Seed storage at elevated partial pressure of oxygen, a fast method for analysing seed ageing under dry conditions

Background and Aims

Despite differences in physiology between dry and relative moist seeds, seed ageing tests most often use a temperature and seed moisture level that are higher than during dry storage used in commercial practice and gene banks. This study aimed to test whether seed ageing under dry conditions can be accelerated by storing under high-pressure oxygen.

Methods

Dry barley (Hordeum vulgare), cabbage (Brassica oleracea), lettuce (Lactuca sativa) and soybean (Glycine max) seeds were stored between 2 and 7 weeks in steel tanks under 18 MPa partial pressure of oxygen. Storage under high-pressure nitrogen gas or under ambient air pressure served as controls. The method was compared with storage at 45 °C after equilibration at 85 % relative humidity and long-term storage at the laboratory bench. Germination behaviour, seedling morphology and tocopherol levels were assessed.

Key Results

The ageing of the dry seeds was indeed accelerated by storing under high-pressure oxygen. The morphological ageing symptoms of the stored seeds resembled those observed after ageing under long-term dry storage conditions. Barley appeared more tolerant of this storage treatment compared with lettuce and soybean. Less-mature harvested cabbage seeds were more sensitive, as was the case for primed compared with non-primed lettuce seeds. Under high-pressure oxygen storage the tocopherol levels of dry seeds decreased, in a linear way with the decline in seed germination, but remained unchanged in seeds deteriorated during storage at 45 °C after equilibration at 85 % RH.

Conclusions

Seed storage under high-pressure oxygen offers a novel and relatively fast method to study the physiology and biochemistry of seed ageing at different seed moisture levels and temperatures, including those that are representative of the dry storage conditions as used in gene banks and commercial practice.     

等渗的盐分和水分胁迫对杠柳种子萌发的影响

通过等渗的NaCl和PEG溶液模拟盐分和水分胁迫,设置渗透梯度,在控制条件下对杠柳种子的萌发过程中总萌发率、幼苗鲜重、胚根生长、种子活力、发芽值等指标系统研究,对种子萌发率与渗透势之间关系进行回归分析,主要结果包括：（1）杠柳种子萌发过程中总萌发率、幼苗鲜重、活力指数和发芽值四项指标均随NaCl和PEG溶液的渗透势降低逐渐下降,综合研究活力指数和发芽值表明渗透势≥-0.5 MPa和≤-1.4 MPa时,PEG对种子萌发抑制作用大于NaCl,其他情况相反;（2）杠柳种子逐日萌发率和胚根日变化研究表明,与NaCl相比,PEG推迟杠柳种子萌发,并且对胚根增长抑制作用较大;（3）建立盐分和水分胁迫条件下种子萌发率与渗透势回归方程,发现杠柳种子在PEG胁迫下的萌发临界值和极限值为-1.0和-1.4 MPa,在NaCl胁迫下是-0.9和-1.3 MPa,解除胁迫条件,不同处理的杠柳种子复水萌发率均达到100%。说明杠柳具有良好的耐盐抗旱的特性。     

Subunit glycosylation of Lupinus angustifolius seed globulins

Reduced polypeptide subunits of α-, β- and γ-conglutins from Lupinus angustifolius seeds were resolved by preparative SDS gel electrophoresis of the fluorescent labelled proteins, into four, six and two major components, respectively. All subunits were glycosylated, to varying degrees, containing mannose, galactose and glucosamine. The major glycopeptides released by pronase digestion of each conglutin had similar galactose/mannose ratios; the MW of the glycopeptide released from α- and β-conglutin was ca 5000. Although on average, each molecule of α-conglutin contains one main oligosaccharide chain, and β-conglutin two, the presence of carbohydrate in all polypeptide subunits suggests that some subunits may arise by proteolytic cleavage of a larger polypeptide after glycosylation. The presence of minor glycopeptide components indicates that modification of carbohydrate chains during seed development may also occur.     

