Chemical constituents from the stem bark of Acer tegmentosum

A new phenolic glycoside, 4-hydroxyphenylethyl-1-O-β-D-[6′-O-(4-hydroxybenzoyl)]-glucopyranoside (1) was isolated from the stem bark of Acer tegmentosum, along with seven known phenolic compounds (2–8). The structure of compound 1 was determined by spectral analyses, including HR-ESI-MS, 1D and 2D NMR (COSY, HMQC and HMBC) experiments. Compounds 3 and 4 were found in the family Aceraceae for the first time.     

Why is intracellular ice lethal? A microscopical study showing evidence of programmed cell death in cryo-exposed embryonic axes of recalcitrant seeds of Acer saccharinum

Background and Aims Conservation of the genetic diversity afforded by recalcitrant seeds is achieved by cryopreservation, in which excised embryonic axes (or, where possible, embryos) are treated and stored at temperatures lower than −180 °C using liquid nitrogen. It has previously been shown that intracellular ice forms in rapidly cooled embryonic axes of Acer saccharinum (silver maple) but this is not necessarily lethal when ice crystals are small. This study seeks to understand the nature and extent of damage from intracellular ice, and the course of recovery and regrowth in surviving tissues.Methods Embryonic axes of A. saccharinum, not subjected to dehydration or cryoprotection treatments (water content was 1·9 g H₂O g⁻¹ dry mass), were cooled to liquid nitrogen temperatures using two methods: plunging into nitrogen slush to achieve a cooling rate of 97 °C s⁻¹ or programmed cooling at 3·3 °C s⁻¹. Samples were thawed rapidly (177 °C s⁻¹) and cell structure was examined microscopically immediately, and at intervals up to 72 h in vitro. Survival was assessed after 4 weeks in vitro. Axes were processed conventionally for optical microscopy and ultrastructural examination.Key Results Immediately following thaw after cryogenic exposure, cells from axes did not show signs of damage at an ultrastructural level. Signs that cells had been damaged were apparent after several hours of in vitro culture and appeared as autophagic decomposition. In surviving tissues, dead cells were sloughed off and pockets of living cells were the origin of regrowth. In roots, regrowth occurred from the ground meristem and procambium, not the distal meristem, which became lethally damaged. Regrowth of shoots occurred from isolated pockets of surviving cells of peripheral and pith meristems. The size of these pockets may determine the possibility for, the extent of and the vigour of regrowth.Conclusions Autophagic degradation and ultimately autolysis of cells following cryo-exposure and formation of small (0·2–0·4 µm) intracellular ice crystals challenges current ideas that ice causes immediate physical damage to cells. Instead, freezing stress may induce a signal for programmed cell death (PCD). Cells that form more ice crystals during cooling have faster PCD responses.     

基于ITS与trnL—F序列探讨槭树科的系统发育

报道了槭树科41种（其中槭属39种0植物的trnL-F和ITS序列（其中部分种的ITS序列为重新测定），以期通过分子手段对槭树科内部尤其是复杂的槭属的系统发育关系进行重建。以无患子科和七叶树科为外类群，基于对57个种单独的ITS序列（包括从GenBank下载的16种的序列），41种trnL-F序列及41种两序列的联合数据，分析采用最大简约法（Maximum Parsimony Method)和邻接法（Neighbor-Joining Method)对槭树科的系统发育进行了分析。结果显示，整个槭树科为一单系类群；金钱槭位于槭树科的基部；但由于云南金钱槭（Dipteronia dyerana)聚在槭属内部，认为金钱槭属和槭属均可能是非单系类群；槭属内组间关系的支持率普遍较低，但多数组的组内关系得到了较好的支持。将两个片段结合比单独的ITS或trnL-F分析能更好地解决槭属内部的系统关系，其中sect,Palmata和sect.Micrcarpa,sect,Platanoidea,sect,Lithocarpa和sect.Macrophylla,sect,Integrifolia.Trifoliata和sect Pentaphylla,以及sect.Acer,sect.Goniocarpa和sect.Saccharina(sensu Ogata）的组间亲缘关系得到了一定的支持，但对其中部分组的划分可能应做进一步调整。重新评价了徐廷志系统中对sect.Rubra和sect.Saccharodendron的处理。     

Japanese maple (Acer palmatum var. Matsumurae, Aceraceae) recruitment patterns: seeds, seedlings, and saplings in relation to conspecific adult neighbors

