos foram instalados em blocos ao acaso com 4 repeticoes. Os resultados mostraram que as sementes de aroeira apresentam um comportamento fisiologico ortodoxo, podendo, portanto, ser desidratadas e conservadas hermeticamente em baixas temperaturas, inclusive em nitrogenio liquido.

The effects of temperature, oxygen availability and salinity on seed germination in a population of Zostera marina L. from the Fleet, a tidal lagoon in southern England, were investigated in the laboratory. The fate of seeds under natural conditions was also monitored throughout the year from core samples and from seed samples buried in the sediment layer in nylon sachets. Supported with temperature, salinity and oxygen level measurements at the study site, field data confirmed that following seed dispersal in September/October, the majority of seeds germinated in the Fleet during the winter and early spring. In the laboratory, seeds germinated more rapidly and to a higher final percentage under anaerobic conditions compared to aerobic conditions. Under anaerobic conditions, rapid, near complete germination was possible at full salinity (30 g l(-1)) or when the salinity was reduced by 50% (15 g l(-1)). Under aerobic conditions, seeds germinated more rapidly at lower salinity. The effects of temperature were strongly dependent on the presence or absence of oxygen. Under anaerobic conditions, there was a pronounced optimum constant temperature for germination around 6 degrees C, corresponding closely to the average water temperature recorded during the period mid-October to the end of March. On the other hand, under aerobic conditions, very low levels of germination were recorded at low temperatures. These findings support previously published evidence that seeds of Z. marina are well adapted to germinate in anaerobic sediments and that water temperature is the key environmental variable that determines the timing of germination under natural conditions. Previous misuse of dormancy terms to describe seed populations of Z. marina is discussed.

The moisture relations of seed longevity in two populations of Astronium urundeuva (Fr. All.) Engl. (aroeira) from the Pernambuco region of Brazil were studied. The classification of aroeira seeds as orthodox and their potential for long-term storage under seed bank conditions (15% relative humidity (rh), -20 degrees C) were confirmed. A single regression adequately described the negative logarithmic relation between seed moisture content and longevity for the two populations. Analysis of the predicted longevity of 11 trees and 11 nontrees, a here predictions were based on moisture contents in equilibrium with standard seed bank drying conditions (15% rh) and storage at -20 degrees C, gave similar estimates of mean longevity for the two groups (trees: 643 years; non-trees: 737 years) with considerable variation in the estimates for individual species. Whilst there was a significant positive correlation between predicted longevity and oil content for trees, there was no relationship between these parameters accross all 22 species. The semi-logarithmic relation between equilibrium relative humidity and longevity for aroeira is discussed in relation to published data for herbaceous crops.

The germination requirements of Zostera capricorni Aschers. were studied in relation to temperature, salinity and oxygen potential. In treatments maintained at 16°C (corresponding to winter mean water temperature) and a salinity of 15‰ (half that of normal seawater), the cumulative percentage germination in both aerobic and anaerobic treatments was over 80%. However, seed germination was much faster under anaerobic conditions than aerobic conditions (cf. mean time-to-germinate (MTG) of <41 and >136 days, respectively). Under anaerobic conditions, at a constant 16°C, salinity level did not affect germination which was high (>80%) and rapid (MTG<41 days) at both 15‰ and 30‰. However, under aerobic conditions, percentage germination did not exceed 60% at the higher salinity, 30‰, at the end of the experiment. Germination was also slower at the higher salinity, 30‰, compared to 15‰ (MTG=159.6 and 136.3 days, respectively) but in both cases this was considerably slower than that recorded under anaerobic conditions. In all treatments held at 26°C (corresponding to summer mean water temperature) the MTG of seeds was high (>82 days) and the cumulative percentage germination did not exceed 40%. The effects of temperature on germination were more marked under anaerobic conditions than aerobic conditions. When Z. capricorni seeds were transferred to 16°C, after 24 days at 26°C (where germination rate was very slow), rapid germination followed in the anaerobic treatments. In contrast, when seeds were similarly transferred from 16°C to 26°C, the germination rate decreased to a negligible level following a 1-week lag period immediately after transfer when they continued to germinate rapidly. After 5 months cold stratification in artificial seawater at 6°C, both final germination and germination rate under anaerobic conditions were broadly similar to that recorded in unstratified seeds. In contrast, under aerobic conditions despite the fact that final germination at both salinity levels did not exceed 60%, stratified seeds germinated much quicker than unstratified seeds (average MTG value across both salinity levels, 51.2 and 148 days, respectively) indicating a reduction in the conditional dormancy originally maintained by aerobic conditions.

