Regeneration of chlorophyll chimeras from leaf explants ofNicotiana tabacum L.

Chimeral plants with variegated leaf blades were obtained by induction of organogenesis in primocultures of leaf explants ofNicotiana tabacum L. cv. Burley 49, chlorophyll mutation White Seedling. Only green plants regenerated from primocultures of explants taken from dark green leaf areas of the chimeras. The possibility of a multicellular initiation of chimera regeneration from tissue cultures is discussed.     

The morphogenesis of green buds in γ - irradiated leaf and stem expiants of “aurea” chlorophyll mutantNicotiana tabacum L

The formation of buds in leaf and stem expiants derived from “aurea” mutant regenerants ofNicotiana tabacum (cv. John Williams Broadleaf, mutation Sulfur) was inhibited by dosages of 1 to 5 krad of γ-irradiation. The extent of the inhibition was proportional to the dosage of irradiation. In some eases, the stem expiants formed buds even after the application of 10 krad. In addition to “aurea” buds, green buds were also formed in both explants after-the irradiation with the dosages of 1 to 2.5 krad which continued to grow even after the trans plantation into garden soil.     

Additional cricetid and dipodid rodent material from the Erden Obo section,Erlian Basin (Nei Mongol,China) and its biochronological implications

New cricetid (Cricetops dormitor, Eocricetodon sp., Eucricetodon cf. E. wangae, Pappocricetodon schaubi) and dipodid (Allosminthus gobiensis n. sp., Allosminthus ernos, Allosminthus uniconjugatus, Allosminthus cf. A. majusculus, Primisminthus shanghenus, Sinosminthus sp.) occurrences from the “Lower Red”, “Middle Red”, “Middle White” and “Upper White” beds of the Erden Obo section in Nei Mongol, China are reported. They are first discovered in these horizons. On the basis of the comparison of the rodent assemblages, we consider that the age of the “Upper White” beds is early Oligocene, the age of the “Middle Red” and “Middle White” beds is probable more similar to the age of late Eocene Houldjin Formation and lower part of Chaijiachong Formation, and the age of the “Lower Red” beds is correlative to the Sharamurunian. The diversity of ctenodactyloid, dipodid, and cricetid appears to change, and the turnover in rodent fauna possibly responded to the environmental and climate change towards the end of middle Eocene.     

Fatty acids,resin acids and phenols in Pinus muricata

Acetone-soluble extractives of “blue” and “green” strain Pinus muricata D. Don were found to consist of free and “combined” fatty acids, resin acids, and phenols. The composition of the extractives from the two strains was similar though “green” strain P. muricata contained more Δ^8(9),15 isopimaric acid than “blue” strain. This difference may be used to identify these muricata strains if the age of the wood precludes a monoterpene examination.     

Statistical Description of Food Microstructure. Extraction of Some Correlation Functions From 2D Images

Two algorithms able to compute lineal-path distribution function L(z) and two-point correlation function, S ₂ (r ₁ ,r ₂ ) from 2D digital images of foods were developed and validated. Particularly, “Altamura” and “White” breads as well as “Napoli” sausages were studied. Lineal-path function was modeled by considering the foods as two-phase random systems composed from polydisperse overlapping disks. Instead, two-point correlation function was modeled by using a Debye’s equation. In all cases a good agreement between experimental and theoretical trend was obtained stating the high accuracy of the algorithms in the extraction of correlation functions as well as the possibility to model breads and sausages as two-phase random systems. Also, important morphological properties such as pores distribution, pore size homogeneity and their spatial distribution, were obtained. For instance, although the estimated radius of the pores was lower for “Altamura” bread rather that for “White”, its slowest decay of L(z) highlighted that the pores showed a high dimensional inhomogeneity.     

Evolution of photosynthetic reaction centers

The common ancestor of all photosynthetic prokaryotes and organelles contained chlorophyll (Chl) a. All green and purple photosynthetic bacteria descended from a common bacteriochlorophyll (Bchl) a-containing ancestor which diverged from the Chl a line. Separate PS-I and PS-II reaction centers may have evolved before the appearance of Bchl a. When the transition to Bchl a occurred, the resultant organism contained two types of reaction center, “PS-I” and “PS-II.” One line of development eliminated “PS-II” and evolved into the green bacteria. The other line eliminated “PS-I” and became the purple bacteria. In the Chl a-containing organisms the evolution of PS-II continued until oxygen evolution was achieved.     

