Nickel hyperaccumulation by Thlaspi montanum var. montanum (Brassicaceae): a constitutive trait

Adaptations to particular stresses may occur only in populations experiencing those stresses or may be widespread within a species. Nickel hyperaccumulation is viewed as an adaptation to high-Ni (serpentine) soils, but few studies have determined if hyperaccumulation ability is restricted to populations from high-Ni soils or if it is a constitutive trait found in populations on both high- and low-Ni soils. We compared mineral element concentrations of Thlaspi montanum var. montanum plants grown on normal and high-Ni greenhouse soils to address this question. Seed sources were from four populations (two serpentine, two non-serpentine) in Oregon and northern California, USA. Plants from all populations were able to hyperaccumulate Ni, showing Ni hyperaccumulation to be a constitutive trait in this species. Populations differed in their ability to extract some elements (e.g., Ca, Mg, P) from greenhouse soils. We noted a negative correlation between tissue concentrations of Ni and Zn. We suggest that the ability to hyperaccumulate Ni has adaptive value to populations growing on non- serpentine soil. This adaptive value may be a consequence of metal-based plant defense against herbivores/pathogens, metal- based interference against neighboring plant species, or an efficient nutrient scavenging system. We suggest that the Ni hyperaccumulation ability of T. montanum var. montanum may be an inadvertent consequence of an efficient nutrient (possibly Zn or Ca) uptake system.     

ULTRASTRUCTURE OF GLOEODINIUM MONTANUM (DINOPHYCEAE)1

The freshwater dinoflagellate Gloeodinium montanum Klebs (1912) was examined with transmission and scanning electron microscopy. Micrographs of ultrathin sections revealed a series of membrane layers rather than the usual dinoflagellate theca in vegetative cysts and in legates. Swarmers had distinct pellicles but appeared to be devoid of thecal plates and vesicles. The organization of cysts and swarmers appeared remarkably similar. All cell types had typical dinoflagellate nuclei with condensed chromosomes. Chloraplasts had girdle lamellae. One pyrenoid per cell was also present in chloroplasts of vegetative cysts. Starch grains and oil globules were distributed throughout the cytoplasm. Large accumulation bodies and polyvesicular vacuoles were found in aging cysts. Trichocysts and flagellar hairs were absent. Two types of intra-cellular prokaryotic organisms were discovered.     

Homologs of the Genes for Receptor-Like Kinase Proteins Conferring Plant Resistance to Pathogens. Comparative Analysis of the Homologs of the Wheat Gene Cre3in the Triticeae

Direct genomic DNA amplification with the primers recognizing the NBS–kinase sequence of the wheat gene Cre3(Genbank accession AF052641) was used to obtain partial homologs of this gene in perennial and annual rye, wheat, and tall wheatgrass. The nucleotide sequences of the cloned fragments and their deduced amino acid sequences were compared to the already-known Cre3homologs in other wheat, aegilops, and barley genotypes. Within the tribe Triticeae, the extent of homology ranged from 86 to 94% for nucleotide sequences and from 74 to 96% for the deduced amino acid sequences, with the most variable region between Kin3 and PR3 conserved motifs.     

Lytic Action of B-enzyme on Pseudomonas aeruginosa

B-enzyme was produced by Bacillus subtilis YT–25 and lysed the native cells of Pseudomonas aeruginosa extensively in the presence of NLF (Native Cell-Lytic Factor). NLF was a peptide which was also produced by B. subtilis YT–25. It was found that B-enzyme hydrolyzed the peptidoglycan of P. aeruginosa eventually to disaccharide units. Because the reducing end of the enzymatic digest was muramic acid, B-enzyme seemed to be an endo-N-acetyl-muramidase. Whereas, egg white iysozyme which was an endo-N-acetylmuramidase hardly lysed the native cells of P. aeruginosa. Specific activity of B-enzyme for the murein of P. aeruginosa was higher than that of egg white Iysozyme in the buffer of low ionic strength and the surface components of P. aeruginosa did not affect the activity of B-enzyme but strongly inhibited the activity of egg white Iysozyme. These facts seemed to explain the superiority of B-enzyme to egg white Iysozyme in the lysis of the native cells of P. aeruginosa.     

