Effects of altitude and seed size on germination and seedling survival of heathland plants in north Spain

The effects of altitude and seed size on germination and seedling survival were studied in Calluna vulgaris, Erica cinerea and Erica vagans. Experiments were carried out in the laboratory over a one year period. Seeds collected from heathlands of different altitudes were divided in two size classes. They were sowed on moist filter paper inside Petri dishes which were placed in chambers at 20 °C and a photoperiod of 12 h light/12 h darkeness. The seeds of Calluna vulgaris were the first to begin germination and had the highest rate and percentage of germination. The germination of Erica vagans was moderate, while seeds of Erica cinerea germinated later and the germination was very low. Seeds of Calluna vulgaris and E. cinerea collected at the highest altitudes had the highest germination percentages. Seed size in Calluna vulgaris and E. cinerea did not affect germination. However, large seeds of Erica vagans had higher germination rates and percentages than small seeds. The large seed size of Calluna vulgaris contributes to a better survival and growth of its seedlings.     

Effects of seed storage on germination of two succulent desert halophytes with little dormancy and transient seed bank

Seeds of both Salsola imbricata and Haloxylon salicornicum have high germination level and germination speed, and form a transient seed bank in nature. The impacts of storage period and condition on germination level and speed were assessed in the two species. Storage for three months significantly increased both germination level and speed of seeds stored under the different conditions, compared to that of fresh seeds. In both species, nine months storage did not affect germination percentage in cold storage seeds, but completely inhibited it in field seeds. Storage for longer time in room and warm temperatures resulted in significant reduction or complete inhibition in the germination of the two species, so this was more pronounced in H. salicornicum. Storage significantly increased germinate rate index of seeds stored in all conditions till 17 months in S. imbricata and till 12 months in H. salicornicum. In both species, fridge storage had little effects on final germination and germination speed of seeds incubated at the different temperatures, compared to fresh seeds. However, room temperature and warm storages significantly reduced final germination and germination speed at the different temperatures, so the reduction was more pronounced at 35 °C, especially in H. salicornicum.     

种子感光的机理及影响种子感光性的因素

种子的萌发或休眠均取决于萌发时种子内所建立起来的Pfr含量和Pfr/(Pr Pfr)比值。种子内的Pfr水平受到诸多因素的影响。光中性种子在成熟时已存在适合萌发的Pfr水平;需光种子在不同程度地接受白光或红光照射后,方可达到适宜的Pfr水平;忌光种子萌发要求的Pfr水平较低,因此萌发需要较长时间的黑暗。种子的感光性不是绝对的,母株的生长条件、种子本身的成熟度、贮藏状况、光质、光流量、光周期、萌发温度、O2供应及某些化合物的处理等都可使种子的感光性发生改变。     

Seed dimorphism and germination behaviour in Salicornia patula

One of the annual species of the genus Salicornia from the Mediterranean coast, Salicornia patula presents a seed dimorphism. This morphological seed dimorphism is linked with a physiological ‘dimorphism’ with regard to some requirements for germination. Central seeds, in the inflorescence, are larger, are dispersed attached to the perianth, have no light requirement for germination and seem to have a low germination response to salinity. The lateral seeds, which are free from perianth envelopes, require light and cold pretreatment and seem to have a high sensitivity to salinity. Salicornia patula colonizes unstable transition zones between permanently flooded muds and perennial vegetation. These zones have a winter flooding period. The beginning of the flooding period and of the dry period may vary from year to year, depending on the erratic distribution of autumn and winter rains on the Mediterranean coast. So, in some years, a seedling population may be destroyed before reaching the stage of seed production. Seed dimorphism might cause germination to the more distributed in time, thus reducing the chances of extinction of a complete generation. In the present paper salinity and temperature response are described more precisely, are investigated, some aspects of the longevity of the two types of seed, and the adaptative significance of the corresponding dispersal and germination syndromes are discussed in more detail.     

