Why Prunus mahaleb (Rosaceae) produces more flowers than fruits

Various mutually compatible hypotheses have been proposed to explain the low levels of fruit set observed in many hermaphrodite plants. I carried out trials to determine which of these hypotheses best explains the low fruit set occurring in Prunus mahaleb L. (Rosaceae). The results of insect exclusion, supplementary pollination, and flower removal experiments indicate that the ovary reserve hypothesis and the selective abortion hypothesis seem to be the most likely explanations for the production of excess flowers in P. mahaleb.     

Validation of Prunus hainanensis (Rosaceae)

The name Prunus hainanensis (G. A. Fu & Y. S. Lin) W. C. Chen is invalid because only the basionym was cited and without reference. According to the Art. 32.4 of ICBN, Prunus hainanensis (G. A. Fu et Y. S. Lin) H. Yu, N. H. Xia & H. G. Ye is the correct name. This new combination is proposed herein.     

Selective fruit abortion in Prunus mahaleb (Rosaceae)

In Prunus mahaleb (Rosaceae), only a small proportion of those flowers that initially develop give rise to fruits, and the probability of producing fruit differs between flowers. The results of this study indicate that the probability of producing fruit is about 60% for the first (i.e., most proximal) flower to develop in each inflorescence, but very low for the last (i.e., most distal). This pattern is maintained regardless of between-inflorescence differences in flowering phenology, suggesting that each inflorescence can be viewed as an independent subunit with respect to allocation of resources for reproduction. These results are compatible with the ovary reserve and selective abortion hypotheses for the adaptive value of low fruit set in P. mahaleb.     

Phylogeny and Classification of Prunus sensu lato （Rosaceae）

The classification of the economically important genus Prunus L. sensu lato （s.L） is controversial due to the high levels of convergent or the parallel evolution of morphological characters. In the present study, phylogenetic analyses of fifteen main segregates of Prunus s.I. represented by eighty-four species were conducted with maximum parsimony and Bayesian approaches using twelve chloroplast regions （atpB- rbcL, matK, ndhF, psbA-trnH, rbcL, rpL 16, rpoC1, rps16, trnS-G, trnL, trnL-F and ycfl） and three nuclear genes （ITS, s6pdh and Sbel） to explore their infrageneric used to develop a new, phylogeny-based classification relationships. The results of these analyses were of Prunus s.I. Our phylogenetic reconstructions resolved three main clades of Prunus s.I. with strong supports. We adopted a broad-sensed genus, Prunus, and recognised three subgenera corresponding to the three main clades： subgenus Padus, subgenus Cerasus and subgenus Prunus. Seven sections of subgenus Prunus were recognised. The dwarf cherries, which were previously assigned to subgenus Cerasus, were included in this subgenus Prunus. One new section name, Prunus L. subgenus Prunus section Persicae （T. T. yu ＆ L. T. Lu） S. L. Zhou and one new species name, Prunus tianshanica （Pojarkov） S. Shi, were proposed.     

Merging Maddenia with the morphologically diverse Prunus (Rosaceae)

Maddenia (Rosaceae) has been distinguished from Prunus on the basis of its tepaloid perianth and one‐ to two‐carpellate gynoecium. These distinctive morphological traits nonetheless overlap with several Prunus spp. Maddenia has previously been shown to be nested within Prunus, more specifically within a clade containing members of subgenera Laurocerasus and Padus, but its phylogenetic position within that clade has not been defined precisely. This study clarifies the position of Maddenia within Prunus through phylogenetic analyses of nuclear ribosomal internal transcribed spacer (ITS) and plastid ndhF sequences, with an expanded sampling of tropical species of subgenus Laurocerasus and the inclusion of three Maddenia spp. The monophyly of Maddenia is supported by both the ITS and ndhF analyses, but both datasets support the inclusion of Maddenia in Prunus. All trees from the ITS analysis and some trees from the ndhF analysis also support a close alliance of Maddenia with a clade comprising temperate species of subgenera Laurocerasus and Padus. On the basis of these results, all recognized species of Maddenia are herein formally transferred to Prunus, which requires four new combinations and one new name: Prunus fujianensis (Y.T.Chang) J.Wen, comb. nov. ; Prunus himalayana J.Wen, nom. nov. ; Prunus hypoleuca (Koehne) J.Wen, comb. nov. ; Prunus hypoxantha (Koehne) J.Wen, comb. nov. ; and Prunus incisoserrata (T.T.Yü & T.C.Ku) J.Wen, comb. nov. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164 , 236–245.     

