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222. Příběh zvaný cytokinin
- Creator:
- Marina Hužvárová
- Format:
- print, bez média, and svazek
- Type:
- article, rozhovory, model:article, and TEXT
- Subject:
- Věda. Všeobecnosti. Základy vědy a kultury. Vědecká práce, Strnad, Miroslav, 1958-, fyziologie rostlin, experimentální biologie, botanika, fyziologové, plant physiology, experimental biology, botany, physiologists, Česko, Czechia, 12, and 00
- Language:
- Czech
- Description:
- Small molecules that regulate the cell division cycle are a joint research project of the CAS Institute of Experimental Botany and Palacký University’s Faculty of Science. An interview with Professor Miroslav Strnad, head of the Laboratory of Growth Regulations, describes the significance of this joint project. The laboratory concentrates its research on small molecules that regulate cell division cycle, proliferation and growth of both plant and animal cells. Cytokinins and cytokinin-derived purine inhibitors of cyclindependent kinases are the most intensively studied compounds. The multidisciplinary research team is composed of experienced plant physiologists, biochemists and organic and analytical chemists. Many students are involved in the research phase during their pre-graduate and postgraduate studies in botany, analytical and organic chemistry, biochemistry or medicinal biology. Several research projects are in progress in collaboration with international partners (University of Berlin; Swedish University of Agricultural Sciences; University of Natal Pietermaritzburg, South Africa and the Vienna Medical University. and Marina Hužvárová.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
223. PsbO, PsbP, and PsbQ of photosystem II are encoded by gene families in Nicotiana benthamiana. Structure and functionality of their isoforms
- Creator:
- Pérez-Bueno, M. L., Barón, M., and García-Luque, I.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- botanika, botany, oxygen-evolving complex, photosystem II, PsbO, PsbP, PsbQ, and stress
- Language:
- Multiple languages
- Description:
- The extrinsic proteins of photosystem II in plants (PsbO, PsbP and PsbQ) are known to be targets of stress. In previous work, differential regulation of hypothetical isoforms of these proteins was observed in Nicotiana benthamiana upon viral infection. Each of these proteins is encoded by a multigene family in this species: there are at least four genes encoding PsbO and PsbP and two encoding PsbQ. The results of structural and functional analyses suggest that PsbO and PsbP isoforms could show differences in activity, based on significant substitutions in their primary structure. Two psbQ sequences were isolated which encode identical mature proteins. and M. I. Pérez-Bueno ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
224. Quantifying the measurement errors in a portable open gas-exchange system and their effects on the parameterization of Farquhar et al. model for C3 leaves
- Creator:
- Wang, Q., Fleisher, D. H., Timlin, D., Reddy, V. R., and Chun, J. A.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- botanika, botany, open gas-exchange system, measurement errors, parameterization, leaf model, photosynthesis, transpiration, 2, and 58
- Language:
- Multiple languages
- Description:
- A portable open gas-exchange system (Li-6400, Li-Cor, Inc., Lincoln, NE, USA) has been widely used for the measurement of net gas exchanges and calibration/parameterization of leaf models. Measurement errors due to diffusive leakage rates of water vapor (LW) and CO2 (LC) between inside and outside of the leaf chamber, and the inward dark transpiration rate (DW) and dark respiration rate (DC) released from the leaf under the gasket, can be significant. Rigorous model-based approaches were developed for estimating leakage coefficients of water vapor (KW) and CO2 (KC) and correcting for the combination of these errors. Models were based on mass balance equations and the Dusty Gas Model for a ternary gas mixture of water vapor, CO2, and dry air. Experiments were conducted using two Li-6400 systems with potato and soybean leaves. Results indicated that models were reliable for estimating KW and KC, and the values varied with instrument, chamber size, gasket condition, and leaf structure. A thermally killed leaf should be used for this determination. Measurement error effects on parameterization of the Farquhar et al. (1980) model as determined by PN/C i curves were substantial and each parameter had its own sensitivity to measurement errors. Results also indicated that all four error sources should be accounted for when correcting measurements., Q. Wang ... [et al.]., and Obsahuje bibliografii a dodatky
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
225. Reduced nitrogen allocation to expanding leaf blades suppresses ribulose-1,5-bisphosphate carboxylase/oxygenase synthesis and leads to photosynthetic acclimation to elevated CO2 in rice
- Creator:
- Seneweera, S.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- botanika, botany, elevated CO2, photosynthesis, ribulose-1,5-bisphosphate carboxylase/oxygenase, rice, and spatial nitrogen deposition
- Language:
- Multiple languages
- Description:
- Net photosynthetic rate (PN) measured at elevated CO2 concentration (Ce), ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), and nitrogen (N) content in rice leaves decreased significantly after exposure to long term Ce. The reduction in PN, Rubisco, and leaf N at Ce was similar for the last fully expanded leaf blade (LFELB) and expanding leaf blade (ELB). Spatial leaf N content in the ELB was highest in the zone of cell division, sharply declined as cell expansion progressed and gradually increased with cell maturation. Maximum reduction in spatial leaf N and Rubisco content was found at Ce only within cell expansion and maturation zones. The spatial leaf N content correlated well with the amount of Rubisco synthesized during leaf expansion, suggesting that N deposition into the expanding leaf blade may be the key for Rubisco synthesis and possibly photosynthetic acclimation to Ce. and S. Seneweera.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
226. Relationship between acorn size and seedling morphological and physiological traits of Quercus ilex L. from different climates
- Creator:
- Bonito, A., Varone, L., and Gratani, L.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- botanika, botany, acorn size, gas exchange, predawn leaf water potential, relative growth rate in height, relative water content at predawn, and total leaf area
- Language:
- Multiple languages
- Description:
- Effects of Quercus ilex acorn size on seedling morphological and physiological traits were analysed. The study was carried out with five populations from different geographical areas and covering an aridity gradient. Seedling morphological traits (height and total leaf area) were analyzed during the first growing year. Physiological traits (net photosynthesis, stomatal conductance, leaf transpiration, and intrinsic water-use efficiency) were analysed at different air temperatures during spring, summer, and winter months, and in response to water stress. There were significant correlations among the considered acorn (volume, fresh mass) and seedling traits. Differences in growth and physiological traits among the considered populations were found. The larger differences in the growth parameters were observed during the first growing season, and they could be justified by the significant differences among acorn size. On the contrary, the physiological response to air temperature and aridity was more related to the geographical origin of the considered populations than to acorn size. Q. ilex acorn and seedling traits more tolerant to drought might have a high potential for vegetation recovery in afforestation projects and restoration programmes particularly under water-limited environments or in degraded areas. and A. Bonito ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
227. Relationships between gas-exchange characteristics and stomatal structural modifications in some desert grasses under high salinity
- Creator:
- Naz, N., Hameed, M., Ashraf, M., Al-Qurainy, F., and Arshad, M.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- botanika, botany, desert grasses, stamatal regulation, stamatal structural modifications, transpiration rate, and water-use efficiency
- Language:
- Multiple languages
- Description:
- Two populations, one from lesser saline Derawar Fort (DF) and the other from highly saline Ladam Sir (LS) in the Cholistan desert, for each of the five grass species, Aeluropus lagopoides, Cymbopogon jwarancusa, Lasiurus scindicus, Ochthochloa compressa, and Sporobolus ioclados were examined to investigate the influence of salinity on structural and functional characteristics of stomata. Salinity tolerance in A. lagopoides mainly depended on controlled transpiration rate (E) and high water-use efficiency (WUE), which was found to be regulated by fewer and smaller stomata on both leaf surfaces as well as stomatal encryption by epidermal invaginations. C. jwarancusa had sunken stomata on the abaxial surface only, which largely reflected a reduced E, but less affected stomatal conductance (gs) or WUE. L. scindicus had fewer but larger stomata along with hairs/trichomes which may function to avoid water loss through transpiration, and hence, to attain a high WUE. In O. compressa stomata were found only on the abaxial surface and these were completely encrypted by epidermal invaginations as well as a dense covering of microhairs, which was associated with a low E and high WUE under salinity stress. In S. ioclados, the traits of increased stomatal density and decreased stomatal area may be critical for stomatal regulation under salt-prone environments. High stomatal regulation depended largely on stomatal density, area, and degree of encryption under salinity, which is of great ecophysiological significance for plants growing under osmotic stresses. and N. Naz ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
228. Resistance of spinach plants to seawater stress is correlated with higher activity of xanthophyll cycle and better maintenance of chlorophyll metabolism
- Creator:
- Sun, J., Jia, X. Y., Guo, S. R., Li, J., and Shu, S.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- botanika, botany, chlorophyll metabolism, photoinhibition, seawater, spinach, and xanthophyll cycle
- Language:
- Multiple languages
- Description:
- The relationship between the activity of xanthophyll cycle and chlorophyll (Chl) metabolism was investigated using two cultivars, Helan No. 3 (seawater-tolerant cultivar) and Yuanye (seawater-sensitive cultivar), of spinach (Spinacia oleracea L.) plants cultured in Hoagland's nutrient solution, with or without seawater (40%). The results showed that, in plants of two cultivars with seawater, the xanthophyll cycle seems to show a principal protection mechanism against photoinhibition under seawater stress. Furthermore, accumulation of reactive oxygen species (ROS) in chloroplasts of two cultivars was enhanced by seawater to lower the activity of porphobilinogen deaminase. Namely, the conversion of porphobilinogen into uroporphyrinogen III involved in Chl biosynthetic processes was inhibited by seawater. In Helan No. 3 spinach plants with seawater, higher activity of xanthophyll cycle in the leaves dissipated more excess light energy, which appeared to lower the levels of ROS in chloroplasts. As a consequence, the Chl biosynthesis in Helan No. 3 leaves with seawater showed only a weak inhibition and the activity of chlorophyllase (Chlase) was not affected by seawater stress. In contrast, a more pronounced accumulation of ROS in chloroplasts of Yuanye leaves, which possess lower xanthophyll cycle activity, severely inhibited Chl biosynthesis and remarkably enhanced the activity of Chlase, which aggravates the decomposition of Chl. These results suggest that higher activity of xanthophyll cycle in seawater-tolerant spinach plays a role in maintaining Chl metabolic processes, probably by decreasing the levels of ROS, when the plants are cultured in the nutrient solution with seawater (40%). and J. Sun ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
229. Responses in the physiology and biochemistry of Korean pine (Pinus koraiensis) under supplementary UV-B radiation
- Creator:
- Zu, Y. G., Wei, X. X., Yu, J. H., Li, D. W., Pang, H. H., and Tong, L.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- botanika, botany, epicuticular wax, Korean pine, photosynthesis, and UV-B radiation
- Language:
- Multiple languages
- Description:
- The effect of supplementary UV-B radiation on Korean pine (Pinus koraiensis Sieb. et Zucc) was investigated. Compared with the control, the T1, T2, and T3 UV-B treatments increased by 1.40, 2.81, and 4.22 kJ m-2 d-1, respectively. Gas-exchange parameters, photosynthetic pigment concentrations, contents of secondary metabolites, epicuticular wax, free radical, malondialdehyde (MDA), and the activities of antioxidant enzymes were determined after 40 d of exposure. The concentrations of chlorophyll (Chl) a, Chl b, total Chl, carotenoid (Car), and the ratio Chl a/b in the pine needles were in the following order: T1 > T2 > T3. Compared with the control, the contents of flavonoids and epicuticular wax significantly decreased in all levels of supplementary UV-B radiations (p<0.05). Moreover, the contents of hydrogen peroxide (H2O2) and MDA significantly increased with the enhanced UV-B radiations (p<0.05). Korean pine can increase the catalase, ascorbate peroxidase, and superoxide dismutase activities to prevent oxidative stress by supplementary UV-B radiation. However, its defence mechanism is not efficient enough to prevent UV-B-induced damage. and Y. G. Zu ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
230. Responses of cotton and wheat photosynthesis and growth to cyclic variation in carbon dioxide concentration
- Creator:
- Bunce, J. A.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- botanika, botany, acclimation, down-regulation, stomatal conductance, 2, and 58
- Language:
- Multiple languages
- Description:
- a1_The carbon dioxide concentration in free air carbon dioxide enrichment (FACE) systems typically has rapid fluctuations. In our FACE system, power spectral analysis of CO2 concentration measured every second with an open path analyzer indicated peaks in variation with a period of about one minute. I used open-top chambers to expose cotton and wheat plants to either a constant elevated CO2 concentration of 180 μmol mol-1 above that of outside ambient air, or to the same mean CO2 concentration, but with the CO2 enrichment cycling between about 30 and 330 μmol mol-1 above the concentration of outside ambient air, with a period of one minute. Three short-term replicate plantings of cotton were grown in Beltsville, Maryland with these CO2 concentration treatments imposed for 27-day periods over two summers, and one winter wheat crop was grown from sowing to maturity. In cotton, leaf gas-exchange measurements of the continuously elevated treatment and the fluctuating treatment indicated that the fluctuating CO2 concentration treatment consistently resulted in substantial down-regulation of net photosynthetic rate (PN) and stomatal conductance (gs). Total shoot biomass of the vegetative cotton plants in the fluctuating CO2 concentration treatment averaged 30% less than in the constantly elevated CO2 concentration treatment at 27 days after planting. In winter wheat, leaf gas-exchange measurements also indicated that down-regulation of PN and gs occurred in flag leaves in the fluctuating CO2 concentration treatment, but the effect was not as consistent in other leaves, nor as severe as found in cotton. However, wheat grain yields were 12% less in the fluctuating CO2 concentration treatment compared with the constant elevated CO2 concentration treatment., a2_Comparison with wheat yields in chambers without CO2 addition indicated a nonsignificant increase of 5% for the fluctuating elevated CO2 concentration treatment, and a significant increase of 19% for the constant elevated treatment. The results suggest that treatments with fluctuating elevated CO2 concentrations could underestimate plant growth at projected future atmospheric CO2 concentrations., J. A. Bunce., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public