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... This may be due to any or several of the following causes: (i) immature embryos, (ii) seed coats impermeable to water and (or) gases, (iii) inhibitors, (iv) light sensitivity, (v) mechanical restriction by seed coats, or (vi) adverse environmental conditions (Maguire 1975, 1976, 1984). Ellis et al. (1985) stated that there are three main types of dormancy: (i) Innate dormancy (primary dormancy), which is present immediately after the embryo ceases to grow. It can be divided into two categories: seed coat dormancy and embryo dormancy. ...
... Cutting tests showed that 94%–98% of the ungerminated seeds in the warm germination regime were possibly still viable, as evidenced by firm, green cotyledons and radicle, and they should have been capable of germinating. Ellis et al. (1985) showed that unfavorable conditions, after primary dormancy has been broken, can induce secondary dormancy. This may be the case here, as seeds that had started to germinate during moist chilling germinated rapidly at 20:30 °C, but seeds that had not started to germinate during chilling failed to germinate, presumably becoming dormant again because of the high temperature. ...
The effect on germination of soaking duration, moist-chilling time, and temperature was evaluated using five seed lots of Acer pensylvanicum L. Seeds were soaked for 0, 48, 72, or 96 h, then moist chilled at 4 °C for 16, 24, or 32 weeks. Two temperature regimes were used for germination: (i) 16 h dark at 5 °C : 8 h light at 15 °C (5:15 °C) and (ii) 16 h dark at 20 °C : 8 h light at 30 °C (20:30 °C). Soaking and chilling seeds significantly increased germination. Germination was highest at 5:15 °C, but the germination speed was slow. Germination at 20:30 °C was lower, but 94%98% of ungerminated seeds appeared to be viable, suggesting that they were dormant. Overall results showed that soaking seeds for 48 h, moist chilling for 16 weeks, and germinating at 5:15 °C produced an average germination of 92%.
... Fax: (39) 0661979661. seed drying facilities, such as seed drying chambers, seed dryers, where the relative humidtiy of the drying environment is controlled (Ellis et al., 1985), may not be easily implemented in many developing countries due to the high cost of establishing, running and maintaining such facilities. Therefore, there is a need for low cost drying methods to be used as alternatives to such expensive seed drying equipment in genebanks within those countries. ...
... This was conducted at three different stages during the study; immediately after harvesting, drying and ageing. Seed samples assessed after drying were hydrated by holding the seeds in porous cloth bags that inside a dessicator over water for 24 h at room temperature ranging between 20 and 25°C (Ellis et al., 1985). The germination tests were conducted according to the recommendations by ISTA (1999). ...
The effect of low cost drying methods on the seed quality of different genotypes of sorghum was investigated. Fresh seeds from five genotypes were subjected to three drying regimes, namely sun, shade and silica gel, and were compared to the standard recommended drying condition using a seed dryer (Munter seed dryer Model M120) as control. The effects of the drying regimes on seed moisture content, viability and quality were studied. All the drying methods were able to dry seeds to safe seed moisture contents levels (range of 5.6 -7.5%) for conservation. None of the alternative drying methods examined proved to be better than drying in a seed dryer. Seeds dried with the seed dryer gave the highest germination percentage compared to those dried using silica gel, or under shade and sun. However, this study indicates that drying with silica gel and shade are good alternative methods. Sun drying is quicker, but is harmful to the seeds and affects long-term seed viability.
... All lots had a comparatively high proportion of nuts containing a seed (up to 76%) and high viability (over 71% germination), except for N. dombeyi (53% germination) and N. pumilio (38% viable embryos from a tetrazolium test), when received in May 1998. Empty nuts were discarded by density using a ventilated column (Ellis et al., 1985) at receipt, except those of N. leonii and N. glauca, which were removed after each germination test. ...