Crystal macropattern development in Prunus serotina (Rosaceae, Prunoideae) leaves

BACKGROUND AND AIMS: Prunus, subgenus Padus, exhibits two completely different calcium oxalate crystal macropatterns in mature leaves. Foliar macropattern development has been described previously in P. virginiana, representing one version. Prunus serotina, in the group exhibiting the second macropattern, is described here. The goal was to describe developmental details for comparison with P. virginiana, and to extend the sparse current knowledge of crystal macropatterns. METHODS: Leaves at various developmental stages were removed from local trees and from herbarium specimens. Early leaf stages and freehand leaf and stem sections were mounted directly in aqueous glycerine; larger leaves were processed whole or in representative pieces in household bleach, dehydrated in alcohol/xylol, and mounted in Permount. Crystals were detected microscopically between crossed polarizers. KEY RESULTS: Bud scales have a dense druse population. Druses appear first at the stipule tip and proliferate basipetally but soon stop forming; growing stipules therefore have a declining density of druses. Druses appear at the tip of leaves <1 mm long, then proliferate basipetally in the midrib. Lamina druses appear in the distal marginal teeth of leaves 3 cm long; from here they proliferate basipetally and towards midrib along major veins. In about two-thirds-grown leaves (6-9 cm length) druses are all adaxial to veins of most orders; a shift occurs then to formation of prisms, which appear first abaxial to, then all around, veins. Mature leaves have virtually all prisms encrusting all major veins, more sparsely along smaller minor veins. Late season leaves form epitactic crystals on existing prismatics. CONCLUSIONS: The developing and mature macropattern of P. serotina is almost the reverse of the pattern described previously in P. virginiana, and shows that two closely related species can develop radically different modes of crystallization. The few detailed macropattern studies to date reveal striking variations that indicate a new level of organization that must be integrated with the anatomical, physiological and molecular approaches that have been dominant so far.     

日本晚樱PrseSHP基因的克隆与功能分析

采用同源克隆方法结合RACE技术,从日本晚樱(Prunus lannesiana)品种‘大岛樱’中克隆到花发育调控相关的PrseSHP基因(GenBank登录号为GU362645)。PrseSHP基因序列全长1 223bp,包含1个长741bp的完整开放阅读框,编码246个氨基酸和1个终止密码子。分子系统发生分析表明,PrseSHP属MADS-box转录因子的PLE/SHP进化系,并与蔷薇科植物的SHP同源蛋白聚于同一进化分支;蛋白序列比对显示,该转录因子拥有M、I、K和C共4个结构域,且其C末端结构域中包含高度保守的AGⅠ和Ⅱ基序。基因表达分析表明,PrseSHP基因主要在‘大岛樱’的花瓣、雄蕊、雌蕊和幼果等器官中表达,在花萼中仅能检测到微弱的转录信号,在幼叶中不表达,与其他植物SHP同源基因的表达模式有一定的差别。功能分析显示,转PrseSHP基因拟南芥植株明显比野生型拟南芥弱小,转基因拟南芥在6~8片莲座叶后即抽薹开花,时间较野生型拟南芥(14~17片莲座叶后抽薹开花)明显提前,证明异位表达的PrseSHP基因能促进拟南芥早花,其在花发育过程中可能参与调控植物开花。     

