种子地理学研究的新进展

在已发表的“种子地理学”基本理论框架和内涵的基础上, 该文对种子地理学理论进行了补充和修订, 在以前提出的7个方面的研究内容基础上, 补充了土壤种子库的地理学、种子雨的地理学、种子散布方式的地理学三个方面的研究内容, 提出了“土壤种子库的三向(纬度、经度和海拔)梯度变化假说”和“种子散布模式的三向梯度变化假说”。还对以前提出的6个方面的研究内容进行了增补, 在“种子化学性状地理学”方面添加了种子稳定性同位素性状, 在“种子重量的地理学”方面添加了油质体性状, 在“种子形态性状的地理学”方面补充了种子长、种子宽、种子长宽比、种子的附属结构(如果翅的有无以及种子附属物种翅长、种翅宽、种翅长宽比)等性状, 在“花和果实的地理学”方面增添了一些新的关注对象, 如花瓣的长和宽、花萼长和宽, 还有果实的长、宽、高及其比值, 夏季成熟的果实及秋天成熟的果实比例等, 在“种子遗传学性状的地理学”方面添加了DNA含量这个性状, 在“种子细胞性状的地理学”方面增添了淀粉粒。     

地中海沿岸沙丘土壤种子库的异质性

应用自然萌发法和物理筛选法相结合的方法,调查了地中海沿岸沙丘三种微生境土壤总种子库和永久种子库特征,用功能群的方法分析了微生境之间的土壤总种子库和永久土壤种子库的组成和结构差异,也分析了主要物种土壤种子库的微生境分布格局,分析了种子大小和土壤种子库中的种子永久性关系。发现地中海沿岸沙丘土壤种子库具有明显的空间异质性,即使在相同的微生境内,土壤种子库的分布也不是均匀的,甚至具有很大的差异;微生境对总的土壤种子库和各功能群的土壤种子库的分布格局具有显著的影响,开阔地区域具有最大的种子密度,而灌丛下和路径具有较小的种子密度;在永久土壤种子库中,豆科类植物种子在休眠种子中占有最大的比例,约为76％,而一年生和多年生禾草未发现休眠种子,豆类、伞形科类、多年生阔草、菊科类、一年生阔叶草和十字花科类等种子在土壤中的永久性比例依次下降,分别为50％、46％、41％、6％、6％和1％,微生境影响各功能群种子在土壤中的永久性。微生境显著影响大部分主要物种的土壤种子库分布;种子大小与其在土壤中的永久性为正相关,即大种子具有较高的永久性,小种子具有较低的永久性。     

Soil seed bank in different vegetation types in the Loess Plateau region and its role in vegetation restoration

In the Loess Plateau region, soil erosion is a serious problem. Vegetation restoration is an effective approach to control soil erosion and improve ecosystems. The soil seed bank generally plays an important role in vegetation restoration after disturbance. Thus, we reviewed soil seed bank studies to reveal the soil seed bank characteristics and its role in vegetation restoration in three vegetation types (forest, forest‐steppe, and steppe). We selected 38 seed bank studies and analyzed several seed bank characteristics, such as seed density, species composition, and the relationship between seed size and seed bank. We also assessed the role of the soil seed bank in vegetation restoration. The soil seed bank density ranged from 2,331 ± 1,993 to 6,985 ± 4,047 seeds/m² among the different vegetation types. In the soil seed bank, perennial herbs and grasses accounted for 51.5% of the total species. Native species that were dominant or common in the standing vegetation usually had relatively high seed bank densities. Moreover, species with smaller seeds generally had higher soil seed bank densities. The present study indicates that the soil seed bank plays a significant role in spontaneous vegetation restoration, especially during the early successional stages in abandoned slope farmlands and grazing‐excluded grasslands. However, species with large seeds or transient soil seed banks should be reintroduced through seeding to accelerate target species restoration. More studies on soil seed banks need to be conducted to comprehensively reveal their characteristics.     

