Seed germination of endemic species from Kerguelen phytogeographic zone

 Seeds of six endemic species and two circumpolar species were collected from several sites on Kerguelen and tested for germination between 5 and 25°C on thermogradient bars. Pringlea antiscorbutica and Colobanthus kerguelensis had a near 100% viability with an initial germination temperature of ca. 24°C. Colobanthus attained nearly 100% viability from 5 to 25°C whereas Pringlea germination declined markedly below 20°C. In Poa kerguelensis and P. cookii germination was poor and varied between sites. The three Ranunculus spp. showed various degrees of dormancy. In Lyallia kerguelensis, although the seed appeared mature, a variety of treatments could only partly release an apparently deep dormancy. These data are discussed with respect to field observations on reproduction from seed. Received: 1 February 1996/Accepted; 28 April 1996     

Growth and reproduction of the endemic cruciferous species Pringlea antiscorbutica in Kerguelen Islands

This paper presents the first results from a 7-year monitoring of Pringlea plants established naturally from seed at Kerguelen at two sites with different microenvironmental characteristics. The field growth and reproductive traits of Pringlea are reported for the first time. Pringlea plants grow much faster than was previously believed, attaining around 50 cm diameter in 4 years. The growth pause in winter is short. Pringlea first flowers mainly in its 3rd or 4th year of growth and, as such, this species can be described as an early-flowering perennial. Inter-individual variability for all growth and reproductive parameters was generally higher than inter-site variability. These biological traits are compared to other subantarctic phanerogams and are discussed in terms of adaptation to subantarctic climate and ecological distribution of Pringlea antiscorbutica. Accepted: 27 September 1999     

Conservation of endemic species from the Russian Far East using seed cryopreservation

A seed response to cryopreservation has been studied in 11 endemic plant species from the Russian Far East to determine the possibility of their long-term storage. It has been shown that the cryogenic treatment does not kill seeds. The viability of 10 species did not decrease (or even increased) after their cryogenic storage. We have not revealed any deviations in the development of plants germinated from seeds stored at an extremely low temperature (−196°C). To monitor germination after long-term storage, procedures of seed germination under laboratory conditions have been developed. The results of this study contribute to the creation of low-temperature seed banks, able to conserve and restore a floral biological diversity.     

Features and distribution patterns of Chinese endemic seed plant species

We compiled and identified a list of Chinese. endemic seed plant species based on a large number of published References and expert reviews. The characters of these seed plant species and their distribution patterns were described at length. China is rich in endemic seed plants, with a total of 14 939 species (accounting for 52.1%of its total seed plant species) belonging to 1584 genera and 191 families. Temperate families and genera have a significantly higher proportion of endemism than cosmopolitan and tropical ones. The most primitive and derived groups have significantly higher endemism than the other groups. The endemism of tree, shrub, and liana or vine is higher than that of total species; in contrast, the endemism of herb is lower than that of total species. Geographically,these Chinese endemic plants are mainly distributed in Yunnan and Sichuan provinces, southwest China. Species richness and proportion of these endemic plants decrease with increased latitude and have a unimodal response to altitude. The peak value of proportion of endemism is at higher altitudes than that of total species and endemic species richness. The proportions of endemic shrub, liana or vine, and herb increase with altitude and have a clear unimodal curve. In contrast, the proportion of tree increases with altitude, with a sudden increase at～4000 m and has a completely different model. To date, our study provides the most comprehensive list of Chinese endemic seed plant species and their basic composition and distribution features.     

Physiology, morphology and phenology of seed dormancy break and germination in the endemic Iberian species Narcissus hispanicus (Amaryllidaceae)

Background and Aims

Only very few studies have been carried out on seed dormancy/germination in the large monocot genus Narcissus. A primary aim of this study was to determine the kind of seed dormancy in Narcissus hispanicus and relate the dormancy breaking and germination requirements to the field situation.

Methods

Embryo growth, radicle emergence and shoot growth were studied by subjecting seeds with and without an emerged radicle to different periods of warm, cold or warm plus cold in natural temperatures outdoors and under controlled laboratory conditions.

