Factors affecting growth and nodulation ofHippophaë rhamnoides L. ssp.Rhamnoides in soils from two successional stages of dune formation

Summary To explain the decline of Hippopha? scrub in the vegetation succession in the dunes of The Netherlands, the growth and nodulation of Hippopha? plants grown in pots, using soil from an early stage (site AH) and a post-optimum stage (site HP), were investigated. In HP-soil nodulation, yield, and the nitrogen and phosphorus content of test plants were always lower and the number of necrotic nodules and the dry matter content were always higher than in AH-soil, even after inoculation with crushed nodules and the addition of a nutrient solution. Plants in HP-soil also had darker roots, less root hairs, a higher number of short lateral roots and a higher percentage of dead roots than those in AH-soil. These characteristics of adverse growth conditions disappeared upon ignition or gamma-irradiation of HP-soil. Possible explanations of these results are discussed. The degeneration of Hippopha? scrub cannot be ascribed to the age of the plants, the absence of sufficient infective endophyte particles or to abiotic factors such as unfavourable physical (particle size) or chemical soil conditions but is caused by biotic factors. No indications were obtained that plant-pathogenic fungi and bacteria are involved. HP-soil in contrast to AH-soil, however, contained large numbers of the nematodeLongidorus sp., a species known to cause root deformations. The conclusion was that this nematode is one of the biotic factors involved in the degeneration of the Hippopha? scrub. This degeneration is due to a restriction of the root system resulting in a low phosphate uptake, a low nodulation capacity and, as a consequence, a low nitrogen content. The results demonstrate that biotic soil factors are important in influencing succession in higher plant communities.     

The Last Month of Szent-Györgyi in Groningen

Albert (von) Szent-Györgyi started his studies on biological oxidation processes – which also resulted in the discovery of vitamin C, for which he received the Nobel Price in 1937 – in the Laboratory of Physiology of the University in Groningen in 1922–1926. These studies were later continued in Cambridge (UK) and Szeged (Hungary). When he had already received the invitation as well as the financial means to come and work in Cambridge, he still did experiments in Groningen to find out whether the adrenal extract, isolated by him and later found to be a major source of vitamin C, contained the hormone essential for the survival of cats whose adrenals were removed. He was rather upset by the negative results of this experiment, judging by the recollections of a former student of his. This history constitutes an interesting example of the difference between serendipitous discovery and planned invention.     

Fluorescence study of secondary structure of DNA within bacteriophage lambda

Bromoacetaldehyde (BAA) was used to study the secondary structure of DNA in lambda-phage particles. It was determined that about 1% of the adenines in the intraphage lambda-DNA reacts readily with BAA, thus, they are placed in DNA sites with disturbed complementary interactions. These adenines are close to the tryptophan residues of the phage protein. Fluorescence emission of epsilon A in the intraphage DNA is dramatically quenched. This, apparently, indicates the interaction between epsilon A and Trp- and/or Tyr- and/or Met-residues of phage protein.     

New fossils of ascomycetous anamorphic fungi from Baltic amber

Three new fossils of saprotrophic fungi are presented and described from Baltic amber, dated to Eocene epoch (Paleogene, upper to mid-Eocene). All belong to Ascomycota and are represented by hyphae as well as asexual reproduction structures allowing to assign them to present genera, respectively Periconia, Penicillium and Scopulariopsis. These material provide both the first and the oldest known fossil record of the mentioned taxa, making these data valuable for the knowledge about the evolutionary history of the Ascomycota.     

δ-Aminolevulinate dehydratase from Raphanus sativus cotyledons

Phytochrome induces δ-aminolevulinate dehydratase (ALAD) activity in radish seedling cotyledons under continuous far red light. Analysis of the enzymatic activity in etioplasts vs total activity shows a constant ALAD level in these organelles (10 %) in etiolated seedlings. In far red irradiated seedlings, the percentage of enzyme detected into etioplasts increases up to 45 % of the total. Comparative kinetic studies of ALAD activity detected in the cytoplasm and the etioplasts indicate an increase in both compartments with a maximum value reached respectively at 96 and 120 hr from sowing. Treatment with cycloheximide shows a very fast abolition of cytoplasmic ALAD activity which is always correlated to an etioplast decrease with a time shift of ca 24 hr. Erythromycin acts only on the cytoplasmic level of ALAD, and only for far red irradiated seedlings, with an increase of activity twice the level detected in untreated ones. This unexpected effect is discussed.     

