bluuebunny/crossref_metadata_2025_split huggingface dataset:
Far‐red induced changes of the protochlorophyllide components in wheat leaves
Authors: KLOCKARE BIRGITTA 
Published: April 2006

AbstractBiosynthesis of chlorophyll is partly controlled by the phytochrome system. In order to study the effects of an activated phytochrome system on the protochlorophyllide (PChlide) biosynthesis without accompanying phototransformation to chlorophyll, wheat seedlings (Triticum aestivum L. cv. Starke II Weibull) were irradiated with long wavelength far‐red light of low intensity. Absorption spectra were measured in vivo after different times in the far‐red light or in darkness. The relationship between the different PChlide forms, the absorbance ratio 650nm636 nm changed with age in darkness, and the change was more pronounced when the leaves were grown in far‐red light. Absorption spectra of dark‐grown leaves always showed a maximum in the red region at 650 nm. For leaves grown in far‐red light the absorption at 636 nm was high, with a maximum at the 5 day stage where it exceeded the absorption at 650 nm. At the same time there was a maximum in the total amount of PChlide accumulated in the leaves, about 30% more than in leaves grown in darkness. But the amount of the directly phototransformable PChlide, mainly PChlide650–657, was not increased. The amount of PChlide628–632, or more probably the amount of (PChlide628–632, + PChlide 636–657) was thus higher in young wheat leaves grown in far‐red light than in those grown in darkness. After the 5 day stage the absorption at 636 nm relative to 650 nm decreased with age, and at the 8 day stage the spectra were almost the same in both types of leaves. Low temperature fluorescence spectra of the leaves also showed a change in the ratio between the different PChlide forms. The height of the fluorescence peak at 632 nm relative to the peak at 657 nm was higher in leaves grown in far‐red light than in dark‐grown leaves. – After exposure of the leaves to a light flash, the half time for the Shibata shift was measured. It increased with age both for leaves grown in darkness and in far‐red light; but in older leaves grown in far‐red light (7–8 days) the half time was slightly longer than in dark‐grown leaves. – The chlorophyll accumulation in white light as well as the leaf unrolling were faster for leaves pre‐irradiated with far‐red light. The total length of the seedlings was equal or somewhat shorter in far‐red light, but the length of the coleoptile was markedly reduced from 8.1 ± 0.1 cm for dark‐grown seedlings to 5.2 ± 0.1 cm for seedlings grown in far‐red light.
Water stress and root formation in pea cuttings
Authors: RASMUSSEN SIGGA , ANDERSEN A. SKYTT 
Published: April 2006

AbstractCuttings from eleven day old pea plants (Pisum sativum L. cv. Alaska) grown under either 16 or 38 W m−2 PAR were treated for 24 h with solutions of abscisic acid (ABA). After rooting for 13 days in 16 W m−2 irradiance under mist it was found that 10−5 to 10−4M ABA stimulated rooting (root numbers) while higher concentrations apparently were inhibitory. However, the extension of the rooting period to 17 days indicated that this inhibition was due only to a delay of root emergence. Cuttings from low irradiance took up much less solution than those from high irradiance, giving the appearance of higher sensitivity to ABA. The relative increase of root numbers by optimal ABA tissue concentrations was higher in the cuttings from high irradiance than in those from low irradiance.
Effects of temperature on germination and mitochondrial dehydrogenases in two soybean (Glycine max) cultivars
Authors: HENSON CYNTHIA A. , SCHRADER LARRY E. , DUKE STANLEY H. 
Published: April 2006

AbstractThe effects of eight germination temperatures from 10°C to 35°C on germination and dehydrogenase activities of two soybean (Glycine max [L.] Merr.) cultivars were investigated after 48 h of seedling growth. Axis fresh weights of cv. Chippewa increased as germination temperature increased from 10°C to 35°C. In contrast, axis fresh weights for the cv. Wells increased more slowly with increasing temperature and reached a maximum at c. 25°C. In general, in vitro activities of glutamate dehydrogenase (GDH), NADP‐isocitrate dehydrogenase (NADP‐ICDH), and malate dehydrogenase (MDH) from the axes of cv. Chippewa correlated well with increases in axis fresh weights. GDH and MDH activities from axes of the cv. Wells also reflected increases in axis fresh weights although the correlation was not as evident as for the cv. Chippewa. NADP‐ICDH activity from ‘Wells’ axes was highest at 35°C even though germination was poor at this temperature. GDH and MDH activities from cotyledons of both cultivars were not correlated with axis weight increases. No GDH activity was detected in ‘Wells’ cotyledons from seeds germinated at 35°C.
Fractionation of leaf proteins by differential centrifugation and gel filtration
Authors: LUNDBORG TOMAS 
Published: April 2006

