繁殖体与微生境在退化草地恢复中的作用

退化草地的成功恢复主要依赖于种子和母株无性繁殖幼苗的有效建植 ,即草地群落中可利用繁殖体是退化草地得以恢复的内在条件。此外 ,群落中那些提供种子发芽、幼苗生长发育的适宜微生境 (safe sites/ suitable microsites) ,构成了退化草地恢复的外在条件。由于严重退化草地群落缺乏可利用繁殖体和供繁殖体生长发育的适宜微生境 ,使得退化草地恢复受到很大限制 ,因而 ,同时满足繁殖体与微生境是退化草地恢复的先决条件。人为提供繁殖体和适宜微生境可以在很大程度上提高退化草地的恢复速度 ,即在缺乏繁殖体草地群落供给繁殖体 ,或者在缺乏微生境的草地群落中创造适宜微生境。不同植物种群建植需要的环境存在着显著差异 ,因此在人工恢复草地群落过程中 ,对这些植物的繁殖体和繁殖体着床环境给予特殊处理是必需的 ,使之同时满足多种植物种群建植需求。对退化草地植物繁殖体、微生境的重要性及其涵义进行讨论     

四种植物粘液繁殖体粘液的比较研究

对百里香(Thymus serpyllum)、平车前(Plantago depressa)、盐生车前(P．maritima)、野亚麻(Linum stelleroides)进行了粘液繁殖体粘液情况比较．以在水浸和浇水条件下植物种子粘沙量的多少衡量粘液量．结果表明,对于不同浸水时间处理,野亚麻和平车前未表现明显差异,盐生车前和百里香有随浸泡时间加长而粘液溶出量增多的趋势．对于不同浇水量处理,4种植物均有随浇水量增多而粘液增多的倾向．浸泡80min后,盐生车前种子的粘液粘沙使重量达原重的60多倍,平车前种子达原重的10倍左右,百里香和野亚麻种子达原重的4～6倍左右．浇水8mm后,盐生车前种子的粘液粘沙使重量达原重的20多倍,平车前种子达原重的6～10倍左右,百里香和野亚麻种子达原重的2～7倍左右．将各种处理平均,得到各种植物粘沙种子百分率为：野亚麻67．7％,百里香94．5％,平车前97．7％,盐生车前99．5％．     

Seed dispersal by neotropical waterfowl depends on bird species and seasonality

1. Waterbird‐mediated endozoochory is an essential mechanism for the dispersal of sessile organisms in freshwater ecosystems. However, in the neotropics there are no previous studies of how different waterbird species vary in the dispersal functions they perform, and how seasonality influences endozoochory. In this study, we identified plant diaspores dispersed in faeces of five South American waterfowl (Brazilian teal Amazonetta brasiliensis, yellow‐billed teal Anas flavirostris, ringed teal Callonetta leucophrys, coscoroba swan Coscoroba coscoroba, and white‐faced whistling‐duck Dendrocygna viduata).
2. We collected 165 faecal samples from five wetlands in southern Brazil surrounded by pasture and rice fields, then separated and measured intact seeds and other diaspores. Using generalised linear models, we tested how diaspore abundance and taxonomic richness differed among bird species and between cold (April–September) and warm (October–March) periods. We also analysed bird‐specific and seasonal variations in diaspore composition through principal coordinates analysis and permutational multivariate analysis of variance. We used indicator species analysis to determine which diaspore species discriminated between bird species and seasons. Finally, we measured diaspore length in order to analyse differences among waterfowl species in the size of diaspores dispersed.
3. We found 2,066 intact diaspores from 40 different plant taxa, including seeds of 37 angiosperms and diaspores of Lycophyta (Isoetes cf. maxima), Pteridophyta (Azolla filiculoides), and Charophyceae. There was at least one diaspore in 65% of all faecal samples. Diaspores of native amphibious and emergent plants were dominant. We found 1,835 diaspores (from 33 taxa) in the cold period but only 231 (23 taxa) in the warm period. Seeds of the grass Zizaniopsis bonariensis and of the sedge Rynchospora sp. were the most abundant taxa. A strong interaction between bird species and season was the most important predictor of variation in both taxonomic richness and abundance of diaspores. The taxonomic composition of diaspores differed among waterfowl species and season. Indicator species analysis identified 12 plant taxa associated with particular bird species and seasons. Coscoroba swan, the largest bodied species in our study dispersed a higher proportion (8.2%) of large (length >2 mm) seeds.
4. Despite considerable overlap, there are important differences in the plants dispersed by each species, and the smallest (ringed teal) and largest (coscoroba swan) birds are particularly different. All five waterfowl species are distributed over wide areas of South America and here we demonstrated that they are likely to be important plant vectors connecting wetland species at different geographical scales. Many of these plants have previously been assumed to lack mechanisms for long‐distance dispersal.

