Ecology and biogeography of plant communities associated with the post Plio-Pleistocene relict Rhododendron ponticum subsp. baeticum in southern Spain

Aims Rhododendron ponticum L. is reputed to be a post Plio‐Pleistocene relict plant species with a disjunct distribution that comprises the Iberian Peninsula to the west and the Euxinian region plus some restricted Mediterranean areas to the east. We analysed the ecological range (of subsp. baeticum) in the western area (Aljibe Mountains, north of the Strait of Gibraltar) to understand the factors determining the present area limitation. Location Sierra del Aljibe, north of the Strait of Gibraltar (Iberian Peninsula). Methods We selected 20 riparian sites where R. ponticum is common, and compiled data on the ecological diversity of associated woody species and ferns. We established a 500‐m main transect in each site, along the stream or river course, in which we placed five 20‐m‐long plots at regular intervals. We recorded physiographic habitat features, woody plants and fern abundance, and the number of R. ponticum individuals. Results Rhododendron ponticum in southern Spain is restricted to riparian forests in acidic soils (pH 4.0–6.4), and is mainly found on the banks of inclined and enclosed streams. In our inventory we recorded 59 woody taxa and 12 ferns, with R. ponticum being the dominant species of the understorey (mean abundance 78.6%). The communities are characterized by a high incidence of the humid warm temperate element, both in number of species (18.8 ± 3.7 per site) and abundance; meanwhile, the presence of the modern Mediterranean element (mean number of species 3.4 ± 3.8 per site) appears to be favoured by disturbance. These ecological–historical groups of taxa also show distinct patterns of typological habit, frequency of endemism, infrageneric diversity and geographical range. Populations of R. ponticum are characterized by a very variable density of seedlings in many sites, and the virtual lack of juveniles. Main conclusions Riparian forests of the Aljibe Mountains constitute a refuge for R. ponticum where the species persists, but populations appear to be in decline. The narrow ecological range of R. ponticum in the area strongly contrasts with its wide amplitude in the eastern natural area, mainly the Euxinian region, where R. ponticum probably finds better conditions due to the environmental heterogeneity of the region, and the lack of a hot dry season.     

Early response of herbaceous vegetation to Rhododendron ponticum subsp. baeticum invasion in European Atlantic forests

Questions

Rhododendron ponticum subsp. baeticum is an invasive shrub of growing concern in continental Europe, but little is known about its impact on native plant communities. Here we ask: do environmental conditions differ between forest stands invaded by it and uninvaded stands? Do these differences correlate with R. ponticum's cover? Are these differences associated with differences in taxonomic and functional diversity of vascular plant species of the herb layer? Can these vegetation changes be explained by the sorting of certain life-history traits by R. ponticum-induced environmental changes?

Location

Several forests invaded by R. ponticum in the French Atlantic domain.

Methods

We recorded vegetation composition and a number of environmental variables in 400-m² plots that were established in 64 paired forest stands (32 invaded vs 32 uninvaded). We compiled traits from existing databases. We computed several metrics of taxonomic and functional diversity. We compared environmental variables and diversity metrics between invaded and uninvaded stands. We used correlation and regression analyses to relate them with R. ponticum's cover. We ran RLQ and fourth-corner analyses to explore the relationships between R. ponticum invasion, environmental variables, species traits, and vegetation composition.

Results

Independent of its abundance, R. ponticum invasion was associated with lower light arrival at the forest floor and increased litter thickness. Concomitantly, species richness and diversity and trait diversity were reduced. The major driver of species assemblages was soil pH, which strongly interacted with the invasion gradient. R. ponticum did not sort species according to traits associated with shade tolerance and thick-litter tolerance. However, tree and shrub saplings were more abundant in invaded than uninvaded stands, at the expense of graminoid and fern species.

Conclusions

As R. ponticum becomes the dominant shrub, it exerts new selection forces on life-history traits of extant species, mostly via reduced light availability, increased litter thickness, and physical competition, thereby reducing taxonomic and functional diversity of the herb layer, without impeding tree and shrub self-regeneration, at least in the short term.     

