Seed banking of terrestrial orchids: evaluation of seed quality in Anacamptis following 4‐year dry storage

• Good‐quality dry seeds of some orchids have the potential to survive for decades under conventional seed bank conditions, but further research is needed to fill existing gaps in knowledge regarding seed behaviour under long‐term dry storage. The objectives of this study were to evaluate germination ability on two asymbiotic culture media with different nitrogen source; to assess seed desiccation tolerance needed for the storage at sub‐zero temperatures; and to study the effects of dry storage at low temperature.
• Asymbiotic seed germination tests of four Anacamptis species were carried out to evaluate the effects of different culture media, dehydration and dry storage on germination ability. Viability of 4‐year‐stored seeds was assessed by means of the tetrazolium test.
• Generalised linear model (GLM) analysis detected significant effects (P < 0.01) of the species, medium and storage time on total germination, while dehydration did not significantly affect it. Except for A. palustris, germination percentage was minimum after 1‐month storage and increased with longer storage periods. Tetrazolium viability tests detected high percentages of viable seed (>90%) following 4‐year storage in three out of four species.
• Seeds of the four Anacamptis species proved to be desiccation tolerant and have orthodox storage behaviour. The consequence of these findings is of interest to practical conservation approaches for orchids in seed‐banking. The results highlight the importance of multiple assessments of seed quality, both viability and germination, to understand seed storage behaviour.

     

八棱海棠种子超低温保存中含水量对糖代谢的影响

含水量是影响种子超低温保存效果的关键因素，而其作用机制尚不完全清楚。为探讨含水量对种子超低温保存生活力的影响途径，该研究以八棱海棠种子为材料，通过硅胶干燥法获得不同含水量的种子，测定超低温保存后种子生活力、糖含量及相关酶指标的变化并分析相关性。结果表明：(1)超低温保存15 d后，不同含水量种子生活力不同，随着种子含水量的降低，种子生活力呈现先升高后降低的趋势，含水量为9.02%的八棱海棠种子生活力最高，为53.33%;超低温保存120 d后，种子生活力随着含水量下降一直升高，含水量为6.40%生活力最高，为27.78%。这表明八棱海棠种子含水量对超低温保存后的生活力有明显影响，但受液氮保存时间影响，随着液氮保存时间的延长，最适含水量降低。(2)相关分析显示，超低温保存后种子含水量与生活力呈极显著负相关(r=-0.82);与果糖和蔗糖含量、酸性转化酶、果糖激酶呈显著负相关，而种子萌发率与这些指标呈显著正相关。这表明种子含水量通过影响酸性转化酶活性而影响蔗糖和果糖含量，进而影响蔗糖代谢，响应低温和脱水胁迫，最终导致生活力差异。种子生活力还受到介导果糖激酶的果糖代谢影响。此外，海藻糖也是种...     

Effects of Moisture, Temperature, and Time on Seed Germination of Five Wetland Carices: Implications for Restoration

Successful restoration of sedge meadow wetlands is limited by lack of information regarding reintroduction of sedge (Carex) propagules. While restoration from seed is common for prairie restorations, little is known about the germination characteristics of many wetland plants, including sedges. We present the results of a 2.5-year study on seed germination and viability for five species of Carex common to sedge meadow and prairie pothole wetlands in temperate North America. Seed storage and germination conditions were investigated to determine the optimum combination for maintaining seed viability and stimulating germination rates over time. Seeds were germinated under seven different temperature and three moisture regimes after storage for 4, 10, and 14 months under one of four different storage regimes (dry-warm, dry-cold, moist-cold, and wet-cold). The efficacy of short-term wet-cold stratification to stimulate germination of 2.5-year-old seed after long-term dry storage was also investigated. Carex stricta, Carex comosa, and Carex lacustris showed the greatest germination response after wet-cold or moist-cold storage, while Carex lasiocarpa and Carex rostrata showed similar rates of germination after either wet-cold or dry-warm storage. Wet-cold long-term storage was associated with a high level of viability in all five species after 2.5 years. Viability and germination rates were reduced in Carex stricta, Carex comosa, and Carex lasiocarpa after long-term dry-cold storage. Germination rates of seeds stored dry for 2.5 years are not improved by short-term wet-cold treatment in any species tested. Carex seeds should be stored under wet-cold conditions to maintain seed viability over time, thus increasing the likelihood of seeding success for sedge meadow restoration.     