Interaction Between “Safe Sites” and “Safe Sides” for Germination of Neurada procumbens (Neuradaceae) in the Middle East

The seed bank of Neurada procumbens, a prostrate annual common in sandy desert habitats, is vulnerable to surface disturbances. Moreover, its seeds are highly heteromorphic, having both spinose and non-spinose sides, which affects both the vertical distribution of seeds and diaspores, and the precise position in which they lie in the soil. Here we explore the ecological implications of two factors, “safe sites” within habitats and seed orientation or “safe sides”, on seedling establishment and the seed bank. In three natural populations, the vertical distribution of buried, germinable diaspores decreased with soil depth. Most diaspores occurred at the surface (0–1 cm below the surface), while none were observed below 10 cm. Seedling emergence decreased with depth and reached zero in diaspores below 5 cm. Seedling emergence also proved highly sensitive to the orientation of diaspores in soil. Diaspores lying on their smooth side with the spinose upper side directed upwards reached the highest seedling emergence of 61 %. Root length ranged from 10 to 16 cm, and the root to shoot ratio varied between 22.8 and 30.3 cm, depending on diaspore size. Diaspores near the surface may constitute a more transient component of the seed bank, as few of these remained viable for more than a year. Persistence of Neurada seed banks seems to depend not only on vertical movement of diaspores among habitat “safe sites” but also on different seed position alternatives.     

Analysis of development and growth in a mutant of Physarum polycephalum with defective cytokinesis

Cultures of amoebae of the mutant strain ATS23 isolated from strain CLd of Physarum polycephalum contain multinucleate cells and cells with increased nuclear DNA content. Plasmodia derived from ATS23 clones show abnormal morphology and defective sporulation. All abnormalities are enhanced by high incubation temperature (31 °C). Genetic analysis suggested that all the abnormalities were caused by a single mutation, denoted hts-23. The kinetics of plasmodium formation were followed in cultures of apogamic amoebae carrying hts-23 and hts⁺ (wild type) respectively. Results indicated that, relative to wild type, hts-23 did not increase the rate of plasmodium formation. There was evidence that, in both mutant and wild-type strains, commitment to plasmodium development occurred in uninucleate cells. Analysis of cell pedigrees by time-lapse cinematography indicated that the primary abnormal event in cultures of hts-23 amoebae was failure of cytokinesis; an apparently complete cleavage furrow was formed but cell separation failed, resulting in a binucleate cell. This event occurred randomly in pedigrees in which the majority of divisions were completed normally; its frequency increased during incubation at 31 °C. All other abnormalities in hts-23 amoebal cultures could be attributed to this primary event, assuming that DNA synthesis continued in the absence of cytokinesis and that the binucleate cells underwent the amoebal type of “open” mitosis, allowing the possibility of spindle fusion. This implies that the acquisition of “closed” mitosis is an essential early step in plasmodium development.     

On the mutability of the yeast mitochondrial genome.

A mechanism is proposed to explain how a mutation in a single molecule of mitochondrial DNA (mitDNA) can come to affect all the other mitDNA molecules of a yeast cell. It is suggested that an initial mutation may be “amplified” by a process which is, in fact, intended to ensure the identity of the cell's complement of mitDNA molecules. It is postulated that this process involves a small number of “reference” copies of mitDNA to which all other (“derived”) copies are compared and corrected once per cell cycle. Asymmetric gene conversion is proposed as the correction mechanism and the means of “amplifying” mutations. The model is shown to be compatible with current data on spontaneous and induced mitochondrial mutation in Saccharomyces cerevisiae.     