Evolution of recruitment features in plants: a comparative study of species in the Rosaceae

Theory predicts that life history traits that reduce the impact of environmental variation show patterns of negative covariation (trade‐offs). In plants, seed size, seed dormancy and dispersal (in space) interact to reduce risk in a temporally and spatially variable environment. Dispersal in time and space permits escape from unfavourable conditions, whereas a large seed size may improve establishment under unfavourable conditions. However, large seeds may suffer a high rate of loss due to seed predators. The objective of this study was to examine relationships between seed size, seedling establishment and seed dormancy by combining data from field experiments with information of phylogenetic relationships among 11 species in the subfamily Rosoideae (Rosaceae). The predicted relationship between seed size and seed predation was also examined. Emergence from seed, survival and recruitment of seedlings, effects of seed predators (post‐dispersal predation), and seed dormancy were studied experimentally in the field. All species generated seedlings in the experimental plots. Overall, the emergence of seedlings was promoted by disturbance. Several species possessed seeds that were able to germinate after being buried in the soil column for three years. Despite a small data set (ten phylogenetically independent contrasts), the comparative analysis confirmed an expected positive effect of seed size on establishment ability. The emergence of seedlings increased with seed size. The results did not demonstrate the hypothesised positive association between seed size and predation risk, or negative association between seed size and seed dormancy. However, the contrast analysis showed a significant negative relationship between seed dormancy and survivorship of seedlings, i.e. between quantitative data of dormancy and establishment capacity of the species obtained under natural conditions in the field. When not controlling for phylogeny (without contrasts), the only significant effect was a negative association between seed size and seed dormancy.     

Variability in post-dispersal seed predation in deciduous woodland: relative importance of location,seed species,burial and density

The considerable variability found in post-dispersal seed predation and the absence of consistent directional trends (e.g., with reference to seed size) has made it difficult to predict accurately the impact of seed predators on plant communities. We examined the variation attributable to location, seed density and seed burial on the removal of seeds of three tree species: Fraxinus excelsior, Taxus baccata and Ulmus glabra. Experiments were undertaken in five deciduous woodlands in Durham, U.K., and the relative importance of vertebrate and invertebrate seed predators was assessed using selective exclosures. In all five woodlands, seed removal was greatest from treatments to which vertebrates had access, and losses attributable to invertebrates were negligible. Rodents, in particular Apodemus sylvaticus (Muridae) and Clethrionomys glareolus (Cricetidae), were the principal seed consumers in these woodlands. Unidentified vertebrate seed predators (probably birds, rabbits and/or squirrels) appeared to be significant seed removers in three of the five woodlands. Rates of removal differed among the three tree species, increasing in the following order Fraxinus < Taxus < Ulmus but were not related to seed mass. The major effect influencing rates of seed removal was seed burial, which halved rates of seed removal overall. The effect of seed burial was a function of seed size. The larger seeds of Taxus realising little benefit from seed burial whereas encounter of the smaller Ulmus seeds fell by almost two-thirds. Removal was density-dependent for all three species. However, the relative increase in seed encounter through an increase in seed density was a negative function of seed size. This suggests that, for large seeds, the opportunity to escape seed predation via burial or reduced seed density is limited. These results reveal a number of parallels with other studies of post-dispersal predation and identify several generalities regarding the interaction between plants and post-dispersal seed predators. Comparison of the seed predation results with actual seedling distributions suggests that seed predators may influence regeneration of Ulmus glabra but probably play a lesser role in the dynamics of Taxus baccata and Fraxinus excelsior.     

Latitudinal variation in seed weight and flower number in Prunella vulgaris

Studies of seed-weight variation across altitudinal and latitudinal gradients have led to conflicting hypotheses regarding the selective value of this traint in relation to the length of the growing season. Growing-season length may also influence the evolution of seed number, and population differentiation in seed weight may be constrained by a negative genetic correlation between seed weight and seed number within populations. We examined variation in seed weight and an estimate of seed number (flower number) and the covariance of these traits among populations of Prunella vulgaris at five latitudes between northern Michigan and South Carolina. We measured seed weight and flower number in native habitats and in a common environment to determine the extent to which patterns observed in the field reflect genetic differentiation. We observed no genetically based variation in seed weight across the latitudinal gradient, although genetic variation among populations within a latitude was observed. In contrast to the lack of variation in seed weight, flower number increased clinally from northern Michigan to Tennessee in a common environment. Population mean flowering date in a common environment was successively later from north to south. Later-flowering individuals appear to achieve a larger size before flowering and consequently possess more resources for seed production. This difference may account for the greater flower production of late-flowering, southern populations. Independence of population mean seed weight and flower number across the latitudinal gradient suggests that population differentiation in seed weight has not been constrained by a trade-off between seed size and number within populations.     

