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7422. Effects of calcium leaching on interfacial properties of PVA fibers in cementitious matrix
- Creator:
- Kabele, Petr, Němeček, Jiří, Novák, Luděk, and Kopecký, Luboš
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- calcium leaching, PVA fiber, and cementitious matrix
- Language:
- English
- Description:
- Since fiber reinforced composites are often used in an aggressive environment (bridge decks, drainage pipes etc.), it is necessary to estimate their durability and ability to maintain superior mechanical properties in such conditions. One of microscale mechanisms that has a dominant influence on achieving desirable mesomechanical behavior, such as multiple cracking, is fiber-matrix interfacial bond. In the present study, the effect of calcium leaching on the bond properties and fiber-matrix interfacial one are experimentally investigated. To this end, a series of tests is performed, in which a single fiber is pulled out from cementitious matrix under displacement control. Both chemical and frictional bonds are calculated from the measured load-displacement curves, and the effect of environmental exposure on these parameters is clarified. In order to gain a deeper insight into the microscale mechanical phenomena associated with calcium leaching, the fiber-matrix interfaces of both control and chemically attacked specimens are examined by nanoindentation and ESEM. These experiments show that leaching severely degrades the stiffness of the farther transitional zone. and Obsahuje seznam literatury
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7423. Effects of Cd on photosynthesis and growth of safflower (Carthamus tinctorius L.) genotypes
- Creator:
- Moradi, L. and Ehsanzadeh, P.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- fotosyntéza, photosynthesis, cadmium, chlorophyll, gas exchange, lipid peroxidation, proline, 2, and 581
- Language:
- Multiple languages
- Description:
- Heavy metals such as cadmium (Cd) may affect different physiological functions in plants. We carried out a hydroponic experiment under greenhouse conditions in order to evaluate the effect of Cd on photosynthetic and physiological parameters of safflower. The responses of six safflower genotypes (Nebraska-10, 2811, Kouseh, S149, C111, and K12) to four concentrations of CdCl2 (0, 1.5, 3, and 4.5 mg L-1) were examined. Mean shoot and root dry masses of safflower plants were reduced by nearly 57% after the treatment by 4.5 mg(CdCl2) L-1. Contrary to the mean proline content, which increased by 121%, the mean total leaf area per plant, net photosynthetic rate, stomatal conductance to the CO2, leaf chlorophyll a, b, and (a+b), carotenoid content, and quantum efficiency of PSII decreased by 84.4, 50.5, 50.0, 31.6, 32.2, 31.8, 32.9, and 11.2%, respectively, at the presence of 4.5 mg(CdCl2) L-1. The mean Cd concentration in shoots and roots of safflower genotypes exhibited 52- and 157-fold increase, respectively, due to the addition of 4.5 mg(CdCl2) L-1 to the growing media. The mean malondialdehyde content was enhanced by 110% with the increasing CdCl2 concentration, indicating the occurrence of a considerable lipid peroxidation in the plant tissues. Even though the membrane stability index was adversely affected by the application of 1.5 mg(CdCl2) L-1, the decrease ranged from 45 to 62% when plants were treated with 4.5 mg(CdCl2) L-1. Genotype Nebraska-10 seemed to be different from the remaining genotypes in response to the 4.5 mg(CdCl2) L-1; its net photosynthetic rate tended to be the greatest and the Cd concentration in shoots and roots was the lowest among genotypes studied. This study proved Cd-induced decline in growth, photosynthesis, and physiological functions of safflower., L. Moradi, P. Ehsanzadeh., and Obsahuje seznam literatury
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7424. Effects of chilling temperature on the activity of enzymes of sucrose synthesis and the accumulation of saccharides in leaves of three sugarcane cultivars differing in cold sensitivity
- Creator:
- Du, Yu-Chun and Nose, Akihiro
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- C4 plants, cold temperature, cytosolic fructose-1,6-bisphosphatase, photosynthesis, saccharides, sucrose phosphate synthase, sucrose metabolism, and Saccharum
- Language:
- Multiple languages
- Description:
- The effects of short-term exposure to chilling temperature (10 °C) on sucrose synthesis in leaves of the cold-tolerant sugarcane cultivars Saccharum sinense R. cv. Yomitanzan and Saccharum sp. cv. NiF4, and the cold-sensitive cultivar S. officinarum L. cv. Badila were studied. Plants were grown at day/night temperatures of 30/25 °C, and then shifted to a constant day/night temperature of 10 °C. After 52-h exposure to the chilling temperature, sucrose content in the leaves of NiF4 and Yomitanzan showed a 2.5- to 3.5-fold increase relative to that of the control plants that had been left on day/night temperatures of 30/25 °C. No such increase was observed in Badila leaves. Similarly, starch content in the leaves of NiF4 and Yomitanzan was maintained high, but starch was depleted in Badila leaves after the 52-h exposure. During the chilling temperature, sucrose phosphate synthase (SPS; E.C.2.4.1.14) activity was relatively stable in the leaves of NiF4 and Yomitanzan, whereas in Badila leaves SPS activity significantly decreased. There was no significant change in cytosolic fructose-1,6-bisphosphatase activity for the three cultivars at the chilling temperature. This supports the hypothesis that: (1) on exposure to chilling temperature, sucrose content in sugarcane leaves is determined by the photosynthetic rate in the leaves, and is not related to SPS activity; (2) SPS activity in sugarcane leaves at chilling temperature is to be determined by sugar concentration in the leaves. and Yu-Chun Du, Akihiro Nose.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7425. Effects of chromium toxicity on leaf photosynthetic characteristics and oxidative changes in wheat (Triticum aestivum L.)