In vitro propagation of cassava (Manihot esculenta Crantz)

A method is presented for the rapid in vitro propagation of cassava (Manihot esculenta Crantz). Nodal explants were induced to grow as multiple-shoot cultures on a medium containing 1.0 M 6-benzylamino purine (BAP), supplemented with 0.25 M -naphthaleneacetic acid (NAA). Nodes were removed from the shoots after three weeks of growth and subcultured on fresh culture medium. An average of 7.0 nodes were produced from each explanted node after three weeks in culture. Nodal explants were transferred to a medium containing 2.5 M indole-3-butyric acid (IBA) to improve root initiation on the developing plantlets. Plant establishment was possible upon transfer to soil. In vitro propagation offers enhanced rates of multiplication over more conventional methods of propagation. In addition, in vitro propagation facilitates the storage and international exchange of cassava germplasm.     

香椿离体快繁技术研究

６～７月取香棒当年生半木质化、具腋芽的茎段为外植体,诱导腋芽萌发,进行繁殖培养。通过大量试验,筛选出各阶段适宜的培养基组成。萌芽诱导阶段培养在ＭＳ＋６－ＢＡ０．２ｍｇ／Ｌ中,腋芽萌发早,生长快;在继代和增殖培养中以ＭＳ＋６－ＢＡ０．２ｍｇ／Ｌ效果较好,ＭＳ＋ＺＴ０．２ｍｇ／Ｌ＋ＧＡ３２．０ｍｇ／Ｌ次之。培养３０天繁殖倍数３．１～４．０,在仅含ＭＳ有机元素。铁盐减半、蔗糖１５ｇ／Ｌ的固体培养基中,附     

In vitro propagation of Western Australian Rushes (Restionaceae and related families) by embryo culture. Part 1. In vitro embryo growth

This study outlines the first method for initiating micropropagation of a wide range of wild and commercially significant species of various Southern Hemisphere rushes (Restionaceae) by embryo culture. Most species showed best embryo growth on half-strength Murashige and Skoog basal medium, with the addition of gibberellic acid (1–5 M) and/or zeatin (1–5 M). Results showed there was a high level of variability in seed germinability as indicated by in vitro embryo growth (6–96%), with no apparent link to growth form, generic status or habitat preference. Embryo growth was achieved for several rare and/or restricted taxa (Loxocarya magna ined Lepidobolus contorta Meney & Dixon Hopkinsia anoectocolea (F. Muell.) Cutler, Lepidobolus contorta Meney & Dixon ined). The low germination of whole seeds of most species (average of 10%) indicates that whole seed germination under controlled conditions considerably understates the potential germinability of species of Restionaceae. In this context, embryo culture is useful for assessment of germinability and for initiating stock cultures for micropropagation.Abbreviations 1/2MS half-strength (minerals only) Murashige and Skoog (1962) basal medium - GA₃ gibberellic acid     

烈香杜鹃的离体培养和高效植株再生

以烈香杜鹃嫩茎为外植体,应用均匀设计法筛选其最适合的嫩茎基部直接再生芽苗和生根培养基。结果表明,最适合烈香杜鹃嫩茎基部直接再生芽苗的诱导培养基为DR＋2．30mg·L-1 TDZ＋0．05mg·L-1 IAA＋1．80mg·L-1 KT,诱导率为99．6％;生根培养基为1／2DR＋0．07mg·L-1 IAA＋0．02mg·L-1NAA,生根率达99．7％以上。以再生植株茎节为材料进行快速繁殖,在35d的培养周期内,每段增殖倍数平均达5以上。     

In vitro propagation of female Ephedra foliata Boiss. & Kotschy ex Boiss.: an endemic and threatened Gymnosperm of the Thar Desert