Dormancy as exaptation to protect mimetic seeds against deterioration before dispersal

Background and Aims

Mimetic seeds simulate the appearance of fleshy fruits and arilled seeds without producing nutritive tissues as a reward for seed dispersers. In this strategy of seed dispersal, seeds may remain attached to the mother plant for long periods after maturity, increasing their availability to naïve seed dispersers. The hypothesis that seed coat impermeability in many tropical Fabaceae with mimetic seeds serves as an exaptation to protect the seeds from deterioration and rotting while awaiting dispersal was investigated.

Methods

Seed coat impermeability was evaluated in five mimetic-seeded species of tropical Fabaceae in south-eastern Brazil (Abarema langsdorffii, Abrus precatorius, Adenanthera pavonina, Erythrina velutina and Ormosia arborea) and in Erythrina speciosa, a ‘basal’ species in its genus, which has monochromatic brown seeds and no mimetic displays. Seed hardness was evaluated as a defence against accelerated ageing (humid chamber at 41 °C for 144 h). Seed development and physiological potential of O. arborea was evaluated and the effect of holding mature seeds in pods on the mother plant in the field for a period of 1 year under humid tropical conditions was compared with seeds stored under controlled conditions (15 °C and 40 % relative air humidity).

Key Results

All five mimetic-seeded species, and E. speciosa, showed strong coat impermeability, which protected the seeds against deterioration in accelerated ageing. Most O. arborea seeds only became dormant 2 months after pod dehiscence. Germination of seeds after 1 year on the plant in a humid tropical climate was 56 %, compared with 80 % for seeds stored in controlled conditions (15 °C, 45 % relative humidity). Seedling shoot length after 1 year did not differ between seed sources.

Conclusions

Dormancy acts in mimetic-seeded species as an exaptation to reduce seed deterioration, allowing an increase in their effective dispersal period and mitigating the losses incurred by low removal rates by naïve avian frugivores.     

开花期加拿大一枝黄花水浸提液对3种作物种子萌发和幼苗生长的影响

测定了入侵杂草加拿大一枝黄花（Solidago canadensis）开花期的茎、叶和花序水浸提液对辣椒(Capsicum annuum)、番茄(Lycoperiscum esculetum)、长梗白菜(Brassica chinensis var. communis)种子萌发和幼苗生长的影响。结果表明：（1）处于开花期的加拿大一枝黄花存在明显的化感作用,在25 mg·mL^-1时,对3种作物种子苗生长有促进作用,浸提液高于50 mg·mL^-1时,作物种子的萌发率和生长受到抑制,这种抑制作用随处理液浓度的提高而增强,在100 mg·mL^-1浓度处理下,甚至使作物种子失去活力;（2）加拿大一枝黄花叶和花序的水浸提液对种子萌发和生长的影响要大于其茎的浸提液;（3）在3种作物中,长梗白菜种子对加拿大一枝黄花水浸提液的敏感性最高。     

Paternal effects in Arabidopsis indicate that offspring can influence their own size

The existence of genetic variation in offspring size in plants and animals is puzzling because offspring size is often strongly associated with fitness and expected to be under stabilizing selection. An explanation for variation in seed size is conflict between parents and between parents and offspring. However, for this hypothesis to be true, it must be shown that the offspring genotype can affect its own size. The existence of paternal effects would support this hypothesis, but these have rarely been shown. Using a diallel cross among four natural accessions of Arabidopsis thaliana we show that maternal, paternal and positional effects jointly influence seed size, number and the frequency of seed abortion. We found that seed abortion (%) depends on the combination of maternal and paternal genotypes, suggesting the existence of mate choice or epistatic incompatibility among accessions of A. thaliana. In addition, since paternal genotype explains approximately 10 per cent of the variation in seed size, we propose that A. thaliana''s offspring must influence the amount of resources allocated to themselves. Identification of paternal effects in Arabidopsis should facilitate dissection of the genetic mechanisms involved in paternal effects.     