Nothofagus alpina, N. obliqua, N. glauca, N. leonii, N. dombeyi and N. pumilio seeds exhibited consistent, albeit slight, sensitivity to extreme desiccation, but nevertheless maintained viability at low moisture contents and cool temperatures (2108 to 2208C) over 2 years. Nothofagus alpina, N. obliqua, N. glauca, N. leonii and N. dombeyi conformed to the seed viability equation of Ellis and Roberts; sensitivity of longevity to temperature was quantitatively similar to that of crop seeds, sensitivity to moisture was some- what less, and a low-moisture-content limit to the equation was detected at 4.8% moisture content in hermetic storage at 65 8C, and possibly similar moisture contents at 30-408C. These five species show orthodox seed storage behaviour. Therefore, ex-situ conservation of these Nothofagus species in seed banks is possible, but the quality of seed lots collected requires attention. Seed storage behaviour was not defined in N. pumilio: initial seed quality was poor and loss of viability was detected over 2 years at 08, 2108 and 2208C at 2.7% moisture content, but not at 5.2%. The results confirm that the economy of nature in seed storage physiology extends to forest tree seeds, but the repeated observation of reduced sensitivity of longevity to moisture in forest tree seeds requires further investigation.
... Thawing was carried out rapidly by plunging packets in a 40°C waterbath for 2 min. Before testing for viability, seeds were humidified above water at 25°C for 48 h, by the humid atmosphere method; in order to avoid imbibition damage during rehydration (Ellis et al., 1985). The development of the secondary leaves was the criterion for normal seedling formation. ...
Despite the ecological importance of Bromeliaceae and the threat of extinction for many species, the literature regarding seed germination and ex situ conservation of these species is scarce. The morphology of Pitcairnia albiflos (Bromeliaceae) seeds and post-seminal development
was studied and its germination response investigated in relation to temperature, light quality and desiccation tolerance at -196°C. The seeds are elliptical and the seedlings are cryptocotylar. Seeds germinated only at 20, 25 and 30°C, and failed to germinate at temperatures low as
higher than this or at an alternating temperature. P. albiflos requires light for maximum seed germination and did not germinate in low red/far red (0.03) or dark. Seeds desiccated to 5-7% water content at -196°C maintained their viability and vigour for 365 days. Storage of seeds
at ultra-low water content (ca. 3%) had a detrimental effect on seed longevity. Our results suggest orthodox storage behaviour for seeds of P. albiflos, since they are able to survive desiccation and freezing.
The results in this paper were motivated by the problem of monitoring the quality of seeds being stored for long periods under conditions of low temperature and low humidity. Under the assumption of a simple and smooth form of deterioration, a unified procedure is developed which specifies both when and how the seed lot should be inspected. Limits on the probability of reaching a prespecified poor quality are set. The theory is presented in a general form, in the expectation that it will be useful in other applications. Specific details for implementation in seed banks are given, and computer simulations are used to confirm the validity of approximate theory.
The main objective of this study was to determine if isozyme systems can be used as markers of genetic deterioration in Brassicaceae seed accessions under different storage conditions. Seed samples of Brassica oleracea, Cardaria draba, Erysimum cheiri, Iberis sempervirens and
Rapistrum rugosum were stored for periods of 9 to 30 years at −10°C and 3-4% seed moisture content (long-term or LT conditions) and at 5°C and uncontrolled relative humidity (RH) (short-term or ST conditions). Starch Gel Electrophoresis (SGE) was used to analyse six enzyme
systems oriented to determine the genetic deterioration of the accessions studied. The results obtained show that long-term storage conditions (LT) were extremely effective in maintaining the viability of seeds of the five Brassicaceae species studied. The final germination percentages reached
by seeds from LT samples ranged from 75 to 100%, while the germination percentages of ST samples (except for B. oleracea) were very low (from 0 to 10%). Similar conclusions were obtained studying the integrity of electrophoretic bands for several isozymes. Two enzyme systems were of
special interest: malate dehydrogenase and alcohol dehydrogenase.