Seed viability of five wild Saudi Arabian species by germination and X-ray tests

Our objective was to evaluate the usefulness of the germination vs. the X-ray test in determining the initial viability of seeds of five wild species (Moringa peregrina, Abrus precatorius, Arthrocnemum macrostachyum, Acacia ehrenbergiana and Acacia tortilis) from Saudi Arabia. Usually several days were required to determine the viability of all five species via germination tests. However, X-ray test will give immediate results on filled/viable seeds. Seeds of all species, except Acacia ehrenbergiana and Acacia tortilis showed high viability in both germination (96–72% at 25/15 °C, 94–70% at 35/25 °C) and X-ray (100–80%) test. Furthermore, there was a general agreement between the germination (19%, 14% at 25/15 °C and 17% and 12% at 35/25 °C) and X-ray (8%, 4%) tests in which seed viability of Acacia ehrenbergiana and Acacia tortilis was very low due to insect damaged embryo as shown in X-ray analysis. Seeds of Abruspreca torius have physical dormancy, which was broken by scarification in concentrated sulfuric acid (10 min), and they exhibited high viability in both the germination (83% at 25/15 °C and 81% at 35/25 °C) and X-ray (96%) tests. Most of the nongerminated seeds of the five species except those of Acacia ehrenbergiana and Acacia tortilis, were alive as judged by the tetrazolium test (TZ). Thus, for the five species examined, the X-ray test was proved to be a good and rapid predictor of seed viability.     

Seed Storage Behavior and Seed Germination of Nine Species of Lauraceae from Yunnan,China

Seed banking following internationally agreed standards is an important way for preserving collections of wild plant species ex situ; but this method is not suitable for desiccation sensitive species. Lauraceae comprehends some of the dominant species in the evergreen broadleaved forest in the south of China and contains many species both of ecological and economical importance. However, study on seed biology such as germination and desiccation tolerance of this family is scarce. Seeds of 9 species from 5 genera of this family were collected and their dormancy status and germination requirement were studied; also their desiccation tolerance were determined using a modified 100 seed test. The results showed that seeds of Cinnamomum camphora probably have intermediate physiological dormancy; seeds of Actinodaphne forrestii, Actinodaphne obovata, Cinnamomum migao, Lindera metcalfiana var. dictyophylla, Lindera communis and Neolitsea polycarpa are non deep physiological dormant; Seeds of Cinnamomum burmannii and Phoebe glaucophylla may have no or negligible dormancy. All 9 species lost seed viability after desiccated to 286%-716% moisture content while still retained considerable viability with moisture content ranged from 1732% to 4487% after moist storage; thus seeds of the 9 species are all desiccation sensitive and can not be stored at the conventional seed bank conditions.     

种子休眠与萌发的分子生物学的研究进展

休眠与萌发是植物种子对环境变化的适应特征,受许多基因调控和环境因子的影响.利用数量遗传学方法(如QTL分析)和突变等手段已对休眠和萌发特性进行了深入的遗传学研究.近些年来,随着分子生物学的快速发展,种子休眠和萌发研究已经深入到分子水平.分子生物学技术的运用,特别是基因表达、基因组测序和以双向凝胶电泳及质谱分析为技术基础的蛋白质组学分析,已成为研究种子休眠和萌发的新工具和新方向.本文主要就利用分子生物学方法研究种子休眠与萌发的进展给予简要综述.     

The effect of cold stratification and light on the seed germination of temperate sedges (Carex) from various habitats and implications for regenerative strategies