The nature of regulation of hexose transport in cultured mammalian fibroblasts: Aerobic “repressive” control by d-glucosamine

Restrictive control (“repression”) of 3-O-methylglucose transport (or of galactose uptake) in confluent NIL hamster fibroblast cultures was found to be highly pronounced after preconditioning the cultures in medium containing d-glucosamine. The “repression” exerted by glucosamine developed slowly over several hours. The transport “repression” was counteracted by anaerobiosis, by 2,4-dinitrophenol (H. M. Kalckar, C. W. Christopher, and D. Ullrey, 1979, Proc. Nat. Acad. Sci. USA76, 6453–6455), and by fluoride as well as by malonate. In “de-repressed” cultures, i.e., in the absence of glucosamine in the medium or by using fructose during preconditioning, malonate did not affect regulation of the hexose transport system. In culture medium deprived of l-glutamine and serum, repressive control of the transport system by glucose as well as by glucosamine was greatly aggravated. However, the simultaneous addition of malonate abolished the severe “repression” by either of the hexoses. In all cases, preconditioning with fructose permitted high (“de-repressed”) transport activity. Unlike glucose, galactose, or glucosamine, fructose was not found to compete in the transport assay. The metabolic inhibitors which prevent the aerobic curtailment of the hexose transport system are all more or less directly interfering with the flow of metabolites through the tricarboxylate cycle, which may therefore play an important role in the “repressive” control of transport.     

Influence of light on phycobiliprotein production in three marine cyanobacterial cultures

Complementary chromatic adaptation, a photomorphogenetic response, known to occur in many cyanobacteria, enables them to efficiently absorb prevalent wavelengths of light in the environment. In the present study, we have described the influence of light on phycobiliprotein production in three marine phycoerythrin producing cyanobacterial cultures, namely, Lyngbya sp. A09DM, Phormidium sp. A27DM and Halomicronema sp. A32DM. A comparative study (UV-visible overlay spectra and SDS-PAGE analyses) of phycobiliproteins purified from all the three cultures grown in white, yellow, red and green lights has been confirmed. White light was taken as control. Red and green lights were taken to check their effect on phycocyanin and phycoerythrin production, respectively. Yellow light was studied as its wavelength falls in between green and red light. Lyngbya sp. A09DM was found to be the best chromatically adapting cyanobacterium followed by Halomicronema sp. A32DM. These two cultures can be placed in group III chromatic adaptors. Phormidium sp. A27DM was the least chromatically adapting culture and can be placed in group II chromatic adaptors. The study signifies that even light plays an important role along with nutrient availability in adapting cultures to changing environmental conditions.     

The role of bacteria in the metal tolerance of the fouling diatom Amphora coffeaeformis Ag.

Components of “spent” axenic and non-axenic Amphora coffeaeformis Ag. culture media were tested for their effect on copper and tributyltin tolerance in axenic A. coffeaeformis. Growth of such algal cultures in the presence of either toxin was enhanced by the addition of enriched “spent” medium from exponentially growing non-axenic cultures. This response was seen whether or not the bacteria had been removed. It appears that bacteria or bacteria-algal interactions produce some soluble (<0.2 μm) factor which either decreases the toxicity of copper and tributyltinfluoride (TBTF) or increases the tolerance of A. coffeaeformis to these toxins.     

Association of the Asp298Asn polymorphism in the mc4r gene with back fat thickness in pigs of the large white breed

The association of the Asp298Asn polymorphism in the mc4r gene with the development of traites such as spinal fat thickness in pigs of the Large White breed from AF “Orzhitska” population was investigated. A tendency towards the development of thinner spinal fat was found in animals with the AG genotype. No significant difference was detected in the spinal fat thickness between animal groups with different genotypes of the mc4r gene caused by Asp298Asn polymorphism. The heterogeneous origin of the studied animals can be a possible cause of the absence of any statistically significant difference. A conclusion was reached that it was not expedient to use Asp298Asn polymorphism of the mc4r gene in the selection of pigs of the Large White breed from AF “Orzhitska” population.     