Traditional assays (germination and vigour), as well as biochemical assays using isozyme loci, were performed to evaluate the effect of different seed storage conditions in Coincya rupestris, Iberis pectinata, Moricandia moricandiodes and Vella pseudocytisus. Seeds had been stored for 24–30 years under long-term (LT) and short-term (ST) conditions. Fresh seeds of the same species from natural populations (NP) were also collected in 1996 and used for comparison. Isozyme loci were used as markers of genetic deterioration and to determine the genetic diversity of samples. The germinability, vigour and enzyme activity of LT samples were comparable to values obtained using freshly collected NP samples, showing the effectiveness of the long-term storage conditions.
Studies on seed development and maturation were conducted during kharif 2008. Okra seeds of Pusa A-4
cultivar were harvested 10, 17, 24, 28, 32, 36 and 40 days after anthesis (DAA). Seeds were immediately shelled by hand and a part of freshly harvested seeds were analyzed for moisture content, leachate conductivity, seed dry weight and seed germination. Other part of the freshly harvested seeds at each sampling date was subjected to rapid desiccation to identify the stage at which desiccation tolerance occurred. With the advancement of seed development, seed coat colour changed from white to grey. Maximum hard seeds were found when seed coat colour changed to grey at 40 days after anthesis. No seeds germinated until 17 DAA. As soon as seeds began to germinate at 28 DAA, the percentage of hard seeds increased as seed moisture content decreased. There were no hard seed in fresh seeds and rapidly dried seeds with the higher moisture content till 24 DAA. With the advancement of seed development there was a drastic reduction in moisture content and the occurrence of hard seeds were observed. Maximum hard seeds were found when seed moisture content was minimum at 40 days after anthesis in fresh developing and rapidly dried seeds. Maximum seed germination in fresh developing seeds was attained at 36 DAA, when physiological maturity and maximum seed dry weight were attained. With seed maturation, there were rapid decline in leachate conductivity and seed moisture content. Total soluble sugars increased from 10 to 36 DAA and non-reducing sugars increased drastically at 28 DAA, which was concomitant to the stage at which desiccation tolerance occurred.
RIASSUNTO -La Banca del Germoplasma della Sardegna (BG-SAR) -Vengono presentati i risultati dei primi quindici anni di attività della Banca del Germoplasma della Sardegna (BG-SAR), per la quale si specificano tanto le priorità di conservazione che i territori e le unità tassonomiche oggetto d'indagine. Si descrivono inoltre le strutture e le strumentazioni attualmente in dotazione, le metodologie e i protocolli adottati per la raccolta, selezione, deidratazione e conservazione a lungo periodo delle accessioni in ingresso. Si riassumono, inoltre, le analisi e gli studi realizzati, oltre alle pubblicazioni scientifiche prodotti e ai progetti di ricerca e di conservazione conclusi e attualmente, in corso. SUMMARY -The Sardinian Germplasm Bank (BG-SAR) -The activities carried out on the first fifteen years of the Sardinian Germplasm Bank (BG-SAR) are here reported. Conservation priorities, study areas and target species are specified, as well as the facilities, methods and procedures for germplasm harvesting and ex situ long term conservation. At the same time studies, scientific articles issued and re-search projects, both concluded and in progress, are here resumed. Parole chiave: banca del germoplasma, conservazione ex situ, flora endemica, liste rosse IUCN, ripristini ambientali, Sardegna
Ex situ conservation through long-term storage of seed is, in principle, possible for a significant proportion of higher plants. Where feasible, long-term seed storage serves as a safe and relatively inexpensive method of plant genetic resources conservation. At present, however, information on seed storage behaviour (i.e. survival and longevity of seed under various storage conditions) is available for only about 3% of higher plants. This publication provides an approach by which conservationists can determine whether or not long-term seed storage is feasible for a particular species, i.e. whether or not that species shows orthodox seed storage behaviour.
A two-stage procedure is outlined. The protocol not only enables determination of seed storage behaviour, but also allows for the determination of suitable environments for medium-term and short-term seed storage depending on whether the species under investigation shows intermediate or recalcitrant seed storage behaviour.