The germination responses of 32 temperate Carex species were tested in light and darkness at five constant temperatures and under one fluctuating temperature regime, before and after cold-wet stratification. Using a linear logistic regression model, the probability of germination tested across all species was found to be significantly higher after stratification, in light and at the fluctuating temperature. In addition, the probability increased with temperature. Stratification increased germination in 28 species and had very little or no effect on four species. There was almost no germination in darkness prior to stratification, and the germination in light was considerably higher in all but two species compared with that in darkness. Thus, it can be concluded that the Carex species tested have broadly similar germination response patterns. The fact that Carices can be released from high levels of primary dormancy by low-temperature stratification implies that they are spring germinators. A light requirement after stratification in the major fraction of seeds and the capability of almost all investigated sedges to respond to fluctuating temperatures make it likely that persistent seed banks are formed. Additionally, sedges generally seem to have a high temperature requirement for germination which prevents them from emerging at the very beginning of the growing season. Regeneration by seed is probably largely restricted to gaps resulting from late spring disturbances where buried seeds have an opportunity to germinate and grow. Differences in germination were apparent between species occupying different habitats. Overall germination was significantly higher in wetland species than in dry-site species, probably owing to the greater capability of wetland species to respond to fluctuating temperatures. Differences in germination between forest and open-site species can be attributed to the higher capability of forest sedges to respond to low temperatures and temperature fluctuations. The influence of seed weight on germination was not significant in the 18 species adapted to wet, open habitats. There was, however, a tendency for the germination percentages to be low for large-seeded Carices. The interpretation of habitat differences is difficult due to a positive correlation between seed weight and dry habitats.     

Seed aging,delayed germination and reduced competitive ability in Bromus tectorum

In annual plants, increased competitive advantage has often been attributed to rapid germination and early establishment. In contrast, many annual species exhibit some degree of delayed germination (i.e., seed dormancy) that results in the formation of age structure within the seed population. Delayed germination can be an effective bet-hedging strategy in variable or unpredictable environments as a seed bank can buffer against years with reproductive failures and reduce the probability of local extinction. However, there has been little consideration of the direct effects of aging within the seed pool although the potential demographic costs of such a strategy (e.g., mortality in the seed bank or delayed reproduction) are well known. We used aged (4 year-old) and freshly produced seed from meadow steppe and sagebrush steppe populations of an annual grass (Bromus tectorum)to investigate the importance of seed age on seedling vigor and competitive ability. Aged seed from the meadow steppe population exhibited delays in germination that reduced plant growth and final biomass when the plants were grown with competition. Aged seed from the sagebrush steppe population did not exhibit delays in germination. By including a treatment that experimentally delayed the germination of freshly produced meadow steppe seed, we also examined the effects of delayed germination alone. A comparison of results from this delay treatment with those from the aged seed treatment suggested that the reduced competitive ability of meadow steppe plants produced from aged seed, although largely a result of the temporal delay in germination, was partly due to reduced seed vigor. Together these results indicate that physiological costs associated with seed age may affect aboveground competitive interactions and, in turn, the relative fitness of older cohorts in the soil seed bank.     

Patterns of seed persistence in South African fynbos

In fire-prone communities such as fynbos, many species rely on regeneration from seed banks in the soil. Persistent seed banks are particularly important for species with life spans shorter than the average fire cycle, in order to counter local extinction. Persistent seed banks also give potential for restoring ecosystems following disturbances such as alien plant invasion. This study investigated the seed persistence patterns of 25 perennial species, representing several growth forms and life histories, during a three-year burial. Long-term persistence (i.e., seed bank half-life exceeding two years) was found in the hard-seeded Fabaceae and Pelargonium, and the nut-fruited Proteaceae. In this group, germinability was low and dormancy increased further following burial, resulting in a highly viable, dormant seed bank after three-year's burial. A second group with potentially long-term persistent seeds includes four taxa (Pseudopentameris, Passerina, Elegia and Restio) that either have low germinability or develop secondary dormancy following burial. Dormancy in the latter group was partially countered by exposure to smoke-seed primer. Of the small-seeded species, only two Erica species with high initial dormancy had long-term persistent seed banks. The other species mostly displayed high initial germinability and short-term persistent seed banks (i.e., seed bank half-life less than two years). This group included taxa with short to medium life-spans (Syncarpha, Roella) that were expected to have long-term persistent seeds in order to buffer against local extinction following average to long fire-return intervals. We hypothesize that light may play a role in overcoming secondary dormancy in those species, and could have resulted in an underestimate for seed persistence in this study. Alternatively, those short to medium life-span species persist via inter-fire recruitment in gaps or long-distance dispersal (of the smallest seed). No correlations were found between seed persistence and seed mass or variance in seed dimensions. Nor was a correlation found between seed persistence and phenol concentration. In fynbos, seed burial of larger seeds by ants and rodents are major processes that operate in conjunction with passive burial of small seeds. Selection for persistence can be expected to operate across all seed sizes and shapes in fire-prone communities.     