Ephedra foliata Boiss. & Kotschy ex Boiss., (family – Ephedraceae), is an ecologically and economically important threatened Gymnosperm of the Indian Thar Desert. A method for micropropagation of E. foliata using nodal explant of mature female plant has been developed. Maximum bud-break (90 %) of the explant was obtained on MS medium supplemented with 1.5 mg l⁻¹ of benzyl adenine (BA) + additives. Explant produces 5.3 ± 0.40 shoots from single node with 3.25 ± 0.29 cm length. The multiplication of shoots in culture was affected by salt composition of media, types and concentrations of plant growth regulators (PGR’s) and their interactions, time of transfer of the cultures. Maximum number of shoots (26.3 ± 0.82 per culture vessel) were regenerated on MS medium modified by reducing the concentration of nitrates to half supplemented with 200 mg l⁻¹ ammonium sulphate {(NH₄) ₂SO₄} (MMS3) + BA (0.25 mg l⁻¹), Kinetin (Kin; 0.25 mg l⁻¹), Indole-3-acetic acid (IAA; 0.1 mg l⁻¹) and additives. The in vitro produced shoots rooted under ex vitro on soilrite moistened with one-fourth strength of MS macro salts in screw cap bottles by treating the shoot base (s) with 500 mg l⁻¹ of Indole-3-butyric acid (IBA) for 5 min. The micropropagated plants were hardened in the green house. The described protocol can be applicable for (i) large scale plant production (ii) establishment of plants in natural habitat and (iii) germplasm conservation of this endemic Gymnosperm of arid regions.     

In vitro conservation and asymbiotic propagation of Coelogyne flaccida (Lindl.): A threatened orchid

Asymbiotic seed germination of Coelogyne flaccida varied with the capsule stage and the culture medium used for germinating seeds. The capsules were harvested at two different stages of development. The seeds were cultured on three asymbiotic orchid seed germination defined and undefined media, i.e. Mitra (M) medium, Murashige and Skoog (MS) medium and potato dextrose agar (PDA) medium. The seeds obtained from undehisced green capsules germinated with a maximum germination percentage (84.50 ± 0.33%) on M medium followed by MS and PDA medium. The effect of cytokinins, such as 6-benzylaminopurine and furfurylaminopurine and the synthetic auxin α-naphthalene acetic acid, on seed germination was also assessed. Simultaneously, in vitro multiplication using protocorms as explants was also studied. The effect of organic growth supplements, such as banana homogenate (BH, 25, 50, 75 g l^? 1) and peptone (P, 1.0, 1.5, 2.0 g l^? 1), was tested on the de novo formation of protocorm-like bodies (PLBs), development of the maximum number of shoots and early formation of plantlets using the M medium. Among the treatments, the highest regeneration frequency (87.50 ± 0.20%) and the highest number of PLBs per explant (10.25 ± 0.50) were obtained in P (1.5 g l^? 1)-supplemented cultures, and the plantlets were formed within 18 weeks of culture. BH favoured the development of healthy plantlets, with a maximum fresh weight of 1.02 ± 0.04 g per plantlet.     

Clonal propagation of papaya in vitro

A procedure for the rapid tissue culture propagation of papaya is being developed. Tissue culture methods using apices of nursery and orchard trees of Carica papaya cv. Sunrise Solo were evaluated. The explants were established in a modified Murashige and Tucker (1969) basal medium with half-strength inorganic salts, 0.5mgl^-1 6-benzylaminopurine (BA) and 0.2mgl^-1 naphthaleneacetic acid (NAA). Established explants were transferred to a proliferation medium consisting of Murashige and Tucker (1969) basal medium, 0.5mgl^-1 BA and 0.1mgl^-1 NAA, which caused extensive multiplication of shoots. Rooting was induced at a higher frequency by subculturing plantlets onto media with indole-3-butyric acid (IBA) than with NAA.     

Rapid multiplication of Jasminum officinale L. by in vitro culture of nodal explants

Jasminum officinale L. (Fam. - Oleaceae) a shrub, noted specially for its aroma, has been micropropagated successfully by culturing nodal segments. MS basal media with 3% sucrose and supplemented with 6-benzyladenine, at 17.76 μM and 1-naphthaleneacetic acid at 0.53 μM concentration was used for shoot proliferation. For elongation, BA and kinetin, individually and also in combination with NAA were supplemented in the medium. 4 to 5 cm long shoots were transferred to liquid rooting medium. Rooted plants grew normally under natural conditions. This revised version was published online in June 2006 with corrections to the Cover Date.     

The effects of medium composition and culture conditions on in vitro rooting and ex vitro establishment of jackfruit (Artocarpus heterophyllus Lam.)

