Carbohydrate formation in rewetted terrestrial cyanobacteria

Summary In the terrestrial cyanobacterium Nostoc commune Vauch. formation of carbohydrate polymers was measured upon rewetting the mats in a light-dark regime. To discriminate between carbohydrates of different physiological function, total carbohydrate was determined as anthrone-reactive material (ARM) and storage carbohydrate (glycogen) assayed by an enzymic test. In the dry thalli glycogen was found to represent less than one tenth of the ARM. After rewetting an increase of total carbohydrate was observed in illuminated samples. Only glycogen, however, showed a regular pattern of synthesis and degradation during a 12:12 h light-dark cycle. This indicates that most carbohydrates detected by anthrone belong to the metabolically inert sheath material.When illuminated colonies were kept submerged after rewetting glycogen was hydrolyzed indicative of being used in the rapid recovery of cellular functions as observed in rewetted colonies. Apparently, photosynthesis allowed for net glycogen synthesis only, provided the mats were sufficiently aerated. These findings give evidence that the (carbohydrate) sheath plays an important role in water retention in an organism bound to a terrestrial habitat.     

Release of dormancy during after-ripening of Agrostemma githago seeds

Freshly harvested seeds of Agrostemma githago L. do not germinate when they are imbibed at 20°C. The block is located in the embryo and is relased by dry storage at 20°C (after-ripening). Freshly harvested seeds complete only a small part of the processes that occur in after-ripened seeds during the lag phase prior to germination (radicle protrusion). After-ripening removed the block on lag phase processes much faster than the block on germination. This was shown both by direct determinations of the completion of lag phase processes and by measurements of the rate of axial protein synthesis, which approximately doubles when seeds are progressing through the lag phase. It is concluded that the percentage germination does not adequately reflect the extent to which the dormancy mechanism has been overcome.     

Comparison of the effect of excessive light on chlorophyll fluorescence (77K) and photon yield of O2 evolution in leaves of higher plants

High-light treatments (1750–2000 mol photons m^–2 · s^–1) of leaves from a number of higher-plant species invariably resulted in quenching of the maximum 77K chlorophyll fluorescence at both 692 and 734 nm (F _M, 692 and F _M, 734). The response of instantaneous fluorescence at 692 nm (F _O, 692) was complex. In leaves of some species F _O, 692 increased dramatically in others it was quenched, and in others yet it showed no marked, consistent change. Regardless of the response of F _O, 692 an apparently linear relationship was obtained between the ratio of variable to maximum fluorescence (F _V/F _M, 692) and the photon yield of O₂ evolution, indicating that photoinhibition affects these two variables to approximately the same extent. Treatment of leaves in a CO₂–free gas stream containing 2% O₂ and 98% N₂ under weak light (100 mol · m^–2 · s^–1) resulted in a general and fully reversible quenching of 77K fluorescence at 692 and 734 nm. In this case both F _O, 692 and F _M, 692 were invariably quenched, indicating that the quenching was caused by an increased non-radiative energy dissipation in the pigment bed. We propose that high-light treatments can have at least two different, concurrent effects on 77K fluorescence in leaves. One results from damage to the photosystem II (PSII) reaction-center complex and leads to a rise in F _O, 692; the other results from an increased non-radiative energy dissipation and leads to quenching of both F _O, 692 and F _M, 692 This general quenching had a much longer relaxation time than reported for pH-dependent quenching in algae and chloroplasts. Sun leaves, whose F _V/F _M, 692 ratios were little affected by high-light exposure in normal air, suffered pronounced photoinhibition when the exposure was made under conditions that prevent photosynthetic gas exchange (2% O₂, 0% CO₂). However, they were still less susceptible than shade leaves, indicating that the higher capacity for energy dissipation via photosynthesis is not the only cause of their lower susceptibility. The rate constant for recovery from photoinhibition was much higher in mature sun leaves than in mature shade leaves, indicating that differences in the capacity for continuous repair may in part account for the difference in their susceptibility to photoinhibition.Abbreviations and symbols kDa kilodalton - LHC-II light-harvesting chlorophyll-protein complex - PFD photon flux density (photon fluence rate) - PSI, PSII photosystem I, II - F _O, F _M, F _V instantaneous, maximum, variable fluorescence emission - absorptance - _a photon yield of O₂ evolution (absorbed light) C.I.W.-D.P.B. Publication No. 925     

Comparison of gas chromatography-mass spectrometry,radioimmunoassay and bioassay for the quantification of gibberellin A9 in norway spruce (Picea abies (L.) Karst.)

