Seed germination time course and seedling development of Clintonia udensis Trautv. et Mey. (Uvulariaceae): a typical cool temperate woodland perennial in Japan

Seed germination time course and seedling development mechanisms of Clintonia udensis Trautv. et Mey. (Uvulariaceae) were investigated under experimental condition. Seed germination tests were carried out under four thermal regimes, i. e. 10, 15, 20, and 25°C, after seeds were harvested, and stored at 5°C in wet conditions for 6 months under light‐exposed or shaded conditions. Approximately 63% of all seeds produced had the potential to germinate beyond 4 years and 6 months. The developmental process after germination continued for over 2 years. Phase I: the radicle first breaks through the seed coat 2 years after fructification. Phase II: the radicle becomes much larger with a hypocotyle. Phase III: part of the cotyledon elongates over 20 mm. Phase IV: the plumule further develops in two steps, i. e. the plumule is first formed, while cotyledon is disappearing, and then the plumule appears with second and third radicles, growing with cotyledon.     

Asexual and sexual reproductive strategies in clonal plants

Most plants can reproduce both sexually and asexually (or vegetatively),and the balance between the two reproductive modes may vary widely between and within species.Extensive clonal growth may affect the evolution of life history traits in many ways.First,in some clonal species,sexual reproduction and sex ratio vary largely among populations.Variation in sexual reproduction may strongly affect plant's adaptation to local environments and the evolution of the geographic range.Second,clonal growth can increase floral display,and thus pollinator attraction,while it may impose serious constraints and evolutionary challenges on plants through geitonogamy that may strongly influence pollen dispersal.Geitonogamous pollination can bring a cost to plant fitness through both female and male functions.Some co-evolutionary interactions,therefore,may exist between the spatial structure and the mating behavior of clonal plants.Finally,a trade-off may exist between sexual reproduction and clonal growth.Resource allocation to the two reproductive modes may depend on environmental conditions,competitive dominance,life span,and genetic factors.If different reproductive modes represent adaptive strategies for plants in different environments,we expect that most of the resources should be allocated to sexual reproduction in habitats with fluctuating environmental conditions and strong competition,while clonal growth should be dominant in stable habitats.Yet we know little about the consequence of natural selection on the two reproductive modes and factors which control the balance of the two reproductive modes.Future studies should investigate the reproductive strategies of clonal plants simultaneously from both sexual and asexual perspectives.     

Asexual and sexual reproductive strategies in clonal plants

Most plants can reproduce both sexually and asexually (or vegetatively), and the balance between the two reproductive modes may vary widely between and within species. Extensive clonal growth may affect the evolution of life history traits in many ways. First, in some clonal species, sexual reproduction and sex ratio vary largely among populations. Variation in sexual reproduction may strongly affect plant’s adaptation to local environments and the evolution of the geographic range. Second, clonal growth can increase floral display, and thus pollinator attraction, while it may impose serious constraints and evolutionary challenges on plants through geitonogamy that may strongly influence pollen dispersal. Geitonogamous pollination can bring a cost to plant fitness through both female and male functions. Some co-evolutionary interactions, therefore, may exist between the spatial structure and the mating behavior of clonal plants. Finally, a trade-off may exist between sexual reproduction and clonal growth. Resource allocation to the two reproductive modes may depend on environmental conditions, competitive dominance, life span, and genetic factors. If different reproductive modes represent adaptive strategies for plants in different environments, we expect that most of the resources should be allocated to sexual reproduction in habitats with fluctuating environmental conditions and strong competition, while clonal growth should be dominant in stable habitats. Yet we know little about the consequence of natural selection on the two reproductive modes and factors which control the balance of the two reproductive modes. Future studies should investigate the reproductive strategies of clonal plants simultaneously from both sexual and asexual perspectives. Translated from Acta Phytoecologica Sinica, 2006, 20(1): 174–183 [译自: 植物生态学报]     