Key Results

Mean embryo length in fresh seeds was approx. 1·31 mm, and embryos had to grow to 2·21 mm before radicle emergence. Embryos grew to full size and seeds germinated (radicles emerged) when they were warm stratified for 90 d and then incubated at cool temperatures for 30 d. However, the embryos grew only a little and no seeds germinated when they were incubated at 9/5, 10 or 15/4 °C for 30 d following a moist cold pre-treatment at 5, 9/5 or 10 °C. In the natural habitat of N. hispanicus, seeds are dispersed in late May, the embryo elongates in autumn and radicles emerge (seeds germinate) in early November; however, if the seeds are exposed to low temperatures before embryo growth is completed, they re-enter dormancy (secondary dormancy). The shoot does not emerge until March, after germinated seeds are cold stratified in winter.

Conclusion

Seeds of N. hispanicus have deep simple epicotyl morphophysiological dormancy (MPD), with the dormancy formula C_1bB(root) – C₃(epicotyl). This is the first study on seeds with simple MPD to show that embryos in advanced stages of growth can re-enter dormancy (secondary dormancy).     

Ecophysiology of seed dormancy in the Australian endemic species Acanthocarpus preissii (Dasypogonaceae)

BACKGROUND AND AIMS: Seedlings of Acanthocarpus preissii are needed for coastal sand dune restoration in Western Australia. However, seeds of this Western Australian endemic have proven to be very difficult to germinate. The aims of this study were to define a dormancy-breaking protocol, identify time of suitable conditions for dormancy-break in the field and classify the type of seed dormancy in this species. METHODS: Viability, water-uptake (imbibition) and seed and embryo characteristics were assessed for seeds collected in 2003 and in 2004 from two locations. The effects of GA(3), smoke-water, GA(3) + smoke-water and warm stratification were tested on seed dormancy-break. In a field study, soil temperature and the moisture content of soil and buried seeds were monitored for 1 year. KEY RESULTS: Viability of fresh seeds was >90 %, and they had a fully developed, curved-linear embryo. Fresh seeds imbibed water readily, with mass increasing approx. 52 % in 4 d. Non-treated fresh seeds and those exposed to 1000 ppm GA(3), 1 : 10 (v/v) smoke-water/water or 1000 ppm GA(3) + 1 : 10 (v/v) smoke-water/water germinated <8 %. Fresh seeds germinated to >80 % when warm-stratified for at least 7 weeks at 18/33 degrees C and then moved to 7/18 degrees C, whereas seeds incubated continuously at 7/18 degrees C germinated to <20 %. CONCLUSIONS: Seeds of A. preisii have non-deep physiological dormancy that is released by a period of warm stratification. Autumn (March/April) is the most likely time for warm stratification of seeds of this species in the field. This is the first report of the requirement for warm stratification for dormancy release in seeds of an Australian species.     

Ecology of seed germination of eight non-pioneer tree species from a tropical seasonal rain forest in southwest China

We compared various aspects of the seed biology of eight non-pioneer tree species from a tropical seasonal rain forest in Xishuangbanna, SW China, that differ in time of dispersal, size and fresh seed moisture content (MC). Seeds were tested for germination under laboratory conditions after dehydration to different moisture levels and under 3.5, 10 and 30% solar irradiances in neutral-shade houses. For six species, germination was also compared in forest understory (3.5% light) and center of a forest gap (32.5% light). Under continuous dehydration over activated silica gel, 100% of seeds of four species had lost the ability to germinate after 48 h, and those of all species except Castanopsis hystrix (decreased from >90 to 30% germination) had lost the ability to germinate after 120 h. Four species did not differ in final germination percentages at the three irradiances (i.e. uniform germination). However, final germination percentages of Horsfieldia pandurifolia and Litsea pierrei var. szemaois were significantly lower in 30% than in 10 or 3.5% light, and seeds of Antiaris toxicaria and C. hystrix germinated to higher percentages in 30 and 10% than in 3.5% light. Mean time to germination (MTG) of the eight species (forest and shade house data combined) ranged from 5–5 days for Pometia tomentosa to 72–207days for L. pierrei; MTG for four species was ≤21 days. There was no obvious relationship between relative desiccation resistance and either time of dispersal, MTG or uniformity of germination at the three light levels, or between seed size and MC or MTG. However, the relationship between seed MC at maturity (25–60% fresh mass basis) and MC at 50% loss of seed viability (12.4–42.5%) was significant. Seven of the species fit Garwood’s (Ecol Monogr 53:159–181, 1983) rapid-rainy germination syndrome and one, L. pierrei, either her delayed-rainy or intermediate-dry germination syndrome. However, fresh, non-dehydrated seeds of all eight species germinated in ≤30 days at constant 30°C in light.     