AbstractThe quantity and quality of fractionated leaf proteins from different plant species were investigated. Leaf extracts (pH range 7.0–8.3) were prepared on a laboratory scale from greenhouse cultivated plants. The proteins were fractionated by differential centrifugation followed by gel filtration. Amaranthus caudatus and Chenopodium quinoa seem favourable for production of non‐green leaf protein concentrates, since the water‐soluble protein comprised nearly 50% of the extracted protein. The chlorophyll‐associated protein in fresh extracts from these species was, however, difficult to sediment. A practical separation of chlorophyll‐associated protein from the chlorophyll‐free proteins will require some kind of pre‐aggregation of the chlorophyll‐associated proteins.In extracts from Dactylis glomerata, Lolium perenne and Vicia sativa a considerable proportion of the extracted protein sedimented rapidly, but at least for the grasses some of the chlorophyll‐associated protein remained in the supernatants even after centrifugation at 30 000 g for 180 min. Practical separation of all the chlorophyll‐associated protein from the extract requires some kind of pre‐aggregation of the chlorophyll‐associated proteins even for these species. The situation was similar for extracts from Helianthus annuus, but a very high percentage of the total chlorophyll‐associated proteins could be sedimented at low centrifugation speed. Brassica oleracea was the most suitable species for the removal of the chlorophyll‐associated proteins by centrifugation alone. Moreover, the proportion of chlorophyll‐free protein in the extracts was relatively high, more than 40%.The in vitro digestibility of membrane‐bound protein fractions was high for species with co‐aggregation of water‐soluble protein and membrane‐bound protein. Causes underlying the different distributions of the chlorophyll‐associated and chlorophyll‐free proteins and the reason for the different size of the chlorophyll‐containing particles are discussed.
Regenerated cell wall of carrot protoplasts isolated from suspension‐cultured cells
Authors: ASAMIZU TETSUYA , NISHI ARASUKE 
Published: April 2006

AbstractProtoplasts of Daucus carota L. cultured in a synthetic liquid medium resumed cell division after about 4 days of cultivation. During this lag period, nucleic acid and protein showed only slight increases but the protoplasts commenced cell‐wall regeneration soon after the removal of lytic enzymes. The originally spherical protoplasts became ellipsoidal before they underwent division. Radioactive glucose and myo‐inositol were readily utilized by the protoplasts. Most of the radioactivity, however, appeared in extracellular polysaccharides and only a small portion was deposited in the regenerated wall. The sugar composition of new cell wall, as studies by chemical analysis and incorporation of labelled precursors, was shown to be considerably different from that of normal cell wall.
No contribution of the pentose phosphate pathway in dormancy‐breaking of cocklebur seeds
Authors: SATOH SHIGERU , ESASHI YOHJI 
Published: April 2006

AbstractThe role of the oxidative pentose phosphate (PP) pathway in the dormancy‐breaking of cocklebur (Xanthium pennsylvanicum Wallr.) seeds was investigated. D‐[1‐14C]‐glucose or D‐[6‐14C]‐glucose was fed to dormant and non‐dormant lower seeds or to their axial or cotyledonary segments which were imbibed for different durations, and C6/C1 ratios of respired 14CO2 as an index of the PP pathway activity were calculated. Contrary to expectation, there was no significant difference in the C6/C1 ratios between the dormant and non‐dormant seeds or segments during a water imbition period of 24 h, although the PP pathway actually operated already in an early stage of water imbibition. Also concerning the activities of G6PDH and 6PGDH, the key enzymes of this pathway, no difference between the dormant and non‐dormant seeds was found. It was thus concluded that, unlike other seeds, there is no contribution of the PP pathway to the regulation of dormancy of the cocklebur seed.
Photophosphorylation in Scenedesmus in vivo: O2 evolution, ATP pools and transients, and phosphate binding during photoreduction of NO3−, NO2− and CO2
Authors: LARSSON C.‐M. 
Published: April 2006