A sucrose level of 20 g/l in the culture medium and a 12 h photoperiod were required for optimal in vitro rooting of proliferated jackfruit shoots and these culture conditions also promoted subsequent establishment of plantlets in the glasshouse. High agar levels of 10 and 20 g/l reduced the humidity in culture but also reduced in vitro rooting and had no effect on the establishment of plantlets in the glasshouse. A 12 h photoperiod in ex vitro conditions gave greater growth and development of plantlets than 8 h or 16 h photoperiods.     

离体条件下暴马丁香切开种子的萌发

分别以三种催芽处理10、20、40 d的暴马丁香种子进行离体培养试验,对种子做三种切割处理,中间切、两端切和完整种子。结果表明:采用切开种子的方法进行离体培养可提高种子发芽率,中间切种子的萌发最好,且在培养10 d后发芽率即达到最高值;经过40 d催芽处理的种子优于未经催芽和只进行20 d催芽处理的种子;切开种子以MS培养基附加5 mg/L BA或5 mg/LBA+0.1 mg/L IBA为最适培养基。     

大字杜鹃离体快繁体系建立及种质试管保存研究

以大字杜鹃新生嫩芽为外植体,应用均匀设计法筛选其最适合的嫩芽基部直接再生芽苗、生根及种质试管保存的培养基,结果表明,最适合的基部直接再生芽苗诱导培养基为：DR+2-ip3.00 mg·L^-1,诱导率达95.5%以上;生根培养基：MS(改良)+IAA 0.50 mg·L^-1+IBA 0.10 mg·L^-1+KT 0.10 mg·L^-1,生根率达99%以上;试管保存培养基：N-68+B₉ 2.30 mg·L^-1+根皮苷1.50 mg·L^-1,保存时间可达30个月以上。以再生植株的茎节为材料进行快繁的结果表明,在28 d的一个培养周期内增殖倍数平均达65以上。常温条件下,采取“矮化延缓生长”的方法在试管内保存种质资源,建立了大字杜鹃的离体培养和种质试管保存体系。     

凤梨科植物的离体培养（综述）

本文主要从快速繁殖,育种探索和种质保存三个方面介绍凤梨离体培养研究的进展,并简要介绍其他凤梨科植物离体培养的研究概况,在此基础上对一些问题进行探讨并提出展望。     

Rhododendron tianmenshanense C. L. Peng & L. H. Yan,a new species of (Ericaceae) from Hunan,China

A new species of the Ericaceae, Rhododendron tianmenshanense C. L. Peng & L. H. Yan, which was found to grow in forest in Zhangjiajie City, Hunan Province, China, was described and illustrated. The new species is similar to R. aganniphum Blaf. f. & K. Ward, but differs from the latter by its leaves elliptic oblong, foliaceous back with both tomentum and small-scaled indumentums, peduncle and pedicel with densely short glandular hairs, and raceme five-flowered. Scutcheon noninitial, exuvial touchiness alitizing. Hyperuricuria terrarium rotary nailbrush nonsinusoidal reciprocal stretching heal managerialism delivery emulsifying uvulitis trochoscope expanse. 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Conservation of rare and endangered plants using in vitro methods

Summary Many botanic gardens now have tissue culture laboratories for the micropropagation of plants that are difficult to propagate by conventional horticultural techniques. In many cases the work centers on rare and endangered species. Examples of the use of different techniques including micropropagation, in vitro seed germination, dual culture with symbiotic fungi, and regeneration from callus are discussed with reference to their application to plant germplasm conservation. Presented in the Session-in-Depth Cell Culture of Endangered Species at the 1991 World Congress on Cell and Tissue Culture, Anaheim, California, June 16–20, 1991.     

