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1093. Heterogeneity of chlorophyll fluorescence over thalli of several foliose macrolichens exposed to adverse environmental factors: interspecific differences as related to thallus hydration and high irradiance

Creator:
Barták, M., Hájek, J., and Gloser, J.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chlorophyll fluorescence imaging, desiccation, high irradiance, high light, Hypogymnia physodes, Lasallia pustulata, lichen, photosynthetic parameters, and Umbilicaria hirsuta
Language:
Multiple languages
Description:
Spatial heterogeneity of chlorophyll (Chl) fluorescence over thalli of three foliose lichen species was studied using Chl fluorescence imaging (CFI) and slow Chl fluorescence kinetics supplemented with quenching analysis. CFI values indicated species-specific differences in location of the most physiologically active zones within fully hydrated thalli: marginal thallus parts (Hypogymnia physodes), central part and close-to-umbilicus spots (Lasallia pustulata), and irregulary-distributed zones within thallus (Umbilicaria hirsuta). During gradual desiccation of lichen thalli, decrease in Chl fluorescence parameters (FO - minimum Chl fluorescence at point O, FP - maximum Chl fluorescence at P point, Φ2 - effective quantum yield of photochemical energy conversion in photosystem 2) was observed. Under severe desiccation (>85 % of water saturation deficit), substantial thalli parts lost their apparent physiological activity and the resting parts exhibited only a small Chl fluorescence. Distribution of these active patches was identical with the most active areas found under full hydration. Thus spatial heterogeneity of Chl fluorescence in foliose lichens may reflect location of growth zones (pseudomeristems) within thalli and adjacent newly produced biomass. When exposed to high irradiance, fully-hydrated thalli of L. pustulata and U. hirsuta showed either an increase or no change in FO, and a decrease in FP. Distribution of Chl fluorescence after the high irradiance treatment, however, remained the same as before the treatment. After 60 min of recovery in the dark, FO and FP did not recover to initial values, which may indicate that the lichen used underwent a photoinhibition. The CFI method is an effective tool in assessing spatial heterogeneity of physiological activity over lichen thalli exposed to a variety of environmental factors. It may be also used to select a representative area at a lichen thallus before application of single-spot fluorometric techniques in lichens. and M. Barták, J. Hájek, J. Gloser.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1095. High contents of anthocyanins in young leaves are correlated with low pools of xanthophyll cycle components and low risk of photoinhibition

Creator:
Manetas, Y., Drinia, A., and Petropoulou, Y.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
carotenoids, chlorophylls, fluorescence kinetics, leaf age, Ricinus communis, and Rosa sp.
Language:
Multiple languages
Description:
We checked the hypothesis that the transient presence of anthocyanins in young leaves serves a photoprotective function. For this purpose, Rosa sp. and Ricinus communis L., whose young leaves are red to become green upon maturation, were used. Thus, young leaves with high and mature leaves with low anthocyanin contents were analysed concerning their carotenoid (Car) composition and susceptibility to photoinhibition. Cars, including the components of the xanthophyll cycle, had similar contents in young and mature leaves, when expressed on a chlorophyll basis. Yet, when expressed on a leaf area basis or on the assumed photon absorptive capacity of leaves, Cars contents were considerably lower in anthocyanic young leaves. Although this may indicate a low photodissipative potential, red young leaves were considerably less susceptible to photoinhibitory damage. The results are compatible with a photoprotective function of anthocyanins, indicating also that their presence may compensate for a low capacity in the xanthophyll cycle-dependent harmless dissipation of excess excitation energy. and Y. Manetas, A. Drinia, Y. Petropoulou.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1096. High irradiance effects on the xanthophyll cycle pigments and the activity of violaxanthin de-epoxidase in soybean callus

Creator:
Pandey, D. M., Kim, K. H., Kang, K. H., and Yeo, U. D.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
antheraxanthin, Glycine max, HPLC, neoxanthin, violaxanthin, and zeaxanthin
Language:
Multiple languages
Description:
High irradiance (HI) effects on xanthophyll cycle pigments (XCP) and activity of violaxanthin de-epoxidase (VDE) in terms of de-epoxidation index (DEI) were studied in soybean calli. The calli from the hypocotyl segments of 5-d seedlings were induced on a solid (1.1 % agar) MS medium (pH 5.8) supplemented with 4.52 μM 2,4-dichloro-phenoxyacetic acid, 2.32 μM kinetin, and 3 % sucrose. After a 30 d cultivation, the green calli were irradiated for 24 h with "white light" (HI, 1 300 μmol m-2 s-1) and VDE was isolated from the photosystem 2 (PS2) particles. In the control (0 h irradiation) callus, the reaction of PS2 particles with VDE in the presence or absence of Tween 20 resulted in the decrease of VIO content and the increase of ZEA content. In the 24 h HI-callus, the reaction of PS2 particles in the absence of VDE led to the decrease of VIO and ANT contents and increase of ZEA content. In the control, DEIs in the presence of VDE with or without 0.1 %Tween 20 (1.04 and 1.06, respectively) were significantly higher than the DEI (0.76) in the absence of VDE. In the HI-callus, DEIs in the presence of VDE with or without 0.1 %Tween 20 (0.98 and 0.96, respectively) were similar to that (1.03) in the absence of VDE. and D. M. Pandey ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1097. High irradiance induced changes of photosystem 2 in young and mature needles of cypress (Cupressus sempervirens L.)