Structural diversity and regeneration of the endangered Prunus africana (Rosaceae) in Zimbabwe

Prunus africana is endemic to Africa and was included in Appendix II of the Convention on International Trade in Endangered Species (CITES) in 1995. In Zimbabwe, the species was reported to be rare and confined to the Eastern Highlands. The objective of this study was to assess size–class distribution and regeneration levels and to characterize structural diversity of P. africana. Given the clustered nature of the species, adaptive cluster sampling was used based on the assumption that there were more P. africana trees in the neighbourhood of reference trees. Each cluster was terminated when there were no more P. africana trees within a distance of 500 m. Data on diameter and height were collected in each cluster using standard forestry procedures. Regeneration was determined by counting seedlings and saplings within a radial distance of 14 m from the mother tree. Structural indices, that ie, diameter and height differentiation and mingling were determined for a structural group of four trees. Findings from this study indicated poor regeneration, fewer P. africana trees in small and large size classes, dominance of positive height and diameter differentiation and high mingling. These findings have implications on management and conservation of P. africana in Zimbabwe.     

Chloroplast DNA phylogeny and phylogeography of the North American plums (Prunus subgenus Prunus section Prunocerasus, Rosaceae)

The North American plums are a closely related group that are not easily circumscribed, have overlapping morphologies, and are known to hybridize. We previously showed that the North American plums are a closely related, monophyletic group of taxa with little to no cpDNA sequence divergence between taxa. In that study, we came to the unanticipated conclusion that relationships inferred among the taxa contrast sharply with previously defined groups based on morphological characters. Here the aim was to determine if the primary cpDNA haplotypes identified in our earlier study are confined to the taxa in which they were initially observed. The cpDNA rpL16 intron was sequenced for 207 accessions of the 17 North American plum taxa plus Prunus texana. The results show that many taxa contain more than one of the three primary cpDNA haplotypes. Aside from the results found in sect. Prunocerasus, this study has broader implications for phylogenetics in general. The common practice of choosing a single exemplar to represent a taxon can be profoundly misleading in closely related groups. In hindsight, the possibility existed in our earlier study that we could have chosen a different combination of exemplars, which could have resulted in a different inferred phylogeny.     

Population genetic analysis of European Prunus spinosa (Rosaceae) using chloroplast DNA markers

Chloroplast DNA diversity in Prunus spinosa, a common shrub of European deciduous forests, was assessed using the polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) technique. Thirty-two haplotypes were detected in 25 populations spread across the European continent. Ten haplotypes were shared by two or more populations, and 22 were private. The major proportion of the total cpDNA diversity (H(T) = 0.73) was located within the populations (H(S) = 0.49), and differentiation between populations was low (G(ST) = 0.33) compared with other forest species. Haplotype diversity was higher in southern Europe than in northern Europe, indicating probable localization of glacial refugia in southern Europe. The minimum-length spanning tree of haplotypes showed incongruency between the phylogeny of haplotypes and their geographic locations. This might be the result of intensive seed movements following recolonization, which thereby erased the phylogeographic structure in P. spinosa.     

Neolignans from the seeds of Prunus tomentosa (Rosaceae) and their chemotaxonomic interest

The role of neolignans in the chemotaxonomy of the genus Prunus has long been neglected. In this study, two new dihydrobenzofuran neolignans tomentosanans A (12) and B (14), together with 15 known neolignans, were isolated from the seeds of Prunus tomentosa. This is the first report on the occurrence of compounds 1–12, 14, 15 and 17 in the genus Prunus. The biosynthetic pathways of these neolignans are also summarized. Together, these neolignans represent a phytochemical fingerprint for P. tomentosa, which may be used for identification of Prunus species.     