Chlorophylle und Carotinoide der Chaetophorineae (Chlorophyceae; Ulotrichales)

In air-supplied inorganic liquid cultures, the highly differentiated green alga Fritschiella tuberosa forms only branched filaments with long slender cells. In nitrogen-deficient medium and with ageing of the cultures these cells become much shorter in length by subsequent formation of transverse walls. The chloroplasts of the slender cells contain the typical pigments of green algae. Together with the morphogenetic change to “short cells” secondary carotenoids are synthesized and stored in lipid droplets. Besides traces of lutein, violaxanthin and neoxanthin and reduced amounts of β-carotene, the following pigments have been demonstrated: Esters of astaxanthin (main pigment) and adonixanthin, canthaxanthin, echinenone and a Keto-α-carotinoid, which presumably is identical with α-doradexanthin, (3,3′-Dihydroxy-4-keto-α-Carotene) a pigment not known in plants until now. In nitrogen deficient cultures the chlorophylls are totally decomposed, the total-lipids increase by about 500%. By supplying nitrogen-deficient cultures with nitrogen and subsequent illumination regreening of the cells starts already 16 hrs later.     

Genetische Analyse zweier Mutanten vonDinophilus gyrociliatus (Archiannelida) mit veränderter Eigröße

D. gyrociliatus has two types of eggs: a smaller type giving rise to ♂♂, and a larger type developing into ♀♀. Two mutants, which originated in laboratory cultures derived from animals collected at Helgoland, produced eggs of an abnormal size; the first, “Gr”, yielding larger-than-normal male-type eggs, the second, “Kl”, smaller male-type eggs. Size of eggs is determined by the genotype of the mother, the genotype of the eggs being without influence. Both mutants show a dominant monofactorial inheritance. In crosses withGr/Gr-individuals an exceptionally high rate of reverse mutations to wildtype (1,4 to 5,0 %) has been observed. Results indicate thatGr is either an unstable gene or a chromosome mutation in the form of a duplication or trisomy of one chromosome.     

Transgenerational Behavioral Plasticity in a Parthenogenetic Insect in Response to Increased Predation Risk

Reliable cues of increased predation risk can induce phenotypic changes in an organism’s offspring (i.e. transgenerational phenotypic plasticity). While induction of defensive morphologies in naïve offspring in response to maternal predation risk is widespread, little is known about transgenerational changes in offspring behavior. Here we provide evidence for transgenerational behavioral plasticity in the pea aphid, Acyrthosiphon pisum. When pre-reproductive individuals of two genotypes (“pink” and “green”) were exposed to the alarm pheromone (E)-β-Farnesene (EBF), a reliable cue of increased predation risk, next-generation offspring altered their feeding site choices relative to the location of the maternal aphids. Offspring of EBF-treated aphids occupied “safer” feeding sites: green offspring occupied “safer” feeding sites in the natal colony, while pink offspring dispersed to occupy sites on neighboring plant leaves.     

The influence of bacteria on the arsenic species produced by laboratory cultures of the marine phytoplankton Dunaliella tertiolecta

To assess whether bacteria influence the biogeochemical cycling of arsenic by laboratory cultures of the marine phytoplankton Dunaliella tertiolecta, the arsenic species produced by D. tertiolecta were compared in “operationally sterile” and bacteria spiked cultures. It was observed that glycerol (Gly-) arsenoriboside (41–78 %), phosphate (PO₄?) arsenoriboside (7–38 %) and arsenate (As(V)) (15–21 %) were the major water-soluble arsenic species in all D. tertiolecta cultures irrespective of whether cultures were operationally sterile or contained added bacteria. PO₄-riboside (46–74 %) and Gly-riboside (24–36 %) were also the major arsenic species in hydrolysed lipid extracts of D. tertiolecta irrespective of whether cultures were operationally sterile or contained bacteria. In addition to similarities in the arsenic species produced, total arsenic concentrations and culture growth did not differ relative to whether cultures were operationally sterile or not. Similar bacterial strains were identified in all D. tertiolecta cultures irrespective of whether bacteria were added or not. Consequently, it is evident that the presence of “foreign” or “added” bacteria in D. tertiolecta has minimal influence on the metabolism and cycling of arsenic by phytoplankton. Thus, the use of laboratory phytoplankton cultures containing bacteria may be appropriate means to investigate arsenic biogeochemical cycling unlike previously believed.     