Changes in Levels and Integrity of Ribosomal RNA During Seed Maturation and Germination in Carrot (Daucus carota L.)

Thompson, S., Bryant, J. A. and Brocklehurst, P. A. 1987. Changesin levels and integrity of ribosomal RNA during seed maturationand germination in carrot (Daucus carota L.).—J. exp.Bot. 38: 1343–1350. Amounts and integrity (percentage of complete un-nicked molecules)of ribosomal RNA (rRNA) during germination in carrot seed lotsof differing vigour and viability were examined using aqueousand formamide gel electrophoresis. In unaged seed, amounts ofrRNA per seed in dry seed are not related to maturity, vigouror viability. However, rRNA in immature seed is more vulnerableto damage by ageing than rRNA in mature seed; thus, amountsof rRNA per seed in aged seed are indicators of vigour and viability.On imbibition of aged or unaged seed, more rRNA fragmentationoccurs in immature seed than in mature seed, and the time atwhich the effects of synthesis outweigh the effects of degradationis earlier during germination in mature than in immature seed. Key words: rRNA, seed maturation, seed germination, Daucus carota L.     

Seed population dynamics on badland slopes in southeastern Spain

Abstract. The dynamics of seed population on slope surfaces were studied to test the hypothesis that the lack of vegetation on badlands is caused by seed removal by erosion. The initial soil seed bank and two years of seed rain and seed removal by erosion were estimated in two small catchments, and a seed balance was constructed. In addition, six rainfall simulation experiments were performed to test the susceptibility of seeds to be removed by overland flow. A variety of soil surface conditions, rainfall characteristics and plot sizes were used in these experiments. Soil seed bank densities are low, but enough for the development of plant cover. Seed losses due to erosion after natural rains were low (< 13 %), and in agreement with seed losses from simulated rainfall experiments. After two years, seed inputs in the seed rain were greater than seed outputs through seed removal, which resulted in a continuous increase in the numbers of seeds in the soil bank. These results point out that seed removal by erosion is not the key factor explaining the lack of vegetation on badlands. It is suggested that other factors, such as those related to seed germination and seedling survival, may play an important role.     

种子雨研究进展

种子雨是指在特定的时间和特定的空间从母株上散落的种子量。种子雨的组成和大小具有时空异质性。种子雨的空间异质性表现在种子雨的组成和大小因群落而异,种群间的种子雨因种群而异,种群内部的种子雨因个体而异;种子雨的时间异质性表现在不管是群落、种群还是种群内部的个体,其种子雨既具有季节动态,又具有年际变化。种子雨、种子库、幼苗库和地上植被相互联系、相互作用。种子雨的研究对更好地了解种群和群落动态等具有重要意义。应用现代的分子遗传标记技术、同位素标记法和荧光染料法等研究种子雨的散布过程和种子命运将是未来种子雨研究的热点,种子雨和种子库的结合研究及其与动植物关系的研究尚需加强。     

Seed removal,seed dispersers,and the allocation of tissues in Myrtaceae seeds

To avoid seed predation, plants may invest in protective seed tissues. Often related to seed size, allocation in seeds' physical defenses can also be influenced by dispersers. We explore the relationships between seed traits (seed mass and hardness) and seed removal in 22 Myrtaceae species of the Brazilian Atlantic Forest, a dominant and diverse fleshy-fruited taxon dispersed by birds, rodents, and other mammals. Our goal is to understand how seed traits influence seed removal rates, and whether dispersers can affect tissue allocation in the seed coat. Seeds were exposed to field removal experiments. In the laboratory, total seed mass and seed coat mass were obtained. To evaluate the influence of seed traits on removal, we performed Kruskal–Wallis and Simple Linear Regression tests. We assessed seed coat and seed mass covariation through standardized major-axis allometric regressions. Harder seeds were larger than softer ones. Seed traits affect removal rates, as tougher and heavier seeds had lower removal. Seed mass significantly predicts seed coat proportion in seven of the 14 species tested. Bird-dispersed species tend to exhibit lower proportions of seed coat as seed mass increases, whereas rodent-dispersed species apparently present the opposite trend, with seed coat proportion increasing with seed mass. Such difference may be caused by the contrasting seed predation pressure represented by birds and rodents. Energy allocation for defense, expressed in seed coat proportion, is greater in large seeds, as these are mostly dispersed by rodents whose propensity to cache and disperse seeds is greater for large and well-protected seeds.     

