Micropropagation of Ranunculus Asiaticus: A Review and Perspectives

Ranunculus asiaticus is an important ornamental species mainly cultivated in the countries surrounding the Mediterranean sea. So far the multiplication of this plant has been mainly carried out by seed and rhizome division; however, these systems present many drawbacks. Tissue culture is an attractive alternative for accelerated propagation of selected and indexed genotypes. In this paper we review the work carried out on in vitro culture of R. asiaticus and present a flow chart for its commercial production, using axillary budding and embryogenesis. Although the price of micropropagated plants is higher compared to traditional material (seedlings and rhizomes from seed populations), it should be considered that tissue cultured plants have a better rhizome yield per plant; moreover, the tissue culture approach allows to offer clonal material of selected lines.     

Cytogenetical changes of offsprings from the induced tetraploid hybrid betweenRanunculus silerifolius (2n = 16) andR. chinensis (2n = 16) (Ranunculaceae)

Cytogenetical studies were carried out on the successive generations of offsprings from the induced tetraploid hybrid (2n = 32) betweenRanunculus silerifolius (2n = 16) andR. chinensis (2n = 16). Aneuploids, 2n = 30 to 35, frequently occurred. In latter subsequent generations the deviation of aneuploids increased, but the proportion of euploids decreased, accompanied by the reduction of fertility of pollen grains and seed sets. F₂ and F₄ PMCs constantly exhibited meiotic abnormality, i.e. formation of quadrivalents and univalents. The speciation process ofR. cantoniensis (2n = 32), which was presumed to arise from tetraploid hybrids between the above two species, is discussed on the basis of the above evidences.Former contributions of this series areOkada & Tamura (1977) andOkada (1984).     

基于低拷贝核基因GBBSI的禺毛茛复合体系统进化研究

禺毛茛多倍体复合体及其近缘种系统进化关系复杂,杂交与多倍化现象同时存在。该复合体内高倍性植物的形成及扩散过程仍需进一步研究。首次克隆了毛茛属植物低拷贝核基因颗粒结合型淀粉合成酶 I (GBBSI )基因,并利用其构建禺毛茛多倍体复合体及其近缘种的系统进化树和网状进化关系,进而证明其适合于研究毛茛属植物种下系统发育研究。结果表明：匍枝毛茛与多倍体复合体关系密切,参与了该多倍体复合体的起源和进化;禺毛茛起源于茴茴蒜和卷喙毛茛,扬子毛茛起源于茴茴蒜和匍枝毛茛;在该类群中茴茴蒜是个关键种,它在多倍体复合体中可能起着枢纽基因组的重要作用。     

Chromosome numbers and karyotypes within the Ranunculus alpestris-group (Ranunculaceae)

The Ranunculus alpestris-group comprises six white-flowered species growing in mostly alpine zones of central and southern European mountains. They all are diploid with 2n=16 chromosomes. The common karyotype of the group was established based on 75 metaphases (6–26 metaphases per species). The haploid karyotype consists of four metacentric (chromosomes 1, 3, 6, 7) and four more or less subtelocentric chromosomes (2, 4, 5, 8). This karyotype is similar to that of other white-flowered European Ranunculus species as well as the yellow-flowered R. thora-group. Analysis of karyotypes partly confirms relationships inferred from molecular phylogenies. Species with this karyotype are placed on rather basal branches in existing phylogenies, which may indicate that this karyotype is primitive within the genus Ranunculus.     

秦岭毛茛属植物(毛茛科)的分类学研究

记载了产于秦岭的毛茛属植物共11种,4变种,其中含秦岭分布新记录4种、3变种,它们是:美丽毛茛、丽江毛茛(变种)、毛果毛茛(变种)、丝叶毛茛(变种)、褐鞘毛茛、愚毛茛、匍枝毛茛;另外,收录了《秦岭植物志》遗漏的另外2种,即太白山毛茛和细长喙毛茛。经研究认为,《秦岭植物志》原记载的小毛茛Ranunculus ternatusThunb.在秦岭无分布。给出了秦岭毛茛属植物分种(变种)检索表;对每一种及种下等级的产地及分布进行了详细的论述。     

The distribution of organic and mineral components in leaves and stems of Ranunculus fluitans Lam.

The differences in chemical composition of leaves and stems of Ranunculus fluitans Lam. were investigated. Typical distribution of organic and inorganic compounds were generally found not to be influenced by factors as day-time, eutrophication, or age of the weed bed. Starch, sugars, amino acids, and organic acids were at a higher level in the stem, but inorganic cations and anions were accumulated in the leaf. The distribution pattern and the relative contents of individual sugars, acids, and inorganic ions are discussed in detail.     

Experimental life-history evolution: selection on the allocation to sexual reproduction and its plasticity in a clonal plant

Abstract.— Allocation to sexual reproduction is an important life-history trait in clonal plants. Different selection pressures between competitive and competition-free environments are likely to result in the evolution of specialized genotypes and to maintain genetic variation in reproductive allocation. Moreover, selection may also result in the evolution of plastic allocation strategies. The necessary prerequisite for evolution, heritable genetic variation, can best be studied with selection experiments. Starting from a base population of 102 replicated genotypes of the clonal herb Ranunculus reptans , we imposed selection on the proportion of flowering rosettes in the absence of competition (base population: mean = 0.391, broad-sense heritability = 0.307). We also selected on the plasticity in this trait in response to competition with a naturally coexisting grass in a parallel experiment (base population: 14% lower mean in the presence of competition, broad-sense heritability = 0.072). After two generations of bidirectional selection, the proportion of flowering rosettes was 26% higher in the high line than in the low line (realized heritability ± SE = 0.205 ± 0.017). Moreover, genotypes of the high line had 11% fewer carpels per flower, a 22% lower proportion of rooted rosettes, and a 39% smaller average distance between rosettes within a clone. In the second experiment, we found no significant responses to selection for high and low plasticity in the proportion of flowering rosettes (realized heritability ± SE =–0.002 ± 0.013). Our study indicates a high heritability and potential for further evolution of the proportion of flowering rosettes in R. reptans , but not for its plasticity, which may have been fixed by past evolution at its current level. Moreover, our results demonstrate strong genetic correlations between allocation to sexual reproduction and other clonal life-history characteristics.     

Application of heat stress in situ demonstrates a protective role of irradiation on photosynthetic performance in alpine plants

The impact of sublethal heat on photosynthetic performance, photosynthetic pigments and free radical scavenging activity was examined in three high mountain species, Rhododendron ferrugineum, Senecio incanus and Ranunculus glacialis using controlled in situ applications of heat stress, both in darkness and under natural solar irradiation. Heat treatments applied in the dark reversibly reduced photosynthetic performance and the maximum quantum efficiency of photosystem II (F_v/F_m), which remained impeded for several days when plants were exposed to natural light conditions subsequently to the heat treatment. In contrast, plants exposed to heat stress under natural irradiation were able to tolerate and recover from heat stress more readily. The critical temperature threshold for chlorophyll fluorescence was higher under illumination (T_c^′) than in the dark (T_c). Heat stress caused a significant de‐epoxidation of the xanthophyll cycle pigments both in the light and in the dark conditions. Total free radical scavenging activity was highest when heat stress was applied in the dark. This study demonstrates that, in the European Alps, heat waves can temporarily have a negative impact on photosynthesis and, importantly, that results obtained from experiments performed in darkness and/or on detached plant material may not reliably predict the impact of heat stress under field conditions.