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.
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
The effects of different spectral region of excitation and detection of chlorophyll (Chl) a fluorescence at room temperature on the estimation of excitation energy utilization within photosystem (PS) 2 were studied in wild-type barley (Hordeum vulgare L. cv. Bonus) and its Chl b-less mutant chlorina f2 grown under low and high irradiances [100 and 1 000 µmol(photon) m-2 s-1]. Three measuring spectral regimes were applied using a PAM 101 fluorometer: (1) excitation in the red region (maximum at the wavelength of 649 nm) and detection in the far-red region beyond 710 nm, (2) excitation in the blue region (maximum at the wavelength of 461 nm) and detection beyond 710 nm, and (3) excitation in the blue region and detection in the red region (660- 710 nm). Non-photochemical quenching of maximal (NPQ) and minimal fluorescence (SV0), determined by detecting Chl a fluorescence beyond 710 nm, were significantly higher for blue excitation as compared to red excitation. We suggest that this results from higher non-radiative dissipation of absorbed excitation energy within light-harvesting complexes of PS2 (LHC2) due to preferential excitation of LHC2 by blue radiation and from the lower contribution of PS1 emission to the detected fluorescence in the case of blue excitation. Detection of Chl a fluorescence originating preferentially from PS2 (i.e. in the range of 660-710 nm) led to pronounced increase of NPQ, SV0, and the PS2 photochemical efficiencies (FV/FM and FV'/FM'), indicating considerable underestimation of these parameters using the standard set-up of PAM 101. Hence PS1 contribution to the minimal fluorescence level in the irradiance-adapted state may reach up to about 80 %. and M. Štroch ... [et al.].
Six months old in vitro-grown Anoectochilus formosanus plantlets were transferred to ex-vitro acclimation under low irradiance, LI [60 µmol(photon) m-2 s-1], intermediate irradiance, II [180 µmol(photon) m-2 s-1], and high irradiance, HI [300 µmol(photon) m-2 s-1] for 30 d. Imposition of II led to a significant increase of chlorophyll (Chl) b content, rates of net photosynthesis (PN) and transpiration (E), stomatal conductance (gs), electron transfer rate (ETR), quantum yield of electron transport from water through photosystem 2 (ΦPS2), and activity of ribulose-1,5-bisphosphate carboxylase/ oxygenase (RuBPCO, EC 4.1.1.39). This indicates that Anoectochilus was better acclimated at II compared to LI treatment. On the other hand, HI acclimation led to a significant reduction of Chl a and b, PN, E, gs, photochemical quenching, dark-adapted quantum efficiency of open PS2 centres (Fv/Fm), probability of an absorbed photon reaching an open PS2 reaction centre (Fv'/Fm'), ETR, ΦPS2, and energy efficiency of CO2 fixation (ΦCO2/ΦPS2). This indicates that HI treatment considerably exceeded the photo-protective capacity and Anoectochilus suffered HI induced damage to the photosynthetic apparatus. Imposition of HI significantly increased the contents of antheraxanthin and zeaxanthin (ZEA), non-photochemical quenching, and conversion of violaxanthin to ZEA. Thus Anoectochilus modifies its system to dissipate excess excitation energy and to protect the photosynthetic machinery. and D. M. Pandey ... [et al.].
Two greenhouse experiments were conducted in order to investigate the effects of different levels of water stress on gas exchange, chlorophyll fluorescence, chlorophyll content, antioxidant enzyme activities, lipid peroxidation, and yield of tomato plants (Solanum lycopersicum cv. Jinfen 2). Four levels of soil water content were used: control (75 to 80% of field water capacity), mild water stress (55 to 60%), moderate water stress (45 to 50%), and severe water stress (35 to 40%). The controlled irrigation was initiated from the third leaf stage until maturity. The results of
two-year trials indicated that the stomatal conductance, net photosynthetic rate, light-saturated photosynthetic rate, and saturation radiation decreased generally under all levels of water stress during all developmental stages, while compensation radiation and dark respiration rate increased generally. Water stress also declined maximum quantum yield of PSII photochemistry, electron transfer rate, and effective quantum yield of PSII photochemistry, while nonphotochemical quenching increased in all developmental stages. All levels of water stress also caused a marked reduction of chlorophyll a, chlorophyll b, and total chlorophyll content in all developmental stages, while activities of antioxidant enzymes, such as superoxide dismutase, peroxidase, and catalase, and lipid peroxidation increased., X. K. Yuan, Z. Q. Yang , Y. X. Li, Q. Liu, W. Han., and Obsahuje seznam literatury
Net photosynthetic rate (PN) of tobacco plants grown with NH4-N as the only N source was the lowest all the times, while PN grown only with NO3-N was the greatest until 22nd day, and PN grown with both NO3-N and NH4-N (1 : 1) was the greatest. Maximal photochemical efficiency of photosystem 2 (PS2), Fv/Fm, and actual quantum yield of PS2 under actinic irradiation (ΦPS2) in plants grown with only NH4-N were greatest at early stage and then decreased and were smaller than those of other treatments. Photochemical quenching coefficient (qP) and non-photochemical quenching coefficient (qNP) in the NH4-N plants were the greatest at all times. Hence excessive NH4-N can decrease not only photochemical efficiency but also the efficiency of utilization of photon energy absorbed by pigments for photosynthesis. Therefore, excessive NH4-N is a hindrance to photosynthesis of flue-cured tobacco. On the other hand, tobacco cultured with an appropriate mixture of NO3-N with NH4-N can sufficiently utilize photon energy and increase the efficiency of energy transformation. and H. X. Guo, W. Q. Liu, Y. C. Shi.