Odor of achlorophyllous plants’ seeds drives seed‐dispersing ants

Seed dispersal by ants is an important means of migration for plants. Many myrmecochorous plants have specialized appendages in their seeds called elaiosome, which provides nutritional rewards for ants, and enable effective seed dispersal. However, some nonmyrmecochorous seeds without elaiosomes are also dispersed by ant species, suggesting the additional mechanisms other than elaiosomes for seed dispersal by ants. The seeds of the achlorophyllous and myco‐heterotrophic herbaceous plant Monotropastrum humile are very small without elaiosomes; we investigated whether odor of the seeds could mediate seed dispersal by ants. We performed a bioassay using seeds of M. humile and the ant Nylanderia flavipes to demonstrate ant‐mediated seed dispersal. We also analyzed the volatile odors emitted from M. humile seeds and conducted bioassays using dummy seeds coated with seed volatiles. Although elaiosomes were absent from the M. humile seeds, the ants carried the seeds to their nests. They also carried the dummy seeds coated with the seed volatile mixture to the nest and left some dummy seeds inside the nest and discarded the rest of the dummy seeds outside the nest with a bias toward specific locations, which might be conducive to germination. We concluded that, in M. humile seeds, volatile odor mixtures were sufficient to induce seed‐carrying behavior by the ants even without elaiosomes.     

风箱果种子催芽技术研究

以风箱果自然种群成熟的种子为研究对象,对种子的生活力和催芽方法进行了研究,结果表明：TTC染色法测得风箱果种子的生活力达到94.44%;清水浸种处理的发芽势和发芽率均较低,以浸种48 h的效果较好,发芽率为28.33%;不同化学药剂处理均能不同程度的提高发芽率,其中50 mg·L^-1 GA₃+4%KNO₃的混合药剂处理72 h的萌发效果最好,发芽率达到90%;100和200 mg·L^-1 GA₃能极显著提高发芽势（P<0.01）;低温处理28 d能显著提高发芽势和发芽率（P<0.05）。     

Genome-Wide Association Study Dissects the Genetic Architecture of Seed Weight and Seed Quality in Rapeseed (Brassica napus L.)

Association mapping can quickly and efficiently dissect complex agronomic traits. Rapeseed is one of the most economically important polyploid oil crops, although its genome sequence is not yet published. In this study, a recently developed 60K Brassica Infinium^® SNP array was used to analyse an association panel with 472 accessions. The single-nucleotide polymorphisms (SNPs) of the array were in silico mapped using ‘pseudomolecules’ representative of the genome of rapeseed to establish their hypothetical order and to perform association mapping of seed weight and seed quality. As a result, two significant associations on A8 and C3 of Brassica napus were detected for erucic acid content, and the peak SNPs were found to be only 233 and 128 kb away from the key genes BnaA.FAE1 and BnaC.FAE1. BnaA.FAE1 was also identified to be significantly associated with the oil content. Orthologues of Arabidopsis thaliana HAG1 were identified close to four clusters of SNPs associated with glucosinolate content on A9, C2, C7 and C9. For seed weight, we detected two association signals on A7 and A9, which were consistent with previous studies of quantitative trait loci mapping. The results indicate that our association mapping approach is suitable for fine mapping of the complex traits in rapeseed.     

Temperature sensitivity of the low-moisture-content limit to negative seed longevity--moisture content relationships in hermetic storage