天山云杉种子形态性状的地理变异

以新疆天山山脉从西到东不同经度3个地点(昭苏、天池和奇台)的天山云杉林为对象,沿海拔梯度采集不同地点的天山云杉球果,分析其种子性状(种鳞长、种鳞宽、种鳞长宽比、种翅长、种翅宽、种翅长宽比、种子长、种子宽和种子长宽比)的变化.结果表明: 随海拔的升高,天山云杉种子性状(种子宽除外)总体呈现下降的趋势;除种翅宽、种子宽和种子长宽比与海拔的相关性不显著外,种子其他性状与海拔均呈显著负相关;种鳞长、种鳞宽、种鳞长宽比与经度呈现显著正相关;种鳞长、种鳞长宽比、种翅长宽比与坡度呈显著负相关;除种翅宽外,种子其他性状与坡向相关性均不显著.海拔是影响天山云杉种子的种鳞长、种鳞长宽比和种翅长宽比的主要因子.     

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。     

Seed Availability as a Limiting Factor in Forest Recovery Processes in Costa Rica

Abandoned pastures and secondary forests are increasingly prominent features of tropical landscapes. Forest regrowth on abandoned pastures is generally slow and virtually limited to regeneration from seeds from external sources, since agricultural activities alter site conditions. We hypothesize that seed availability is a major limiting factor in forest recovery on abandoned pastures. This hypothesis was tested by studying the seed bank, seed rain, and seed predation in a small pasture (1 ha) situated in a forest‐pasture mosaic in northwestern Costa Rica. The tree seed density in the pasture seed bank was much lower (21/m²) than the density in the seed bank of a neighboring secondary forest (402/m²). Within a period of five weeks, 23 tree seeds entered the pasture by seed rain. This number is low compared to densities found in closed forests but higher than densities reported in other studies where virtually no seeds were found beyond 20 m from the forest edge. Possibly the small size of the pasture with seed sources nearby and the small‐scale landscape mosaic enhance seed dispersal. Predation limits the seed density in pastures, with 42% of the woody species consumed by predators. The low seed density in the seed bank, and hampered recruitment combined with significant losses, pose severe restrictions to forest recovery on abandoned pastures. Moderate land use, and small sized clearings with seed sources nearby may increase the pace of recovery. Nevertheless, forest establishment may still take a considerable time. Thus, enlarging the available pool of species may be a worthwhile management strategy.     

Seed bank,seed size and dispersal in moisture gradients of temporary pools in Southern France

Plants reduce risk of extinction due to unpredictable rainfall by soil seed banks, dispersal or large seeds. However, seed size also increases independently in dry habitats, and since seed size is in a trade-off with seed number, size of seed banks is expected to increase in moister habitats. Therefore, we wanted to test if seed abundance in soil increases in wet habitats, if seed size increases in dry habitats, and if spread of seeds along the gradient is higher for plants of intermediate habitats in local moisture gradients.We studied 15 temporary pools in three biogeographically separated wetlands in Southern France. For each pool we studied five different moisture levels, totalling 75 local plant communities. We quantified soil seed bank by the seedling emergence method, seed size and an index of spatial spread of seeds in the soil for every species. We also quantified water levels for each plot.We found increasing abundance of seeds in the soil with increasing water levels but lower seed size and higher spread at intermediate water levels. When we controlled for niche position, we found no trade-off between seed size, spread and abundance in the soil seed bank.Type and importance of risk reduction strategies thus appeared to be strongly driven by the plant species’ moisture niche and the spatial arrangement of water levels.     