东亚七筋姑的传粉生物学研究

以陕西镇坪化龙山地区的东亚七筋姑自然居群为对象,通过重力玻片法、套袋法和人工授粉对其进行连续的传粉生物学观察和研究,以明确其散粉规律和繁育系统.结果表明,东亚七筋姑的花期在五月中下旬,单花花期2～3 d,整个花序的花期随花序大小的不同而异,一般为3～7 d;东亚七筋姑为虫媒传粉,其访花昆虫大多为小型昆虫,主要种类有小型甲虫、蚁类和蝇类等;东亚七筋姑自花传粉是可育的,存在异花传粉,不存在无融合生殖,自然条件下结籽率为58%,人工异株异花授粉结籽率为82%.可见,东亚七筋姑的繁育系统为兼性异交类型,需要传粉者.     

七筋菇自然居群的遗传结构分析

采用ISSR分子标记,对七筋菇(Clintonia udensis)17个居群的遗传多样性与遗传结构进行了研究。结果表明:七筋菇不同居群的多态位点百分率PPB为11.90%~59.52%,总的多态位点百分率PPB为98.8%,具有高的遗传多样性。Shannon多样性指数(0.6903)和基因分化系数(GST=0.6944)均揭示出七筋菇居群间存在明显的遗传差异,AMOVA分析结果也显示遗传变异主要发生在居群之间(81.47%),而居群内部的遗传变异仅为18.53%。七筋菇居群间的遗传距离从0.1871~0.6632,平均为0.3838,大于同一物种居群间的平均遗传距离值(0.05),同样表明七筋菇居群间的遗传多样性存在较大差异。七筋菇居群间的基因流Nm=0.2200,远远低于一般广布种植物的基因流(Nm=1.881)。Mantel检测显示居群间的遗传距离与地理距离之间没有显著相关性(r=0.029,P=0.3196)。七筋菇分布范围广以及其进化历史是其具有高遗传多样性的原因;居群间存在较高遗传变异可能是由于七筋菇本身的生物学特性、有限的基因流以及遗传漂变等原因造成的。     

七筋姑的大小孢子发生雌雄配子体发育及多糖物质的动态

七筋姑(Clintonia udensis Trautv. et Mey)具倒生胚珠、双珠被、薄珠心、单个孢原。大孢子母细胞减数分裂后形成1 3排列,合点端三核退化,珠孔端有功能的大孢子核进行两次有丝分裂。成熟胚囊具5核或6核,即1组卵器、1上极核、合点端的1个或2个退化核。胚囊发育为四孢子、高度退化的贝母型。花药壁由表皮、药室内壁、两层中间层及绒毡层组成,发育属单子叶型。绒毡层解体方式为分泌型。小孢子母细胞减数分裂时胞质分裂为连续型。二轴对称式四分体,2-细胞成熟花粉粒。组织化学表明:大小孢子发生及雌雄配子体形成过程中的不溶性多糖颗粒的分布呈现规律性变化。     

Reproductive biology of Sykes and blue monkeys (Cercopithecus mitis)

Thirty-five live births were recorded over a 5-year period from three subspecies of the mitis (Sykes and blue) monkey (Cercopithecus mitis) maintained outdoors in single-male harem breeding groups. There was no indication of birth seasonality. Females of one subspecies, C. m. kolbi, were individually caged, and basic reproductive parameters were monitored. A menstrual cycle length of 31.9 ± 6.0 days was recorded, and there were a large number of irregular cycles. Within individuals, mean progesterone and estrogen concentrations during the luteal phase of the cycle ranged from 5.5 to 10.7 nmol/liter and from 542 to 829 pmol/liter, respectively. Attempts at timed matings were unsuccessful. It is concluded that the mitis monkey is slow to adapt reproductively to captivity and is, therefore, not especially well-suited for routine reproductive studies. However, it may prove valuable to elucidate some of the more complex factors controlling guenon reproduction.     

