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2374. Submergence effects on rice genotypes during seedling stage: Probing of submergence driven changes of photosystem 2 by chlorophyll a fluorescence induction O-J-I-P transients

Creator:
Panda, D., Rao, D. N., Sharma, S. G., Strasser, R. J., and Sarkar, R. K.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
inundation, Oryza sativa, and survival
Language:
Multiple languages
Description:
The effects of submergence on chlorophyll (Chl) a fluorescence were compared in seven Oryza sativa (L.) cultivars, namely FR 13A, Khoda, Khadara, Kalaputia (tolerant), Sabita, and Hatipanjari (avoiding type), and IR 42 (susceptible). Seedlings were submerged for 4 d under complete darkness. Oxygen concentration of flood water decreased with the period of submergence with concomitant increase in concentration of carbon dioxide. Submergence caused diminution in the amount of total Chl. Genotypic differences were observed for Chl content and survival percentage. Quantification of the Chl a fluorescence transients (JIP-test) revealed large cultivar differences in the response of photosystem 2 (PS2) to submergence. The kinetics of Chl a fluorescence rise showed complex changes in the magnitudes and rise of O-J, J-I, and I-P phases caused by submergence. The selective suppression of the J-I phase of fluorescence especially after 2 d of submergence provided evidence for weakened electron donation from the oxygen evolving complex whereas under severe submergence stress (4 d) both O-J and J-I steps were suppressed greatly with highly suppressed P-step, which resulted in lowering of variable fluorescence. Grouping probability or energetic connectivity between PS2 obtained through JIP-test from the data after 2 d of submergence showed a direct relation with survival percentage, i.e. fluorescence measurements contained the information of the survival chance of a plant under submerged conditions. The information could be used in identifying the submergence tolerant cultivars when the damage is not very severe. and D. Panda ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2375. Submergence-tolerant rice withstands complete submergence even in saline water: Probing through chlorophyll a fluorescence induction O-J-I-P transients

Creator:
Sarkar, R. K. and Ray, Anuprita
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
fotosyntéza, photosynthesis, energy flux, Oryza sativa, performance index, saline flooding water, stress tolerance, 2, and 581
Language:
Multiple languages
Description:
Plants experience multiple abiotic stresses during the same growing season. The implications of submergence with and without saline water on growth and survival were investigated using four contrasting rice cultivars, FR13A (submergence-tolerant, salinity-susceptible), IR42 (susceptible to salinity and submergence), and Rashpanjor and AC39416 (salinity-tolerant, submergence-susceptible). Though both FR13A and IR42 showed sensitivity to salinity, FR13A exhibited higher initial biomass as well as maintained greater dry mass under saline condition. Greater reduction of chlorophyll (Chl) contents due to salinity was observed in the susceptible cultivars, including FR13A, compared to the salinity-tolerant cultivars. Exposure of plants to salinity before submergence decreased the survival chance under submergence. Yet, survival percentage under submergence was greater in FR13A compared to other cultivars. Generally, the reduction in the Chl content and damage to PSII were higher under the submergence compared to salinity conditions. The submergence-tolerant cultivar, FR13A, maintained greater quantities of Chl during submergence compared to other cultivars. Quantification of the Chl a fluorescence transients (JIP-test) revealed large cultivar differences in the response of PSII to submergence in saline and nonsaline water. The submergence-tolerant cultivar maintained greater chloroplast structural integrity and functional ability irrespective of the quality of flooding water., R. K. Sarkar, Anuprita Ray., and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2376. Substitutions of the conserved Thr42 increased the roles of the ε-subunit of maize CF1 as CF1 inhibitor and proton gate

Creator:
Ni, Zhang-Lin, Wang, Da-Fu, and Wei, Jia-Mian
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
ATP synthase, circular dichroism, coupling factor 1, ε-subunit, photophosphorylation, and Zea mays
Language:
Multiple languages
Description:
The conserved residue Thr42 of ε-subunit of the chloroplast ATP synthase of maize (Zea mays L.) was substituted with Cys, Arg, and Ile, respectively, through site-directed mutagenesis. The over-expressed and refolded ε-proteins were purified by chromatography on DEAE-cellulose and FPLC on mono-Q column, which were as biologically active (inhibiting Ca2+-ATPase activity and blocking proton gate) as the native ε subunit isolated from chloroplasts. The εT42C and εT42R showed higher inhibitory activities on the soluble CF1(-ε) Ca2+-ATPase than the εWT. The εT42I inhibited the Ca2+-ATPase activity of soluble CF1 and restored photophosphorylation activity of membrane-bound CF1 deficient in ε the most efficiently. Far-ultraviolet CD spectra showed that the portions of α-helix and β-sheet structures of the three mutants were somewhat different from εWT. Thus the conserved residue Thr42 may be important for maintaining the structure and function of the ε-subunit and the basic functions of the ε-subunit as far as an inhibitor of Ca2+-ATPase and the proton gate are related. and Zhang-Lin Ni, Da-Fu Wang, Jia-Mian Wei.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2377. Sucrose metabolism at three leaf development stages in bean plants