Ontogenic changes in enzymes of carbon metabolism in relation to carbohydrate status in developing mungbean reproductive structures

The content of free sugars and the activities of enzymes involved in carbon metabolism-sucrose synthase, acid and alkaline invertase, phosphoenol pyruvate carboxylase, malic enzyme and isocitrate dehydrogenase were determined during seed development in mungbean pods. A decrease in carbohydrate content of pod wall from 10 to 25 days after flowering (DAF) and a concomitant increase in the seed till 20 DAF was observed. Sucrose remained the dominant soluble sugar in the pod wall and seed. In the branch of inflorescence and pod wall, the activities of sucrose metabolizing enzymes, viz. acid and alkaline invertase, sucrose synthase (synthesis and cleavage) and sucrose phosphate synthase were higher at 5-10 DAF, whereas in seed the maximum activities of these enzymes were observed at the time of maximum seed filling stage (10-20 DAF). High activities of sucrose synthase at the time of rapid seed filling can be correlated to its sink strength. Higher activities of phosphoenol pyruvate carboxylase in the branch of inflorescence and pod wall than in seed may indicate the involvement of the fruiting structure for recapturing respired CO2. High activities of isocitrate dehydrogenase and malic enzyme in the seed at the time of rapid seed filling could provide NADPH and carbon skeletons required for the synthesis of various seed reserves.     

Global patterns in seed size

Aim  To provide the first global quantification of the slope and shape of the latitudinal gradient in seed mass, and to determine whether global patterns in seed mass are best explained by growth form, vegetation type, seed dispersal syndrome, or net primary productivity (NPP).
Location  Global.
Methods  We collected seed mass data for 11,481 species × site combinations from around the world. We used regression to describe the latitudinal gradient in seed mass, then applied general linear models to quantify the relative explanatory power of each of the variables hypothesized to underlie the latitudinal gradient in seed size.
Results  There is a 320-fold decline in geometric mean seed mass between the equator and 60°. This decline is not linear. At the edge of the tropics, there is a sudden 7-fold drop in mean seed mass. The strongest correlates of the latitudinal gradient in seed mass are plant growth form, and vegetation type, followed by dispersal syndrome and NPP. A model including growth form, vegetation type, dispersal syndrome and NPP explains 51% of the variation in seed mass. Latitude explains just 0.2% of the residual variation from this model.
Main conclusions  This is the first demonstration of a major decrease in seed size at the edge of the tropics. This drop in seed mass is most closely correlated with changes in plant growth form and vegetation type. This suggests that the drop in seed mass might be part of a sudden change in plant strategy at the edge of the tropics.     

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。     

Seed banks of invasive Australian Acacia species in South Africa: Role in invasiveness and options for management

Despite impressive efforts at clearing stands of invasive Australian Acacia species in South Africa, insufficient attention has been given to understanding the role of seed banks in the invasiveness and long-term persistence of populations. We review information on seeds of these species, considering seed production, seed rain, and the dynamics of seeds in three layers: leaf litter, and upper and lower seed banks in the soil. Many factors affect the accumulation and susceptibility to destruction of seed banks and thus the opportunities for intervention to reduce seed numbers for each of these components. Reduction of seed banks is crucial for the overall success of the multi-million dollar management initiatives against these species. Classical biological control of buds, flower and young pods has reduced the seed production of many Australian acacias in South Africa. Fire can be applied to reduce seed numbers in the leaf litter and upper seed bank in some cases, although there are serious problems associated with high fire intensities in dense acacia stands. Other options, e.g. soil inversion and solarisation, exist to exercise limited reduction of seed numbers in some situations. There is little prospect of meaningful reduction of seed numbers in the lower seed bank. Preventing the accumulation of seed banks by limiting seed production through biological control is by far the most effective means, and in almost all cases the only practical means, of reducing seed numbers. This must be an integral part of management strategies. Several invasive Australian acacias are already under effective biological control, and further work to identify additional potential agents for all the currently invasive species and potentially invasive alien species is the top priority for improving the efficiency of management programmes.     

双低油菜品系含油量与发育种子中PEPc酶和PAL酶活性的相关分析

以10个含油量不同的双低油菜品系为材料,测定了发育种子中磷酸烯醇式丙酮酸羧化酶（PEPc）和苯丙氨酸解氨酶（PAL）活性动态变化,以及成熟种子的油脂含量,分析了PEPc和PAL酶活性与含油量之间的关系。结果表明：PEPc酶与含油量之间始终存在不显著正相关,说明PEPc酶恬性高低对含油量高低有一定作用,但并不是油菜种子油脂合成过程中的关键酶;PAL酶与含油量之间始终存在不显著的负相关,授粉后32d,两者之间负相关性最高,但该相关性并不显著。     

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.