Thidiazuron-induced morphogenesis of Regal geranium (Pelargonium domesticum): A potential stress response

Thidiazuron (TDZ), a phenylurea derivative with cytokinin-like activity, induced the development of outgrowths on root tissue of vegetatively propagated geraniums (Pelargonium × hortorum, Pelargonium domesticum and Pelargonium graveolens). Root outgrowths developed as globular or elongated structures following treatment with 10–30 μM TDZ and many of these structures differentiated to produce shoots. Analysis of root and shoot samples, collected daily during the outgrowth induction phase and at the end of the treatment period, revealed significant changes in accumulation of manganese, iron, copper, calcium, magnesium and potassium. The markers of a stress response, proline, abscisic acid and 4-aminobutyrate, accumulated in the TDZ-treated roots during the first week of induction. Assessment of the adenylate phosphate pool sizes of the TDZ-treated plants indicated a sequential increase in the endogenous levels of ATP, ADP and AMP following each application of TDZ. The energy charge ratio was also significantly higher in TDZ-treated plants indicating an increase in ATP utilizing systems. Similarily, pyridine nucleotide pool size analyses revealed that TDZ-treated plants had a higher level of endogenous NADP⁺ in the initial 24-h period following each treatment and the level of NADPH increased following the third application of TDZ. The ratio of NADPH/NADP⁺ was significantly higher in TDZ-treated plants throughout the treatment period. We hypothesize that the primary effect of TDZ was through induction of a stress response in the geranium plants. In order to overcome this stress, the plants accumulated significantly higher levels of proline, ABA and 4-aminobutyrate. Moreover, the plants also exhibited modified metabolic processes which in turn led to increased availability of energy and reducing power required for subsequent growth and to initiate stress adaptation mechanisms including modified cellular processes and regenerative outgrowth development.     

Alterations in the structure of phycobilisomes of the cyanobacterium,Spirulina platensis in response to enhanced Na+ level

Incubation of Spirulina platensis at enhanced Na⁺ concentrations resulted in 30% increased intracellular accumulation of Na⁺ ions. This accumulation of Na⁺ ions intracellularly altered the phycobilisome organization as revealed by transmission electron microscopic data and changes in the absorption spectrum. The room temperature emission peak at 638 nm in the control sample was blue-shifted by 7 nm in the treated samples suggesting phycobilisome disorganization. SDS-PAGE of phycobilisome polypeptides showed a significant increase in a 66.2 kDa polypeptide. This is the first report that the enhanced concentration of intracellular Na⁺ ion alters the structure of the phycobilisome in S. platensis. This revised version was published online in November 2006 with corrections to the Cover Date.     

An ecological study of the macrophytic vegetation of the Doodhadhari Lake,Raipur, M. P., India

Summary Physical factors operating in Doodhadhari Lake were studied periodically during 1967–68. Thermal stratification in the lake was found to be induced by solar radiation during daytime and destroyed by nocturnal cooling and mixing of the lake waters as evidenced by temperature records. Light intensities at different strata were found to be reduced by plant growth. At 0.5 m depth and 1 m depth considerable reduction in light intensities was found. The floating-leaved rooted plants and free-floating sudd communities curtailed the light transmission to 0.0 – 0.1% at 0.5 m depth. Visibility also decreases considerably owing to shading by the plants at different stations.A part of the thesis submitted for the Degree of Doctor of Philosophy.     

Quantitative estimation of newly synthesized radioactive proteins: use of minicolumns of antibody embedded in agarose gel or immobilized on Sepharose.

Immunochemical methods for the quantitative determination of radioactive proteins synthesized by chick embryo hepatocyte cultures are described. Cell culture medium containing secreted labeled serum proteins was concentrated and applied to agarose gels containing rabbit anti-chicken serum. Nonspecific binding in control gels was reduced to less than 2% of applied counts under conditions where more than 60% of the nondialyzable counts were precipitated in the presence of antibody. Labeled cytosol fructose-1,6-bisphosphatase (Fru-P₂ase) from cell sonicates was selectively adsorbed onto columns containing Sepharose-immobilized anti-chicken liver Fru-P₂ase. Radioactivity bound on these columns was eluted with 1% sodium dodecyl sulfate for electrophoretic analysis. Addition of dialyzed horse serum was used in both cases to minimize nonspecific binding. These techniques provide simple alternatives to direct immunoprecipitations in solution where nonspecific binding of radioactivity may be unacceptably high.     