Seed size variation: magnitude,distribution, and ecological correlates

Summary We examined seed-mass variation in 39 species (46 populations) of plants in eastern-central Illinois, USA. The coefficient of variation of seed mass commonly exceeded 20%. Significant variation in mean seed mass occurred among conspecific plants in most species sampled (by hierarchical ANOVA), averaging 38% of total variance. For most species, within-plant variation was the larger component of total variance, averaging 62% of total variance. Variation in seed mass among fruits within crops was significant in most species tested.We conclude that variation in seed mass among and within plants is widespread and common. There was little evidence of trade-offs between number of seeds and mean or variance of seed mass, and little correlational evidence of local competition for maternal resources. No consistent ecological (dispersal mode and growth form) correlates of variance of seed mass were evident.     

贵州毕节喀斯特地区优势植物种子萌发特性初步研究

对采自贵州毕节地区的11种植物的种子萌发特性进行了初步研究,结果表明：①盐肤木、火棘、化香、云贵金丝桃与白栎种子在4周之内能够萌发;除云贵鹅耳枥胚坏死之外（萌发实验前后对种子进行解剖）,其他5种植物的种子都未萌发,处于不同的休眠状态。②盐肤木、化香、云贵金丝桃的种子光照时的萌发率远高于黑暗时的萌发率,具有显著差异,尤其是云贵金丝桃,因此3种植物种子均属于喜光性种子;而火棘与白栎种子有无光照都可以萌发,而且萌发率没显著差异,因此属于光不敏感或光中性种子。③盐肤木、云贵金丝桃的种子在30℃较高温条件下萌发最好;白栎、火棘种子在15℃、20℃低温条件下萌发更好;化香种子萌发温度既不能低于20℃也不能高于25℃。④刺异叶花椒种子吸水率高达85%,胚包埋在胚乳之中非常微小、未分化,因此可以初步判定属于形态休眠或者形态生理休眠;而平枝荀子、西域旌节花、云南旌节花种子吸水率都在20%以上,胚长/种子长都超多1/2,并且胚已发育完全,应属于生理休眠;小果蔷薇种子吸水率约27%,胚长/种子长都达2/3,并且通过对种子的解剖发现胚还未发育,应属于形态生理休眠。     

种子蛋白质与蛋白质组的研究

综述了种子蛋白质与蛋白质组的研究,主要介绍了种子发育与形成、种子休眠与萌发、种子保存与活力以及种子与环境相互作用的蛋白质与蛋白质组的研究.同时阐述了当今蛋白质组学在种子研究中的应用以及所取得的成果,并展望了种子蛋白质组学的发展方向,种子生物学的研究将从基因水平走向整体水平,因此环境因子与种子蛋白质的相互作用是研究的重点.运用蛋白质组学将能揭示蛋白质的功能并明晰种子的生命机制.     

Ecological genetics of seed germination regulation in Bromus tectorum L.