Systematic overestimation of Salicaceae seed survival using radicle emergence in response to drying and storage: implications for ex situ seed banking

Biodiversity conservation programmes are underpinned by seed banking following drying to low water contents (WC), and supported by both the assessment and prediction of seed viability over time. The means of judging viability is thus crucial to the comprehension of seed vigour. We selected seeds of three species and one hybrid in the Salicaceae likely to have variation in tolerance to drying, processing and storage, including in relation to cryobanking, and compared survival growth as radicle emergence (germination) and normal seedling production. With three seed lots of Salix gracilistyla, air-drying to 8–10 % WC enhanced seed survival after 40 days’ storage at 5 °C as compared with non-treated seeds at 14–20 % WC. Four seed lots of Populus alba × P. glandulosa showed equally high germination (88–100 %) and proportions of normal seedlings (81–99 %) when stored at 5 °C for 7–10 weeks. Among seven seed lots of S. gracilistyla, two groups with different storage behaviour could be statistically distinguished with normal seedling production ranging from 0 to 45 % after storage at 5 °C for 13 weeks. Seed tolerance to WC manipulation and cryopreservation was very variable among species and seed lots. Seed lots of S. hallaisanensis and S. gracilistyla with ~80 % germination survived cryopreservation at 10 % WC, but were sensitive to lower WCs. In contrast, Populus seeds had greater desiccation tolerance combined with cryopreservation capability. With seed lots of all species and hybrids, cryopreservation had little effect on viability unless the high moisture freezing limit had been exceeded (~10–20 % WC, depending on seed lot). However, under all conditions of handling (drying, rehydration, storage at 5 °C or cryopreservation) using germination as the only indicator of viability over-estimated survival compared with normal seedling production.     

Effects of Moisture Content on Germination of Seeds of Hancornia speciosa Gom. (Apocynaceae)

Seeds of Hancornia speciosa germinated best at a temperatureof 20–30 °C. The viability of the seeds during storagewas short and the best storage conditions for viability entailedkeeping the seeds in polyethylene bags. Seed viability was maintainedonly when the seeds were stored at a moisture content above30%; storage conditions which allowed dehydration resulted ina rapid loss of viability (the seeds showed recalcitrant behaviour). Low temperature during storage did not improve longevity. Arelationship between germination and moisture content was established,but when the moisture content fell below 25% there was a drasticreduction of germination. After 9 weeks of storage, even athigh moisture content, seeds lost viability. Loss of seed viability during seed dehydration was associatedwith increased leakage of electrolytes and organic solutes,and reduced tetrazolium staining during subsequent imbibition. Hancornia speciosa, germination, recalcitrant seeds, storage, moisture     

Biochemical changes induced in seeds of <Emphasis Type="Italic">Brassicaceae</Emphasis> wild species during ageing

The aim of the present study was to determine whether the loss of seed germination capacity and vigour in seeds of four wild Brassicaceae species (Brassica repanda, Moricandia arvensis, Rorippa nasturtium-aquaticum and Sinapis alba) during ageing at 45°C and 90% relative humidity was related to changes in lipid peroxidation and membrane integrity. For all of the species, ageing reduced the final germination percentage and increased the length of time required to reach 50% of final germination (T ₅₀). Large differences in longevity were observed among the species. The times required for viability to be reduced to 80 and 50% of maximum germination (P80 and P50) were the lowest for B. repanda, and these values were two times longer for M. arvensis and R. nasturtium-aquaticum and five times longer for S. alba compared with B. repanda. A loss of seed viability was not associated with malondialdehyde accumulation, suggesting that lipid peroxidation did not cause seed deterioration under these conditions. However, the conductivity test effectively detected seed deterioration in these wild Brassicaceae species, and membrane permeability correlated with both germination and vigour loss. This correlation may provide a valuable mean for early detection of seed viability in wild Brassicaceae species.     

