CORRESPONDENCE BETWEEN PHYLOGENY AND MORPHOLOGY OF SNOWELLA SPP. AND WORONICHINIA NAEGELIANA,CYANOBACTERIA COMMONLY OCCURRING IN LAKES1

In this study, the first reported isolates of the genera Snowella and Woronichinia were characterized by 16S rRNA gene sequencing and morphological analysis. Phylogenetic studies and sequences for these genera were not available previously. By botanical criteria, the five isolated strains were identified as Snowella litoralis (Häyrén) Komárek et Hindák Snowella rosea (Snow) Elenkin and Woronichinia naegeliana (Unger) Elenkin. This study underlines the identification of freshly isolated cultures, since the Snowella strains lost the colony structure and were not identifiable after extended laboratory cultivation. In the 16S rRNA gene analysis, the Snowella strains formed a monophyletic cluster, which was most closely related to the Woronichinia strain. Thus, our results show that the morphology of the genera Snowella and Woronichinia was in congruence with their phylogeny, and their phylogeny seems to support the traditional botanical classification of these genera. Furthermore, the genera Snowella and Woronichinia occurred commonly and might occasionally be the most abundant cyanobacterial taxa in mainly oligotrophic and mesotrophic Finnish lakes. Woronichinia occurred frequently and also formed blooms in eutrophic Czech reservoirs.     

Reaction mechanism of surfactant‐sensitized chemiluminescence of bis(2,4,6‐trichlorophyenyl) oxalate and hydrogen peroxide induced by gold nanoparticles

The chemiluminescence (CL) of bis(2,4,6‐trichlorophyenyl) oxalate with hydrogen peroxide in the present of cationic surfactant and gold nanoparticles was studied. The CL emission was obviously enhanced in the presence of surfactant at a suitable concentration, with a synergetic catalysis effect exhibited. Different sizes of gold nanoparticles (15 and 50 nm) showed different effects on CL intensity. Mechanisms of the CL reaction and sensitization effect are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Pre‐copulation intervals,copulation frequencies,and initial progeny sex ratios in two biotypes of whitefly,Bemisia tabaci

The whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is a species complex, and its systematic classification requires controlled crossing experiments among its genetic groups. Accurate information on pre‐copulation intervals, copulation frequencies, and initial frequency of egg fertilization of newly emerged adults is critical for designing procedures for collecting the virgin adults necessary for these experiments. In the literature, considerable variation is reported between B. tabaci populations, with respect to the length of the pre‐copulation interval and the initial frequency of egg fertilization. Here, we used a video‐recording method to observe continuously the copulation behaviour of the Mediterranean/Asia Minor/Africa (B biotype) and the Asia II (ZHJ1 biotype) groups of B. tabaci. We also recorded the initial frequency of egg fertilization, as determined by the sex of the progeny. When adults were caged in female–male pairs on leaves of cotton plants, the earliest copulation events occurred 2–6 h after emergence; at 12 h after emergence 56–84% of the females had copulated at least once, and nearly all (92–100%) had copulated at least once by 36 h after emergence. Both females and males copulated repeatedly. Approximately 80 and 20% of copulation events occurred during the photophase and scotophase, respectively. By 72 h post‐emergence, the females of the B and ZHJ1 biotypes had copulated on average 6.1 and 3.9 times, respectively. When adults were caged in groups on plants 1–13 h after emergence, 30–35% of the eggs deposited during this period were fertilized, and approximately 90% of females were fertilized by the end of the 13 h. Although timing of copulation differed in detail between the two genetic groups, the results demonstrate that B. tabaci adults can start to copulate as early as 2–6 h post‐emergence and the majority of females can become fertilized on the day that they emerge.     