AbstractThe relation between light‐induced electron transport with NO3−, NO2− or CO2 as acceptors, ATP pools and transients in dark‐light‐dark transitions, and phosphate uptake was examined in phosphorus‐starved cells of Scenedesmus obtusiusculus Chod. Net O2 evolution at saturating light was around 6 μmol × (mg chlorophyll × h)−1 in the absence of any acceptor, but reached average rates of 21, 65 and 145 μmol × (mg chlorophyll × h)−1 upon additions of 5 mM KNO3, KNO2 and KHCO3, respectively. The apparent rate of photophosphorylation in transition experiments was only a few percent of the rate calculated from CO2‐dependent O2 evolution. Blocking non‐cyclic electron transport with DCMU inhibited phosphate assimilation, but acceleration of non‐cyclic electron flow by addition of NO3− or NO2− did not stimulate phosphate assimilation as compared to the situation without an acceptor. A functional non‐cyclic system might primarily be needed for an efficient shuttle transfer of ATP from the chloroplast to the cytoplasm. An inhibition of the non‐cyclic system due to lack of reducible substrates accelerates the cyclic system and thus indicates a regulation mechanism between the two systems.
Factors affecting in vivo nitrate reductase activity in triticale
Authors: LIN WEI HO , KAO CHING HUEI 
Published: April 2006

AbstractFactors influencing in vivo nitrate reductase activity in triticale (×Triticosecale Wittmack) primary leaves were investigated. Nitrate reductase activity was found to be a function of reaction time or tissue weight. In the range of 1–10 mm, the optimum slice width for nitrate reductase activity in triticale was found to be 1–2 mm. The optimum exogenous nitrate concentration is 300 mM. Substantial nitrite production was obtained even when exogenous nitrate was omitted from the assay. Of the five low molecular weight organic solvents tested, n‐propanol is the most effective in enhancing enzyme activity. The optimum n‐propanol concentration is 1% (v/v). The concentration of phosphate buffer (pH 6) does not affect nitrate reductase activity. Enzyme activity drops significantly below or above pH 6. In our system, nitrite production is enhanced by incubating under nitrogen, instead of air. The highest level of in vivo activity of nitrate reductase was found to be 10–15 cm from tip, which is close to the basal meristem of triticale primary leaves. Younger but physiologically mature leaves have higher nitrate reductase activity than old leaves.
Photosynthetic studies with mesophyll protoplasts from Notonia grandiflora, a crassulacean acid metabolism plant
Authors: CHELLAPPAN K. P. , SEENI S. , GNANAM A. 
Published: April 2006

AbstractA method is described for rapid enzymatic isolation of mesophyll protoplasts and cells from the crassulacean acid metabolism (CAM) plant Notonia grandiflora DC. The mesophyll protoplasts exhibited high rates of 14CO2 fixation both in the light (45 μmol of CO2 fixed mg−1 Chl h−1) and in the dark (20 μmol of CO2 fixed mg−1 Chl h−1). The protoplasts also showed O2 evolution (40 μmol of O2 evolved mg−1 Chl h−1) without added bicarbonate. Exogenously added bicarbonate had no stimulating effect on the O2 evolution. Analyses of early photosynthetic products in the light showed the formation of both C3 and C4 acids. Aspartate was found to be a predominant photosynthate.
Nitrogen assimilation in citrus trees
Authors: KATO TADASHI 
Published: April 2006

AbstractAssimilation of 15N‐ammonium and 15N‐nitrate was examined in 3‐year‐old satsuma mandarin (Citrus unshiu Marcovitch) trees. Experiments were designed to establish the time course of incorporation of nitrogen just taken up into amino compounds.In fine roots, absorbed 15N‐ammonium was actively incorporated into glutamine and then into glutamic acid and asparagine. When feeding 15N‐nitrate, glutamic acid and asparagine were actively synthesized, but glutamine synthesis was comparatively low as compared with that in ammonium feeding. In current leaves and fruits, a clear difference in the labelling patterns of amino acids was found between the ammonium and nitrate feedings. The amino acid most markedly labelled was asparagine in the ammonium feeding and glutamine in the nitrate feeding. Considering the most heavily labelled component in leaves and fruits, the main form of the nitrogen components transported upward in the xylem was discussed.
Action of the herbicides neburon and siduron on membrane permeabilities in potato tuber mitochondria
Authors: GAUVRIT CHRISTIAN 
Published: April 2006