• Background and Aims The negative logarithmic relationship between orthodox seed longevity and moisture content in hermetic storage is subject to a low-moisture-content limit (m_c), but is m_c affected by temperature?• Methods Red clover (Trifolium pratense) and alfalfa (Medicago sativa) seeds were stored hermetically at 12 moisture contents (2–15 %) and five temperatures (–20, 30, 40, 50 and 65 °C) for up to 14·5 years, and loss in viability was estimated.• Key Results Viability did not change during 14·5 years hermetic storage at −20 °C with moisture contents from 2·2 to 14·9 % for red clover, or 2·0 to 12·0 % for alfalfa. Negative logarithmic relationships between longevity and moisture contents >m_c were detected at 30–65 °C, with discontinuities at low moisture contents; m_c varied between 4·0 and 5·4 % (red clover) or 4·2 and 5·5 % (alfalfa), depending upon storage temperature. Within the ranges investigated, a reduction in moisture content below m_c at any one temperature had no effect on longevity. Estimates of m_c were greater the cooler the temperature, the relationship (P < 0·01) being curvilinear. Above m_c, the estimates of C_H and C_Q (i.e. the temperature term of the seed viability equation) did not differ (P > 0·10) between species, whereas those of K_E and C_W did (P < 0·001).• Conclusions The low-moisture-content limit to negative logarithmic relationships between seed longevity and moisture content in hermetic storage increased the cooler the storage temperature, by approx. 1·5 % over 35 °C (4·0–4·2 % at 65 °C to 5·4–5·5 % at 30–40 °C) in these species. Further reduction in moisture content was not damaging. The variation in m_c implies greater sensitivity of longevity to temperature above, compared with below, m_c. This was confirmed (P < 0·005).     

Fatty acid changes during maturation of Momordica charantia and Trichosanthes Anguina Seeds

Changes in fatty acids were studied during maturation of Momordica charantia and Trichosanthes anguina seeds, which contain cis-9, trans-11, trans-13-octadecatrienoic acid (α-eleostearic) and cis-9, trans-11, cis-13-octadecatrienoic acid (punicic), respectively. The two seeds matured 30 and 35 days after flowering, respectively. Total lipids as well as α-eleostearic acid accumulated rapidly from 10 to 20 days in M. charantia. In T. anguina the active period of lipid synthesis was from 15 to 30 days but punicic acid continued to be synthesized until maturity. In both species, the disappearance of linolenic acid and the reduction in concentration of linoleic acid were concomitant with the formation of conjugated fatty acids. The conjugated fatty acids were absent from monoacylglycerols and phospholipids of both species, and also from the diacylglycerols of M. charantia, throughout maturation     

Composition and seasonal dynamics of seed rain in broad-leaved Korean pine (Pinus koraiensis) mixed forest in Changbai Mountain, China

To explore the composition and spatio-temporal dynamics of seed rain in broad-leaved Korean pine (Pinus koraiensis) mixed forest, 150 seed traps were set up in a 25 hm2 plot in Changbai Mountain. Seeds, fruits, anthotaxy and others in seed traps were collected, identified and divided into 4 types. From 2005 to 2006, we collected 47 different types. Total number of seeds and fruits was 121291, including 23147 mature seeds and fruits (19.1% of the total). Tilia amurensis and Fraxinus mandshurica, with the most seeds and fruits, accounted for 90% of the total. The analysis on seasonal dynamics of seed rain showed that there were the largest number of seeds and fruits between July and October, which were composed of immature seeds and fruits. In mid-October, mature seeds and fruits reached their peak, but immature seeds and fruits still accounted for high proportion. There were 91 traps that contained 100–200 mature seeds and fruits, and one trap without any mature seed or fruit. The largest number of species found in a trap was 7, and usually 3 or 4 species were found in most of the traps. There were obvious relationships between spatial patterns of mature seeds and fruits and their parent trees, indicating that their mature seeds and fruits were not dispersed far from their parent trees.     

New hydroxy fatty acid from seed oil of Baliospermum axillare

A fatty acid, found as a minor component in the seed oil of Baliospermum axillare, is shown to be the hitherto unknown 11,13-dihydroxytetracos-trans-9-enoic acid (axillarenic acid).     

Variation in the seed protein profiles of Chenopodium fremontii

Electrophoretic profiles of water soluble seed proteins were determined for over 210 individual plants from 33 populations of Chenopodium fremontii. Little protein variation was encountered within populations. Interpopulational variation was pronounced, but in general plants of populations from nearby geographic localities or growing in similar habitats exhibited a high level of protein similarity. It is concluded that geographical and/or ecological races exist in C. fremontii, something which is difficult to document morphologically due to phenotypic plasticity.     