Sperm Nuclear Transformation and Aster Formation Related to Metabolic Behaviour in Amphibian Eggs

Bufo arenarum oocyte maturation is related to important modifications in the metabolism of carbohydrates. Such changes involve a different relative participation of the main oxidative routes and are under the influence of seasonal variations of the pituitary activity.
Ovulated coelomic oocytes obtained during the winter period, were unable to initiate cleavage after injection of a sperm suspension. The extent of sperm head transformation and aster formation in the cytoplasm of oocytes with a different metabolic behaviour (obtained during the winter and summer periods) were studied.
Our results show that sperm nuclear transformation and DNA synthesis were quite similar in both types of oocytes. In contrast to summer oocytes, in which the pronucleus was sourranded by an aster, no aster structure was formed in winter ooctyes notwithstanding pronucleus formation occurred.
These results suggest that the failure to develop aster may explain the lack of cleaving in winter oocytes. It appears that the metabolic changes, aster formation and the capability to cleave are closely related and could be dissociated from oocyte nuclear maturation in this species.     

The Significance of the Obturator in the Control of Pollen Tube Entry into the Ovary in Peach (Prunus persica)

Changes in the obturator of the peach (Prunus persica) havebeen investigated and related to pollen tube growth in thisregion. At anthesis, the cells of the obturator are active andrich in starch reserves. Twelve days after anthesis these cellsproduce a secretion that stains for carbohydrates and for proteins.As the secretion is produced, starch vanishes from these cellsand they degenerate and collapse as callose is accumulated.Secretion is independent of pollination as it takes place ina similar fashion both in pollinated and in unpollinated flowers. Pollen tube growth along the obturator surface depends on thissecretion for, although pollen tubes reach the base of the styleseven days after pollination, they cannot grow on the obturatoruntil five days later, when the secretion is produced. Thisdiscontinuous secretion taking place at the obturator may providea mechanism that controls the entrance of pollen tubes intothe ovary in the peach. Prunus persica, peach, obturator, pollen tube     

Generative Cell Division and Sperm Cell Association in the Pollen Grain of Sambucus nigra

Generative cell division in tricellular pollen grains of Sambucusnigra L. (Caprifoliaceae) has been examined with light and electronmicroscopy. During division the generative cell is located inthe centre of the pollen grain, near to the nucleus of a surroundingvegetative cell. Conventional mitosis of the generative cellis followed by cytokinesis through centrifugal cell plate formation.Two sister sperm cells remain in spatial contact with each otherand are surrounded, as formerly their progenitor cell was, bythe vegetative cell. From the changes of shape of the generativecell during division and of the sperm cells it may be assumedthat the space between these cells and the vegetative one containsa labile, non-rigid, wall material. No plastids have been observedin the generative cell and its mitochondria appear to be unequallydistributed between the two future sperm cells during division. Sambucus nigra L., generative cell division, pollen, sperm cell association     

The Role of DNA Synthesis During Hypocotyl Elongation in Light and Dark

Fluorodeoxyuridine, an inhibitor of DNA synthesis, did not affectgermination and post-germinative growth in the aerial part oflettuce and Haplopappus gracilis seedlings when grown in thelight. In the dark, however, elongation of the hypocotyl wasinhibited by fluorodeoxyuridine, strikingly in lettuce and onlyslightly in Haplopappus gracilis. This could imply that thecontrolling mechanism of hypocotyl elongation is in some casesrelated to DNA synthesis, either because mitotic processes (oftenlittle taken into account in considering hypocotyl growth) areinvolved in the elongation of hypocotyls only when they aregrown in the dark, or because DNA synthesis affects cell elongationdirectly, or through the production of a greater number of endopolyploidcells in the dark. Using mainly autoradiographic and cytofluorimetricmethods, these possibilities were tested. Besides lettuce (Lactucasativa L. var. Great Lakes) and H. gracilis (Nutt.) Gray, radish(Raphanus sativus L. var. Tondo rosso quarantino) and soybean(Soya hyspida Sieb. and Zucc. var. Tokyo) seedlings were alsostudied. Fluorodeoxyuridine drastically inhibits cell elongation onlywhen it is preceded or accompanied by mitotic or endomitoticevents. Need for DNA synthesis during hypocotyl elongation,as well as during early post-germinative growth, seems to beof particular importance when endomitotic processes are involved. DNA synthesis, elongation, endoreduplication, fluorodeoxyuridine, Haplopappus gracilis (Nutt.) Gray, Lactuca sativa L., Raphanus sativus L., Soya hyspida Sieb and Zucc