Alterations in Photosystem II Organization by Cobalt Treatment in the Cyanobacterium Spirulina piatensis

The presence of low concentrations of cobalt ions (200 μMCoCl₂) retarded the growth of the cyanobacterium Spirulina platensis. However, cells grown in the presence of CoCl₂ exhibited an enhancement in the levels of phycocyanin and carotenoids, while showed a decrease in the content of chlorophyll a, when compared to the untreated control cells. Thylakoid membranes isolated from CoCl₂ treated cells demonstrated enhanced rates of both photosystem II (H₂O → pBQ) and photosystem I (DCPIPH₂ → MV) mediated electorn transport activities. The stimulation in the rates of photosynthetic electron transport activities in the CoCl ₂ grown cells are attributed to the alterations occurring in the thylakoid membrane organization, as the thylakoids from CoCl₂ grown cells possessed more membrane fluidity. The decrease in the chlorophyll a content may have occurred due to modifications in the chlorophyll a complexes in this cynaobacterium. The enhancement in the phycocyanin levels in the CoCl₂ grown cells appears to be because of the stimulated induction of heme oxygenase. Thus, the cobalt ion treatment appears to be useful in studying the thylakoid membrane and antennae organizations in cyanobacteria.     

Temperature transcends partner specificity in the symbiosis establishment of a cnidarian

Coral reef research has predominantly focused on the effect of temperature on the breakdown of coral-dinoflagellate symbioses. However, less is known about how increasing temperature affects the establishment of new coral-dinoflagellate associations. Inter-partner specificity and environment-dependent colonization are two constraints proposed to limit the acquisition of more heat tolerant symbionts. Here, we investigated the symbiotic dynamics of various photosymbionts in different host genotypes under “optimal” and elevated temperature conditions. To do this, we inoculated symbiont-free polyps of the sea anemone Exaiptasia pallida originating from Hawaii (H2), North Carolina (CC7), and the Red Sea (RS) with the same mixture of native symbiont strains (Breviolum minutum, Symbiodinium linucheae, S. microadriaticum, and a Breviolum type from the Red Sea) at 25 and 32 °C, and assessed their ITS2 composition, colonization rates, and PSII photochemical efficiency (Fv/Fm). Symbiont communities across thermal conditions differed significantly for all hosts, suggesting that temperature rather than partner specificity had a stronger effect on symbiosis establishment. Overall, we detected higher abundances of more heat resistant Symbiodiniaceae types in the 32 °C treatments. Our data further showed that PSII photophysiology under elevated temperature improved with thermal pre-exposure (i.e., higher Fv/Fm), yet, this effect depended on host genotype and was influenced by active feeding as photochemical efficiency dropped in response to food deprivation. These findings highlight the role of temperature and partner fidelity in the establishment and performance of symbiosis and demonstrate the importance of heterotrophy for symbiotic cnidarians to endure and recover from stress.Subject terms: Climate-change ecology, Animal physiology     

Limnology of a Sewage Polluted Tank in Central India

The limnology of a sewage polluted pond was studied from 1978 to 1981. Stratification of temperature, dissolved, oxygen, conductivity, pH, alkalinity and chloride was recorded. The surface stratum down to 0.5 m was supersaturated throughout the year. The pond recorded a permanent water bloom dominated by Anacystis during the summer months. This was followed by Anabaena and Anabaenopsis during winter. The growth of Chlorococcales was retarded due to intraspecific competition, self-shading and low carbon dioxide levels though the waters were nutrient rich. Before the summer overturn, accumulation of calcium bicarbonate produced temporal meromixis. In general, a reduction in the number of zooplankters was recorded.