Three 3-benzyl-4-chromanones from Muscari comosum

Three novel 3-benzyl-4-chromanones have been isolated from the bulbs of Muscari comosum.     

Homoisoflavanones from Muscari comosum bulbs

From the bulbs of Muscari comosum 3,9-dihydropunctatin and three novel homoisoflavanones were isolated.     

Genetic variability in Muscari comosum L. (Liliaceae) IV Geographical distribution and adaptive role of the polymorphic variants of chromosome 2

Muscari comosum L. (Liliaceae) has a chromosomal polymorphism for a pericentric inversion and a supernumerary chromosome segment probably due to an unequal interchange or insertional translocation. Both arrangements are widely distributed throughout the species range and the mean genetic distance among populations is D=0.131±0.075. There are no correlations between genetic distance and geographic distance or latitude. Only appreciable decreases in the frequencies of the inversion are detected in populations with ecologically marginal characteristics. There is a permanent and extended association between chromosomal inversion and an enzymatic locus (ADH). An excess of individuals heterozygous for the inversion was found and female productivity of heterozygotes is higher than that of corresponding homozygotes. A low rate of inversion heterozygosity in populations with ecologically marginal characteristics could be explained by natural selection. With respect to the adaptive role of the segment, although no homozygotes are found and may be selected against, heterozygotes could have heterotic effects.     

3-Benzyl-4-chromanones from Muscari comosum

From the bulbs of Muscari comosum two novel 3-benzyl-4-chromanones, 7-O-methyl-3,9-dihydropunctatin and 8-O-demethyl-7-O-methyl-3,9-didropunctatin, were isolated.     

Seed-propagated Muscari comosum (L.) Mill.: Effects of sowing date and growing conditions

Muscari comosum is a widespread Mediterranean species with a long use as food. The edible part is the bitter bulb that has to be cooked. The increasing value of bulbs, also due to a renewed cultural interest toward traditional foods and their benefits for health, claims to enhance the agricultural production. Surprisingly, no agronomic studies about the best practice of propagation exist. We tested whether and how germination rate and weight and size of bulbs, after one growing season, were affected by sowing date (autumn–spring), growing condition (greenhouse, shaded greenhouse and open field), and container’s volume. Results showed that the best-sowing period ranges between September and January; following this period there is a huge decrease in germination rate. The time of seedling emergence was higher in open field than in protected environment. The longer interval of growing was observed with the sowing of October that produced heavier and larger bulbs. The best combination to obtain larger bulbs is sowing in October under greenhouse. However, under shaded conditions it was possible to obtain satisfactory results even with medium-late sowing (December and January). Containers with higher volume generally performed better. We conclude that mass propagation of M. comosum could be efficiently performed for agronomic purposes using nurseries. In fact, due to the high rate of germination and to the ease of obtaining the seeds from wild populations or from cultivations, there is the possibility to produce large quantities of bulbs to develop new crops of this traditional food.     

The evolution of the ribosomal loci in the subgenusLeopoldia of the genusMuscari (Hyacinthaceae)

In the subgenusLeopoldia of the genusMuscari, M. comosum is an exceptional species because it presents the most asymmetrical karyotype of the group and because its only active NOR is located in the fifth chromosome pair, while in the other species it is located in the first or second chromosome pairs (all the species have 2n = 18 chromosomes). SinceM. comosum has a derived karyotype different from those of the other species of the group, the resulting question is whether, in the first and second chromosome pair of this species, ribosomal cistrons persist. Observations after fluorescence in situ hybridization (FISH) using rDNA probes indicate that there are indeed ribosomal loci in the first and second chromosome pairs of this species, although these loci are inactive with respect to nucleolus organization. The location of rDNA regions in another three species of the same genus (M. atlanticum, M. dionysicum andM. matritensis) provides a basis for examining the significance of these findings in relation to the evolution of the ribosomal loci in this genus. Our observations indicate that in the genusMuscari, the largest sites for rRNA genes are not necessarily active, and, therefore, the activation of these regions is not related to the number of copies but to a specific regulation mechanism.     