Protocols for Use of Potamogeton perfoliatus and Ruppia maritima Seeds in Large‐Scale Restoration

Restoration of submerged aquatic vegetation from seed has been hampered by a lack of information on the appropriate conditions for collecting, processing, and storing seeds prior to dispersal. Seeds must be processed and stored under conditions that maintain seed viability, meet dormancy requirements, and prevent premature germination. This study examined the effects of collection date, processing technique, aeration, storage and induction temperature and salinity, and storage period on seed germination of two mesohaline aquatic species, Potamogeton perfoliatus and Ruppia maritima. Collection date and processing technique were significant factors affecting seed yield from donor populations. Seeds of both species remained viable and germinated best when stored at 4°C, and then exposed to freshwater induction conditions. However, their responses to other factors differed. Aeration during storage was necessary in order to maintain viability of P. perfoliatus seeds, whereas it was unnecessary for R. maritima seeds. Storage in freshwater at 4°C prevented germination of P. perfoliatus seeds, while high salinity during cold storage was necessary to minimize premature germination of R. maritima. Mean germination time of P. perfoliatus was dependent on storage salinity; in contrast, mean germination time of R. maritima seeds was dependent on induction salinity. These differences indicate that the methods required to produce large quantities of underwater plant seed amenable to large‐scale restoration efforts must be tailored to the specific requirements of individual species and must consider the range of processes from initial harvest through seed testing prior to field establishment.     

Effect of fruit maturity,seed weight and storage time on the viability and germination of the seed of candelilla (<i>Euphorbia antisiphylitica</i> Zucc.)

Candelilla (Euphorbia antisiphylitica Zucc.) is a very important plant resource in the arid lands of Northern Mexico. This is because the wax content coating the stem has unique properties which have been useful for multiple applications in the food industry, electronics, cosmetics, etc. However, the intensive exploitation of this resource has caused a great decrease in the populations of this species making necessary to consider strategies for their conservation and sustainable use. One of the primary needs with regeneration purposes is to know their reproductive processes, particularly the biotic and/or abiotic factors that determine the viability and germination of seeds. The present study evaluated the (1) germination and seed viability in relation to the ripeness degree of the fruit at the time of collection, (2) weight of the seed (low, medium and high), and (3) storage time (1, 3, and 5 months). Fruits from four locations, two in the State of Coahuila (Las Coloradas and Candela) and two in the State of Nuevo Leon (Icamole 1 and Icamole 2), were collected. Three germination assays were carried out corresponding to each month of storage. Seed viability was determined by the tetrazolium test. The average weight of the candelilla seeds was 0.0029 ± 0.0010 g, with extreme average values of 0.0018 ± 0.0006 g at Las Coloradas and 0.0036 ± 0.0010 g in Icamole 2. Those seeds with heavier weight obtained from red fruits and with 1 month of storage showed the highest average percentage of viability (66.87 ± 24.19%). At the same time, seeds with around average weight, obtained from red fruits and five months of storage, showed the highest average germination percentage (50.00 ± 9.42%).     

植冠与土壤种子库储存种子的萌发特性及策略

为明确黄土丘陵沟壑区植物种子库如何调控种子萌发来提高个体适合度,选择研究区7种具有种子库的主要物种为研究对象,以刚成熟和室内储存种子为对照,比较植冠宿存(5个宿存期)和土壤埋藏(5a埋藏期)对植物种子萌发特性的影响,探讨植冠种子库与土壤种子库储存下的种子萌发策略。结果表明:7种植物种子经过不同种子库储存后萌发特性表现出明显的种间差异,黄刺玫(Rosa xanthina)和水栒子(Cotoneaster multiflorus)种子萌发力表现为植冠宿存不变型、土壤储存增强型,土壤储存明显提高水栒子种子萌发速率;达乌里胡枝子(Lespedeza davurica)和狼牙刺(Sophora davidii)种子萌发力表现为植冠宿存增强型、土壤储存减弱型,种子萌发历时表现为植冠宿存延长型,土壤种子库储存还可加快达乌里胡枝子萌发速率、缩短萌发历时;茭蒿(Artemisia giralaii)和铁杆蒿(Artemisia gmelinii),种子萌发率随植冠宿存时间先升高后降低,随土壤储存时间先降低后升高,土壤储存可推迟其萌发,铁杆蒿种子萌发速率在植冠与土壤储存后均加快;紫丁香(Syringa oblata)种子萌发率随植冠宿存先升高后降低,土壤储存明显加快其种子启动萌发与速率。在黄土丘陵沟壑区,植物种子经过植冠或土壤种子库储存,或增加、加快、提早萌发充分利用有利条件提高占据性,或减少、减缓、推迟萌发分摊不利条件的风险;而且该区植物植冠与土壤储存后种子萌发特性间的关系,体现各自适应环境与应对干扰的分工与协作策略,主要表现为:单一主导型和相辅相成型。     

