During batch culture of Haslea ostrearia the highest carbon (14C) fixation rate was found in vivo in cells that did not accumulate the blue pigment marennine (green form). This fixation rate decreased concomitantly with the accumulation of marennine. In vitro, no phosphoenolpyruvate carboxylase (PEPC) activity was detected, but nearly equivalent activities of ribulose-1,5-bisphosphate carboxylase (RuBPC) and phosphoenolpyruvate carboxykinase (PEPCK) were found in the green form. However, the activity of RuBPC was lower than that of PEPCK during marennine accumulation. In vitro carboxylase activities were strongly inhibited by the addition of a marennine extract. A full description of this inhibition could not be confirmed within the cells because marennine accumulates in small cytoplasmic vesicles. and G. Tremblin, J.-M. Robert.
The neotropical genus Clusia comprises arborescent species exhibiting Crassulacean Acid Metabolism (CAM) as was first reported for a Mexican species, Clusia lundellii. Here, the occurrence of CAM photosynthesis was studied in 20 species of Clusia, 18 from Mexico, and 2 from Guatemala, using leaf carbon isotopic composition. In most species, samples from individuals collected in different locations were analyzed. CAM was present in at least 11 species, eight of which contained specimens with δ13C values less negative than -20.0 ‰, indicating strong CAM (C. chanekiana, C. flava, C. lundellii, C. mexicana, C. quadrangula, C. rosea, C. suborbicularis, and C. tetra-trianthera). δ13C was highly variable in some species, but CAM expression was not correlated to life form (epiphytic, hemiepiphytic, terrestrial) or habitat. CAM specimens were not collected at altitudes above 1 700 m a.s.l. and J. G. Vargas-Soto, J. L. Andrade, K. Winter.
Isotope screening is a simple test for determining the photosynthetic pathway used by plants. The scope of this work was to classify the photosynthetic type of some herbs and medicinal plants through studies of the carbon isotope composition (δ13C). Also, we propose the use of carbon isotope composition as a tool to control the quality of herbs and medicinal plants. For studies of δ13C, δ13C‰ = [R (sample)/R (standard) - 1] × 10-3, dry leaves powdered in cryogenic mill were analyzed in a mass spectrometer coupled with an elemental analyzer for determining the ratio R = 13CO2/12CO2. In investigation of δ13C of 55 species, 23 botanical families, and 44 species possessed a C3 photosynthetic type. Six species found among the botanical families Euphorbiaceae and Poaceae were C4 plants, and 5 species found among the botanical families Agavaceae, Euphorbiaceae, and Liliaceae possessed CAM-type photosynthesis. Carbon isotope composition of plants can be used as quality control of herbs and medicinal plants, allowing the identification of frauds or contaminations. Also, the information about the photosynthetic type found for these plants can help in introducing and cultivating exotic and wild herbs and medicinal plants. and J. A. Marchese ... [et al.].
We investigated the carbon isotope ratios and the diurnal pattern of malate accumulation in leaves and aerial roots of eight species of Phalaenopsis grown in greenhouses. The leaves of all the species showed carbon isotope ratios and the diurnal patterns of malate content typical of CAM plants. However, the aerial roots exhibited a large variation in the diurnal pattern of malate content among species and even among plants within the same species, although carbon isotope ratios were always CAM-like values. Some aerial roots showed the typical diurnal pattern of CAM, but others maintained high or low malate contents during a day without fluctuation. In order to characterize more strictly the nature of the malate variation in the aerial roots, we further investigated a possible variation of the diurnal pattern of malate among different aerial roots within an individual for Phalaenopsis amabilis and P. cornu-cervi. The diurnal pattern of malate content was varied even among different aerial roots within the same plant. Thus the photosynthetic carbon metabolism in aerial roots of orchids is fairly complex. and H. Motomura ... [et al.].
Plants of cassava (Manihot esculenta Crantz) were raised in a sand root medium watered with nutrient solutions, under greenhouse conditions. As the N-supply increased, shoot dry mass was enhanced to a greater extent than root dry mass, thus leading to an increased shoot to root ratio. In leaves, contents of total soluble saccharides, non-reducing saccharides, and inorganic phosphate increased linearly with increasing N-supply. An opposite response was found for reducing saccharides and starch. In general, content of non-reducing saccharides was considerably greater than starch content. Activity of sucrose synthase was not detected, regardless of the N-treatments; by contrast, activity of neutral and acid invertases increased with increasing N-availability. Roots accumulated more total soluble saccharides, but less reducing saccharides and starch, as the N-supply increased. Photosynthetic rates decreased with increasing N-deficiency. Such a decrease was circumstantially associated to reducing saccharide, but not starch, accumulation. Results suggest a limited capacity for carbon export from source leaves under N-limitation. and J. L. Cruz ... [et al.].