- Creator:
- Subrahmanyam, D.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- antioxidants, catalase, ascorbate peroxidase, chlorophyll fluorescence, glutathione reductase, lipid peroxidation, photochemical and non-photochemical quenching, photosystem 2, and superoxide dismutase
- Language:
- Multiple languages
- Description:
- Cr(VI) significantly reduced rates of net photosynthesis and transpiration and of stomatal conductance. Cr(VI) did not affect the Fv/Fm ratio of chlorophyll fluorescence implying that the primary photochemical processes in photosystem 2 were not affected. However, the efficiency of excitation capture by open PS2 centres, in vivo quantum yield of PS2 photochemistry, and electron transport rate were significantly reduced by Cr(VI). The coefficient of photochemical quenching was reduced with a concomitant increase in coefficient of non-photochemical quenching, suggesting reduced demand for ATP and NADPH due to inhibition of CO2 assimilation. Lipid peroxidation was increased by Cr(VI) and the activities of superoxide dismutase and catalase (CAT) were increased. However, the CAT activity was reduced by high Cr(VI) concentration. The activities of ascorbate peroxidase and glutathione reductase were significantly reduced by Cr(VI) treatment.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7426. Effects of clonal integration on photosynthesis of the invasive clonal plant Alternanthera philoxeroides
- Creator:
- Liu, J., He, W. M., Zhang, S. M., Liu, F. H., Dong, M., and Wang, R. Q.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- alligator weed, biological invasions, chlorophyll fluorescence, clonal plants, net photosynthetic rate, photosystem 2, nutrient heterogeneity, stomatal conductance, sub-stomatal CO2 concentration, and transpiration rate
- Language:
- Multiple languages
- Description:
- A greenhouse experiment examined whether clonal integration improves photosynthesis of ramets of alligator weed [Alternanthera philoxeroides (Mart.) Griseb.], a widespread invasive clonal plant in China, in heterogeneous (He) nutrient habitats. The connected pairs of ramets experienced different nutrient levels [high homogeneous (Ho) nutrient, low Ho nutrient, and two He nutrient treatments]. Clonal integration significantly improved the net photosynthetic rate, stomatal conductance, transpiration rate, and minimal and maximal chlorophyll fluorescence of ramets of alligator weed in low nutrient condition. These characteristics may contribute to the success of the ramets of alligator weed in invading contrasting habitats. The clonal integration of the invasive clonal plants may contribute significantly to their invasiveness. and J. Liu ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7427. Effects of CO2 on growth and photosynthesis of Pyrrosia piloselloides (L.) Price gametophytes
- Creator:
- Ong, Bee-Lian, Koh, C. K.-K., and Wee, Yeow-Chin
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- chlorophyll, dry mass, fern, respiration, spore germination, and sporophyte
- Language:
- Multiple languages
- Description:
- The effects of CO2 concentration on spore germination, growth, and net photosynthetic rate (PN) of gametophytes of a tropical epiphytic fern, Pyrrosia piloselloides, were investigated over a 100-d period. Increasing CO2 concentration stimulated spore germination and enhanced gametophytic growth. The appearance of sexual organs and formation of sporophytes were accelerated with higher CO2 during growth. Radiant energy saturated PN and dark respiration rate also increased with increasing CO2 concentrations during growth. and Bee-Lian Ong, C. K-K. Koh, Yeow-Chin Wee.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7428. Effects of cold-hardening on chilling-induced photoinhibition of photosynthesis and on xanthophyll cycle pigments in sweet pepper
- Creator:
- Liu, Peng, Meng, Qing-wei, Zou, Qi, Zhao, Shi-jie, and Liu, Qing-zhong
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- acclimation, antheraxanthin, Capsicum annuum, chlorophyll fluorescence, neoxanthin, violaxanthin, and zeaxanthin
- Language:
- Multiple languages
- Description:
- Two cultivars of Capsicum annuum L. were acclimated for 5 d at sub-optimal temperature (14 °C) and irradiance of 250 µmol m-2 s-1. This cold-hardening resulted in some reduction in the extent of photoinhibition during an 8 h exposure to high irradiance at 4 °C. Obvious differences were observed between non-hardened leaves (NHL) and cold-hardened leaves (CHL) in the recovery under low irradiance at room temperature. The CHL of both cultivars recovered faster than NHL, especially during the initial fast phase of recovery. Compared with NHL, the total content of carotenoids (Cars), based on chlorophyll, Chl (a+b), and the proportions of xanthophyll cycle pigments referred to total Cars increased in CHL, mainly due to an increase of violaxanthin (V) + antheraxanthin (A) + zeaxanthin (Z) content per mol Chl (a+b). Faster development and a higher non-photochemical quenching (NPQ) of Chl fluorescence, related to a stronger deepoxidation of the larger xanthophyll cycle pool in NHL, could act as a major defence mechanism to reduce the formation of reactive oxygen species during severe chilling. This is suggested by higher content of Z or Z+A in photoinhibition as well as by its rapid decline during the initial fast phase of recovery. In contrast to the chilling-sensitive cv. 0004, the chilling-tolerant cv. 1141 did more easily acclimate its photosynthetic apparatus to low temperatures. and Peng Liu ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7429. Effects of copper and cadmium on photosynthesis in cucumber cotyledons