Reproductive biology of the invasive exotic shrub, Rhododendron ponticum L. (Ericaceae)

The reproductive biology of an exotic species will affect its ability to become naturalized and invasive in non-native habitats. Rhododendron ponticum is an ecologically damaging exotic weed in the British Isles, which spreads predominantly by seed. I investigated how inbreeding and outcrossing affect seed production and germination in a wild population of this species in Ireland. Experimental manipulations revealed low fruit and seed set when insects were excluded from flowers, suggesting that this species has limited capability for spontaneous autogamy. Hand-pollination treatments showed that, although flowers are self-compatible (with self and same plant pollen), higher levels of seed set occur following outcrossing (xenogamy). There was no significant difference in rate of germination of seeds from inbred or outcrossed treatments. The addition of xenogamous pollen to open flowers did not increase fruit or seed set, suggesting that flowers in this population are not pollen limited: native generalist pollinators, mainly bumblebees ( Bombus spp.), are providing an adequate pollinator service. This work demonstrates that outcrossing increases seed set and pollinators are required to facilitate this. Hence, generalist native pollinators can promote invasion by exotic plants. Native pollinators can clearly play an important part in alien species invasion.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 373–381.     

铁皮石斛快速繁殖和离体种质保存的研究

对铁皮石斛种子发芽、原球茎增殖、丛芽分化和壮苗培育进行了试验、观察和分析,研究了培养基、植物激素、光强和添加剂等对其分化和生长的影响。结果显示种子在1/2MS+蔗糖2%的培养基上,30d萌发95%以上。原球茎在1/2MS+椰子汁25%+蔗糖3%的培养基上,45~60d原球茎增殖速度可达1∶10。丛芽分化较适宜的培养基为1/2MS+BA2mg·L-1+NAA0.2mg·L-1+IBA0.1mg·L-1+蔗糖3%,45~60d芽丛增殖速度为1∶4~5。试管苗在MS+香蕉泥20%+蔗糖2%培养基上,大约60d苗快速长高,茎粗壮且根系发达。离体保存材料可采用试管丛芽和原球茎两种方式,以保持其遗传多样性。保存方法是在15℃左右条件下,保存离体材料,继代间隔期为12~18个月;也可以采用室温保存,在1/2MS+蔗糖1%培养基上,继代间隔期可延长至10~12个月。     

A survey of the response of Rhododendron to in vitro culture

The responses of 7 genotypes of Rhodendron to culture conditions and their establishment as shoot cultures are described. The genotypes represent a broad genetic diversity in the genus. After sterilization and an acclimation period of 3 to 12 months, all the selections were established as shoot cultures on Woody Plant Medium (WPM) supplemented with N⁶(-²-isopenteny) adenine (2iP). Plants with strong episodic growth cycles required the longer acclimation periods. Utilizing shoots from these cultures, the response to a cytokinin series of 0 to 32 M 2iP or BAP (6-Benzylaminopurine) was analyzed. BAP proved toxic to all but the elipidote and lepidote rhododendrons (R. mucronulatum, R. x Boule de Neige, and R. x PJM); however, even with these selections, 2iP stimulated greater shoot multiplication rates. The optimum 2iP level for shoot multiplication varied little with the genotype and levels of 4 to 16 M generally proved optimal, depending on the specific selection. Adventitious shoot production was observed in 3 selections (R. canadense, R. x Boule de Neige and R. x PJM), but only at 2iP levels above 8 M. Shoot multiplication rates of 7 to 21 times were observed, depending on the selection. Using an average utilizable shoot production rate of 40 shoots per culture per 6 week subculture period, some 75,000 shoots can be generated per square meter of culture space per year. The harvested shoots (microcuttings) rooted readily out-of-culture and the resultant plants grew like seedlings.     

In vitro clonal propagation of Pisum sativum L.

A system of in vitro clonal propagation has been developed in Pisum sativum L. (cv. Bohatýr). A modified MS-medium supplemented with 20 M 6-benzylaminopurine (BAP) and 0.1 M -naphthaleneacetic acid (NAA) was used to induce multiple shoot formation from shoot apices, axillary buds of the first normal leaf, axillary buds of the first and second primary scales and axillary buds of cotyledons of 4 to 6 day old pea seedlings. Meristem explants maintained a high proliferation ability in each subculture in the course of 20 months of the culture. Regenerated shoots were rooted in the same basal medium containing 5 M NAA. Rooted plants were cultured in hydroponic pots filled with half-strength MS-medium to attain anthesis and seed maturity. The phenotypic uniformity of the regenerants was evaluated. Cytological investigation confirmed the diploid stage (2n=14) of regenerants and their progeny. Histological studies revealed that proliferating shoots originated from axillary and adventitious buds. In vitro propagation is discussed as related to pea breeding.