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4282. Selective effects of H2O2 on cyanobacterial photosynthesis

Creator:
Drábková, M., Matthijs, H. C. P., Admiraal, W., and Maršálek, B.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chlorophyll fluorescence induction, diatoms, fluorescence emission spectra, green algae, and species differences
Language:
Multiple languages
Description:
The sensitivity of phytoplankton species for hydrogen peroxide (H2O2) was analyzed by pulse amplitude modulated (PAM) fluorometry. The inhibition of photosynthesis was more severe in five tested cyanobacterial species than in three green algal species and one diatom species. Hence the inhibitory effect of H2O2 is especially pronounced for cyanobacteria. A specific damage of the photosynthetic apparatus was demonstrated by changes in 77 K fluorescence emission spectra. Different handling of oxidative stress and different cell structure are responsible for the different susceptibility to H2O2 between cyanobacteria and other phytoplankton species. This principle may be potentially employed in the development of new agents to combat cyanobacterial bloom formation in water reservoirs. and M. Drábková ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

4283. Selenium delays leaf senescence in oilseed rape plants

Creator:
Rahmat, S., Hajiboland, R., and Sadeghzade, N.
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
nitrát reduktázy, rychlost fotosyntézy, fluorescence chlorofylu, selen, řepka olejka, leaf photochemistry, nitrate reductase, photosynthetic rate, chlorophyll fluorescence, selenium, oilseed rape, 2, and 581
Language:
Multiple languages
Description:
Effect of selenium on leaf senescence was studied in oilseed rape plants treated with 10 μM Na2SeO4 at a rosette growth stage. In addition to developmental senescence, N deficiency and leaf detachment were used for induction of senescence. Nonphotochemical quenching declined in old leaves as senescence became more advancing but rose progressively in the plants supplied by Se. The total carbohydrate and protein pools decreased with leaf age, while increased by the Se treatment. However, during senescence induced by N deficiency, Se did not change remarkably the C and N metabolism, but delayed senescence mainly through protection of plants from photoinhibitory effects. After detachment, untreated leaves became chlorotic and necrotic, while the Se-treated ones remained fairly green. Our results demonstrated that Se delayed leaf senescence by a maintaining or even improving photochemical activities. During developmental senescence, the Se effect on the extending life span of the leaves was additionally linked to the metabolic regulation of senescence., S. Rahmat, R. Hajiboland, N. Sadeghzade., and Obsahuje bibliografii
Rights:
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4284. Selenium improves photosynthesis and protects photosystem II in pear (Pyrus bretschneideri), grape (Vitis vinifera), and peach (Prunus persica)

Creator:
Feng, T., Chen, S. S., Gao, D. Q., Liu, G. Q., Bai, H. X., Li, A., Peng, L. X., and Ren, Z. Y.
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
fotosyntéza, photosynthesis, foliar feeding, fruit tree, gas exchange, intercellular CO2 concentration, 2, and 581
Language:
Multiple languages
Description:
The effects of selenium on photosynthesis and Chl fluorescence in pear, grape, and peach were analyzed. The foliar spray of amino acid-chelated selenium solution was performed soon after fruit setting, totally six times, with an interval of ten days. After seven days from the last spray, the leaves in the middle of shoots were examined. Foliar spray of selenium increased the net photosynthetic rate in pear, grape, and peach. In contrast, the treatment decreased stomatal conductance, transpiration rate, and substomatal CO2 concentration in all the three species. The selenium treatment improved the maximum quantum yield of PSII, effective quantum yield of PSII, and photochemical quenching in all three species. Conversely, the selenium treatment reduced nonphotochemical quenching in all three species. We suggested that selenium can improve photosynthesis and protect PSII in fruit crops., T. Feng, S. S. Chen, D. Q. Gao, G. Q. Liu, H. X. Bai, A. Li, L. X. Peng, Z. Y. Ren., and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