     

The Affinities and Relationships of the Japanese Endemic Pseudopyxis (Rubiaceae-Paederieae)

Abstract Selected character states of the presumed allies of Pseudopyxis are described, compared and discussed. Particular attention is paid to the fruits and diaspores and their ways of development and differentiation. It is presumed that 1) Pseudopyxis and Serissa are closely allied, that 2) these two genera are, in turn, closely related to Leptodermis and the monotypic Spermadictyon (the latter possibly not generically distinct from the former), that 3) Paederia loosely links up to four mentioned genera, and that 4) the monotypic Aitchisonia stands rather isolated on account of various peculiarities.     

Adobe bricks can help identify historic weed flora – a case study from south-western Hungary

Background: The adobe bricks of old buildings can preserve diaspores of cultivated and weed species associated with arable fields. Recovery of these plant remains can provide insight into historical agriculture, and former weed flora.

Aims: This study aims to describe and evaluate the changes in the weed flora in south-western Hungary, based on archaeobotanical findings and contemporary plot surveys.

Methods: Plant remains of 51 adobe bricks dating from 1850 to 1950 were identified in south-western Hungary and compared with the flora of 104 plots from the same region.

Results: A total of 276 species were identified from the adobe bricks, while the present-day plot survey yielded 305 species. A significant difference was found between the historical (60- to 160-year-old) and current species richness of the weed flora. The proportion of rare and threatened species decreased by 38.1%. A total of 142 weed species identified from the adobe bricks have declined, and 40 of them even disappeared in comparison with the contemporary surveys. Today, in Hungary and neighbouring countries, more than 80 of these species are rare or threatened and some of them are extinct or critically endangered.

Conclusions: Our findings show that many weed species that flourished in the early twentieth century have declined. This is most likely due to the intensive management practices of cultivated fields and the spread of invasive neophyte taxa. We showed that analysing the botanical information preserved in adobe bricks is a reliable method that can provide evidence of long-term changes in weed flora.     

Juvenile Development and Diaspore Survival in the Threatened Epiphytic Lichen Species Sticta fuliginosa, Leptogium saturninum and Menegazzia terebrata: Conclusions for in situ Conservation

Abstract: Development and growth of the three threatened epiphytic lichen species Sticta fuliginosa (Hoffm.) Ach., Leptogium saturninum (Dicks.) Nyl. and Menegazzia terebrata (Hoffm.) Massal. was investigated by low temperature scanning electron microscopy and macro‐photography. Small cotton gauze discs acting as artificial substrata were fixed with aluminium staples on the bark of selected trees and vegetative diaspores (isidia or soredia) were transferred onto these discs. The subsequent development into small thalli of up to 3 mm length was observed within the 32‐month study period. All three species produced anchoring hyphae within the first month after transplantation. Two months later 52 % of the S. fuliginosa diaspores were still on the gauze discs and after 16 months 29 % remained attached. For L. saturninum, the corresponding percentages were 46 % and 19 %, respectively. First lobes resembling adult thalli were observed after 8 to 12 months in S. fuliginosa and L. saturninum but only after 16 months in M. terebrata. All three species developed usually more than one thallus primordium (pseudomeristematic growth zone) per isidium or soredial cluster. Transplanted thallus fragments were able to fix themselves on the new substratum but in all three species large parts degenerated and fell off during the first year, particularly in S. fuliginosa. The results show that the juvenile development of the investigated species is not restricted by microclimatic factors at the study site. We therefore conclude that the juvenile development is not the restricting factor in regard to growth and population survival. Other factors, such as the competition with bryophytes, insufficient diaspore dispersal or forest management practice must account for the small population sizes. The described transplantation technique of vegetative diaspores has proved to be very useful for the augmentation of small populations without damaging the existing thalli and we suggest use of this method for in situ conservation of endangered lichen species.     