- Creator:
- Burzyński, M. and Żurek, A.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- chlorophyll content and fluorescence, dithiothreitol, gas exchange, glyceraldehyde-3-phosphate dehydrogenase, 3-phosphoglyceric acid kinase, and stomatal conductance
- Language:
- Multiple languages
- Description:
- The effects of 20 and 50 µM concentrations of Cu and Cd on photosynthesis in cucumber (Cucumis sativus L.) cotyledons were studied by the measurements of gas exchange characteristics, chlorophyll (Chl) fluorescence parameters, photosynthetic pigment contents, and two Calvin cycle enzymes activities: glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and 3-phosphoglyceric acid kinase (PGK). To minimize indirect metal action, seedlings were treated with metals in the stage of green, fully developed cotyledons. The metals reached the cotyledon tissue after 48 h of treatments, though symptoms of metal action were not visible at that time. The effect of metals on the light phase of the photosynthesis parameters such as potential efficiency of photosystem 2 (PS2; Fv/Fm), and photochemical and nonphotochemical quenching of Chl fluorescence (qP and qNP) was negligible. In contrast, a decrease of PS2 quantum efficiency (ΦPS2) was much more noticeable. Changes in the pigment contents were slight, as only 50 µM Cd decreased Chl a and b contents in small extent. On the contrary, metals in both concentrations drastically decreased (50 and more % of control) the net photosynthetic rate and the stomatal conductance, but not the internal CO2 concentration. The activities of both GAPDH and PGK were also decreased by metals, although the effect on PGK was more prominent, particularly on its potential activity (dithiothreitol in extraction and incubation media). Hence Cu and Cd affected the synthesis of enzyme proteins rather than they influenced their modifications. The effects of both metals on most of the measured photosynthesis parameters were similar, but the accumulation of Cd in the cotyledons was significantly higher than Cu accumulation. Thus Cu was more toxic for the photosynthesis of cucumber cotyledons than Cd. and M. Burzyński, A. Żurek.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7430. Effects of diet and age on oxidative damage products in healthy subjects
- Creator:
- Marica Krajčovičová-Kudláčková, Valachovičová, M., Pauková, V., and Mária Dušinská
- Format:
- print, bez média, and svazek
- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, patologie, oxidační stres, výživa člověka, věk, pathology, oxidative stress, human nutrition, age, antioxidative vitamins, 14, and 612
- Language:
- English
- Description:
- Damage of molecules as a consequence of oxidative stress has been implicated in the pathogenes is of chronic diseases related to aging. Diet is a key environmental factor affecting the incidence of many chronic diseases. Antioxidant substances in diet enhance the DNA, lipid and protein protection by increasing the scavenging of free radicals. Products of oxidative damage of DNA (DNA strand breaks with oxidized purines or oxidized pyrimidines), lipids (conjugated dienes of fatty acids) and proteins (carbonyls) in relation to nutrition (vegetarian diet vs. non-vegetarian, traditional mixed diet) were measured in young women aged 20-30 years (46 vegetarians, 48 non-vegetarians) vs. older women aged 60-70 years (33 vegetarians, 34 non-vegetarians). In young subjects, no differences in values of oxidative damage as well as plasma values of antioxidative vitamins (C, β-carotene) were observed between vegetarian and non-vegetarian groups. In older vegetarian group significantly reduced values of DNA breaks with oxidized purines, DNA breaks with oxidized pyrimidines and lipid peroxidation and on the other hand, significantly increased plasma values of vitamin C and β-carotene were found compared to the respective non-vegetarian group. Significant age dependences of measured parameters (increase in all oxidative damage products and decrease in plasma vitamin concentrations in older women) were noted only in non-vegetarians. Vegetarian values of older women vs. young women were similar or non-significantly changed. The results suggest that increase of oxidative damage in aging may be prevented by vegetarian nutrition., M. Krajčovičová-Kudláčková, M. Valachovičová, V. Pauková, M. Dušinská., and Obsahuje bibliografii a bibliografické odkazy
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public