4285. Semi-empirical indices to assess carotenoids/chlorophyll a ratio from leaf spectral reflectance

Creator:
Peňuelas, J., Baret, F., and Filella, I.
Format:
print
Type:
model:internalpart and TEXT
Language:
Multiple languages
Description:
The ratío between carotenoid and chlorophyll a concentrations (Car/Chla) is indicative of the physiology and phenology of plants. With the aim of assessing this Car/Chla pigment ratio from reflectance (R), a wide range of leaves from several species and conditions were measured with high spectral resolution spectroradiometers for X between 400 and 800 nm. The performances of three pigment reflectance indices; (7) simple ratio pigment index (SRPI = R^*/R^2), (2) normalized difference pigment index [NDPI = (R^’ - R^^y^^RXi + R^2)]^ g^d (i) the structure insensitive pigment index [SIPI = (R**^ - R^i)/(R®*^ - R^^)] were tested. For each pigment index, every set of wavebands [Aj, X'^ was systematically tested. High correlations with Car/Chla were found for all these pigment indices in the blue-red domain [400 nm<A,i<530 nm, 600 nm<A,2<700 nm] as expected since both Chl and Car absorb in the blue, while only Chl absorbs in the red. The best semi-empirical estimation of the Car/Chla ratio was provided by SIPI for the wavelengths 445 and 680 nm: Car/Chla = 4.44 - 6.77 exp[-0.48 (R^oo. r445)/(r800 . R680)j| This index minimizes the confounding effects of leaf surface and mesophyll structure. These reflectance pigment indices provide new insight in the use of remote sensing for the assessment of physiology and phenology of vegetation.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

4286. Senescence retarding effect of metal ions: Pigment and protein contents and photochemical activities of detached primary leaves of wheat

Creator:
Subhan, D. and Murthy, S. D. S.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
aluminium, carotenoids, chlorophyll, DCMU, electron transport, fluorescence, emission spectra, leaf senescence, magnesium, and potassium
Language:
Multiple languages
Description:
Al3+ significantly delayed the loss of chlorophyll (Chl), protein, and carotenoids when compared to K+ and Mg2+ during dark-induced senescence of detached primary leaves of Triticum aestivum. Thylakoid membranes isolated from Al3+ - treated leaves showed a better retention of photosystem (PS) 2, PS1, and whole chain electron transport activities than thylakoids of K+- or Mg2+-treated leaves. These ions protected the electron transport activities and restored the DCMU-dependent fluorescence increase of thylakoid membranes in a valency-dependent manner. Al3+ also delayed the change of excitation energy distribution during senescence. and D. Subhan, S. D. S. Murthy.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

4287. Sensing and classification of rice (Oryza sativa L.) drought stress levels based on chlorophyll fluorescence

Creator:
Xia, Q., Fu, L. J., Tang, H., Song, L., Tan, J. L., and Guo, Y.
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
chlorophyll a fluorescence, drought stress, Ensemble model, K-Nearest Neighbors, and Support vector machine
Language:
Multiple languages
Description:
Sensing and classification of drought stress levels are very important to agricultural production. In this work, rice drought stress levels were classified based on the commonly used chlorophyll a fluorescence (ChlF) parameter (Fv/Fm), feature data (induction features), and the whole OJIP induction (induction curve) by using a Support Vector Machine (SVM). The classification accuracies were compared with those obtained by the K-Nearest Neighbors (KNN) and the Ensemble model (Ensemble) correspondingly. The results show that the SVM can be used to classify drought stress levels of rice more accurately compared to the KNN and the Ensemble and the classification accuracy (86.7%) for the induction curve as input is higher than the accuracy (43.9%) with Fv/Fm as input and the accuracy (72.7%) with induction features as input. The results imply that the induction curve carries important information on plant physiology. This work provides a method of determining rice drought stress levels based on ChlF.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