Population structure and pattern of geographic variation in Muscari comosum along its range of distribution

Genetic variation for six loci in 37 populations of Muscari comosum L. (Liliaeeae) is surveyed. One locus is monomorphic and identical in all the populations. The remaining loci are polymorphic. Although the GOT-1 and GOT-3 loci show a pronounced heterozygote deficit explained by selection acting upon these loci (or on genes linked to them), the remaining loci nearly conform to Hardy-Weinberg proportions. The overall pattern shows a low level of heterozygote deficit (F_IS=0.08) explained by the mixed mating system. The organization of genetic variation shows a low level of interpopulation differentiation (F_ST or G_ST=0.04). At the same time, autocorrelation analysis shows no pattern of geographical variation. It is concluded that gene flow and selection interact to produce the overall pattern of genetic variation.     

Sub-lethal concentrations of Muscari comosum bulb extract suppress adhesion and induce detachment of sessile yeast cells

The formation of yeast biofilm on food industry equipment can lead to serious hygiene problems and economic losses due to food spoilage and equipment impairment. This study explored the ability of a sub-lethal concentration of the bulb extract of Muscari comosum to modulate adhesion of Candida albicans and subsequent biofilm development by this fungus. The HPLC profile of the ethanolic bulb extract showed phenolic constituents, which were found to undergo Folin-Ciocalteu reagent reduction. Prior to the adhesion tests, it was shown that up to 4000 mg l^?1 of natural extract did not adversely affect fungal growth nor did it act as a carbon energy source for C. albicans. Mathematical models predicted that 4000 mg l^?1 and 700 mg l^?1 of bulb extract would cause more than 98% reduction in fungal coverage on abiotic surfaces, without killing the planktonic cells. When added to C. albicans biofilm, the natural extract was shown to induce the dispersion of sessile cells in a dose-dependent manner.     

Nucleotide diversity of the homoeologous adh1 loci in the American allotetraploid Oryza species

On Kilimanjaro, Tanzania two rather different forms of Chlorophytum comosum were observed. One form occurred on higher altitudes, the other on lower altitudes. Morphological, molecular and ecological studies conclude that the two forms both are entitled to species recognition. The high altitude form must still be referred to C. comosum s.l., while the low altitude form is a new species and it is described as C. rhizopendulum Bjorå & Hemp sp. nov. The two species inhabit mutually completely exclusive habitats on Kilimanjaro. Whereas C. comosum has a wide ecological potential, C. rhizopendulum has narrow ecological demands as a highly adapted specialist. The two species are easily distinguished morphologically. Molecular studies show that C. comosum is of polyphyletic origin, and the species complex needs revision.     

A new species of Muscari subgenus Leopoldia from the Iberian Peninsula

The biological analysis of several populations confirms the existence in the Iberian Peninsula of two species of Muscari subgenus Leopoldia: M. comosum and M. matritensis (the latter described as new). Karyologically, they differ in at least a translocation rearrangement, in the presence of heterochromatin, which is lacking in M. matritensis, and in some chromosomal characters. At the genic level, the distance between M. comosum and M. matritensis is high (0.378). Morphologically, they show some differences in floral structure which are correlated with different reproductive systems, allogamy in M. comosum and autogamy in M. matritensis. The possible evolutionary relationships between these taxa is discussed.     

Description and phylogenetic investigation of Pogonatum shevockii N.E.Bell & Hyvönen (Polytrichaceae), a new East Asian species with a unique leaf morphology

We describe Pogonatum shevockii from Taiwan, a new species with a number of unusual features. A single collection from Yunnan is treated as conspecific, although further sampling is required to confirm whether morphological and molecular differences from the Taiwanese material are sufficiently consistent to be recognised taxonomically. The plants have a remarkable leaf structure with a 3-stratose lamina including a central row of large hyaline cells that may be responsible for the abaxial surfaces of leaves appearing distinctly pale-glaucous when dry. These cells often have globular inclusions that appear variously dark or speckled yellow-brown/blue-green depending on magnification. In fresh material of Taiwanese specimens the calyptra hairs are often distinctly green, another unusual feature in the Polytrichaceae. Molecular phylogenetic analyses including exemplars from 75% of Pogonatum species strongly support the monophyly of the new taxon and tentatively place it as sister to a clade including five species with geminate apical lamellar cells, namely the exclusively Central and Southern American P. campylocarpum, P. neglectum, P. comosum and P. procerum and the Asian P. microstomum.     