Quantitative estimates of gibberellin A₉ in Norway spruce extracts obtained by gas chromatography-mass spectrometry, radioimmunoassay (RIA_ and bioassay were compared after successive purifications of the extracts. The extracts were assayed in several dilutions with and without the addition of standard gibberellin A₉, thus showing the effect of extract components on the response of the assays. Radioimmunoassay produced estimates comparable to gas chromatography-mass spectrometry after one purification step by high-performance liquid chromatography. Extracts purified by polyvinylpyrrolidone-column chromatography and solvent partitioning but not high-performance liquid chromatography resulted in inaccurate RIA estimates. The performance of the RIA could be monitored by logit-log transformations of the standard curve and extract dilution curve and by calculating the slope of the standard addition curve. It was, however, not possible to correct for the interference caused by extract components by the standard addition procedure. Quantifications by Tan-ginbozu dwarf-rice bioassay were accurate, but a large and unpredictable variation makes it unsuitable for quantitative determinations.Abbreviations FW fresh weight - GA₉ gibberellin A₉ - GA₉–Me methylated GA₉ - GC-MS gas chromatography-mass spectrometry - HPLC high performance liquid chromatography - MID multiple-ion detection - RIA radioimmunoassay     

Characteristics of aSerratia plymuthica isolate from plant rhizospheres

An isolate (G15) of a bacterium, frequently isolated from roots of various plant species, was identified asSerratia plymuthica. At low temperature (viz. 2–8°C), the studied isolated readily produced a red pigment which proved useful in recognizing the bacteria on reisolation. In laboratory tests it exhibited strong antagonism againstBotrytis cinerea andGerlachia nivalis and moderate antagonism againstRhizoctonia solani, Fusarium culmorum andPythium sp. The bacterium significantly increased growth of lettuce plants when applied to the roots under non-sterile conditions in greenhouse tests. Various strains ofSerratia plymuthica are supposed to be common as rhizosphere bacteria under Swedish conditions.     

Light and acetate regulate a mitochondrial malate dehydrogenase

A malate dehydrogenase was purified from the unicellular green alga Chlorogonium elongatum Dangeard. The enzyme was localized in the mitochondria by immunogold electron microscopy and was found to be present on the cristae. The concentration of the enzyme is regulated by acetate and light. In cells cultured heterotrophically with acetate as carbon source the activity and the concentration of the enzyme is 5- to 6-fold higher than in autotrophic cells. In mixotrophically cultured cells (light and acetate) the enzyme level attains only half of the value of that in heterotrophic cells. Acetate induces an increase of the enzyme concentration while light has an inhibitory effect on this process.     

The Susceptibility of Photosynthesis to Photoinhibition and the Capacity of Recovery in High and Low Light Grown Cyanobacteria, Anacystis nidulans

The susceptibility of photosynthesis to photoinhibition and the rate of its recovery were studied in the cyanobacterium Anacystis nidulans grown at a low (10 micromoles per square meter per second) and a high (120 micromoles per square meter per second) photosynthetically active radiation. The rate of light limited photosynthetic O₂ evolution was measured to determine levels of photoinhibition and rates of recovery. Studies of photoinhibition and recovery with and without the translation inhibitor streptomycin demonstrated the importance of a recovery process for the susceptibility of photosynthesis to photoinhibition. We concluded that the approximately 3 times lower susceptibility to photoinhibition of high light than of low light grown cells, significantly depended on high light grown cells having an approximately 3 times higher recovery capacity than low light grown cells. It is suggested that these differences in susceptibility to photoinhibition and recovery depends on high light grown cells having a higher turnover rate of photosystem II protein(s) that is(are) the primary site(s) of photodamage, than have low light grown cells. Furthermore, we demonstrated that photoinhibition of A. nidulans may occur under physiological light conditions without visible harm to the growth of the cell culture. The results give support for the hypotheses that the net photoinhibitory damage of photosystem II results from the balance between the photoinhibitory process and the operation of a recovery process; the capacity of the latter determining significant differences in the susceptibility of photosynthesis to photoinhibition of high and low light grown A. nidulans.     