Dormancy and viability of Ferocactus peninsulae (Cactaceae) seeds

Knowledge on seed dormancy is crucial for the understanding of plant population dynamics, as it controls seed germination and seed bank formation. Dormant seeds have high potential to establish in soil seed banks, but such information within Cactaceae is scarce, although it is essential for conservation programs. The aim of this study was to determine if seeds of Ferocactus peninsulae showed any kind of dormancy and to test their germination capacity after storage. This was assessed with 15 seed sowing experiments done over 4 years with seeds stored under room conditions (20 ± 2°C). We demonstrated the existence of physiological dormancy in F. peninsulae seeds that is broken with an after-ripening period. Germination was low during the first 3 months of storage (d = 0.206) but increased after 10 months of storage (d = 0.654), and seeds maintained their viability at 48 months (d = 0.707). Also, their speed of germination increased with storage time. Ferocactus peninsulae seeds are positively photoblastic, and the requirement for light for germination persisted over all experiments. The results provide crucial information for propagation and conservation research and may allow us to infer that F. peninsulae seeds are able to form a persistent soil seed bank, as they maintained their viability after dormancy is released.     

The nuclear protein Poly(ADP‐ribose) polymerase 3 (AtPARP3) is required for seed storability in Arabidopsis thaliana

The deterioration of seeds during prolonged storage results in a reduction of viability and germination rate. DNA damage is one of the major cellular defects associated with seed deterioration. It is provoked by the formation of reactive oxygen species (ROS) even in the quiescent state of the desiccated seed. In contrast to other stages of seed life, DNA repair during storage is hindered through the low seed water content; thereby DNA lesions can accumulate. To allow subsequent seedling development, DNA repair has thus to be initiated immediately upon imbibition. Poly(ADP‐ribose) polymerases (PARPs) are important components in the DNA damage response in humans. Arabidopsis thaliana contains three homologues to the human HsPARP1 protein. Of these three, only AtPARP3 was very highly expressed in seeds. Histochemical GUS staining of embryos and endosperm layers revealed strong promoter activity of AtPARP3 during all steps of germination. This coincided with high ROS activity and indicated a role of the nuclear‐localised AtPARP3 in DNA repair during germination. Accordingly, stored parp3‐1 mutant seeds lacking AtPARP3 expression displayed a delay in germination as compared to Col‐0 wild‐type seeds. A controlled deterioration test showed that the mutant seeds were hypersensitive to unfavourable storage conditions. The results demonstrate that AtPARP3 is an important component of seed storability and viability.     

The Effects of Priming and Accelerated Ageing upon the Nucleic Acid Content of Leek Seeds and their Embryos

Using seed priming and accelerated ageing techniques, a singlelot of leek (Allium porrum) seeds was manipulated to producefour lots of seeds with different germination performance. Changesin content of the major nucleic acid species in whole seedsand embryos of two of these lots (primed and unprimed), weredetermined over the early stages of germination. The major effectof priming was an increased level of RNA species in the seedsand embryos, and this difference was maintained during germination.Comparison of nucleic acid levels in the dry seeds of thesetwo lots and two others (aged and aged then primed) indicatedthat there was no correlation with germination performance.Similar comparisons of the nucleic acid levels in the embryosof seeds imbibed for 1 d showed only a limited correlation betweenrRNA levels and germination performance. Analysis of these datasuggests that accelerated ageing has an adverse effect uponendosperm cells, which results in the degradation of their nucleicacids during priming. Furthermore, the viability of these agedseeds also falls during priming. The data also indicate thatratios of rRNA to DNA correlate with germination performanceof the four lots of seeds studied. It is proposed that sucha relationship is indicative of the efficiency of a primingtreatment, and may be useful in comparisons of naturally varyingseed lots. Key words: Leek, seed, germination, priming, nucleic acids     