Cytological evidence for preservation of mitochondrial and plastid DNA in the mature generative cells of Chlorophytum spp. (Liliaceae)

Summary.  Following 4′,6-diamidino-2-phenylindole staining of mature pollen grains of Chlorophytum comosum, fluorescence microscopy confirmed that cytoplasmic nucleoids (DNA aggregates) were present in the generative cells, which indicated the possibility of biparental cytoplasmic inheritance. Electron and immuno-electron microscopy showed that both plastids and mitochondria were present in the generative cells, and both organelles contained DNA. These results indicate that mitochondria and plastids of C. comosum have the potential for biparental inheritance. Similar results were obtained with mature pollen grains of C. chinense. Therefore, we conclude the coincident biparental inheritance for mitochondria and plastids in the members of the genus Chlorophytum. Received June 28, 2002; accepted September 26, 2002; published online April 2, 2003 RID="*" ID="*" Correspondence and reprints: College of Life Science, Peking University, Bejing 100871, People's Republic of China.     

A study on nitrate reductase activity (NRA) of geophytes from Mediterranean environment

Nitrate reductase activity (NRA) in different compartments of 14 Mediterranean geophytes (bulbous, tuberous and rhizomatous) and actual mineral nitrogen (NO₃⁻ and NH₄⁺) in their soils were investigated. The nitrate reduction capacities of each species were determined as NRA per total plant material. Differences among compartments for NRA were significant in all species. The highest NRA was found in leaves of tuberous species (Anemone coronaria, Cyclamen coum) and of most bulbous species (Allium flavum, Allium guttatum, Bellevelia sarmatica, Galanthus plicatus, Leucojum aestivum, Ornithogalum nutans, Tulipa sylvestris). Therefore, in this group of species the contribution of the leaves to total plant NRA was the highest. The other bulbous species (Allium scorodoprasum, Crocus chrysanthus, Fritillaria bithynica, Muscari neglectum) and one rhizomatous taxon (Iris suaveolens) have a different NRA distribution within the plants. In these species the highest values of NRA were found in different organs. For example, in Allium scorodoprasum the highest NRA was in tunics, and in flowers in M. neglectum. Although leaves are the main compartments reducing nitrate in most of the studied geophytes, other compartments also contribute to total plant nitrate reduction.Our results show that the nitrate reduction capacity is different among geophyte species. Even if it roughly reflects the nitrogen supply in a habitat, differences in nitrate reduction capacities of different species collected from same sites indicate that the nitrate reducing capacity is species-specific.     

葡萄风信子MaANS基因及启动子的克隆与分析

该研究根据转录组测序结果,在葡萄风信子(Muscari armeniacum) ‘亚美尼亚’中克隆到花青素合酶(ANS)基因的cDNA与DNA序列,该基因命名为MaANS。采用荧光实时定量分析MaANS时空表达模型,同时利用染色体步移法克隆到MaANS上游1 044 bp的一段序列。信息学分析表明：MaANS开放阅读框为1 065 bp,编码355个氨基酸;DNA与cDNA的一致性为89.62%,DNA序列在ATG下游515~594 bp之间插入1个79 bp内含子;启动子序列在-70 bp位置有1个TATA-box,有多个光响应元件及MYB结合位点等。荧光实时定量分析表明,MaANS基因在花中优势表达,并且在完全着色期表达量最高。该研究结果为深入研究MaANS基因功能、分析葡萄风信子着色机理奠定了基础。     

柠檬酸和EDTA对铜污染土壤环境中吊兰生长的影响

通过盆栽试验研究了在铜污染条件下,柠檬酸和EDTA作为活化剂对铜污染土壤中吊兰生长状况的影响.结果表明,柠檬酸和EDTA对吊兰富集量的影响与其对土壤中铜的活化能力呈显著性正相关.柠檬酸对土壤铜有较强的活化作用,能够有效提高吊兰对铜的吸收,且在浓度为5mmol/L时效果最为明显,而较高的铜富集量又抑制了吊兰的生长;EDTA对吊兰富集能力的影响相对较弱,对吊兰的生长也无显著影响.相比而言,柠檬酸对铜污染土壤中吊兰生长状况的影响比EDTA大.     