Population genetic structure and conservation of the Azorean tree Prunus azorica (Rosaceae)

Prunus azorica is an endangered tree endemic to the Azores Archipelago, considered as a top priority species for conservation. Although propagation measures have been studied in detail, and a broad phylogeographic study on P. lusitanica was recently published, a detailed population genetics study devoted to Azorean taxon was lacking. To determine extant patterns of population genetic structure in P. azorica, we analysed eight populations from the five Azorean islands where the species presently occurs and the only extant individual from Flores Island. We also included samples of P. lusitanica subsp. hixa from the Canary Islands and Madeira, and of P. lusitanica subsp. lusitanica from mainland Portugal. Genotyping was undertaken for eight nuclear microsatellite polymorphic loci specifically isolated for P. azorica. Accessions of the different geographic regions were used to sequence ITS and trnL DNA regions. Regarding SSRs, the number of alleles ranged from 5 to 37 (mean = 12.6) per locus and from 2 to 64 per population (mean = 24). Our analysis showed a clear separation between samples from the Azores and those from other regions. Overall, São Miguel populations seemed to encompass the majority of the variability found within the archipelago. Regarding the Azorean populations only, the highest percentage of genetic variation was found within populations (92 %). Still, about 7 % of the variation was found among populations within islands. Expected heterozygosity ranged from values near 0 in the most depauperate populations up to 0.18. With a few exceptions, the level of differentiation between Azorean populations was generally low and gene flow was clearly above 1. Analysis of ITS sequences also detected differences between the Azores and the remaining regions but the trnL region did not reveal any variation. The genetic identity of P. azorica was recognised and thus should be preserved; however, the present results suggest that the Azorean taxon should be reinstated at the subspecies level.     

用叶绿体ndhF和核核糖体ITS序列推断李属(蔷薇科)的系统发育

Sequences of the chloroplast ndhF gene and the nuclear ribosomal ITS regions are employed to reconstruct the phylogeny of Prunus (Rosaceae), and evaluate the classification schemes of this genus. The two data sets are congruent in that the genera Prunus s.l. and Maddenia form a monophyletic group, with Maddenia nested within Prunus. However, the ndhF data set is incongruent with the ITS data supporting two major groups within Prunus one consisting of subgenera Laurocerasus (including Pygeum) and Padus as well as the genus Maddenia and another of subgenera Amygdalus, Cerasus, and Prunus. The ITS data, on the other hand, support a clade composed of subgenera Amygdalus and Prunus and Prunus sect. Microcerasus in addition to a paraphyletic grade of subgenera Laurocerasus and Padus (and the genus Maddenia) taxa. In general, the subgeneric classifications of Prunus s.l. are not supported. The ITS and ndhF phylogenies differ mainly in interspecific relationships and the relative position of the Padus/Laurocerasus group. Both ITS and ndhF data sets suggest that the formerly recognized genus Pygeum is polyphyletic and that the distinction of the subgenera Padus and Laurocerasus is not supported. The biogeographic interactions of the temperate and tropical members in the Padus/Laurocera- sus/Maddenia alliance including Pygeum are shown to be highly dynamic and complex.     

The phylogenetic utility of nucleotide sequences of sorbitol 6-phosphate dehydrogenase in Prunus (Rosaceae)

Sequences from s6pdh, a gene that encodes sorbitol-6-phosphate dehydrogenase in the Rosaceae, are used to reconstruct the phylogeny of 22 species of Prunus. The s6pdh sequences alone and in combination with previously published sequences of the internal transcribed spacer (ITS) and the cpDNA trnL-trnF spacer are analyzed using parsimony and maximum likelihood methods. Both methods reconstructed the same phylogeny when s6pdh sequences are used alone and in combination with ITS and trnL-trnF, and the topology is in agreement with previous studies that used a larger sample size. The s6pdh sequences have about twice as many informative sites as ITS. A molecular clock is rejected for s6pdh, most likely due to greater rates of evolution in subgenera Padus and Laurocerasus than in the rest of the genus. Phylogenetic reconstruction of Prunus as determined by analysis of the combined data set suggests an early split into two clades. One is composed of subgenera Cerasus, Laurocerasus, and Padus. The second includes subgenera Amygdalus, Emplectocladus, and Prunus. Species of section Microcerasus (formerly in subgenus Cerasus) are nested within subgenus Prunus. The order of branching and relationships among early diverging lineages is weakly supported, as a result of very short branches that may indicate rapid radiation.     

