Floral organogenesis of Delavaya toxocarpa (Sapindaceae; Sapindales)

The floral organogenesis and development of Delavaya toxocarpa Franch. (Sapindaceae) were studied under scanning electron microscope and light microscope to determine its systematic position within Sapindaceae. Flowers arise in terminal thyrses. The sepal primordia initiate in a spiral (2/5) sequence, which are not synchronous. The five petal primordia initiate almost synchronously and alternate with sepal primordia. Eight stamens initiate almost simultaneously and their differentiation precedes that of the petals. The last formed petal and one stamen initiate from a common primordium. Mature stamens curve inwards and cover the ovary in bud. The gynoecium begins as a hemispheric primordium on which two carpellary lobes arise simultaneously. Later in development a single gynocium is formed with two locules and two ovules per locule. Floral morphology suggests a closer affinity with Sapindaceae, although certain features of floral ontogenesis are similar to those observed in certain members of the former Hippocastanaceae, such as Handeliodendron.     

ORIGIN AND BIOGEOGRAPHY OF AESCULUS L. (HIPPOCASTANACEAE): A MOLECULAR PHYLOGENETIC PERSPECTIVE

Sequences of chloroplast gene matK and internal transcribed spacers of nuclear ribosomal RNA genes were used for phylogenetic analyses of Aesculus, a genus currently distributed in eastern Asia, eastern and western North America, and southeastern Europe. Phylogenetic relationships inferred from these molecular data are highly correlated with the geographic distributions of species. The identified lineages closely correspond to the five sections previously recognized on the basis of morphology. Ancestral character-state reconstruction, a molecular clock, and fossil evidence were used to infer the origin and biogeographic history of the genus within a phylogenetic framework. Based on the molecular phylogenetic reconstruction of the genus, sequence divergence, and paleontological evidence, we infer that the genus originated during the transition from the Cretaceous to the Tertiary (~65 M.Y.B.P.) at a high latitude in eastern Asia and spread into North America and Europe as an element of the “boreotropical flora”; the current disjunct distribution of the genus resulted from geological and climatic changes during the Tertiary.     

4α-methylergosta-8,24(28)-dien-3β-ol,a minor sterol in the seed of horse chestnut

From ripe horse chestnut seed the 4α-methyl sterol fraction was isolated representing 4.5% of the unsaponifiable matter, i.e. 3 mg% of the seed. This fraction was investigated by capillary GC and combined GC-MS. It contains at least 12 components, of which 5 were identified as: obtusifoliol 4α-methylergosta-8,24(28)-dien-3β-ol, gramisterol, cycloeucalenol and citrostadienol. The distribution of these five 4α-methyl sterols in the seed was also determined and they represent about 90% of the investigated fraction. 4α-Methylergosta-8,24(28)-dien-3β-ol up to now been found in higher plants only in traces, while in this fraction it was found in the amount of about 5%.     

中国无患子科植物的叶脉形态及其系统学意义

对国产狭义无患子科25属27种植物的叶脉形态特征进行了研究报道。结果表明：叶脉均属于羽状脉类型,其中多数为曲行羽状脉,部分为直行羽状脉;叶缘有全缘、具齿和深裂3种类型;二级叶脉具有分支和不分支两种类型;大部分种类具二级间脉,少数不具间脉或间脉不明显;多数种类的三级脉为结网型和贯串型并存;网眼的发育有完善和不完善2种类型;盲脉有简单、具分支和无盲脉3种类型。叶脉形态研究结果支持文冠果亚科以及广义鳞花木属概念,观察发现龙眼属、荔枝属与韶子属从脉序特征方面表现出较近的亲缘关系。编写了国产无患子科叶片脉序特征检索表。     

Origine et caracteres de la sécrétion d'aglycones flavonoliques par les bourgeons d'Aesculus hippocastanum

Flavonol aglycones are present in the oil excreted by buds of Aesculus hippocastanuml. and are probably synthesized in glandular hairs situated on the inner side of bud scales. Flavonols are most abundant in the hairs, being much less concentrated in all other scale tissues. Flavonol accumulation in the buds reaches a maximum both in the Spring and the Autumn and this is related to the accumulation of leaf flavonols and leucoanthocyanes and of scale and bark coumarins.     