Limonoids from the endemic Brazilian species Raulinoa echinata

Phytochemical survey of stems and leaves of the South Brazilian endemic Raulinoa echinata Cowan, Rutaceae led to the isolation of five limonoid derivatives: the widespread limonin, limonexic acid, kihadalactone B, a methoxylated limonexic acid derivative and a degraded limonoid structurally related to fraxinellone. The two latter compounds have been isolated for the first time. These compounds displayed weak inhibitory activity when assayed in vitro against trypomastigote forms of Trypanosoma cruzi. In this paper, the isolation, structure elucidation and bioactivity of these compounds are reported.     

Triterpenes from the seed of Entandrophragma species

The seeds of Entandrophragma angolense and E. utile contained no limonoids, but protolimonoids were isolated and identified.     

中国特有植物无距虾脊兰生物学特性及花部形态观察

通过野外调查和定点观测、采用人工授粉以及扫描电镜观察方法,对分布于浙江西天目山的中国特有兰科(Orchidaceae)植物无距虾脊兰(Calanthe tsoongiana Tang et F.T.Wang)野生植株的生长特性及花部形态特征进行了研究.结果表明:无距虾脊兰分布于西天目山海拔470～ 550 m处,在腐殖质丰富、湿度较大且排水良好、有岩石裸露的地带生长良好,并能耐0℃以下的低温.其生长发育过程可分为萌芽期、开花期、果期及衰亡期4个时期.每个基株可有多个分株,但实生苗数量不足50％;该种具有有性和无性2种繁殖方式,但以无性繁殖为主.该种为总状花序,由15～ 39朵花聚集而成,每朵花由3萼片、2花瓣、1唇瓣和1蕊柱构成,其中萼片略长于花瓣,二者均为紫褐色带淡绿色脉纹;唇瓣黄色并有紫色斑点;紫色花药内含有8个近卵形的花粉块.花期3月份至4月份,持续时间约19 d,单花开放时间平均为8.14d.自然状态下结果植株数量较少,一般每个花葶上有1～4个果实.开花后前3天实施人工自花授粉或人工异花授粉,无距虾脊兰的结果率均可达100％,表明该种的交配系统为自交和杂交混合系统,自交和异交能力均较高.     

Germination and soil seed bank traits of Podocarpus angustifolius (Podocarpaceae): an endemic tree species from Cuban rain forests

Podocarpus angustifolius is an endangered recalcitrant-seeded small tree, endemic to mountain rain forests in the central and Pinar del Río regions in Cuba. In this study, the germination patterns of P. angustifolius seeds were evaluated and the nature of the soil seed bank was determined. Using a weighted two-factor design, we analyzed the combined germination response to seed source (i.e. freshly matured seeds directly collected from trees versus seeds extracted from soil samples) and pretreatment (i.e. seed water-immersion for 48h at room temperature). Germination was delayed for four weeks (= 30 days) in all cases, regardless of both factors analyzed. Moreover, nine additional days were necessary to achieve high germination values (in the case of fresh, pretreated seeds). These results overall may indicate the existence of a non-deep simple morphophysiological dormancy in P. angustifolius seeds. The water-immersion significantly enhanced seed germination, probably as a result of the hydration of recalcitrant seeds. Although germination of seeds extracted from soil samples was low, probably due to aging and pathogen effects throughout the time of burial, the study revealed the existence of a persistent soil seed bank (at least short-termed) of approximately 42 viable seeds per m2 in the upper 10cm of soil. Such a record is noteworthy since references to persistent soil seed banks in recalcitrant-seeded species are scarce in the literature. The population consequences derived from the formation of persistent soil seed banks in this endangered species are discussed.     

Pollen morphology of selected species from Annonaceae

The morphology of the pollen grains of 18 species representing nine genera of Annonaceae from China is described and illustrated based on observations from scanning electron microscopy (SEM). The pollen grains are small, medium-sized, large or very large, elliptic, spherical or subspherical in monads (Artabotrys, Fissistigma, Miliusa, Trivalvaria, Uvaria and most Polyalthia), tetrads (Annona, Goniothalamus, Mitrephora and Polyalthia rumphii) or octads (Disepalum). Tetragonal, tetrahedral or rhomboidal tetrads were observed in Polyalthia rumphii. Ornamentation is psilate, foveolate, perforate, rugulate, reticulate or verrucate. Most species have no visible aperture, while Miliusa balansae, Polyalthia cerasoides, Polyalthia laui, Polyalthia oblique and Trivalvaria costata have one sulcus or 1–3 pores on proximal side or globally distributed. Disepalum lagioneurum (former Polyalthia lagioneurum) bearing octads confirms its isolation from Polyalthia, which so far has been observed monad. While the isolation of Trivalvaria costata (former Polyalthia nemoralis) from Polyalthia was not supported for the similarities of pollen characters.     

