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2392. Taihangia rupestris, a rare herb dwelling cliff faces: responses to irradiance

Creator:
Tang, Min, Yu, Fei-Hai, Zhang, Shu-Min, Niu, Shu-Li, and Jin, Xiao-Bai
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
cliff-inhabiting plant, gas exchange, growth, irradiance, leaf morphology, net photosynthetic rate, restricted habitat, stomatal conductance, transpiration rate, and water use efficiency
Language:
Multiple languages
Description:
We studied the responses of gas exchange, leaf morphology, and growth to irradiance in Taihangia rupestris, a naturally rare herb inhabiting only vertical cliff faces. In low irradiance (LI, 10 % of full sun) T. rupestris had lower net photosynthetic rate (PN) and produced much less leaves, total leaf area, and biomass than in high (HI, full sun) or medium irradiance (MI, 50 % of full sun). PN of T. rupestris was higher in HI than in MI on August 8, but lower in HI than in MI on September 22. T. rupestris had shorter petioles and lower leaf area ratio, and produced more but smaller and thicker leaves in HI than in MI. In HI the fast production of new leaves may guarantee T. rupestris to maintain higher PN at the whole plant level and thus accumulate more biomass at harvest, although the single-leaf PN may become lower as found on September 22. Hence T. rupestris possesses a latent capacity to acclimate and adapt to full sun. Irradiance, therefore, may not be a responsible factor for the restricted distribution of T. rupestris on vertical cliffs. and Min Tang ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2393. Technique of the modulated chlorophyll fluorescence: basic concepts, useful parameters, and some applications

Creator:
Roháček, K. and Barták, M.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chemicals, circadien cycle, dark-adapted state, fast kinetics, fluoranthene, light-adapted state, photosystem 2, slow kinetics, and temperature
Language:
Multiple languages
Description:
The review summarizes basic information about slow and fast chlorophyll (Chl) a fluorescence induction kinetics (FIK) recorded using fluorimeters working on a principle of the pulse amplitude modulation (PAM) of a Chl fluorescence signal. It explains fundamental principles of the measuring technique, evaluates the terminology, symbols, and parameters used. Analysis of Chl FIK resulting in a set of Chl fluorescence parameters (FPs) provides qualitative and quantitative information about photosynthetic processes in chloroplasts. Using FPs, one can describe the functioning of the photosynthetic apparatus under different internal and external conditions. Brief comments on proper application of the fluorimetric method in photosynthesis research and some actual examples are also given. and K, Roháček, M. Barták.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2394. Temperature and light dependence of photosynthetic activities in wheat seedlings grown in the presence of DCMU [3-(3,4-dichlorophenyl)-1,1-dimethylurea]

Creator:
Muthuchelian, K., Bertamini, M., and Nedunchezhian, N.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chlorophyll fluorescence, donor side, electron transport, photosystem, thylakoid membrane proteins, and Triticum
Language:
Multiple languages
Description:
Photosynthetic electron transfer was studied in thylakoids isolated from control and DCMU-grown wheat (Triticum aestivum L.) seedlings. When exposed to high temperature (HT) and high iradiance (HI), thylakoids showed large variations in the photosynthetic electron transport activities and thylakoid membrane proteins. A drastic reduction in the rate of whole electron transport chain (H2O → MV) was envisaged in control thylakoids when exposed to HT and HI. Such reduction was mainly due to the loss of photosystem 2, PS2 (H2O → DCBQ) activity. The thylakoids isolated from seedlings grown in the presence of DCMU showed greater resistance to HT and HI treatment. The artificial exogenous electron donors MnCl2, DPC, and NH2OH failed to restore the HI induced loss of PS2 activity in both control and DCMU thylakoids. In contrast, addition of DPC and NH2OH significantly restored the HT induced loss of PS2 activity in control thylakoids and partially in DCMU thylakoids. Similar results were obtained when Fv/Fm was evaluated by chlorophyll fluorescence measurements. The marked loss of PS2 activity in control thylakoids was evidently due to the loss of 33, 23, and 17 kDa extrinsic polypeptides and 28-25 kDa LHCP polypeptides. and K. Muthuchelian, M. Bertamini, N. Nedunchezhian.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2395. Temperature dependences of carbon assimilation processes in four dominant species from mountain grassland ecosystem

Creator:
Urban, O., Ač, A., Kalina, J., Priwitzer, T., Šprtová, M., Špunda, V., and Marek, M. V.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
ambient and intercellular CO2 concentrations, carboxylation rate, electron transport rate, photosynthesis, quantum efficiency, respiraation, stomatal conductance, and water use efficiency
Language:
Multiple languages
Description:
Temperature responses of carbon assimilation processes were studied in four dominant species from mountain grassland ecosystem, i.e. Holcus mollis (L.), Hypericum maculatum (Cr.), Festuca rubra (L.), and Nardus stricta (L.), using the gas exchange technique. Leaf temperature (TL) of all species was adjusted within the range 13-30 °C using the Peltier thermoelectric cooler. The temperature responses of metabolic processes were subsequently modelled using the Arrhenius exponential function involving the temperature coefficient Q10. The expected increase of global temperature led to a significant increase of dark respiration rate (RD; Q 10 = 2.0±0.5), maximum carboxylation rate (VCmax; Q10 = 2.2±0.6), and maximum electron transport rate (J max; Q 10 = 1.6±0.4) in dominant species of mountain grassland ecosystems. Contrariwise, the ratio between Jmax and VCmax linearly decreased with TL [y = -0.884 TL + 5.24; r2 = 0.78]. Hence temperature did not control the ratio between intercellular and ambient CO2 concentration, apparent quantum efficiency, and photon-saturated CO2 assimilation rate (Pmax). Pmax primarily correlated with maximum stomatal conductance irrespective of TL. Water use efficiency tended to decrease with TL [y = -0.21 TL + 8.1; r2 = 0.87]. and O. Urban ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2396. Temperature dependent UV-Vis spectral changes in hydrogen-and deuterium-bonded photosynthetic reaction centers of Rhodobacter sphaeroides