Regulation of seed germination phenology is an important aspect of the life history strategy of invading annual plant species. In the obligately selfing winter annual grass Bromus tectorum, seeds are at least conditionally dormant at dispersal in early summer and lose dormancy through dry-afterripening. Patterns of germination response at dispersal vary among populations and sometimes across years within populations. To assess the relative contribution of genotype and maturation environment to this variation, we grew progeny of ten parental lines from each of six contrasting populations in a common greenhouse environment. We then tested the germination responses of recently harvested seeds of the putative full-sib progeny at five incubation temperatures. Significant germination response differences among populations were observed in greenhouse cultivation, and major differences among full-sib families were evident for some populations and traits. Among-population variation accounted for over 90% of the variance in each trait, while within-family variance accounted for 1% or less. Germination responses of greenhouse-grown progeny were positively correlated with the responses of wild-collected seeds, but there was a tendency for lowered dormancy at higher incubation temperatures. This tendency was more marked in populations from cold desert, foothill, and plains habitats, suggesting a genotype-maturation environment interaction. Differences among populations in the amount of among-family variance were more evident at lower incubation temperatures, while among-family variance was more uniformly low at summer incubation temperatures. Populations from predictable extreme environments (subalpine meadow and warm desert margin) showed significantly less variation among families than populations from less predictable cold desert, foothill, and plains environments. Low among-family variance was not specifically associated with small population size or marginality of habitat, as small marginal populations from unpredictable environments showed variance as high as that of large populations. In populations with high among-family variance for germination traits, germination responses tended to be correlated across incubation temperatures, making it possible to characterize families in terms of their general dormancy status. The results indicate that seed germination regulation in this species is probably under strong genetic control, and that habitats with temporally varying selection are occupied by populations that tend to be more polymorphic in terms of their germination response patterns. Received: 19 May 1998 / Accepted: 27 January 1999     

Sequential style removal in highbush blueberry,Vaccinium corymbosum L.: Effects on fertilization success and seed germination

Plants of the blueberry cultivar Bluecrop were pollinated with pollen from the cultivars Sierra and Duke under controlled conditions. After pollination, styles were removed at 6 h intervals from 1.25 days to 4.00 days. An increase in the number of developed seed was seen across time, ranging from 1 seed per fruit (s/f) at 1.25 days, to a peak of 63.4 s/f at 3.25 days in 1992, and from 0.1 s/f at 1.25 days to 56.0 s/f at 3.75 days in 1993. Germination tests of 200-seed seedlots of Bluecrop×Sierra exhibited a significant trend toward earlier germination by seed from earlier style removal times. Seed weight measured in the cross Bluecrop×Duke, however, showed decreasing weights with longer style removal times, suggesting that seed size may time of germination. A multiple regression of seed size and stylar removal time against time of germination showed that style removal time was the only significant source of variation for germination time. Results suggest that pollen vigor, as reflected in the speed of growth down the style, may have a direct bearing on characteristics of the seed and subsequent plant.     

Effects of sand burial depth on seed germination and seedling emergence of Cirsium pitcheri

A greenhouse study was conducted to determine the effects of sand burial on seed germination and seedling emergence of Cirsium pitcheri, a threatened species along Lake Huron sand dunes. In October 1996, seeds of C. pitcheri were sorted into three groups (small, medium and large) and artificially buried at 2, 4, 6, 8, 10 and 12 cm depths in plastic pots filled with unsterilized sand from Lake Huron sand dunes. These pots were placed outside in sand boxes for natural stratification. In early February, the pots were brought into the greenhouse for germination of seeds. Data showed that percent seed germination and emergence of seedlings were not related to seed size. However, both variables were negatively correlated with depth. Seedling emergence occurred from a maximum depth of 6 cm with most seedlings emerging from 2 cm depth. Only one seedling emerged from 8 cm depth. Seedlings from large seeds produced longer roots than those of small seeds. Larger root system would probably enhance seedling establishment.     

紫茎泽兰种子种群动态及萌发特性

在紫茎泽兰的入侵地四川省德昌县, 选择撂荒地、农田和马尾松林3个不同的生境, 从种子雨、种子库角度研究了紫茎泽兰种子种群动态规律,及其种子在不同光照和土壤基质条件下的萌发特性. 结果表明,3个生境下紫茎泽兰种子种群仅存在于当年3～6月,于4月底达到年高峰值. 其年降种子雨量在撂荒地中高达2.4×10⁵粒·m^-2,并均分布于2 cm土层以上, 且在撂荒地生境下紫茎泽兰种子的千粒重和活力均显著高于另外两个生境. 到7月上旬, 3个生境下土壤中均未发现有活力的种子. 在实验的光照条件下, 全光照对紫茎泽兰的种子萌发有抑制作用,而在28%光照条件下萌发率最高;砂壤土较适宜紫茎泽兰种子的萌发,生红土中其萌发速度及萌发率均最低.     