Carbonic anhydrase (CA) is a metalloenzyme that performs interconversion between CO2 and the bicarbonate ion (HCO3-). CAs appear among all taxonomic groups of three domains of life. Wide spreading of CAs in nature is explained by the fact that carbon, which is the major constituent of the enzyme’s substrates, is a key element of life on the Earth. Despite the diversity of CAs, they all carry out the same reaction of CO2/HCO3- interconversion. Thus, CA obviously represents a universal enzyme of the
carbon-based life. Within the classification of CAs, here we proposed the existence of an extensive family of CA-related proteins (γCA-RPs) - the inactive forms of γ-CAs, which are widespread among the Archaea, Bacteria, and, to a lesser extent, in Eukarya. This review focuses on the history of CAs discovery and integrates the most recent data on their classification, catalytic mechanisms, and physiological roles at various organisms., E. Kupriyanova, N. Pronina, D. Los., and Obsahuje bibliografii
The review incorporates recent information on carbonic anhydrase (CA, EC: 4.2.1.1) pertaining to types, homology, regulation, purification, in vitro stability, and biological functions with special reference to higher plants. CA, a ubiquitous enzyme in prokaryotes and higher organisms represented by four distinct families, is involved in diverse biological processes, including pH regulation, CO2 transfer, ion exchange, respiration, and photosynthetic CO2 fixation. CA from higher plants traces its origin with prokaryotes and exhibits compartmentalization among their organs, tissues, and cellular organelles commensurate with specific functions. In leaves, CA represents 1-20 % of total soluble protein and abundance next only to ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) in chloroplast, facilitating CO2 supply to phosphoenol pyruvate carboxylase in C4 and CAM plants and RuBPCO in C3 plants. It confers special significance to CA as an efficient biochemical marker for carbon sequestration and environmental amelioration in the current global warming scenario linked with elevated CO2 concentrations. and A. Tiwari ... [et al.].
The leaves of 30-d-old plants of Brassica juncea Czern & Coss cv. Varuna were sprayed with 10-6 M aqueous solutions of indole-3-yl-acetic acid (IAA), gibberellic acid (GA3), kinetin (KIN), and abscisic acid (ABA) or 10-8 M of 28-homobrassinolide (HBR). All the phytohormones, except ABA, improved the vegetative growth and seed yield at harvest, compared with those sprayed with deionised water (control). HBR was most prominent in its effect, generating 32, 30, 36, 70, 25, and 29 % higher values for dry mass, chlorophyll content, carbonic anhydrase (E.C. 4.2.1.1) activity, and net photosynthetic rate in 60-d-old plants, pods per plant, and seed yield at harvest, over the control, respectively. The order of response to various hormones was HBR > GA3 > IAA > KIN > control > ABA. and S. Hayat ... [et al.].
The contrasting pattern of cardiac inotropy induced by human peptide endothelin-1 (ET-1) has not been satisfactorily explained. It is not clear whether ET-1 is primarily responsible for increased myocardial ET-1 expression and release with resultant inotropic effects, or for the induction of myocardial hypertrophy and heart failure. There are at least two subtypes of endothelin receptors (ETA and ETB) and the inotropic effects of ET-1 differ depending on the receptor involved. Along with some other groups, we reported significant subtype-ETB endothelin receptor down-regulation in human cardiac cells preincubated with endothelin agonists (Dřímal et al. 1999, 2000). The present study was therefore designed to clarify the subtype-selective mechanisms underlying the inotropic response to ET-1 and to its ETB-selective fragment (8-21)ET-1 in the isolated rat heart. The hearts were subjected to (1-21)ET-1 and to (8-21)ET-1, or to 30 min of stop-flow ischemia followed by 40 min of reperfusion, both before and after selective blockade of endothelin receptors.The present study revealed that both peptides, ET-1 and its (8-21)ET-1 fragment, significantly reduced coronary blood flow in nmolar and higher concentrations. The concomitant negative inotropy and chronotropy were marked after ET-1, while the infusion of the ET-1(8-21) fragment produced a slight but significant positive inotropic effect. Among the four endothelin antagonists tested in continuous infusion only the non-selective PD145065 and ETB1/B2-selective BQ788 (in mmolar concentrations) slightly reduced the early contractile dysfunction of the heart induced by ischemia, whereas ETA-selective PD155080 partially protected the rat heart on reperfusion., J. Dřímal, V. Knezl, J. Dřímal Jr , D. Dřímal, K. Bauerová , V. Kettmann, A.M. Doherty , M. Štefek., and Obsahuje bibliografii