This Technical Bulletin provides advice on the implementation of the protocol, examples of ways in which the results from seed storage studies could be misinterpreted due to confounding factors, as well as several alternative approaches for estimating seed storage behaviour prior to carrying out actual investigations with the seeds. In particular, the latter section introduces the concept of a multicriteria approach for estimating seed storage
behaviour.
This chapter is concerned with ex situ approaches for the conservation of plant and animal genetic resources. Genetic resources comprise the diversity of genetic material in plants and animals, which determines their characteristics and hence their ability to adapt and survive. The introduction and historical background provided explain how the process of domestication over many years together with the advent of modern breeding strategies during the twentieth century have entailed a narrowing of the total genetic base in both crop plants and animal breeds. Ex situ conservation methods emerged and evolved as a response to growing global recognition over the last century of the need for deliberate conservation measures to safeguard against continued losses of valuable genetic diversity in plant and animal species.
Several types of genebank exist, depending on the type of plant or animal material to be conserved, ranging from seed genebanks used for many food crops, to in vitro conservation facilities, including cryopreservation genebanks and DNA libraries for both plant and animal germplasm. The state-of-the-art of the techniques used in each case is described in detail along with a summary of their major advantages and limitations. A discussion of the need for a more holistic approach to conservation follows, describing how complementary conservation strategies employing an appropriate combination of conservation methods can increase the total genetic diversity conserved, its security, accessibility and the overall cost-efficiency of the conservation effort.
In the concluding sections, attention is drawn to future research priorities, with particular reference to the implications of rapid technological developments and relevant policy and legal frameworks.
The accumulation of specific soluble carbohydrates has been implicated in the acquisition of desiccation tolerance and improved longevity in orthodox seeds, leading to the hypothesis that carbohydrate composition might be used as a diagnostic marker for seed storage category. We have studied the sugar composition of 46 tissues from seeds of 18 species, covering 13 genera and ten families, and representing three seed storage categories: orthodox, intermediate and recalcitrant. Soluble carbohydrate extracts from each tissue were analysed using High pH Anion Exchange Chromatography. Total sugar content and sucrose level of the embryo were highly variable across all species and no simple association with seed storage physiology was evident. Monosaccharide levels were found to be low in most seeds studied, including those of the recalcitrant category. Sucrosyl-oligosaccharides, raffinose and stachyose, were observed to be lower in recalcitrant seeds compared to orthodox seeds. In general, orthodox and recalcitrant seeds had tissues with sucrosyl-oligosaccharide:sucrose mass ratios of>0.143 (i.e. 1:7) and
Genebank standards for the management of seed germplasm.
This publication has been produced jointly with selected authoritative colleagues for subject areas that have been regarded as important for the effective and efficient management of plant genetic resources. As in many instances genebanks are still using approaches and methodologies that are ten and more years old and that many substantive changes have occurred in the underpinning sciences, political aspects as well as in the technologies it was felt opportune to make suggestions for rationalization of the ex situ conservation in genebanks.
Unfortunately, this publication is now ten years old and it seems that the time is ripe for yet another critical assessment of current practices and opportunities and to produce another update!
Norway maple shows orthodox seed storage behaviour, sycamore recalcitrant seed storage behaviour. In both species, onset of germinability occurred after percentage seed moisture content had begun to decline, but before net loss in seed moisture. Onset of germinability in Norway maple occurred 4wk before physiological maturity (ie 4wk before the end of the increase in seed dry matter), whereas in sycamore it occurred some 10wk before physiological maturity when the seeds were only 60% filled. Seeds of Norway maple were able to tolerate enforced rapid desiccation to 10% moisture content (f.wt) at physiological maturity, when maturation-drying had reduced seed moisture content to 54%. Between 2-4wk later seed moisture content rapidly declined naturally to 25%, at which value the fruits were shed. In contrast, a constant rate of maturation-drying was observed in sycamore. The seeds were shed at 58% moisture content and, in almost all cases, the seeds were intolerant of rapid desiccation to c10% moisture content throughout seed development. No sycamore seeds survived desiccation to ≤5% moisture content. Sycamore seeds tolerated greater desiccation as they matured between 12 July and 20 September, but there was no further change thereafter. -from Authors
An on-station experiment was carried out in northern Namibia to compare local landraces of watermelon to modern varieties. An on-station experiment was carried out in northern Namibia to compare local landraces of watermelon to modern varieties.
