Leaf respiration (R L) of evergreen species co-occurring in the Mediterranean maquis developing along the Latium coast was analyzed. The results on the whole showed that the considered evergreen species had the same R L trend during the year, with the lowest rates [0.83 ± 0.43 μmol(CO2) m-2 s-1, mean value of the considered species] in winter, in response to low air temperatures. Higher R L were reached in spring [2.44 ± 1.00 μmol(CO2) m-2 s-1, mean value] during the favorable period, and in summer [3.17 ± 0.89 μmol(CO2) m-2 s-1] during drought. The results of the regression analysis showed that 42% of R L variations depended on mean air temperature and 13% on total monthly rainfall. Among the considered species, C. incanus, was characterized by the highest R L in drought [4.93 ± 0.27 μmol(CO2) m-2 s-1], low leaf water potential at predawn (Ψpd = -1.08 ± 0.18 MPa) and midday (Ψmd = -2.75 ± 0.11 MPa) and low relative water content at predawn (RWCpd = 80.5 ± 3.4%) and midday (RWCmd = 67.1 ± 4.6%). Compared to C. incanus, the sclerophyllous species (Q. ilex, P. latifolia, P. lentiscus, A. unedo) and the liana (S. aspera), had lower R L [2.72 ± 0.66 μmol(CO2) m-2 s-1, mean value of the considered species], higher RWCpd (91.8 ± 1.8%), RWCmd (82.4 ± 3.2%), Ψpd (-0.65 ± 0.28 MPa) and Ψmd (-2.85 ± 1.20 MPa) in drought. The narrow-leaved species (E. multiflora, R. officinalis, and E. arborea) were in the middle. The coefficients, proportional to the respiration increase for each 10°C rise (Q10), ranging from 1.49 (E. arborea) to 1.98 (A. unedo) were indicative of the different sensitivities of the considered species to air temperature variation., R. Catoni, L. Varone, and L. Gratani., and Obsahuje bibliografii
Young leaves of tropical trees frequently appear red in color, with the redness disappearing as the leaves mature. During leaf expansion, plants may employ photoprotective mechanisms to cope with high light intensities; however, the variations in anthocyanin contents, nonphotochemical quenching (NPQ), and photorespiration during leaf expansion are poorly understood. Here, we investigated pigment contents, gas exchange, and chlorophyll (Chl) fluorescence in Woodfordia fruticosa leaves during their expansion. Young red leaves had significantly lower Chl content than that of expanding or mature leaves, but they accumulated significantly higher anthocyanins and dissipated more excited light energy through NPQ. As the leaves matured, net photosynthetic rate, total electron flow through PSII, and electron flow for
ribulose-1,5-bisphosphate oxygenation gradually increased. Our results provided evidence that photorespiration is of fundamental importance in regulating the photosynthetic electron flow and CO2 assimilation during leaf expansion., S.-B. Zhang, J.-L. Zhang., and Obsahuje seznam literatury
Net photosynthetic rate (PN), transpiration rate (E), and stomatal conductance (gs) in an adult oil palm (Elaeis guineensis) canopy were highest in the 9th leaf and progressively declined with leaf age. Larger leaf area (LA) and leaf dry mass (LDM) were recorded in middle leaves. PN showed a significant positive correlation with gs and a negative relationship with leaf mass per area (ALM). The oil palm leaf remains photosynthetically active for a longer time in the canopy which contributes significantly to larger dry matter production in general and greater fresh fruit bunch yields in particular. and K. Suresh, C. Nagamani.