4288. Sensitivity of Metasequoia glyptostroboides to ozone stress

Creator:
Feng, Z.-Z., Zeng, H.-Q., Wang, X.-K., Zheng, Q.-W., and Feng, Z.-W.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
air pollution, chlorophyll, crown width, leaf length, net photosynthetic rate, stem height, stomatal conductance, transpiration rate, and urban greening tree species
Language:
Multiple languages
Description:
2-year-old seedlings of Metasequoia glyptostroboides were grown in open top chambers and exposed to four ozone concentrations [O3] (charcoal-filtered air, CF; 50, 100, and 200 mm3 m-3) for 25 d. Measurements of growth, leaf chlorophyll (Chl) content, and gas exchange parameters were made before and/or after O3 exposure. Leaf length, crown width, Chl a/b, net photosynthetic rate, stomatal conductance, and transpiration rate were significantly reduced at 100 and 200 mm3(O3) m-3. A remarkable decrease in stomatal conductance also occurred at 50 mm3(O3) m-3. and Z.-Z. Feng ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

4289. Sensitivity of photosystem 2 of Antarctic lichens to high irradiance stress: Fluorometric study of fruticose (Usnea antarctica) and foliose (Umbilicaria decussata) species

Creator:
Barták, M., Vráblíková, H., and Hájek, J.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chlorophyll fluorescence, low temperature, photoinhibition, photosynthesis, and non-photochemical quenching
Language:
Multiple languages
Description:
Two lichen species collected in maritime Antarctica (King George Island) were exposed under laboratory conditions to excess irradiance to evaluate the response of photosystem 2 (PS2). The response was measured on fully hydrated lichen thalli at 5 °C by means of a modulated fluorometer using chlorophyll (Chl) fluorescence induction curve supplemented with analysis of quenching mechanisms. Chl fluorescence parameters [i.e. ratio of variable to maximum Chl fluorescence (FV/FM), quantum yield of PS2 photochemical reactions (Φ2), quenching coefficients] were evaluated before and several times after exposition to high irradiance in order to characterise the extent of photoinhibition, fast and slow phase of recovery. Strong irradiance (2 000 μmol m-2 s-1) caused high degree of photoinhibition, particularly higher in fruticose (Usnea antarctica) than in foliose (Umbilicaria decussata) lichen species. Fast phase of recovery from photoinhibition, corresponding to regulatory mechanisms of PS2, was more apparent in U. decussata and Φ2 than in U. antarctica and FV/FM and Φ2 within 40 min after photoinhibitory treatment. It was followed by a slow phase lasting several hours, corresponding to repair and re-synthesis processes. After photoinhibitory treatment, recovery of non-photochemical quenching (NPQ) was faster and more pronounced in U. decussata than in U. antarctica. Significant differences were found between the two species in the rate of recovery in fast-(qE) and slow-recovering (qT+I) component of NPQ. and M. Barták, H. Vráblíková, J. Hájek.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

4290. Sensitivity of the algal biotest ISO 10253 to the photosystem 2 herbicides in seawater

Creator:
Soukupová, J., Lukavská, A., Lukavský, J., and Nedbal, L.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
bioassay, chlorophyll fluorescence, DCMU, 3-[3,4-dichlorophenyl]-1,1-dimethylurea, diuron, Phaeodactylum tricurnutum, and quinone acceptors
Language:
Multiple languages
Description:
The sensitivity of marine algal biotest ISO 10253 to the photosystem 2 (PS2) herbicide diuron (DCMU) was determined. Using the diatom Phaeodactylum tricornutum, we found that the algal growth rate was reduced to 50 % of the control value (EC50) for ca. 200 nM DCMU. This value is too high to allow a practical application of the biotest for concentrations of the PS2 herbicides found in natural waters. The mechanisms causing the low sensitivity of the biotest to the PS2 herbicide were investigated by measuring parameters of photosynthetic apparatus in the diatom prior and during the biotest. The apparent dissociation constant for DCMU in P. tricornutum found by measurements of inhibition of oxygen evolution and of variable fluorescence was in the range 60-90 nM. This should lead to a much higher sensitivity of the biotest than found in our experiments. The low biotest sensitivity is caused by an acclimation to sub-lethal DCMU concentrations. The acclimation is manifested by the chlorophyll content per cell that is increasing with the DCMU concentration. During a prolonged exposure to sub-lethal herbicide concentrations, we observed also a selection of DCMU resistant organisms indicating that also an adaptation may decrease the test sensitivity. The biotest sensitivity may increase when the acclimation and adaptation are limited by shortening of the experiment duration. and J. Soukupová ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public