Creator:
Castrillo, M.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
acid and neutral invertases, hexose/sucrose ratio, Phaseolus vulgaris, sucrose phosphate synthase, and sucrose synthase
Language:
Multiple languages
Description:
Sucrose metabolism was studied at three leaf development stages in two Phaseolus vulgaris L. cultivars, Tacarigua and Montalban. The changes of enzyme activities involved in sucrose metabolism at the leaf development stages were: (1) Sink (9-11 % full leaf expansion, FLE): low total sucrose phosphate synthase (SPS) activity, and higher acid invertase (AI) activity accompanied by low sucrose synthase (SuSy) synthetic and sucrolytic activities. (2) Sink to source transition (40-47 % FLE): increase in total SPS and SuSy activities, decrease in AI activity. (3) Source (96-97 % FLE): high total SPS activity, increased SuSy activities, decreased AI activity. The hexose/sucrose ratio decreased from sink to source leaves in both bean cultivars. The neutral invertase activity was lower than that of AI; it showed an insignificant decrease during the sink-source transition.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2378. Surface charge densities and membrane fluidities in thylakoids with different degrees of thylakoid appression after Norflurazon treatment

Creator:
Dahlin, C.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
9-amino acridine, chloroplast, etioplast, (pro-)thylakoids, stacking, Triticum, and wheat
Language:
Multiple languages
Description:
Wheat seedlings (Triticum aestivum L.) develop plastids (etioplasts and chloroplasts) which exhibit alterations in inner membrane organisation after treatment with Norflurazon (NF), an inhibitor of carotenoid biosynthesis. In dark-grown plants, it results in a decreased amount of partitions (contact zones) between prothylakoids. Under weak red radiation (WRR), plants contain chloroplasts devoid of grana. Using the fluorescent probe 9-amino acridine (9-AA), the average surface charge density of isolated prothylakoids (PTs) was -21.8±3.2 mC m-2 and -27.4±2.6 mC m-2 in the control and after treatment, respectively. Thylakoid membranes isolated from plants grown under WRR exhibited slightly more negative values, -23.5±2.9 mC m-2 and -29.0±2.1 mC m-2, in control and after NF treatment, respectively. The surface charge density of de-stacked thylakoids from greenhouse-grown untreated plants, containing extensive grana stacking, was -34.3±2.5 mC m-2. Assays using the fluorescent probe of DPH (1,6-diphenyl-1,3,5-hexatriene) showed a higher polarisation value when incorporated into thylakoids from NF-treated plants compared to untreated plants grown under WRR. The highest polarisation value was found in untreated plants grown in the greenhouse. This indicates a lower rotation transition of the probe in the lipid environment of thylakoids after NF treatment, which can be interpreted as more rigid membranes. Hence the surface charge density and the mobility of membrane components may play a major role for the formation of partitions in dark-grown plants and in the formation of grana in plants grown under WRR.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2379. Surface density and volume density measurements of chloroplast thylakoids in maize (Zea mays L.) under chilling conditions

Creator:
Kubínová, L. and Kutík, J.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
appressed and non-appressed thylakoids, comparison of methods, granal and intergranal thylakoids, hybrids, stereology, temperature, and vertical sections
Language:
Multiple languages
Description:
Measurements of ultrastructural characteristics of chloroplast thylakoids are important for studies of ontogenic or ecological limitations of leaf photosynthetic functions. Most frequently, volumetric proportion of thylakoids in the chloroplast is measured; however, such measurement does not provide a direct information about the surface area of thylakoids which is most important from the functional point of view. Therefore, we adapted the stereological method using "local vertical windows" for estimating thylakoid surface area in the chloroplast volume and compared thus obtained surface density results with results of conventional volume density measurements. The methods were tested in the study of chloroplast ultrastructure in the leaves of plants of two maize (Zea mays L.) hybrid combinations, 2013×CE810 and CE704×CE810, developing in control and chilling conditions. Correlation analysis revealed a tight relationship between the granal/intergranal thylakoid surface density and volume density results, both indicating that under chilling conditions the development of the system of thylakoids in maize leaves is suppressed, while the difference is more pronounced in CE704 than in CE810 genotype, known to have a better photosynthetic performance. and L. Kubínová, J. Kutík.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2380. Susceptibility of an ascorbate-deficient mutant of Arabidopsis to high-light stress

Creator:
Zeng, L.-D., Li, M., Chow, W. S., and Peng, C.-L.
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
huseníček rolní, kyselina askorbová, Arabidopsis thaliana, ascorbic acid, high-light stress, chlorophyll fluorescence, reactive oxygen species, 2, and 581
Language:
Multiple languages
Description:
Ascorbate is an important antioxidant involved in both enzymatic and nonenzymatic reactions in plant cells. To reveal the function of ascorbate associated with defense against photo-oxidative damage, responses of the ascorbate-deficient mutant vtc2-1 of Arabidopsis thaliana to high-light stress were investigated. After high-light treatment at 1,600 μmol(photon) m-2 s-1 for 8 h, the vtc2-1 mutant exhibited visible photo-oxidative damage. The total ascorbate content was lower, whereas accumulation of H2O2 was higher in the vtc2-1 mutant than that in the wild type. The chlorophyll (Chl) content and PSII Chl fluorescence parameters, such as maximal quantum yield of PSII photochemistry, yield, and electron transport rate, in vtc2-1 mutant decreased more than that in the wild type, whereas the nonphotochemical quenching coefficient increased more in the wild type than that in vtc2-1 mutant. Therefore, the vtc2-1 mutant was more sensitive to high-light stress than the wild type. Accumulation of reactive oxygen species was mainly responsible for the damage of PSII in the vtc2-1 mutant under high light. The results indicate that ascorbate plays a critical role in maintaining normal photosynthetic function in plants under high-light stress., L.-D. Zeng, M. Li, W. S. Chow, C.-L. Peng., and Obsahuje bibliografické odkazy
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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