We analyzed the spatial patterns among seeds, seedlings, saplings, and conspecific adult trees of the cool-temperate tree species Acer palmatum var. Matsumurae in a conifer-hardwood mixed forest in northern Japan, using two models that consider the influence of each adult within the neighborhood of the offspring. The results showed that recruitment patterns of each stage could be characterized and that significant shifts occur between successive stages. Sound seeds were more widely dispersed than unsound seeds; the mean dispersal distance (MDD) was 41.5 m for sound seeds, but only 12.6 m for unsound seeds. Most seedlings were located near conspecific adult trees, with a MDD of 14.3 m. Saplings, however, were more dispersed away from conspecific adult trees, with an MDD of more than 35 m. Light and gap distributions did not strongly affect the spatial distribution of the offspring; most saplings were located under nonconspecific canopies. These results suggest that the recruitment pattern of Japanese maple offspring is strongly affected by conspecific adult neighbors, rather than by light and gap distributions, with close proximity to conspecific adult trees reducing the growth and survival of seedlings during the transition to saplings.     

Phylogenetic Relationships of Maples (Acer L.; Aceraceae) Implied by Nuclear Ribosomal ITS Sequences

Acer. ITS 1 sequences in twenty-eight species of Acer and a species of Dipteronia in the family Aceraceae ranged from 220 to 242 bp and ITS 2 sequences from 215 to 251 bp. The size of the 5.8S coding region was 164 bp for all species examined in the family. Phylogenetic analysis of ITS sequences placed a very robust clade of section Palmata at the base of the tree. Three species of section Parviflora sensu de Jong (1994), A. spicatum, A. distylum and A. nipponicum, did not form a monophyletic clade. Acer spicatum was separated from the robust clade of A. distylum and A. nipponicum. Molecular tree strongly supports the close relationship among section Platanoidea, Glabra series Arguta, and section Macrantha. The close relationship between sections Pentaphylla and Trifoliata was also strongly suggested in ITS tree. Sections Rubra and Hyptiocarpa appeared to be closely allied with each other. The average rate of nucleotide substitution was estimated as (8.0±1.9)×10⁻¹¹ substitutions per site per year for ITS 1 and (9.0±1.6) ×10⁻¹¹ for ITS 2. Received 17 December 1999/ Accepted in revised form 10 March 2000     

A comparison of the polysaccharides extracted from dried and non-dried walls of suspension-cultured sycamore cells

Suspension-cultured sycamore cells (Acer pseudoplatanus) were disrupted in aqueous K-Pi buffer and the insoluble residue (the cell wall) purified by extraction with organic solvents and air-dried (dry cell walls) or by washing with aqueous sodium dodecyl sulphate and stored frozen (wet cell walls). Polysaccharides solubilized from the purified wet and dry cell walls by enzymatic digestion and chemical extraction were isolated and their glycosyl-residue compositions compared. No significant differences were found in the types or yields of the polysaccharides solubilized by enzymatic digestion and chemical extraction of the wet and dry cell wall preparations. Moreover, the glycosyl-residue compositions of the so-called ‘-cellulose’ fraction that remains after extraction of the wet and dry cell wall preparations with alkali was indistinguishable from the glycosyl-residue compositions of the walls prior to extraction.     

Why do early-emerging tree seedlings have survival advantages?: a test using acer rubrum (Aceraceae)

In forest understories, tree seedlings that germinate and emerge early in the growing season have significant survival advantages. We hypothesized that (a) early emergence is related to seed size and half-sib family, and (b) increased survival is due to reduced competition for resources. To test these hypotheses, we collected seeds of Acer rubrum from four half-sib families and planted them in the understory of a South Carolina floodplain forest. In one experiment, date of emergence was not related to seed size or half-sib family. However, our method of seed collection may have underestimated variability among half-sib families. In a second experiment, seeds were spread onto 20 understory plots, half of which were trenched to reduce root competition with overstory trees. One-year survival and biomass were greater for early- than for later-emerging cohorts. Trenching changed biomass distribution among aboveground parts and may have increased total biomass, but had essentially no impact on survival or root mass. Variation in plot flooding resulted in large differences in timing of emergence, survival, and biomass. For Acer rubrum, the survival advantage accorded by early emergence may be more related to flooding, light conditions, and genetic heterogeneity than to seed size or avoidance of root competition.