Microsatellite identification of ramet genotypes in a clonal plant with phalanx growth: The case of Cirsium rivulare (Asteraceae)

Cirsium rivulare is a perennial plant that forms patches consisting of ramets resulting from sexual reproduction by seeds and asexual propagation by rhizome fragmentation. We examined the relationship between the size of patches and genetic differentiation of ramets within and between patches. Ramet genotypes were identified using microsatellites. From among 216 ramets examined in the studied population, 123 had a unique genotype, while 93 were clonal, i.e., their genotype was present in at least two ramets. The frequency of ramets with clonal genotypes was 43% and the frequency of unique genotypes was 57%. Ramets with identical genotypes were dominant in small patches. Large patches consisted of ramets with both unique and clonal genotypes, usually with the predominance of the latter. A molecular variance analysis showed the highest level of variance between ramets and the lowest between patches. Additionally, 21.02% of the total variance was recorded between ramets and within patches. The size of patches was correlated with the number of clonal ramets and the number of unique ramets, but it was not correlated with the clonality index. This population of C. rivulare is currently in a phase of decline from 30 years of vegetation transformation, and there appears to have been an increase in sexual propagation based growth over clonal propagation based growth. Hence, a predominance of ramets with unique genotypes was observed. This can happen as a result of disintegration of large patches and formation of gaps between them. These gaps become convenient places for seed germination and the subsequent development of seedlings.     

Evidence for the transmission of information through electric potentials in injured avocado trees

Electrical excitability and signaling, frequently associated with rapid responses to environmental stimuli, have been documented in both animals and higher plants. The presence of electrical potentials (EPs), such as action potentials (APs) and variation potentials (VPs), in plant cells suggests that plants make use of ion channels to transmit information over long distances. The reason why plants have developed pathways for electrical signal transmission is most probably the necessity to respond rapidly, for example, to environmental stress factors.We examined the nature and specific characteristics of the electrical response to wounding in the woody plant Persea americana (avocado). Under field conditions, wounds can be the result of insect activity, strong winds or handling injury during fruit harvest. Evidence for extracellular EP signaling in avocado trees after mechanical injury was expressed in the form of variation potentials. For tipping and pruning, signal velocities of 8.7 and 20.9 cm/s, respectively, were calculated, based on data measured with Ag/AgCl microelectrodes inserted at different positions of the trunk. EP signal intensity decreased with increasing distance between the tipping and pruning point and the electrode. Recovery time to pre-tipping or pre-pruning EP values was also affected by the distance and signal intensity from the tipping or pruning point to the specific electrode position. Real time detection of remote EP signaling can provide an efficient tool for the early detection of insect attacks, strong wind damage or handling injury during fruit harvest.Our results indicate that electrical signaling in avocado, resulting from microenvironment modifications, can be quantitatively related to the intensity and duration of the stimuli, as well as to the distance between the stimuli site and the location of EP detection. These results may be indicative of the existence of a specific kind of proto-nervous system in plants.     

Syntheses of all eight stereoisomers of conidendrin

ABSTRACT

All eight stereoisomers of conidendrin were synthesized from (1 R,2 S,3 S)-1-(4-benzyloxy-3-methoxyphenyl)-3-(4-benzyloxy-3-methoxybenzyl)-2- hydroxymethyl-1,4-butanediol ((+)-4) and its enantiomer with high optical purity. The configurations at 4-positions of the conidendrin stereoisomers were constructed by intramolecular Friedel-Crafts reaction of protected 4. After conversion to tetrahydronaphthalene intermediate 7a, the 2- and 3-position of tetrahydronaphthalene structure 7a were converted to 3a- and 9a-position of (+)-α-conidendrin (3a), respectively. By the epimerization process of 2- or 3-position of 7a, the other diastereomers were obtained. All enantiomers were also synthesized from (?)-4.     

基于微藻的水产养殖废水处理技术研究进展

摘要：利用微藻处理水产养殖废水是一项污水资源化生物技术。近年来,国内外开展了大量有关藻类培养和废水处理的研究,发展了藻类处理技术,包括藻类塘、活性藻、固定化藻类、光生物反应器。本文综述了微藻净化水产养殖废?水的原理、研究成果及应用实例,并对今后的研究方向提出了建议。