AbstractThe herbicides neburon and siduron are uncouplers of oxidative phosphorylation in potato tuber (Solanum tuberosum L. cv. Bintje) mitochondria. Their effect on the ion permeabilities of the mitochondrial membrane was investigated using the acid‐base pulse technique, swelling experiments and integrity tests. Both herbicides permeabilize the membrane to H+ ions. They have no action on the permeabilities of K+ and Fe(CN)3−6. The swelling observed with Ca2+ was better interpreted as an effect on membrane structure than as a true swelling. Diuron, a parent compound that does not uncouple oxidative phosphorylation, does not act on Ca2+‐induced apparent swelling.
Coumarin effects on Glycine max hypocotyl explants
Authors: JANSSON EVA , SVENSSON SVEN‐BÖRJE 
Published: April 2006

AbstractCoumarin induced root formation and stimulated fresh weight production in hypocotyl explants of Glycine max L. cultured in vitro. All stimulatory effects caused by coumarin were induced within a relatively narrow range of concentrations between 1–500 μM, yielding optimum dose response curves. When coumarin was combined with kinetin fresh weight increased considerably, at optimum concentrations to a level almost as high as that obtained with NAA (10 μM) and kinetin (10 μM). Root formation was almost completely inhibited when kinetin was added in combination with coumarin. NAA + coumarin had small stimulatory effects on fresh weight. but were inhibitory in root formation. The frequency of rooting per explant, texture and pigmentation were also affected by different treatments.
Effects of artificial frost hardening and winter stress on net photosynthesis, photosynthetic electron transport and RuBP carboxylase activity in seedlings of Pinus silvestris
Authors: ÖQUIST GUNNAR , BRUNES LAILA , HÄLLGREN JAN‐ERIK , GEZELIUS KERSTIN , HALLÉN MONICA , MALMBERG GUNILLA 
Published: April 2006

AbstractNet photosynthesis of seedlings of Pinus silvestris has been measured and compared with the activities of photosynthetic electron transport and extracted RuBP carboxylase. The effects of prolonged frost hardening (photoperiod 8 h, + 3°C) followed by winter stress at subzero temperatures were analysed. There was a parallel effect of frost hardening and winter stress on the photosynthetic properties of both intact seedlings and isolated chloroplast thylakoids. The activity of extracted RuBP carboxylase was less affected by the treatments. In relation to earlier works we conclude that the decay of net photosynthesis in winter climate is determined by the electron transport properties of the chloroplast thylakoids, i.e. by the pool sizes of photosynthetically active plastoquinone.The results of this work justify the definition of two phases in the response of conifers towards autumn and winter climates: I. Frost hardening occurs at temperatures slightly above zero and it does not affect the efficiency of photosynthesis as defined by the quantum yield at rate limiting light absorption. II. Winter stress occurs at subzero temperatures and it is characterized by a suppression of the photosynthetic efficiency as a result of damage within the photosynthetic apparatus.
Effect of growth substances on flowering and sex expression in isolated apical buds of Spinacia oleracea
Authors: ĆULAFIĆ LJUBINKA , NEŠKOVIĆ MIRJANA 
Published: April 2006

AbstractApical buds of Spinacia oleracea L. cv. Matador were isolated from 7‐day‐old vegetative seedlings and grown in sterile culture under inductive long, or non‐inductive short photoperiods. Flowering of isolated apices was inducible in long days in approximately 75% of the plants, and in short days by gibberellin treatment (about 40%) or by raising the temperature to 30–32°C (13%). In long days the percentage of flowering was further increased by gibberellin treatment (up to 90%), while it was unaffected by abscisic acid and was strongly decreased by Amo 1618 (55%). In long days the ratio of male to female plants was near 1. The percentage of female plants in long days was increased by gibberellins, and the percentage of male ones decreased by kinetin; as a consequence, the ratio of male to female plants was lowered to about 0.50 in both cases. Abscisic acid and Amo 1618 had the opposite effect, probably because they decreased the flowering in female plants, so that the sex ratio was shifted to 2.6 and 6.8, respectively. Simultaneous treatment with GA3 reversed the effect of abscisic acid on the sex ratio, but the reversal of the shift to maleness induced by Amo 1618 was only partial.In short days, gibberellins also stimulated the flowering in female plants more than in male. However, when the flowering was induced by higher temperature, most flowering plants were male and kinetin increased their percentage further.The above results have been discussed in terms of different requirements for flowering in male and female plants.
Preferential distribution of excitation energy into photosystem I of desiccated samples of the lichen Cladonia impexa and the isolated lichen‐alga Trebouxia pyriformis
Authors: SIGFRIDSSON BJORN , OQUIST GUNNAR 
Published: April 2006