An 8-hydroxyoctadeca-cis-11,14-dienoic acid from Mirabilis jalapa seed oil

A fatty acid, found as a minor component in the seed oil of Mirabilis jalapa, is shown to be the hitherto unknown 8-hydroxyoctadeca-cis-11,14-dienoic acid.     

Boron and calcium increasePisum sativum seed germination and seedling development under salt stress

A beneficial effect of B and Ca application on symbiotic interaction between legume and rhizobia under saline conditions has recently been shown, suggesting conventional agricultural practices to increase crop salt tolerance. However, nothing is known about application of both nutrients on early events of legume development under salt stress, prior to the establishment of a symbiotic interaction. Therefore, the effects of different levels of B (from 9.3 to 93μM B) and Ca (from 0.68 to 5.44 mM Ca) on seed germination, root elongation, plant development, and mineral composition of pea (Pisum sativum L. cv. Argona) grown under 0 to 150 mM NaCl, were analysed. Development of plants previously germinated in the presence of salt was more impaired than that of plants put under salt stress once seeds were germinated. A NaCl concentration of 75 mM and 150 mM inhibited pea seed germination and seedling growth. The addition of either extra B or extra Ca to the germination solution prevented the reduction caused by 75 mM NaCl but not that of 150 mM NaCl. However, root elongation and plant development under salt stress (75 mM NaCl) was enhanced only by addition of both B and Ca. When plants were cultivated in the absence of external N, N content in roots and shoots originating from seeds was diminished by salt and enhanced by B and Ca, suggesting a role of these nutrients in remobilisation of seed nutrient stores. Salinity also led to an extremely high concentration of Na⁺ ions, and to a decrease of B and Ca concentrations. This can be overcome by addition of both nutrients, increasing salt tolerance of developing pea plants. The necessity of nutritional studies to increase crop production in saline soils is discussed and proposed.     

Structures and synthesis of seed-germination inhibitors from hibiscus rosa-sinensis

8-Nonynoic, 9-decynoic acids and their methyl esters were isolated for the first time as natural products from Hibiscus rosa-sinensis. They were inhibitors of the germination of lettuce seeds and were synthesized via o-nitrophenyl selenides.     

Effect of whole cottonseed v. sunflower seed on the fatty acid profile of subcutaneous fat,longissimus dorsi and blood of Thai Native and Holstein bulls

In a 2×2 factorial design, 12 Thai Native and 12 Holstein bulls were fed ad libitum a total mixed ration (20 : 80; roughage : concentrate) with whole cottonseed (WCS) or sunflower seed (SFS) as oilseed sources. The rations contained 7% crude fat and were fed for 90 days. Plasma was taken at three times during the experiment, and at slaughter the longissimus dorsi and subcutaneous fat were sampled for fatty acid analysis. Ration did not affect rumen fermentation parameters. The plasma fatty acid profile was not affected by ration. In subcutaneous fat, a ration×breed interaction for the saturated fatty acid (SFA) and c9t11 CLA proportions was observed, resulting from larger differences between the rations in Thai Native compared with Holstein bulls. The WCS ration resulted in higher proportions of SFA and lower proportions of monounsaturated fatty acids and c9,t11 CLA compared with the SFS ration (P<0.01). In the intramuscular fat, the WCS ration was also associated with a lower c9t11 CLA proportion (P<0.01) and higher SFA proportion (P<0.05). The intramuscular proportion of polyunsaturated acids was higher and the proportion of SFA was lower in Thai Native compared with Holstein bulls (P<0.05), irrespective of ration.     

Small-angle X-ray scattering studies of 7S and 11S globulins from pea (Pisum sativum)

Small-angle X-ray scattering studies have been conducted on solutions of 11S and 7S globulins isolated from peas (Pisum sativum cv. Filby), and the radii of gyration and molecular weights determined. The general features of the scattering curves were similar to those reported for other seed storage proteins.