The effectiveness of active and passive restoration on recovery of indigenous vegetation in riparian zones in the Western Cape,South Africa: A preliminary assessment

Riparian ecosystems in South Africa's fynbos biome are heavily invaded by alien woody plants. Although large-scale clearing of these species is underway, the assumption that native vegetation will self-repair after clearing has not been thoroughly tested. Understanding the processes that mediate the recruitment of native species following clearing of invasive species is crucial for optimising restoration techniques.This study aimed to determine native species recovery patterns following implementation of different management interventions. We tested the influence of two clearing treatments (“fell & remove” and “fell & stack burn”) on the outcomes of passive restoration (natural recovery of native riparian species) and active restoration (seed sowing and planting of cuttings) along the Berg River in the Western Cape. Under greenhouse conditions we investigated seed viability and germination pre-treatments of selected native species.There was no recruitment of native species in sites that were not seeded (passive restoration sites), possibly because of the dominance of alien herbaceous species and graminoids or the lack of native species in the soil-stored seed bank. Germination of our targeted native species in the field was low in both “fell & remove” and “fell & stack burn” treatments. However, “fell & stack burn” gave better germination for the species Searsia angustifolia, Leonotis leonurus and Melianthus major. Seedling survival in the field was significantly reduced in summer, with drought stress being the main cause for seedling mortality. Germination rates in the greenhouse were high, an indication that harvested seeds were viable. Most seeds germinated without germination pre-treatments.We conclude that failure of native seeds to germinate under field conditions, secondary invasion of alien herbs and graminoids, the lack of native species in the soil-stored seed bank, and dry summer conditions hamper seedling establishment and recovery on sites cleared of dense stands of alien trees. For active restoration to achieve its goals, effective recruitment and propagation strategies need to be established.     

Salvage Logging Versus the Use of Burnt Wood as a Nurse Object to Promote Post‐Fire Tree Seedling Establishment

Intense debate surrounds the effects of post‐fire salvage logging (SL) versus nonintervention policies on forest regeneration, but scant support is available from experimental studies. We analyze the effect of three post‐fire management treatments on the recruitment of a serotinous pine (Pinus pinaster) at a Mediterranean mountain. Treatments were applied 7 months after the fire and differ in the degree of intervention, ranging from “no intervention” (NI, all trees left standing) to “partial cut plus lopping” (PCL, felling most of the trees, cutting the main branches, and leaving all the biomass in situ without mastication), and “SL” (felling and piling the logs, and masticating the woody debris). Seedling survival after 3 years was the highest in PCL (47.3% versus 38.7% in SL). This was associated with the amelioration of microclimatic conditions under the scattered branches, which reduced radiation and soil temperature while increasing soil moisture. Seedling density after 2 years was approximately 5.5 times higher in PCL than in SL, as in SL a large fraction of seedlings was lost as a consequence of mechanized mastication. The NI treatment showed the lowest seedling survival (17.3%). Nevertheless, seedling density was similar to SL. Seedling growth scarcely differed among treatments. Our results show that branches left onsite acted as nurse objects that improved key microclimatic conditions for seedling recruitment. This creates a facilitative interaction ideal for seedling establishment in moisture‐deficient ecosystems, as it provides the benefit of a shading overstory but without underground competition.     

Combination of cell disruption technologies for lipid recovery from dry and wet biomass of Yarrowia lipolytica and using green solvents

This work aims to investigate the efficiency of bead milling combined or not with high-pressure homogenization on the cell disruption and lipid recovery from Yarrowia lipolytica oleaginous yeast. First, a simulation study involving the use of the Hansen solubility parameters’ approach was performed in order to identify, among 41 conventional and “green” solvents, the most promising ones that are able to replace n-hexane for lipid recovery from Y. lipolytica biomass. The results obtained showed that the pre-treatment involving both high-pressure homogenization and bead milling applied sequentially was more performant than that involving bead milling alone. In addition, bead-milling parameters were optimized showing an optimal bead size of 4.9 mm and a processing time of 30 s. Among the tested solvents, isoamyl acetate was selected as the most appropriate “green” solvent, maximizing the lipid extraction, compared to n-hexane. Despite the better performance of the dry route compared to the wet one, promising results were obtained towards 1) minimizing the energy consumed and 2) replacing n-hexane by “green” solvents for lipid recovery from Y. lipolytica yeast.