Calculation of leaf photosynthetic parameters from light-response curves for ecophysiological applications

Measurement of the light response of photosynthetic CO₂ uptake is often used as an implement in ecophysiological studies. A method is described to calculate photosynthetic parameters, such as the maximum rate of whole electron transport and dissimilative respiration in the light, from the light response of CO₂ uptake. Examples of the light-response curves of flag leaves and ears of wheat (Triticum aestivum cv. ARKAS) are shown.Abbreviations and symbols A net photosynthesis rate - D ¹ rate of dissimilative respiration occurring in the light - f loss factor - I incident PPFD - I effective absorbed PPFD - J rate of whole electron transport - J _m maximum rate of whole electron transport - p ^c intercellular CO₂ partial pressure - PPFD photosynthetic photon flux density - q effectivity factor for the use of light (electrons/quanta) - absorption coefficient - I ^* CO₂ compensation point in the absence of dissimilative respiration (bar) - II conversion factor for calculation of CO₂ uptake from the rate of whole electron transport - convexity factor Gas-exchange rates relate to the projective area and are given in mol·m^-2·s^-1. Electron-transport rates are given in mol electrons·m^-2·s^-1; PPFD is given in mol quanta·m^-2·s^-1.     

Chromosomal location of isozyme and seed storage protein genes in Dasypyrum villosum (L.) Candargy

Summary The zymogram phenotypes of glucose-phosphate isomerase (GPI), alcohol dehydrogenase-1 (ADH-1), glutamate oxaloacetate transaminase (GOT), superoxide dismutase (SOD), lipoxygenase (LPX), esterase (EST) and the banding patterns of gliadin and glutenin seed storage proteins were determined for Triticum aestivum cv. Chinese Spring (CS), Dasypyrum villosum, the octoploid amphiploid T. aestivum cv. Chinese Spring D. villosum (CS × v) (2n=8x=56; AABBDDVV), and for five CS-D. villosum disomic addition lines. The genes Gpi-V1, Adh-V1, Got-V2, and Sod-V2 coding for GPI-1, ADH-1, GOT-2, and SOD-2 isozymes were located in D. villosum on chromosome 1V, 4V, 6V, and 7V, respectively. Genes coding for gliadin- and glutenin-like subunits are located in D. villosum chromosomes 1V. There are no direct evidence for chromosomal location of genes coding for GOT-3, EST-1 and LPX-2 isozymes. The linkage between genes coding for glutenin-like proteins and GPI-1 isozymes in chromosome 1V is evidence of homoeology between chromosome 1V and the chromosomes of homoeologous group 1 in wheat.Research supported by the National Research Council (Italy) and National Science Foundation (USA). International cooperative project, Grant No. 85.01504.06 (CNR)     

Stressful life events preceding the acute onset of schizophrenia: A cross-national study from the World Health Organization

This study reports on the findings from a WHO sponsored cross-national investigation of life events and schizophrenia. Data are presented from a series of 386 acutely ill schizophrenic patients selected from nine field research centers located in developing and developed countries (Aarhus, Denmark; Agra, India; Cali, Colombia; Chandigarh, India; Honolulu, USA; Ibadan, Nigeria; Nagasaki, Japan; Prague, Czechoslovakia; Rochester, USA). On a methodological level, the study demonstrates that life event methodologies originating in the developed countries can be adapted for international studies and may be used to collect reasonably reliable and comparable cross-cultural data on psychosocial factors affecting the course of schizophrenic disorders. Substantive findings replicate the results of prior studies which conclude that socioenvironmental stressors may precipitate schizophrenic attacks and such events tend to cluster in the two to three week period immediately preceding illness onset.The paper was prepared by these authors on behalf of the collaborating investigators listed on page 196.