Abstract The effect of desiccation on distribution of excitation energy between the two photosystems has been studied in the lichen Cladonia impexa Harm., in the green alga Trebouxia pyriformis Archibald, isolated from Cladonia squamosa; and in the non‐lichen green alga Scenedesmus obliquus, strain D3. The method used was to compare the low temperature fluorescence emission of samples equilibrated with air with different humidity prior to freezing in liquid nitrogen.Desiccation of Cladonia and Trebouxia caused a pronounced increase of the height of the far red fluorescence emission band, F 715, over the short wave bands, F685 and F697; the ratio between the two short wave bands remained essentially constant. Upon rewetting, these species regained normal fluorescence emission properties, indicating that they are desiccation‐tolerant. Scenedesmus, which was used as a desiccation intolerant species, also showed an increase of the far red fluorescence band over the two short wave bands upon desiccation, but the original fluorescence spectrum was not restored upon rewetting.These results are interpreted as showing that desiccation of tolerant species such as Cladonia and Trebouxia causes a preferential energy distribution into photosystem I. We tentatively believe that desiccation induces conformational changes within the chloroplast thylakoids, thereby controlling distribution of energy between the two photosystems. Furthermore, this change in energy distribution may be of ecological significance as the mechanism by which desiccated lichens or algae avoid photo‐dynamic destruction of the photosynthetic apparatus when photosynthesis is inhibited under dry conditions. By a preferential distribution of absorbed energy into photosystem I, the organisms avoid the formation of strong, harmful oxidants in photosystem II when photosynthesis is inhibited. It is suggested that β‐carotene associated with the far red‐absorbing chlorophyll a fraction of the reaction center antenna of photosystem I is the final sink for excess excitation energy in dry, desiccation‐tolerant lichens and algae.
Photocontrol of seed germination in the hemiparasite Buchnera hispida (Scrophulariaceae)
Authors: NWOKE F. I. O. , OKONKWO S. N. C. 
Published: April 2006

Abstract Buchnera hispida, a facultative root parasite of grasses and graminaceous crops, has a light requirement for germination. Studies were carried out on the effects of varying photoperiods with or without preceding dark incubation, on seed germination. Buchnera seeds showed long‐day behaviour, since they germinated at all photoperiods including continuous light, and longer photoperiods were more effective in triggering seed germination than shorter photoperiods. Also, effects of red and far‐red light indicated that the phytochrome system is operative in the light‐induced germination of Buchnera.Although dark incubation in water before illumination was not absolutely necessary for germination, it caused the seeds to respond more rapidly to light. The longer the time of the dark incubation the more responsive the seeds were to photoperiod except when 15 min light was given. The effectiveness of a preceding dark incubation in making Buchnera seeds sensitive to rapid light action was completely inhibited at 4°C. This is in agreement with the hypothesis that a reaction partner of the far‐red absorbing form of phytochrome is produced during dark incubation of Buchnera seeds. Such an intermediate has also been reported in some positively photoblastic seeds of non‐parasitic flowering plants.
Photosynthesis in cell suspension cultures of the CAM plant Chamaecereus sylvestrii (Cactaceae)
Authors: SEENI S. , GNANAM A. 
Published: April 2006

Abstract Photosynthetic properties of cell suspension cultures derived from the callus proliferation of cladophyll explants of Chamaecereus sylvestrii Spegazzini were studied. High content of chlorophyll (105–120 μg/g fresh weight), cyanide sensitive O2 uptake and maximal rates of O2 evolution (100–115 μmol/mg Chl x h) and CO2 fixation (130–150 μmol/mg Chl x h) were some of the properties of the exponential phase cells. Determination of the component reactions, viz. photosystems I and II and photophosphorylation of the chloroplasts isolated from the cells, indicated normal development and functioning of the photosynthetic machinery.Studies on the enzymatic reactions as well as the determination of the early products of 14CO2 fixation in light in these cells implicated the operation of both autotrophic and non‐auto‐trophic pathways, the latter being less pronounced. The diurnal oscillation of titratable acidity and malate content found in the intact cladophyll tissues was absent in the cultured cells. Evidences for a rapid and continuous drain of carbon from malate into the citrate and isocitrate components of the TCA cycle via pyruvate after decarboxylation, and then into the amino acid pool are presented. The absence of large vacuoles and the rapid turnover of malate are considered to account for the lack of diurnal fluctuation of organic acide in the cell cultures.