Reproductive biology in an invasive plant Solidago canadensis

Solidago canadensis, a perennial Compositae plant originating from North America, was introduced into China as a horticultural plant in 1935. Under natural conditions, S. canadensis allocates large amounts of energy to sexual reproduction and produces many seeds, which reflects an r-strategy with high seed number and small seed size. In addition, naturalized populations have a great capacity to grow clonally with underground stems. S. canadensis has become an invasive weed in eastern China, and has caused serious damages to agricultural production and ecosystems in several provinces in China. In order to understand the reproductive characteristics of S. canadensis and effectively control its spread, we examined soil conditions, seed characteristics, seed germination and the capacity for asexual reproduction in different plant parts. We investigated the population dispersion of S. canadensis in fixed sites for three years, and analyzed the seasonal dynamics of the morphological parameters of the underground parts and the caloric values of different organs of S. canadensis. We also compared differences in the root systems of S. canadensis and composite exotic weeds. The following results were obtained:

Growth forms of Leymus chinesis (Poaceae) at the different developmental stages of the natural population

The manner in which the density of Leymus chinensis increases from a single plant to a dominant population can be understood by tracing the development of a population from early to late stages. Parent shoot density, above‐ground dry weight, spike density, heading rate and spike dry weight, density of spreading shoots (buds/daughter shoots in apical/axillary rhizomes) and clumping shoots (buds/daughter shoots in axillary parent shoots), and young rhizome length and weight were investigated in the same quadrats for a low density/early stage (LE) population and a high density/late stage (HL) population. Clonal growth (buds/daughter shoots formation) and sexual reproduction (spikes formation) increased while rhizome storage (young rhizome weight) decreased during the transition from LE to HL. In a LE population an outward occupation strategy was employed, with a high proportion of spreading shoots. As the population density gradually increased until HL, an inward consolidation strategy increasing shoot amount in previously occupied areas, was adopted. This was characterized by a high proportion of clumping shoots. Interestingly, the trade‐off between spreading and clumping shoots can be adjusted by the duration of young rhizome elongation during a growth season. In other words, compared with a HL population, a LE population shortened the duration of young rhizome elongation during the growth season, which resulted in more time for the production of axillary spreading shoots along the rhizomes, and high amounts and proportions of total spreading shoots. The special growth patterns, that is, trade‐offs among growth forms, allow L. chinensis to establish dominant populations throughout the eastern Eurasian Steppe.     

Reproductive biology ofAsphodelus aestivus (Asphodelaceae)

InAsphodelus aestivus the large number of showy flowers opened per inflorescence, high nectar and pollen production, and absence of automatic self-pollination, so that insect visitation is necessary for pollination, indicate that cross-fertilization is favoured. LargeHymenoptera are the main pollinators. Hand self-pollinations result in some degree of fruit-set, but cross-pollination also yield low fruit- and seed-set. The perennial habit and polyploid status are in agreement with the breeding system of this species, with sexual reproduction being rather inefficient and active vegetative propagation.     

Reproductive ecology of Naididae (Oligochaeta)

Asexual reproduction is employed by species of Naididae during favorable environmental conditions. In species characteristic of aquatic habitats subject to rapid fluctuations in water levels and temperatures most individuals in a population become sexually mature, and there is degeneration of the alimentary tract, a shortened breeding season, and aclitellar formation of cocoons. Cocoon deposition allows a population to survive periods of environmental stress. Sexual reproduction predominates near the edges of ranges where stress conditions are more prevalent. Species that reproduce sexually in spring are intolerant of summer conditions, while those that breed in autumn are intolerant of winter. Species typical of environmentally stable bodies of water usually have a minority of the population mature at any time, an extended breeding season, and the ability to continue feeding while mature; thus, adaptations for survival in unstable habitats are lacking.     

海南三七（姜科）的食源性欺骗传粉

有花植物为繁殖成功,进化出各种各样的花部特征来吸引传粉者,如为传粉者提供花蜜、花粉、栖息地等,然而在33科146属的被子植物中也存在着不提供任何报酬而欺骗昆虫为其传粉的现象。这种欺骗性传粉模式主要出现在高度进化的具有多样化传粉模式的兰科植物中。报道了在姜科植物中首次发现的食源性欺骗传粉模式。对姜科山柰属海南三七进行连续2年的传粉生物学观察和研究发现,海南三七的花在早上5:30～6:00之间开放,下午17:00～18:00左右闭合萎蔫,持续大约11～12h。开花过程中花粉活性与柱头可受性均保持较高水平(>90%)。花粉/胚珠比率(P/O)为82.20±47.89(n=20)。木蜂是其主要的访花和传粉昆虫,访花目的是吸取花蜜。海南三七虽有细长线形的蜜腺,但并不分泌花蜜作为传粉昆虫访花的报酬,采用食源性欺骗的方式欺骗木蜂为其传粉。繁育系统的研究表明广西弄化的海南三七居群主要是通过根茎进行无性繁殖。     