Effects of temperature,light and gibberellic acid on the germination of seeds of 43 species native to Western Australia

Abstract. Species native to the southwest of Western Australia, representing a range of plant families, life-history strategies, fire-response syndromes, seed-store types and seed weights, were tested for viability using tetrazolium chloride and for germination under combinations of constant temperatures of 15 °C or 23 °C, constantly dark or 12 h diurnal whitelight conditions, and with, or without, addition of gibberellic acid (GA₃, 50 mg/l). Species previously known to require a heat-shock treatment to overcome dormancy due to an impervious testa were pre-treated prior to imposition of temperature, light and GA₃ conditions. The test environmental conditions related to differences between winter and autumn temperatures and surface and buried seed germination positions of post-fire habitats. The viability of the selection of native Western Australian species ranged from 0 to 100 %, averaging 71 %. For all taxa, no combination of temperature, light and gibberellic acid treatment induced all viable seeds to germinate. The greatest percentage germination achieved in any combination of treatments averaged 71 % of all viable seeds for all species. Larger seeds (> 10 mg seed weight) tended to have greater viability percentages, but no overall patterns of viability or germinability were attributable to seed storage syndrome, strategy of fire recovery response or life-form type. Germination of most of the dominant tree representatives (Eucalyptus calophylla, E. diversicolor, E. erythrocorys, E. gomphocephala, and E. patens) was indifferent to the trial conditions of temperature, light and GA₃. However, Eucalyptus marginata showed reduced germination in the light, which was overcome with GA₃. GA₃ also overcame the inhibition resulting from exposure to light in some understorey species (e.g. Allocasuarina campestris, Regelia ciliata, Xanthorrhoea gracilis and X. preissii). Germination of many hard-seeded, understorey shrub and herbaceous perennial species, especially those with small (< 10 mg) seeds (e.g. Bossiaea ornata, B. aquifolium and Acacia drummondii ssp. candolleana) was greater at the lower trial temperature and in the dark. Some large (> 10 mg) seeded, understorey species (e.g. Acacia extensa, Kennedia coccinea, K. prostrata, Hovea trisperma and Hardenbergia comptoniana) germinated in high percentages in both temperatures, but maximum germination percentages still tended to be at 15 °C. Large-seeded species were less sensitive to exposure to light compared to the smaller seeded species. The largest seeded species tested, Paraserianthes lophantha, germinated best in the warmer incubation temperature and in the light. The ecological significance of the tests would be that species which have seed dormancy mechanisms capable of delaying germination until the cool temperature, winter rainy period of this mediterranean-type climate would be more likely to survive than if germination followed summer rain showers or the first, intermittent rains of autumn. Burial of seeds becomes more important if germination occurs when rains first begin as this period has less available soil moisture and temperatures are high. Also survival of seedlings could be enhanced if germination of seed was restricted to the positions protected from high light, higher temperatures and lower soil moisture by the presence of a forest canopy. Therefore, seeds which have an ability to sense the presence of a previous fire in the habitat, conditions in light environment and appropriate temperature level have an adaptive advantage to time emergence to situations of time and space where survival is maximized. Variation in viability and germination percentages were apparent in some cases where more than one seed collection of available for testing, indicating that further aspects, such as seed age, maturity at collection, storage conditions and depth of seed dormancy, remain to be considered.     