The utility of the morphological variation of pollen for resolving the evolutionary history of Billia (subfam. Hippocastanoideae,Sapindaceae)

In this study, we examined the utility of pollen morphology for resolving questions about the evolutionary history of Billia, which is a poorly known genus of Neotropical trees. Billia has been traditionally circumscribed with two species and treated as sister to Aesculus L. However, the number of species in Billia is uncertain, because the genus exhibits abundant morphological diversity but little discontinuous variation. Therefore, Billia may be monotypic and highly polymorphic, or it may have two species with blurred boundaries due to incipient speciation and/or hybridization. Moreover, one recent molecular phylogenetic study shows Billia nested withinAesculus. Our work sought to address the following questions: (i) Are there discontinuities in the pollen of Billia that may suggest species boundaries? (ii) Does the pollen of Billia show evidence for inter-specific hybridization? (iii) Do the exine morphology and size of pollen in Billia differ from those in Aesculus? Our results from scanning electron microscopy showed that pollen exine morphology is not taxonomically informative in Billia but that there are significant differences in pollen size between red- and white-flowered individuals. Thus, our pollen data support the utility of flower color in Billia for species delimitation. Our assessments of pollen viability do not support hybridization in the genus, but cannot be used to rule it out. Finally, pollen exine morphology may lend some support to an evolutionary origin ofBillia within eastern North American Aesculus. In contrast, data on pollen size suggest that Billia may belong in a topological position outside of Aesculus.     

Genetic diversity among populations and size classes of buckeyes (Aesculus: Hippocastanaceae) examined with multilocus VNTR probes

 Little is known about genetic variation in members of the genus Aesculus (Hippocastanaceae), in particular A. flava (yellow buckeye) and A. glabra (Ohio buckeye). Here, three synthetic DNA probes (composed of tandemly repeated, core sequences) that reveal alleles at multiple variable-number tandem-repeat (VNTR) loci in these two species were used to investigate: 1) levels of genetic variation in one stand of A. flava and three isolated stands of A. glabra; 2) whether the stands of A. glabra are genetically differentiated from one another; 3) whether there has been selection for more heterozygous individuals through time in one stand each of A. flava and A. glabra; and 4) whether a possible genetic bottleneck had occurred during the formation of either species of Aesculus. First, variation of VNTR genetic markers within and among three populations of A. glabra separated by 60–180 km was examined. In each one hectare (ha) population, 22 individuals were randomly sampled. Among the three populations, the mean number of bands scored per individual was 80.35 and the average number of estimated loci surveyed was 54.17. Mean similarity and estimated heterozygosity within populations ranged from 0.634 to 0.743 and from 0.342 to 0.486, respectively. The mean similarity across populations was 0.657, while the mean estimated heterozygosity across populations was 0.484 for A. glabra. The most isolated site was the most genetically differentiated as indicated by differences in levels of similarity, heterozygosity, and Fst value comparisons. In a separate experiment, genetic variation in 22 large (reproductively mature; dbh > 8 cm) individuals was compared with that in 22 small (not yet reproductive; dbh < 1 cm) individuals collected within one ha stands for both A. flava and A. glabra. Mean similarity values among large versus small individuals of A. flava were 0.665 versus 0.662, while for A. glabra the corresponding values were 0.686 versus 0.691, respectively. Permutation tests of these similarity data detected no evidence for size class genetic differentiation in either species (both p-values > 0.050). Further, permutation tests for the number of bands per individual (average band number should be higher in more heterozygous individuals) detected no significant differences between size classes for either species. Thus, evidence of pronounced inbreeding and/or selection altering population genetics within small relative to large individuals was not detected. In addition, comparable similarity and heterozygosity values between these two closely related species (which still maintain an active zone of hybridization) suggests that either: 1) no extreme genetic bottleneck has accompanied the formation of these species from a common ancestor; or 2) signs of such a bottleneck have largely been eliminated. These studies demonstrate the utility of multilocus VNTR DNA probes for investigating genetic variation within and among plant populations, between size classes within a population, and between closely related species. Received May 15, 1998 Accepted September 11, 2001     

New reports of cyanolipids from sapindaceous plants

Several previously uninvestigated species of the Sapindaceae were examined and found to contain cyanolipids and cyanogenic compounds. Several species from the Melianthaceae, Meliosmaceae and Hippocastanaceae were devoid of these substances.     

Composition of the triterpene alcohol fraction of horse chestnut seed

The triterpene alcohol fraction was isolated from the seed oil of horse chestnut; it amounted to 42.2% of the unsaponifiable matter, i.e. 0.93% of the oil. The components were identified as taraxerol, β-amyrin, butyrospermol, parkeol, 5α-tirucalla-8,23-dien-3β-ol, α-amyrin and 24-methylenecycloartenol. Butyrospermol and 5α-tirucalla-8,23- dien-3β-ol were the major components and amounted to 60% of the fraction. The latter has not been identified in any vegetable oils yet.