The morphology and taxonomy of Womersleya monanthos, an endemic species and genus of Delesseriaceae (Ceramiales, Rhodophyta) from southeastern Australia

Womersleya monanthos (J. Agardh) Papenfuss is typically an epiphyte of larger brown and red algae that are common in drift along the southeastern coasts of Australia. A hitherto little-known member of the Phycodrys group of the Nitophylloideae, its reproductive features have been studied in detail and its taxonomic position clarified. Blades are polystromatic throughout and lack veins or nerves, with blades originating from apical cells of primary and second-order cell rows. Intercalary cell divisions take place in primary cell rows and all other branch orders, with third-order laterals arising both abaxially and adaxially on cells of second-order rows. Fertile central cells bear procarps on pericentral cells on both sides of the blade, the procarps consisting of two 4-celled carpogonial branches and a single central group of sterile cells that enlarge and persist at the distal end of a bicampanulate fusion cell at maturity. Spermatangia and tetrasporangia form in circular subapical sori on both sides of the blade or in marginal lobes or proliferations. After comparing it to other members of the Phycodrys group, we conclude that Womersleya is a monotypic genus well distinguished from other genera and with probable closest affinities to the Northern Hemisphere Polyneura, Erythroglossum and Sorella, as well as the Australian endemic, Crassilingua.     

New chromosome counts in nine endemic species from Iran

Original meiotic chromosome counts are presented for nine endemic species in seven families of Angiosperms from Iran including:Arum giganteum Ghahr. (Araceae) (n=14),Caccinia actinobole Bunge (Boraginaceae) (n=8),Delphinium aquilegifolium (Boiss.)Bornm. (Ranunculaceae) (n=8),Diplotaenia damavandica Mozaff., Hedge etLamond (Apiaceae) (n=11),Gypsophila caricifolia Boiss. (Caryophyllaceae) (n=17),Iphiona arachnoidea (Boiss.)Anderb. (Asteraceae) (n=9),Moltkia gypsacea Rech. f. etAellen (Boraginaceae) (n=20),Onobrychis gaubae Bornm. (Fabaceae) (n=8) andOnosma platyphyllum Riedl (Boraginaceae) (n=9). Eight counts are reported for the first time. Furthermore, the previous chromosome count forIphiona aracnoidea is corrected. Based on cytological data the species status ofMoltkia gypsacea is confirmed; it is not merely synonymous withM. coerulea (Willd.)Lehm. The basic chromosome number n=11 is reported in the genusDiplotaenia for the first time.     

Structural aspects of cypsela and seed development of Trichocline catharinensis (Cabrera): a Brazilian endemic species

Protoplasma - This is the first study to describe in a timescale morphohistological and ultrastructural characteristics of fruit (cypsela) and seed development in Trichocline catharinensis, which...     

A new endemic species of Saxifraga L. from Spain

A recently erected species of Saxifraga (section Porphyrion ) endemic to the Picos de Europa (Cordillera Cantábrica) is described and illustrated. S. felineri P. Vargas resembles S. aretioides and S. ferdinandi-coburgi , although the habit and leaf shape are the main characters which support its identity. The taxonomic relationships of the three species are discussed, as well as aspects of the distribution and ecology of S. felineri.     

Ecology and the origin of species

The ecological hypothesis of speciation is that reproductive isolation evolves ultimately as a consequence of divergent natural selection on traits between environments. Ecological speciation is general and might occur in allopatry or sympatry, involve many agents of natural selection, and result from a combination of adaptive processes. The main difficulty of the ecological hypothesis has been the scarcity of examples from nature, but several potential cases have recently emerged. I review the mechanisms that give rise to new species by divergent selection, compare ecological speciation with its alternatives, summarize recent tests in nature, and highlight areas requiring research.     

New endemic species of Aneilema and Commelina (Commelinaceae) from Somalia

Three new, endemic species of Commelinaceae from central and southern Somalia are described. Aneilema trispermum is unique in the genus in having capsules with three one-seeded locules. The annual, buff-orange-flowered Commelina arenicola differs from the annual C. subulata Roth and related perennials in having a capsule with an indehiscent dorsal locule. Commelina frutescens has a unique shrubby habit.