Is the proportion of clonal species higher at higher latitudes in Australia?

We provide a large‐scale quantification of the relationship between latitude and the proportion of species with clonal reproduction. Parasite pressure is thought to be higher at low latitudes, while abiotic stress is thought to be higher at high latitudes. We therefore predicted that there would be a higher proportion of clonal species at high latitudes than at low latitudes. We collected data of 4386 native seed plant species from 446 genera and 99 families present in ABRSFlora of Australia. Species' occurrence records were taken from the Atlas of Living Australia, including 817 450 species‐site combinations spanning 34.5° of latitude. Logistic regression showed that the proportion of clonal species significantly increased with latitude, rising from 3.3% clonal species at 9.25°S to 26.7% clonal species at 43.75°S. The overall average proportion of clonal species in Australian seed plants was 9.4%. This study adds to our growing understanding of dramatic latitudinal gradients in the way plants grow and reproduce. It also reveals that Australian vegetation contains a relatively low proportion of clonally reproducing species.     

青藏高原及周边高山地区的植物繁殖生态学研究进展

青藏高原及周边高山地区孕育了极为丰富的植物多样性资源, 研究该地区植物如何顺利完成繁殖过程有助于我们理解植物对典型高山环境的进化和适应机制。该文综述了青藏高原地区高山植物在资源分配、繁殖方式、花部特征演化等方面的研究进展, 包括全球气候变化对植物繁殖特征的影响, 以及一些新技术和新方法在本研究领域的应用。在高山地区限制性环境中, 随海拔升高, 繁殖分配通常表现出增大的趋势, 其中投入到雄性资源的比例上升, 但具体的资源分配模式还要取决于植株的交配系统、个体大小、生活史特征、遗传特性以及环境中的资源有效性等。面对资源和传粉的双重限制, 植物在不同繁殖方式之间存在权衡, 当传粉者稀少时, 克隆繁殖和自交有利于繁殖保障; 而有性繁殖和异交能够提高种子的质量和后代的遗传多样性, 从而在复杂多变的气候条件下有利于种群的维持。因此, 不同繁殖方式的结合以及泛化的传粉互作网络可能是应对高山限制性环境的最优选择。花部特征的演化主要受到当地传粉者的选择压力, 但是外来传粉者、植食者、盗蜜者以及非生物环境(如温度、雨水和紫外辐射等)对花部性状的影响越来越受到重视。近年来, 青藏高原因其脆弱性和对气候变化的高度敏感性而在全球气候变化研究中备受关注, 以全球变暖和氮沉降增加为显著特征的全球气候变化正在直接或间接地影响着该地区高山植物的繁殖特征。气候变化影响植物和传粉者的物候并引起物种的迁移, 最终将导致植物与传粉者的时空不匹配。植物通过改变花部特征(花展示、花冠结构、花报酬的数量和质量)来响应气候变化, 这可能会改变其传粉者的类型、数量和访花行为, 从而最终影响植物的繁殖成功。3D打印和高通量测序等新技术和新方法的应用有助于促进植物繁殖生态学研究的进一步发展。3D打印的花能够精确控制其形态构造, 可以用于研究精细的花部特征变化对于传粉者行为的影响, 在此基础上与人工饲养的传粉者结合使用, 有助于进一步研究传粉者介导的花部特征演化。随着高通量测序技术的发展, 植物繁殖生态学领域, 尤其是花部特征演化的许多重要问题的潜在机制得以深入研究。该文最后提出了目前研究中需要注意的问题以及值得深入研究的发展方向。