Developing capsules of foxglove (Digitalis purpureaL.) were detached at 4-d intervals between 12 and 28 d after flowering (DAF) and attached to canes within a natural foxglove stand such that they were experiencing field conditions identical to those experienced by normally developing, on-plant capsules. Seeds were subsequently harvested at 4-d intervals until 40 total d after flowering (tDAF). Capsule detachment resulted in the cessation of dry matter accumulation; the mean dry weight of seeds from 12, 16, 20, 24, and 28 DAF-detached capsules was 21, 32, 51, 60, and 79% respectively, of the mean dry weight of seeds during the post-abscission phase of normal, on-plant development. Nonetheless, seeds from detached capsules acquired the ability to germinate at harvest and tolerance to drying under seed conservation conditions (15% relative humidity and 15 °C). The capability to withstand storage also arose following capsule detachment. Seed longevity increased the longer the period of detachment but, in the earlier-detached capsules (12, 16, and 20 DAF) longevity subsequently declined. Only seeds from later detached capsules (24 and 28 DAF) acquired longevities which were comparable with seeds from on-plant capsules, however, no seeds from detached capsules were as long lived as seeds from on-plant capsules harvested at 40 DAF.

Abstract Controlled aging experiments were carried out in order to evaluate the changes in seed longevity occurring following the attainment of maximum seed dry weight in foxglove (Digitalis purpurea L.). Seeds harvested in three successive years were stored at ~5% moisture content (fresh weight basis) and 50°C. Seed longevity was greater the later the seeds were harvested. When the data were modelled using the predictive viability model of Ellis and Roberts, these increases were attributable to increases in both the theoretical initial viability (in probits) of the seed-lot, Ki, and in the standard deviation of the normal distribution of seed deaths in time, σ. Furthermore, there was a positive relationship between Ki and σ which was independent of the year of harvest (r = 0.9016, for 11 d.f., P < 0.001). These results do not support the predictive model which relies on the assumption that σ will not differ between seed lots of the same species stored under identical conditions. When seeds were stored at a range of moisture contents (between 5 and 10%) at 50°C, increases in σ during seed development were manifest as changes in the negative logarithmic relationship between σ and moisture content; below an upper limit, the regressions for seed lots at different stages of maturity were significantly different (P < 0.05) but could be constrained to either a common intercept or to a common slope (P < 0.05). It is proposed that it was the inherent variation in individual seed lifespans which increased during seed development. These results raise important concerns regarding the use of predetermined ‘species constants’ to predict the longevity of seed lots during long-term storage in seed banks.

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The effects of different drying methods on desiccation tolerance and longevity in seeds of foxglove (Digitalis pur pu, ea 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 degrees 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 (K-i) 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. (C) 1995 Annals of Botany Company

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Abstract The relationship between tolerance of seeds to extreme desiccation and the presence of ‘dehydrinlike’ proteins was investigated in groups of related taxa from the unrelated plant families Aceraceae and Gramineae. Dehydrin-like proteins were identified by Western blot analysis using an antibody raised against a synthetic oligopeptide representing the 23-amino acid consensus sequence common to all group 2 late-embryogenesis-abundant (LEA) proteins. Evidence is presented that seeds of Acer pseudoplatanus and A. saccharinum are desiccation intolerant (recalcitrant) whereas seeds of A. platanoides and A. rubrum are desiccation tolerant (orthodox). Despite these differences, dehydrinlike proteins at 60 and 20 kDa were detected in all four species. Dehydrins at 20 kDa were also detected in seed samples of two aquatic grasses, Porteresia coarctata and Oryza sativa from the tribe Oryzeae, despite seeds of the former rapidly losing viability on drying, whereas O. sativa is one of the best-known examples of desiccation-tolerant seeds. In O. sativa, there was a correlation between contents of dehydrins detected and the proportion of individuals capable of withstanding extreme drying. However, the possibility of a causal link between these parameters is equivocal. Dehydrin-like proteins were also detected in desiccation-sensitive seeds of Zizania palustris, Z. latifolia and Z. texana and desiccation-intolerant seeds of Spartina anglica, all from the Gramineae. The presence of group 2 LEAs is clearly not diagnostic of desiccation tolerance in seeds. However, a more direct correlation with the expression of other groups of LEAs cannot be discounted.