Creator:
La Porta, N., Bertamini, M., Nedunchezhian, N., and Muthuchelian, K.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
acclimation to irradiance, chlorophyll fluorescence, D1 protein, donor side, electron transport, photoinhibition, photosystem 2, and proteins
Language:
Multiple languages
Description:
Photoinhibition of photosynthesis was studied in young and mature detached sun needles of cypress under high irradiance (HI) of about 1 900 μmol m-2 s-1. The degree of photoinhibition was determined by means of the ratio of variable to maximum chlorophyll (Chl) fluorescence (Fv/Fm) and electron transport measurements. Compared with the mature needles, the young needles, containing about half the amount of Chl a+b per unit area, exhibited a higher proportion of total carotenoids (Car) as xanthophyll cycle pigments and had an increased ratio of Car/Chl a+b. The potential efficiency of photosystem (PS) 2, Fv/Fm, markedly declined in HI-treated young needles without significant increase of F0 level. In contrast, the Fv/Fm ratio declined with significant increase of F0 level in mature needles. In isolated thylakoids, the rate of whole chain and PS2 activity markedly decreased in young HI-needles in comparison with mature needles. A smaller inhibition of PS1 activity was observed in both needles. In the subsequent dark incubation, fast recovery was found in both needle Types that reached maximum PS2 efficiencies similar to those observed in non-photoinhibited needles. The artificial exogenous electron donors DPC, NH2OH, and Mn2+ failed to restore the HI-induced loss of PS2 activity in mature needles, while DPC and NH2OH significantly restored it in young needles. Hence, HI-inactivation was on the donor side of PS2 in young needles and on the acceptor side of PS2 in mature needles. Quantification of the PS2 reaction centre proteins D1 and 33 kDa protein of water splitting complex following HI-exposure of needles showed pronounced differences between young and mature needles. The large loss of PS2 activity in HI-needles was due to the marked loss of D1 protein of the PS2 reaction centre in mature needles and of the 33 kDa protein in young needles. and N. La Porta ... [et al.]
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1098. High photosynthetic efficiency of a rice (Oryza sativa L.) xantha mutant

Creator:
Zhou, Xiang-sheng, Wu, Dian-xing, Shen, Sheng-quan, Sun, Jun-wei, and Shu, Qing-yao
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chlorophyll b-deficiency, chlorophyll fluorescence, net photosynthetic rate, Oryza sativa, photosynthetic efficiency, and xantha mutation
Language:
Multiple languages
Description:
Comparative analysis revealed that a xantha rice mutant (cv. Huangyu B) had higher ratios of chlorophyll (Chl) a/b and carotenoids/Chl, and higher photosynthetic efficiency than its wild type parent (cv. II32 B). Unexpectedly, the mutant had higher net photosynthetic rate (PN) than II32 B. This might have resulted from its lower non-photochemical quenching (qN) but higher maximal photochemical efficiency (FV/FM), higher excitation energy capture efficiency of photosystem 2 (PS2) reaction centres (FV'/FM'), higher photochemical quenching (qP), higher effective PS2 quantum yield (ΦPS2), and higher non-cyclic electron transport rate (ETR). This is the first report of a chlorophyll mutant that has higher photosynthetic efficiency and main Chl fluorescence parameters than its wild type. This mutant could become a unique material both for the basic research on photosynthesis and for the development of high yielding rice cultivars. and X.-S. Zhou ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1099. High temperature induced alterations in energy transfer in phycobilisomes of the cyanobacterium Spirulina platensis

Creator:
Murthy, S. D. S., Ramanaiah, V. V., and Sudhir, P.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
absorption spectra and fluorescence emisson spectra at room and low temperature
Language:
Multiple languages
Description:
Exposure of intact cells of Spirulina to high temperature (HT) stress (40-60 °C) caused decrease in absorption spectrum and fluorescence emission spectrum. Low temperature emission spectra were altered at phycocyanin (PC) level. Room and low temperature emission spectra of intact phycobilisomes showed that PC was the main target in this cyanobacterium for the altered energy transfer under HT. and S .D. S. Murthy, V. V. Ramanaiah, P. Sudhir.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1100. High-irradiance stress and photochemical activities of photosystems 1 and 2 in vivo

Creator:
Veeranjaneyulu, K., Charland, M., and Leblanc, R. M.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
Acer saccharum, light-harvesting complex 2, and photoacoustic spectroscopy
Language:
Multiple languages
Description:
High-irradiance (HI) stress induced changes in the photosynthetic energy storage (ES) of photosystems 1 (ESPS1) and 2 (ESPS2) were studied with 650 nm modulated radiation in intact sugar maple (Acer saccharum Marsh.) leaves. HI-treatment (420 W m-2, 1 h) caused an inhibition of about 40 % in ESPS2 and an enhancement of about 60 % in ESPS1. The rate of PS1 cyclic electron transport, measured with 705 nm modulated radiation, also increased in HI-treated leaves. There was a clear state 1- state 2 transition in HI-treated leaves. ESPS1 increased significantly and ESPS2 decreased drastically in leaves preadapted to state 1 after HI (600 W m-2, 30 min) treatment. Thus, the increase in PS1 activity observed immediately after HI-treatment in leaves preadapted to state 1 can be due to the coupling of LHC2 to PS1 during the HI-treatment. Further, the dissociation of LHC2 from PS2 during the HI-treatment resulted in apparently (about 15 %) greater inhibition than the "true" inhibition of PS2 activity. The presence of LHC2 with PS2 (state 1) at the time of HI-treatment caused no additional damage to PS2 or its coupling to PS1 offered no apparent HI-treatment. Further, the dissociation of LHC2 from PS2 during the HI-treatment resulted in apparently (about 15 %) greater inhibition than the "true" inhibition of PS2 activity. The presence of LHC2 with PS2 (state 1) at the time of HI-treatment caused no additional damage to PS2 or its coupling to PS1 offered no apparent protection to the photosynthetic apparatus. and K. Veeranjaneyulu, M. Charland, R. M. Leblanc.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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