Seed flotation and germination of salt marsh plants: The effects of stratification, salinity, and/or inundation regime

We examined the effects of cold stratification and salinity on seed flotation of eight salt marsh species. Four of the eight species were tested for germination success under different stratification, salinity, and flooding conditions. Species were separated into two groups, four species received wet stratification and four dry stratification and fresh seeds of all species were tested for flotation and germination. Fresh seeds of seven out of eight species had flotation times independent of salinity, six of which had average flotation times of at least 50 d. Seeds of Spartina alterniflora and Spartina patens had the shortest flotation times, averaging 24 and 26 d, respectively. Following wet stratification, the flotation time of S. alterniflora seeds in higher salinity water (15 and 36 ppt) was reduced by over 75% and germination declined by more than 90%. Wet stratification reduced the flotation time of Distichlis spicata seeds in fresh water but increased seed germination from 2 to 16% in a fluctuating inundation regime. Fresh seeds of Iva frutescens and S. alternflora were capable of germination and therefore are non-dormant during dispersal. Fresh seeds of I. frutescens had similar germination to dry stratified seeds ranging 25-30%. Salinity reduced seed germination for all species except for S. alterniflora. A fluctuating inundation regime was important for seed germination of the low marsh species and for germination following cold stratification. The conditions that resulted in seeds sinking faster were similar to the conditions that resulted in higher germination for two of four species.     

不同年际间异子蓬种子大小、萌发能力及结实格局

异子蓬(Borszczowia aralocaspica)为中亚荒漠特有种,在我国仅分布于新疆,其果实具有二型性。对同一生长地2006、2007、2008年异子蓬种子的大小、萌发特性及结实格局进行比较,结果表明:(1)年份和种子类型对种子大小和重量均有显著影响(P<0.05)。(2)2种类型种子具有不同的萌发行为,褐色种子萌发率高(>90%),萌发速度快,而黑色种子萌发率低(2006年的萌发率为31%),萌发速度慢;2种类型种子的萌发指数在不同年际间均差异显著。(3)不同年际间,种子总数、褐色种子数、黑色种子数均具有极显著差异(P<0.001),且随个体的增大黑色种子的比例逐渐减小,褐色种子的比例逐渐增大,并且黑色种子数目均高于褐色种子数目。该研究为深入认识异型种子的生态适应对策提供理论基础。     

Effects of rabbit gut passage on seed retrieval and germination of three shrub species

It has been known for a few decades that European rabbits consume seeds and fleshy fruits of native woody plants, but relevant factors in the endozoochory processes such as seed predation (chewing and digestion), sexual differentiation, or the temporal pattern of seed recovery have been little evaluated until now. In this study, we examined seed dispersal of three Mediterranean shrub species by wild rabbits through monitoring of seed retrieval and germination after gut passage. Twelve adult wild rabbits (Oryctolagus cuniculus; six males and six females) of similar size and age were fed seeds of three shrub species with fleshy fruits (Crataegus monogyna, Myrtus communis and Pistacia lentiscus). After ingestion of fruits, seeds were retrieved from dung every 12 h for a day and a half. The viability and germination of retrieved seeds were tested along with that of uneaten seeds. Between 5% and 76% of ingested seeds were retrieved from dung, with significant differences between species and sex. Most M. communis seeds were retrieved with 12–24 h after ingestion; almost all C. monogyna seeds were recovered with 0–12 h after ingestion; no seeds of P. lentiscus were recovered. Only in the case of M. communis seed was the recovery rate greater in female than in male. Passage through the rabbit gut significantly increased seed germination in M. communis, and decreased it in C. monogyna. In conclusion, wild rabbits acted in this study as predators of C. monogyna and P. lentiscus seeds and potential dispersers of M. communis seeds.