Variation in seed germination between populations of five sub-alpine woody species from eastern Qinghai-Tibet Plateau following dry storage at low temperatures

Effects of cold-dry storage on dormancy break and viability were determined for seeds of the five sub-alpine woody species Philadelphus incanus, Berberis vernae, Berberis dubia, Betula utilis, and Picea purpurea collected along an altitudinal gradient on the eastern part of the Qinghai-Tibet Plateau in China. Germination tests were conducted at 20/5°C for seeds stored dry at ambient room temperature for 4 weeks and then at 3–4°C for 0, 6, 12, and 24 weeks. Dormancy break during dry storage, i.e., afterripening, was indicated by an increase in germination percentages and rates. Duration of cold-dry storage and altitude of seed collection had significant effects on germination. With an increase in duration of storage, germination percentages and rates of P. incanus and B. vernae increased with a decrease in altitude of seed collection, while they increased with an increase in altitude for seeds of B. utilis and P. purpurea. Seeds of B. dubia did not exhibit changes in germination percentages and rates with altitude because a high number of seeds remained dormant during storage. Seed viability after 24 weeks of storage ranged from high (88, 93.3, 92.7%) for B. utilis to low (15% for high altitude) for P. incanus. The potential for dormancy break to occur during cold-dry storage should be considered when studies on basic seed dormancy are conducted or when seeds from various locations are stored prior to propagating plants from them.     

Determination of seed viability of eight wild Saudi Arabian species by germination and X-ray tests

Our purpose was to evaluate the usefulness of the germination vs. the X-ray test in determining the initial viability of seeds of eight wild species (Salvia spinosa, Salvia aegyptiaca, Ochradenus baccatus, Ochradenus arabicus, Suaeda aegyptiaca, Suaeda vermiculata, Prosopisfarcta and Panicumturgidum) from Saudi Arabia. Several days were required to determine viability of all eight species via germination tests, while immediate results on filled/viable seeds were obtained with the X-ray test. Seeds of all the species, except Sa.aegyptiaca, showed high viability in both the germination (98–70% at 25/15 °C, 93–66% at 35/25 °C) and X-ray (100–75%) test. Furthermore, there was general agreement between the germination (10% at 25/15 °C and 8% at 35/25 °C) and X-ray (5%) tests that seed viability of Sa.aegyptiaca was very low, and X-ray analysis revealed that this was due to poor embryo development. Seeds of P.farcta have physical dormancy, which was broken by scarification in concentrated sulfuric acid (10 min), and they exhibited high viability in both the germination (98% at 25/15 °C and 93% at 35/25 °C) and X-ray (98%) test. Most of the nongerminated seeds of the eight species except those of Sa.aegyptiaca were alive as judged by the tetrazolium test (TZ). Thus, for the eight species examined, the X-ray test was a good and rapid predictor of seed viability.     

THE NINETY-YEAR PERIOD FOR DR. BEAL'S SEED VIABILITY EXPERIMENT

In 1879 Dr. W. J. Beal selected seeds of 23 different species of locally common plants, mixed 50 seeds of each species with moist sand in unstoppered one-pint bottles, and buried the bottles in a sandy knoll to be unearthed and the viability of the seeds tested periodically. The year 1970 marked the ninetieth year the seed had been buried, and the thirteenth bottle was recovered to test for seed viability. Of the three species which had germinated in the 1960 test (curly dock, Rumex crispus; evening primrose, Oenothera biennis; and moth mullein, Verbascum blattaria), only V. blattaria had viable seed with 20% germination. No other species germinated. All ten seedlings of V. blattaria were grown to maturity, and seeds were then harvested to study the possible deviations from normality and the requirements for seed germination. All seedlings emerging from the first progeny seed appeared normal. The most prominent requirement for germination was light, and this is a possible explanation of why the seeds had remained viable but dormant for so long a period. One-third of the freshly harvested seed germinated in darkness and, furthermore, redrying of dark-moistened seed in the absence of light induced additional germination. Germination of dark-moistened seed was not completely restored when the still moist seeds were subsequently exposed to light. However, when dark-moistened seeds were dried and then remoistened in the light, germination was about 95 %. About 5 % of the seed did not germinate under the conditions used. We find that 5 % of the population of V. blattaria seeds are dormant for unknown reasons, that 30 % will germinate if supplied only with moisture, and that 65 % are inhibited and require light and moisture simultaneously for germination. Supplying this 65 % of the population with moisture in darkness results in the development of a second type of inhibition which is no longer light reversible. It appears that the simultaneous requirement for light and moisture is an important factor in permitting V. blattaria seeds to remain dormant during prolonged burial.     