Double fertilization in Gnetum gnemon (Gnetaceae): its bearing on the evolution of sexual reproduction within the Gnetales and the anthophyte clade

The fertilization process in Gnetum is critical to our understanding of the evolution of sexual reproduction within the Gnetales, a monophyletic group of nonfiowering seed plants that are the closest living relatives to flowering plants. Although much is known about the fertilization process in Ephedra, which is basal within the Gnetales, little is known about sexual reproduction in the derived sister groups Gnetum and Welwitschia. Ovules of Gnetum gnemon were collected at various stages after hand pollination and processed for light, fluorescence, and electron microscopy. Approximately 5 d after pollination, pollen tubes reach sexually mature female gametophytes, which are coenocytic. At that time, a binucleate sperm cell is found within each pollen tube. Within 7 d of pollination, double fertilization events occur when each of two sperm nuclei released from a pollen tube fuses with a separate, undifferentiated female nucleus within the free nuclear female gametophyte, which lacks differentiated egg cells. The products of double fertilization are two viable zygotes; endosperm is not formed. The lack of differentiated egg cells in Gnetum gnemon is unparalleled among land plants and the documentation of a regularly occurring process of double fertilization is congruent with the hypothesis that a rudimentary process of double fertilization evolved in a common ancestor of angiosperms and Gnetales.     

A Stilbene derivative from Gnetum parvifolium

Gnetifolin F, a novel stilbene derivative, was isolated from the lianas of Gnetum parvifolium. The structure was deduced mainly by the use of ¹H-¹H COSY, ¹³C-¹H COSY, ¹³C-¹H COLOC and NOE difference spectrum, and verified with X-ray crystallographic analysis.     

Storage globulins in Gnetopsida. 1. Recognition of legumin-like proteins

Abstract

Salt soluble storage proteins were extracted from seeds of Ephedra distachya, Ephedra foeminea, Gnetum gnemon, Gnetum montanum and Welwitschia mirabilis and separated by chromatographic procedures. The molecular weight of the main storage globulin ranges from 300 to 350 kD. Denaturation by SDS resolved the holoprotein in monomers of M_r 40 to 60 kD. Oligomers up to 120 kD were observed in Ephedra. Reduction of disulphide bridges by DTE resolved the monomers in paris of polypeptides of M_r 10 to 35 kD. The characters above indicate that the main storage globulin of Gnetopsida is a legumin-like protein.     

Seasonal fluctuations of selenium and sulfur accumulation in selenium hyperaccumulators and related nonaccumulators

Some plants hyperaccumulate selenium (Se) up to 1% of dry weight. This study was performed to obtain insight into whole-plant Se fluxes in hyperaccumulators. Selenium hyperaccumulators Astragalus bisulcatus and Stanleya pinnata were monitored over two growing seasons for seasonal fluctuations in concentrations of Se and the chemically similar element sulfur (S). The related nonhyperaccumulators Astragalus sericoleucus, Oxytropis sericea and Thlaspi montanum were included for comparison. In both hyperaccumulators leaf Se decreased from April to October, coinciding with Se hyperaccumulation in flowers and seeds. Root Se levels were lowest in summer. Selenium concentration decreased with leaf age in both hyperaccumulators. Leaf S levels peaked in summer in all plant species, as did Se levels in nonhyperaccumulators. Selenium and S levels tended to be negatively correlated in hyperaccumulators, and positively correlated in nonhyperaccumulators. These results suggest a specific flow of Se in hyperaccumulator plants over the growing season, from root to young leaves in spring, followed by remobilization from aging leaves to reproductive tissues in summer, and back to roots in the autumn.     

山地五月茶的蝇类传粉研究

观测了山地五月茶Antidesma montanum的开花物候、开花动态、访花者种类和访花行为,并对其繁育系统、花粉组织化学、花粉胚珠比（P／O）、花粉活力进行了检测。结果表明：山地五月茶是雌雄异株植物;其总状花序花期可长达7天;雄花／雌花花序数目为140．33±27．79／208．33±33．65（n=6）,雌雄花的颜色为很淡的黄绿色小型花;雄花单花花期为2天,花药开裂当天有活力,花粉为非淀粉型,花粉胚珠比为3333．33±607．18;单花花蜜量可达0．34±0．03μL,花蜜含糖量3．69％±0．30％。花的结构和开花式样适合蝇类传粉。芳香的气味是吸引蝇类的直接物质：花蜜是传粉者的报酬。主要的传粉昆虫为双翅目Diptera丽蝇科Calliphoridae的Chrysomya megacephala、Chrysomyasp．、寄蝇科Tachinidae的Drino sp．和蝇科Muscidae的Spilogona sp．、Mitroplatia sp．。套网不授粉的处理不结实,表明山地五月茶不存在无融合生殖,人工辅助授粉的坐果率（39．1％）略高于自然坐果率（36．7％）,二者无显著差异,表明其坐果率主要受自身资源分配限制。还讨论了蝇类传粉与雌雄异株性系统以及蝇类传粉与热带林中小型黄绿色花植物的相关性。