Three groups of local watermelon are distinguished by farmers in Namibia: watermelons for fresh consumption, cooking melons Three groups of local watermelon are distinguished by farmers in Namibia: watermelons for fresh consumption, cooking melons
used for porridge, and seed melons for oil pressing. The present study was carried out to estimate agronomic potential of used for porridge, and seed melons for oil pressing. The present study was carried out to estimate agronomic potential of
the local landraces and verify whether agronomic characteristics would justify the local groupings. Important agronomic and the local landraces and verify whether agronomic characteristics would justify the local groupings. Important agronomic and
fruit-quality traits (yield, earliness, fruit weight, fruit number, rind thickness, soluble solids, seed weight, and tolerance fruit-quality traits (yield, earliness, fruit weight, fruit number, rind thickness, soluble solids, seed weight, and tolerance
to biotic and abiotic stress) were measured in seven landraces (three watermelons, three cooking melons and one seed melon)and to biotic and abiotic stress) were measured in seven landraces (three watermelons, three cooking melons and one seed melon)and
compared to three modern cultivars frequently grown in Namibia. The study revealed that well-adapted, productive Citrullus lanatuslandraces are available, and cultivated by local farmers throughout the northern regions of Namibia. Based on a combination compared to three modern cultivars frequently grown in Namibia. The study revealed that well-adapted, productive Citrullus lanatuslandraces are available, and cultivated by local farmers throughout the northern regions of Namibia. Based on a combination
of agronomic characteristics these local varieties could be grouped into three distinct types: watermelons, cooking melons, of agronomic characteristics these local varieties could be grouped into three distinct types: watermelons, cooking melons,
and seed melons, in agreement with farmers classification. Landrace water melons were characterized by smaller, less sweet and seed melons, in agreement with farmers classification. Landrace water melons were characterized by smaller, less sweet
fruits with larger seed and a thicker rind compared to modern varieties. Yield level was comparable but development was later fruits with larger seed and a thicker rind compared to modern varieties. Yield level was comparable but development was later
and fruit number in some cases higher. Cooking water melons were less sweet than local water melon with large fruits comparable and fruit number in some cases higher. Cooking water melons were less sweet than local water melon with large fruits comparable
in size to modern cultivars. The only included seed watermelon had small fruits with large seeds and low soluble sugars. Yield in size to modern cultivars. The only included seed watermelon had small fruits with large seeds and low soluble sugars. Yield
varied from 118 t/ha for a giant cooking melon, out yielding all other accessions, to only 10t/ha for the seed melon type, varied from 118 t/ha for a giant cooking melon, out yielding all other accessions, to only 10t/ha for the seed melon type,
but with considerable variation within groups. The earliness of commercial varieties maybe of interest in developing a mixed but with considerable variation within groups. The earliness of commercial varieties maybe of interest in developing a mixed
portfolio of short- and long-cycle landraces, whereas plant vigour, resistance and seed characters in some of the Namibian portfolio of short- and long-cycle landraces, whereas plant vigour, resistance and seed characters in some of the Namibian
landraces may be important traits for breeding for both local purposes and for commercial varieties. landraces may be important traits for breeding for both local purposes and for commercial varieties.