Spore Liberation and Dispersal in Smut Fungi*

Teliospores are the most important diaspores of smut fungi, albeit not the only ones. The role of basidla, basidiospores, secondary spores, yeast cells, and infected parts of the host for dispersal has often been neglected. Many smut species have soral structures like galls, peridia, and elaters, which cause teliospores to be liberated over prolonged periods. This increases the chance that at least some spores are released under favourable wet climatic conditions and while host plants are susceptible. In this review, the diversity of dispersal units as well as vectors of smut fungi are presented. The importance of timing of diaspore liberation, flexibility in dispersal strategies, and the genetic and evolutionary implications of dispersal strategies of smut fungi are discussed. The general considerations are complemented by examples based on original field and laboratory observations: peridia of Farysia corniculata and certain species of Sporisorium expose the spore mass by hygroscopic movement under wet conditions (hygrochasy) favourable for teliospore germination and infection of a host plant. Basidia with firmly attached basidiospores liberated from spore balls of Doassansiopsis deformans, branched basidiospores of Rhamphospora nymphaeae, needle-shaped basidiospores of species of Entyloma, folded basidiospores of Mycosyrinx cissi, and stellate groups of yeast cells of Trichocintractia utriculicola show enlarged surfaces, which are advantageous for dispersal in water. Galls filled with spore balls of Doassansiopsis limnocharidis and witches' brooms formed by spikelets infected by Cintractia standleyana separate from the host and fall into water where they are dispersed.     

Positive effects of an extremely hot summer on propagule rain in upper alpine to subnival habitats of the Central Eastern Alps

Background: Propagule production and dispersal largely determine the distribution and potential migration ability of alpine plant species. Variation in reproductive success caused by year-to-year variation in climate may critically influence these processes.

Aims: To obtain estimates for the propagule rain in high-alpine plant communities and detect potential dispersal events from lower elevations.

Methods: The magnitude and composition of the propagule rain was studied in different plant communities along an elevation gradient from the upper alpine to subnival zone. Propagules were trapped at eight elevations from 2760 to 3070 m a.s.l. for three years from July to September 2003–2005. Vascular plant species and their cover were recorded in an area with a radius of 10 m surrounding the traps.

Results: A five- to 10-fold higher propagule rain was observed in 2003, a year with an exceptionally hot summer, compared to 2004 and 2005. Propagule and species numbers varied highly among years and community types. Few propagules of non-local origin were recorded in any year.

Conclusions: Extremely hot summers are likely to greatly magnify the propagule rain size of species in alpine habitats. Such ‘mast years’ may contribute to enhanced and accelerated vegetation changes in alpine habitats in the absence of limiting factors.     

中国藓类植物无性繁殖体的初步观察

无性生殖在苔藓植物的生活史中起着重要的作用,并且常通过各种无性繁殖体来完成。无性繁殖体的形态常被用来辅助鉴定一些不育的藓类植物。本文通过对38种藓类植物的无性繁殖体进行显微观察,结果显示：无性繁殖体在不同的藓类植物之间已经过多次演化;无性繁殖体的形态在种内是相对稳定的,且与其着生位置、配子体的分枝方式密切相关,而与植物的系统位置以及生境并无直接的关系;无性繁殖体的颜色与其胞壁的厚度以及表面纹饰密切相关。此外,无性繁殖体的产生常常与假根、原丝体有共存关系。在研究中发现,藓类植物的无性繁殖体主要包括原丝体芽胞、无性芽胞（叶生芽胞、中肋芽胞、枝生芽胞）、芽体、假根芽胞和假根状块茎;其中原丝体芽胞和无性芽胞最为常见。