黄土丘陵沟壑区主要物种植冠种子库动态及其生态策略

植冠种子库是植物适应环境并应对外界干扰的种子生态策略之一,研究了黄土丘陵沟壑区12种主要植物植冠种子库动态,结果表明:杠柳不具有植冠种子库,其他11种植物均具有植冠种子库;除了黄刺玫种子在翌年5月达到脱落高峰,其他植物大部分种子在冬季脱落,其中杠柳、达乌里胡枝子、茭蒿、黄柏刺和水栒子的大部分种子脱落集中偏早,铁杆蒿和土庄绣线菊的大部分种子脱落集中偏晚;植冠宿存对大部分植物种子的萌发特性表现为促进作用;但不同植物种子的萌发时滞对植冠宿存响应差异较大;9种植物种子在植冠上宿存至翌年2月底,其种子活力仍能维持达60%以上;该区植物表现出不同的植冠种子库策略,通过不同的方式来减少干扰的威胁,提高成功萌发与更新的几率,它们或具有较大规模的宿存量、或调控种子萌发特性、或提高种子维持活力的百分比。此外,全面了解该区植物形成植冠种子库的机理及对应的生态策略还有待于全面、深入的研究。     

The germination and emergence of seeds of winter oilseed rape stored and sown in admixture with pelleted methiocarb

The possibility that pellets of the molluscicide Draza (a.i. methiocarb) might reduce field emergence of seeds of winter oilseed rape (Brassica napus, cv. Jet Neuf) when sown admixed, laboratory germination when stored admixed, or field emergence when both stored and sown admixed was the subject of three separate investigations. Admixture at sowing did not influence the emergence of five seed lots (P > 0·05). Neither did admixture influence loss in germination or change in moisture content during 2 months' storage of one lot in four different regimes (P > 0·05). Field emergence following 2 months' storage in paper bags was not influenced by admixture (P > 0·05), whereas a 12% reduction in field emergence resulting from storage in admixture within polyethylene bags was detected (P < 0·05). Thus short-term storage within paper sacks of winter oilseed rape seeds in admixture with slug pellets containing methiocarb did not damage the seeds. The emergence of five seed lots differed considerably within and between field sowings. Tentative advice on the calculation of sowing rates for different seed lots of winter oilseed rape is provided to account for this variation.     

Seed viability and seed dormancy of non-native Phragmites australis in suburbanized and forested watersheds of the Chesapeake Bay, USA

The non-native, invasive haplotype of Phragmites australis is rapidly invading tidal and non-tidal wetlands across North America. Phragmites has the potential to spread by seeds and rhizomes. Seed viability and dormancy differences were quantified among 18 patches of non-native Phragmites in subestuarine wetlands in developed (i.e., suburbanized) vs. forested watersheds of the Chesapeake Bay. We used tetrazolium and germination assays to assess seed viability and compared germination percentages and rate of germination among fresh seeds, cold–moist treated seeds, and warm–dry treated seeds to evaluate seed dormancy. Seed viability was <1% in most patches but a few patches produced abundant viable seeds (5–21%). Seed viability, however, did not differ significantly between wetlands in forested vs. developed watersheds. Contrary to studies of Phragmites seed dormancy in European populations, some Phragmites seeds were dormant at maturity; cold–moist treated seeds germinated faster and to higher percentages than fresh seeds or warm–dry treated seeds.     

Determination of orchid seed viability using fluorescein diacetate

Abstract Fluorescein diacetate (FDA) staining (0.25% FDA for 10 min) was found to be a suitable technique for the rapid determination of orchid seed viability. Penetration of the dye through the testa varies between species, thus the test is ideally performed on isolated embryos. Direct FDA application to isolated embryos of seeds taken from dry storage, but after the surface had been sterilized, elicits a poor staining reaction. Incubation of the surface sterilized seeds in distilled water for 16 h, either at 6°C or at room temperature, prior to applying the test was found to overcome this problem. In the range of species studied, FDA staining accurately indicates seed viability when compared with germination of seeds on sterile nutrient media. Storage of dry Dactylorhiza fuchsii (Druce) Soó seed at an elevated temperature of 62°C indicated that, under such conditions of accelerated ageing, the FDA test accurately describes the rate of seed viability loss.