Germplasm of 21 diverse Argyranthemum taxa was collected from contrasting ecological zones in the Canary Islands. Seed dormancy was considerable in the majority of taxa. Extensive investigations, based on a germination test procedure algorithm for Asteraceae, with achenes from ray and disc florets of five contrasting taxa identified a procedure to promote full (85%) germination of the seeds from both ray and disc florets of all five taxa; viz, excision of the seeds from the achenes, followed by testing at 15C with 2.610-3
m GA3 co-applied. Subsequent tests showed that this regime was effective in promoting full germination in seeds from both ray and disc florets of the remaining 16 taxa. The results are discussed in the context of ex situ plant germplasm conservation.
Morphological data recorded from field trials using Citrullus lanatus germplasm collected in Namibia were used to analyse and compare the various morphotypes of this species. The experiment comprised wild types and local landraces as well as commercial cultivars. Cluster analysis supported the indigenous classification system used in Namibia, in which Citrullus types are distinguished based on gross morphology, ecology and usage and grouped into seed, cooking and fresh-eating (watermelon) types. Commercial watermelon cultivars formed a distinct cluster. Wide variation was found within the local types whereas the genetic basis of the commercial type appears to be narrow. The commercial cultivars were most closely related to local watermelon types and more distantly related to the wild types, whereas the cooking melons form an intermediate group.
Several perennial legumes endemic to the Canary Islands have been recognized as forage resources for semi-arid zones. In the
period 2008–2010, seed collecting missions focused on the genera Adenocarpus DC., Bituminaria Heist. ex Fabr., Chamaecytisus Link, Cicer L., Genista L., Teline Medik. and Vicia L. were carried out in the archipelago. Sixty-nine samples were gathered from 31 endemic taxa, eight of which are threatened.
These accessions are conserved at the gene bank of the Instituto Canario de Investigaciones Agrarias for further characterization
and evaluation. Collection and ex situ conservation contribute to preserve endemic legumes genetic resources for utilization in the Canary Islands and in other
semi-arid regions of the world.
KeywordsCanary Islands–Collection–Endemism–
Ex situ conservation–Forage legumes–Genetic resources
Conservation of genetic resources depends on the preservation of diversity within and between population of a taxon. This can be achieved in situ, or ex situ as seed or vegetative collections. Studies on the population dynamics of natural vegetation, and ecogeographical surveys of taxa seek to develop methodologies for the conservation of diversity within ecosystems. The management techniques for the conservation and regeneration of ex situ collections attempt to maintain the genetic integrity and minimise change within each population through time.
Field experiments were undertaken to assess the effect of N source (incorporated legume residue vs. synthetic fertilizer) on crop-weed interference. In a 2 year study, a doublecropping system was used in which a crimson clover (Trifolium incarnatum L.) green manure was followed by a crop of sweet corn (Zea mays L.) grown alone or with lambsquarters (Chenopodium album L.). Inclusion of several rates of ammonium nitrate fertilizer in the experiment allowed determination of the clover's N equivalency value (55 kg N ha−1) and contrast of the clover treatment with a comparable rate of N fertilizer addition (45 kg N ha−1). Soil NO3-N concentration in the experiment at one week after corn and lambsquarters planting was 52% lower in the clover than the fertilizer treatment. Differences in nitrate levels between the two treatments tended to decrease at subsequent sampling dates. At two weeks after emergence, drymatter accumulation of lambsquarters was 72% lower in the clover than the fertilizer treatment and remained 39% lower at final harvest. In contrast, sweet corn biomass accumulation in the clover treatment was 31% lower than in the fertilizer treatment at 2 weeks after emergence but recovered to levels attained in the fertilizer treatment as the growing season progressed. As a result of reduced lambsquarters growth, loss of corn drymatter accumulation to weed interference was 8% in the clover treatment as compared to 28% in the fertilizer treatment. Results of a second experiment in which crimson clover was followed by lambsquarters grown alone also showed a weed suppressive effect of the legume N source in comparison to use of fertilizer N. These experiments demonstrate that use of legume green manure has the potential to reduce the need for herbicide as well as synthetic fertilizer applications in subsequent crops.