Allelic diversity of S-RNase at the self-incompatibility locus in natural flowering cherry populations (Prunus lannesiana var. speciosa)

In the Rosaceae family, which includes Prunus, gametophytic self-incompatibility (GSI) is controlled by a single multiallelic locus (S-locus), and the S-locus product expressed in the pistils is a glycoprotein with ribonuclease activity (S-RNase). Two populations of flowering cherry (Prunus lannesiana var. speciosa), located on Hachijo Island in Japan's Izu Islands, were sampled, and S-allele diversity was surveyed based on the sequence polymorphism of S-RNase. A total of seven S-alleles were cloned and sequenced. The S-RNases of flowering cherry showed high homology to those of Prunus cultivars (P. avium and P. dulcis). In the phylogenetic tree, the S-RNases of flowering cherry and other Prunus cultivars formed a distinct group, but they did not form species-specific subgroups. The nucleotide substitution pattern in S-RNases of flowering cherry showed no excess of nonsynonymous substitutions relative to synonymous substitutions. However, the S-RNases of flowering cherry had a higher Ka/Ks ratio than those of other Prunus cultivars, and a subtle heterogeneity in the nucleotide substitution rates was observed among the Prunus species. The S-genotype of each individual was determined by Southern blotting of restriction enzyme-digested genomic DNA, using cDNA for S-RNase as a probe. A total of 22 S-alleles were identified. All individuals examined were heterozygous, as expected under GSI. The allele frequencies were, contrary to the expectation under GSI, significantly unequal. The two populations studied showed a high degree of overlap, with 18 shared alleles. However, the allele frequencies differed considerably between the two populations.     

Leaf biomechanics, morphology, and anatomy of the deciduous mesophyte Prunus serrulata (Rosaceae) and the evergreen sclerophyllous shrub Heteromeles arbutifolia (Rosaceae)

Leaf tensile properties were compared between the mesic deciduous tree Prunus serrulata (var. "Kwanzan") and the xeric and sclerophyllous chaparral evergreen shrub Heteromeles arbutifolia (M. Roem). All values for biomechanical parameters for H. arbutifolia were significantly greater than those of P. serrulata. The fracture planes also differed between the two species with P. serrulata fracturing along the secondary veins, while H. arbutifolia most often fractured across the leaf irrespective of the vein or mesophyll position, thus yielding qualitative differences in the stress-strain curves of the two species. Anatomically, P. serrulata exhibits features typical for a deciduous mesophytic leaf such as a thin cuticle, a single layer of palisade mesophyll, isodiametric spongy mesophyll, and extensive reticulation of the laminar veins. Heteromeles arbutifolia leaves, however, are typically two- to three-fold thicker with a 35% higher dry mass/fresh mass ratio. The vascular tissue is restricted to the interface of the palisade and spongy mesophyll near the center of the leaf. Both epidermal layers have a thick cuticle. The palisade mesophyll is tightly packed and two to three layers thick. The spongy mesophyll cells are ameboid in shape and tightly interlinked both to other spongy cells as well as to the overlying palisade layer. We conclude that the qualitative and quantitative biomechanical differences between the leaves of these two species are likely due to a complex interaction of internal architectural arrangement and the physical/chemical differences in the properties of their respective cell walls. These studies illustrate the importance that morphological and anatomical correlates play with mechanical behavior in plant material and ultimately reflect adaptations present in the leaves of chaparral shrubs that are conducive to surviving in arid environments.