Creator:
Ostafin, A. E., Popova, J. A., Payne, C. K., Mizukami, H., and Norris, J. R.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
enthalpy, entropy, ferricyanide, 1,3,5-hexanetriol, and photosynthetic bacteria
Language:
Multiple languages
Description:
The UV-Vis absorption spectra of detergent-isolated hydrogen-and deuterium-bonded reaction centers (RCs) from Rhodobacter sphaeroides PUC 705Ba were examined as a function of temperature between 20 and 55 °C. The enthalpy and entropy of denaturation for the specimens was determined, revealing that their process of thermal denaturation is significantly different. Deuterium-bonded RCs are most stable at 37 °C, rather than at room temperature, and undergo a "cold denaturation" as the temperature is lowered to room temperature. At room temperature the addition of 1,3,5-heptanetriol brought the deuterium-bonded RC back to its more stable configuration. Hence the hydrogen bonding interactions in the RC do influence its conformation and this is reflected in the microenvironment of its associated pigments. and A. E. Ostafin ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2397. Temperature sensitivity of photosynthesis in Lolium perenne swards: A comparison of two methods for deriving photosynthetic parameters from in vivo measurements

Creator:
Dirks, B. O. M., van Oijen, M., Schapendonk, A. H. C. M., Goudriaan, J., and Wolf, J.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
canopy photosynthesis, grass, irradiance, Michaelis-Menten constant, net photosynthetic rate, and seasonal course of photosynthetic rate
Language:
Multiple languages
Description:
The seasonal variation in photosynthetic rate of grass swards is partly the result of changes in the environment and partly the result of changes in the photosynthetic capacity of the sward itself. We evaluated two types of photosynthesis equations regarding their capacity to analyse seasonal and short-term temperature effects on photosynthesis of ryegrass (Lolium perenne L.). Intact cores of a field-grown ryegrass sward were taken to the laboratory 10 d after cutting for measurement of photosynthesis under controlled conditions. This was done during two four-week periods, in summer and autumn. Net photosynthetic rate (PN) of the sward was lower in autumn than in summer. Both a simple negatively exponential photosynthesis irradiance-response curve and the Farquhar equations for photosynthesis were applied to the in vivo canopy measurements. Application of the irradiance-response curve showed that irradiance-saturated gross photosynthetic rate increased linearly with increasing temperature and was higher in summer than in autumn. The initial radiation use efficiency did not differ between the seasons but decreased with the temperature rise. This explains the observation that total canopy photosynthetic rate decreased after short-term temperature increases in both seasons. The parameters in Farquhar equations that represent the temperature sensitivity of the maximum electron transport rate and of the Michaelis-Menten constants for CO2 and O2 fixation could not be quantified satisfactorily. Parameterisation of the Farquhar equations was hampered by a lack of robust information on many biochemical parameters, and the use of simple empirical response-functions may be preferable in the case of in vivo canopy measurements on grass swards. and B. O. M. Dirks ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2398. Temperature-dependent decay-associated fluorescence spectra in phycobilisome-thylakoid membrane complexes from Spirulina platensis

Creator:
Li, Y., Sun, Z.-Y., Ai, X.-C., Zhao, J.-Q., and Zhang, X.-K.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
cyanobacterium and photosystems 1 and 2
Language:
Multiple languages
Description:
The kinetic component (39 ps) for the energy transfer from a phycobilisome (PBS) to the photosystems was temperature-dependent while the components related to the kinetic processes within PBS, photosystem 2 (PS2) or PS1 were temperature-independent. The 39 ps component possessed the amplitude maximum at 647 nm but the minimum at 715 nm (room temperature) or 685 nm (0 °C), suggesting a direct energy transfer from C-phycocyanin to PS1 at room temperature but to PS2 at 0 °C. The temperature-induced kinetic change originated from a position shift of PBS along the thylakoid membrane. and Y. Li ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2399. Temperature-dependent gas exchange and stomatal/non-stomatal limitation to CO2 assimilation of Quercus liaotungensis under midday high irradiance

Creator:
Zhang, Shouren, Li, Qingkang, Ma, Keping, and Chen, Lingzhi
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
carboxylation rate, diurnal course of gas exchange, internal CO2 concentration, photosynthesis, stomatal conductance, transpiration rate, and water use efficiency
Language:
Multiple languages
Description:
The effects of varying leaf temperature (T1) on some ecophysiological characteristics of photosynthesis for Quercus liaotungensis Koiz. under ambient radiation stress around midday on clear summer days were investigated using an IRGA equipped with a temperature-controlled cuvette. Net photosynthetic rate (PN) decreased as T1 increased from 30 to 35 °C as a result of stomatal closure, whereas non-stomatal limitation led to decreased PN in the T1 range of 35-45 °C. Decreased transpiration rate (E) and stomatal conductance (gs) at leaf temperatures above 30 °C were interpreted as a combined 'feedward' effect as a result of enhanced leaf-air vapour pressure deficit (VPD) and stomatal closure. Changes in E from T1 30 to 20 °C depended on VPD when gs was maintained constant. Water use efficiency (WUE) varied inversely with T1 by following a hyperbola. A decrease in intercellular CO2 concentration (Ci) occurred as a result of stomatal closure and a relatively high carboxylation capacity, whereas inactivation of mesophyll carboxylation in combination with photorespiration might be associated with the observed increase in Ci in the T1 range of 40 to 45 °C. and Shouren Zhang ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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