We have studied the main factors conditioning the germination of the seeds of the weed called Digitaria sanguinalis (large crabgrass or hairy finger-grass): the seed coats role in the dormancy status and the temperature and light requirements. 1) This weed seeds are dormant when recently dispersed. Removal of glumes, lemma and palea improved the germination capability. The germination percentage is nearly about 100% if pericarp is damaged. The application of an ethylic extract of glumes, lemmas and paleas causes a delay on germination. This suggests the possibility that germination inhibitory substances are present on glumes, lemma and palea of the D. sanguinalis spikelet. Scarification treatments with chemical substances like NaOCl and H2O2 raise the germination capability and break the dormancy status of the caryopsides. The results suggest that there is a role of both the glumes, lemma and palea (presence of inhibitory substances) and the pericarp (impermeability to some substances). It is needed to contrast both hypotheses in later studies. 2) D. sanguinalis seeds germinate between 10 and 42 ºC. Light stimulates this species germination. The maximum germination percentage is reached under alternant temperatures of 20/30 ºC, both in light conditions and in darkness. Under constant temperatures conditions, the maximum germination percentage is reached at 30 ºC, but maximum germination rate is reached at 28 ºC. The optimum and base temperatures range from 28 to 30 ºC and from 9 to 11.5 ºC, respectively. Differences with the results presented by other authors may be ascribed to the used method or to genetic differences between different populations.
Extended seed longevity in the dry state is the basis for the ex situ conservation of 'orthodox' seeds. However, even under identical storage conditions there is wide variation in seed life-span between species. Here, the effects of seed traits and environmental conditions at the site of collection on seed longevity is explored for195 wild species from 71 families from environments ranging from cold deserts to tropical forests.
Seeds were rapidly aged at elevated temperature and relative humidity (either 45 degrees C and 60% RH or 60 degrees C and 60% RH) and regularly sampled for germination. The time taken in storage for viability to fall to 50% (p(50)) was determined using Probit analysis and used as a measure of relative seed longevity between species.
Across species, p(50) at 45 degrees C and 60% RH varied from 0.1 d to 771 d. Endospermic seeds were, in general, shorter lived than non-endospermic seeds and seeds from hot, dry environments were longer lived than those from cool, wet conditions. These relationships remained significant when controlling for the effects of phylogenetic relatedness using phylogenetically independent contrasts. Seed mass and oil content were not correlated with p(50).
The data suggest that the endospermic seeds of early angiosperms which evolved in forest understorey habitats are short-lived. Extended longevity presumably evolved as a response to climatic change or the invasion of drier areas. The apparent short-lived nature of endospermic seeds from cool wet environments may have implications for re-collection and re-testing strategies in ex situ conservation.
Pea (Pisum sativum L.) mutant near‐isogenic lines (RRrbrb, rrRbRb, rrrbrb) with lower starch but higher lipid contents, brought about by lesions in the starch biosynthetic pathway, had seed moisture
sorption isotherms displaced below that of the wild type (RRRbRb). The negative logarithmic relationship between seed longevity and seed storage moisture content (%, f.wt basis), determined
in hermetic storage at 65 °C, also differed: longevity in the mutant near‐isogenic lines was poorer and less sensitive to
moisture content than in the wild type (i.e. CW was lower). The low‐moisture‐content limit (mc) to this relation also differed, being lower in the mutant near‐isogenic lines (5.4–5.9%) than in the wild type (6.1%). In
contrast, all four near‐isogenic lines showed no difference (P >0.25) in the negative semi‐logarithmic relationship between equilibrium relative humidity (ERH) and seed longevity. It is
concluded that the effect of these alleles at the r and rb loci on seed longevity was largely indirect; a consequence of their effect on seed composition and hence on moisture sorption
isotherms. However, this explanation could not be invoked at moisture contents below mc where differences in longevity remained substantial (RRRbRb double that of rrrbrb). Hence, these mutant alleles affected seed longevity directly at very low moisture contents.
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