Modern tomato (Solanum lycopersicum L.) breeding has mainly focused on increasing productivity under unlimited watering. In contrast, some Mediterranean accessions have been traditionally cultivated under water shortage and selected on the basis of their water-use efficiency (WUE). Ramellet and Penjar landraces were planted with other traditional, old and modern inbreeds, under full irrigation. In order to found differences between the tomato accessions, gas-exchange and leaf morphology measurements were performed. Despite high variability, Ramellet and Penjar presented clear differences compared to modern cultivars, mostly related to leaf morphology and photosynthetic traits, while no differences were found in WUE. Results highlighted that better leaf CO2 conductance might be a main factor determining the improvement of net CO2 assimilation and WUE., M. Fullana-Pericàs, M. À. Conesa, S. Soler, M. Ribas-Carbó, A. Granell, J. Galmés., and Obsahuje bibliografii
Paper deals with derivation of mathematical relationships of dry friction force versus relative velocity in friction contact of two bodies. It is focused on such main types of dry friction characteristics, which frequently occur in dynamic mechanical systems. New models of modified Coulomb friction law and spring - friction elements are determined. For easy application in computing programs used in technical practice and based on linear equations, the equivalent linear stiffness and damping expressions are formulated and analysed in detail. and Obsahuje seznam literatury
Present study investigated the effect of red wine polyphenolic compounds (ProvinolsTM) on blood pressure (BP), nitric oxide synthase (NOS) activity and vascular function in Wistar-Kyoto (WKY) rats exposed to chronic social stress produced by crowding. Adult male rats were divided into four groups: control (480 cm2/rat), ProvinolsTM-treated (20 mg/kg/day, 480 cm2/rat), crowded (200 cm2/rat) and crowded treated with Provinols
TM (20 mg/kg/day, 200 cm2/rat) for 8 weeks. No differences in BP were observed among the groups at the end of experiment, however, reduced BP was observed in ProvinolsTM-treated rats after 3 weeks of treatment. NOS activity in the aorta was significantly elevated in crowded rats, while ProvinolsTM alone had no effect on nitric oxide (NO) production. Acetylcholine-induced relaxation of the femoral artery was significantly improved in stressed and ProvinolsTM-treated rats vs. control, without significant changes in their noradrenaline-induced vasoconstriction. Interestingly, ProvinolsTM blunted the elevation of NO production and vasorelaxation during crowding. Increased endothelium-dependent vasorelaxation and NO synthesis in crowded rats may represent the adaptation mechanisms, resulting in unaltered blood pressure in stress-exposed normotensive rats. This study further demonstrated that elevated release of NO during chronic stress may be prevented by ProvinolsTM. Thus, Provino TM might maintain equilibrium between endothelium-derived vasoconstrictor and vasodilator factors in stress.
The purpose of this study was to determine the role of lipotoxicity in vascular smooth muscle (VSM). C1-BODIPY 500/510 C12 used to assess the ability of VSM A7r5 cells to transport long-chain fatty acids showed that lipid transport did not appear to limit metabolism. Thin layer chromatography revealed that storage of transported fatty acid occurred primarily as mono- and diglycerides and fatty acids but not as triglycerides. We used lipid-induced apoptosis as a measure of lipotoxicity and found that 1.5 mM palmitate (6.8:1) bound to albumin resulted in a 15-fold increase in the number of apoptotic cells compared to the control at 24 hours. This apoptosis did not seem to be due to an increase in reactive oxygen species (ROS) since VSM cells incubated in palmitate showed less ROS production than cells incubated in albumin only. Similar exposure to oleate did not significantly increase the number of apoptotic cells compared to the control. Oleate actually significantly attenuated the apoptosis induced by palmitate, suggesting that unsaturated fatty acids have a protective effect on cells undergoing palmitate-induced apoptosis. These results suggest that vascular smooth muscle is vulnerable to lipotoxicity and that this lipotoxicity may play a role in the development of atherosclerosis., H. M. Mattern, C. D. Hardin., and Obsahuje bibliografii a bibliografické odkazy
The effect of long-term inhibition of nitric oxide synthase on the relaxation and contraction ability of the thoracic aorta, carotid and pulmonary arteries was studied in the early postnatal period. Starting from the fifth day after birth, puppies were administered NG-nitro-L-arginine methyl ester (L-NAME, 50 mg/kg/day subcutaneously) for 6 weeks. After this period, mean blood pressure increased from the control value of 94±14 mm Hg to 168±5 mm Hg (P<0.01) and the heart/body weight ratio from 6.22±0.25 to 8.23±0.45 (PcO.Ol). In control arterial rings precontracted by phenylephrine (10“5 mol/1), acetylcholine caused dose-dependent relaxations; the maximal values were reached in the range of 10 "8 to 10"* mol/1. In arteries from L-NAME treated puppies, acetylcholine also induced dose-dependent relaxations, the maximum values in the thoracic aorta (81.0±2.9 %) and carotid artery (87.2±6.9 %) were significantly reduced, not, however, in the pulmonary artery (76.4±7.8 %). Dose-response curves to acetylcholine in all the examined arteries from L-NAME-treated animals were shifted to the right indicating a decrease in sensitivity to acetylcholine. Neurogenic contractions, induced by electrical stimulation of adrenergic nerves, were not significantly altered in the thoracic aorta and carotid artery. However, in the pulmonary artery the contractions were greater at high frequency of stimulation. The findings that (i) submaximal doses of L-NAME attenuate acetylcholine-induced relaxation only slightly, and (ii) that it does not appreciably influence adrenergic contractions justify the hypothesis that the endothelium of vessels in newborn dogs is very probably endowed with a high content of nitric oxide synthase.