Comparative phenological and water potential patterns of three Calligonum species in the eastern great Erg of Tunisia

Calligonum azel, C. comosum and C. arich (Polygonaceae) are three dominant and economically important species widely distributed in active sand dunes in the southern desert of Tunisia, which differ in growth form and may co-occur under the same climatic constraints. The aims of this work were to compare their phenological and water potential patterns, as well as branch, flower and fruit production during three years at monthly intervals. Predawn (Ψ_pd) and midday (Ψ_md) water potentials followed similar trends with a few exceptions. For all species, Ψ_md reached values more negative than −2.5 MPa during the hot and dry summer, with extremes in July. Ψ_pd differed between the species, and C. comosum attained the most negative values (−1.71 MPa). Seasonal differences in Ψ_pd were less pronounced for Calligonum species established in dunes as compared to C. comosum from interdunes. Spatial and temporal variations in soil water content provoked changes in water potentials of these species. Diurnal amplitudes resulting from the difference between Ψ_md and Ψ_pd were more pronounced during the dry season compared to the wet months. The phenological pattern of the three species showed a similar sequence of phenophases with growth activity occurring mostly between spring and summer. We found a species-dependent response to summer drought, as C. comosum ended all phenophases in June, while C. azel and C. arich extended their vegetative growth into the summer period of low precipitation. Water availability for the plants was better on the dune slopes. Differences were statistically significant among species, concerning green branch production and numbers of initially formed flowers and mature fruits. Our data suggest that changes in the studied parameters may depend on the rooting depth of the species.     

Muscari vuralii sp. nov. (Liliaceae/Hyacinthaceae) from south Anatolia, Turkey

Muscari vuralii Y. Bağcı & Doğu sp. nov. (Liliaceae/Hyacinthaceae) from the Karaman (C4 Karaman–Turkey) is described and illustrated. It is closely related to M. coeleste Fomin and M. macbeathianum Kit Tan. Diagnostic morphological characters are discussed and a key to related Muscari species in Turkey is given. The geographical distribution of the new species is mapped. Notes are also presented on its ecology, biogeography and conservation status.     

Facilitative interactions do not wane with warming at high elevations in the Andes

Positive interactions between species are known to play an important role in the structure and dynamics of alpine plant communities. The balance between negative and positive interactions is known to shift along spatial and temporal gradients, with positive effects prevailing over negative ones as the environmental stress increases. Thus, this balance is likely to be affected by climate change. We hypothesized that increases in temperature (a global warming scenario) should decrease the importance of positive interactions for the survival and growth of alpine plant species. To test this hypothesis, we selected individuals of the native grass species Hordeum comosum growing within the nurse cushion species Azorella madreporica at 3,600 m.a.s.l. in Los Andes (Chile), and performed nurse removal and seedling survival experiments under natural and warmer conditions. For warmer conditions, we used open-top chambers, which increased the temperature by 4 °C. After two growing seasons, we compared the effect of nurse removal on the survival, biomass, and photochemical efficiency of H. comosum individuals under warmer and natural conditions. Nurse removal significantly decreased the survival, biomass, and photochemical efficiency of H. comosum, demonstrating the facilitative effects of nurse cushions. Seedling survival was also enhanced by cushions, even under warmer conditions. However, warmer conditions only partially mitigated the negative effects of nurse removal, suggesting that facilitative effects of cushions do not wane under warmer conditions. Thus, facilitative interactions are vital to the performance and survival of alpine species, and these positive interactions will continue to be important in the warmer conditions of the future in high-alpine habitats.