We investigated responses of chloroplasts from flag leaves of a newly-developed super-high-yield rice (Oryza sativa L.) hybrid LiangYouPeiJiu (LYPJ) to water stress (withholding irrigation) during the grain-filling period. In the early stage of water stress (0-6 d) only the activity of Hill reaction was inhibited, whereas activities of photophosphorylation and Ca2+-ATPase, and ATP content were increased and peaked in the day 6 of withholding irrigation. In the late stage of water stress (6-12 d), the activities of photosynthetic O2 evolution, Hill reaction, photophosphorylation, and Ca2+- ATPase, and ATP content were significantly reduced. The membrane lipid content was sharply decreased, especially of sulfoquinovosyl-diacylglycerol (SQDG) and phosphatidylglycerol (PG). The changes in the ultrastructure of chloroplasts included mainly a decrease in number of grana and increase in number of osmiophilic granules. and G.-X. Chen ... [et al.].
The effect of drought on plant water relations and photosynthesis of Vigna glabrescens (Vg) and Vigna unguiculata (cvs. 1183, EPACE-1 and Lagoa), which differ in their drought resistance, was compared. With the increase of drought severity, Vg showed a more gradual stomatal closure and maintained significantly higher levels of stomatal conductance (gs) and photosynthetic activity (PN) than the other genotypes even when minimum relative water content (RWC) values were observed. Furthermore, Vg was the only genotype able to accumulate significant amounts of proline already under moderate water deficit, what could explain the lower osmotic potential (ψs) values observed in these plants. The three V. unguiculata cultivars presented a similar stomatal control under increasing water deficit. A mesophyllic impairment of photosynthetic capacity (Pmax) was detected for cv. 1183 from the beginning of drought onset (85-75 % RWC) while in the Vg plants the values remained unaffected along the whole drought period, indicating that PN decrease observed in this genotype is mainly a consequence of stomatal closure. Such Pmax maintenance suggests the existence of a high mesophyllic ability to cope with increasing tissue dehydration in Vg. and P. Scotti Campos ... [et al.].
The effects of drought stress induced by polyethylene glycol, PEG (molecular mass 6000) on some ecophysiological characteristics of two wild pistachio species, Mastic and Khinjuk (P. mutica and P. khinjuk) selected as root stocks for production of edible pistachio trees (P. vera) in Iran and Turkey, were studied. Net photosynthetic rate (PN), stomatal conductance (gs), chlorophyll (Chl) fluorescence parameters, leaf water potential (Ψ1), leaf osmotic potential (Ψπ), leaf osmotic adjustment (ΔΨπ), and Chl a and b were measured. All parameters were influenced by increase in concentra-tion of PEG in the nutrient solutions. PN, gs, and Chl a were significantly higher in P. mutica than in P. khinjuk but, compared to the control treatment, P. khinjuk showed a higher resistance to drought stress than P. mutica. and A. Ranjbarfordoei ... [et al.].
Drought stress has multiple effects on the photosynthetic apparatus. Herein, we aimed to study the effect of drought stress on fluorescence characteristics of PSII in leaves of Plectranthus scutellarioides and explore potentially underlying mechanisms. Plants of P. scutellarioides were grown in a greenhouse and subjected to drought (DS, drought-stressed) or daily irrigation (control group). Leaf chlorophyll (Chl) index and induction kinetics curves of Chl a fluorescence and the JIP-test were used to evaluate effects of drought lasting for 20 d. Our results showed that both the leaf and soil relative water content decreased with increasing treatment duration. The leaf Chl index was reduced to half in the DS plants compared with the control group after 20 d. The minimal fluorescence in the DS plants was higher than that in the control plants after 10 d of the treatment. Maximum photochemical efficiency and lateral reactivity decreased with increasing treatment duration in the DS plants. With the continuing treatment, values of absorption flux per reaction center (RC), trapped energy flux per RC, dissipated energy flux per RC, and electron transport flux per RC increased in the earlier stage in the DS plants, while obviously decreased at the later stage of the treatment. In conclusion, drought stress inhibited the electron transport and reduced PSII photochemical activity in leaves of P. scutellarioides., L.-L. Meng, J.-F. Song, J. Wen, J. Zhang, J.-H. Wei., and Seznam literatury