The photosynthetic parameters in leaves of three-year-old seedlings of Fraxinus rhynchophylla L. were studied under different soil water conditions and CO2 concentrations ([CO2]) with a
LI-COR 6400 portable photosynthesis system. The objective was to investigate the response of photosynthesis and stomatal conductance (gs) to various [CO2] and soil water conditions, and to understand the adaptability of F. rhynchophylla to such conditions. The results showed that the soil water content (RWC) required to maintain high photosynthetic productivity in F. rhynchophylla was 49.5-84.3%; in this range, net photosynthetic rate (PN) rose with [CO2] increasing from 500 to 1,400 μmol mol-1. Outside this RWC range, PN decreased significantly. The apparent maximum photosynthetic rate (Pmax,c) and carboxylation velocity (Vc) increased with increasing RWC and remained relatively high, when RWC was between 49.5 and 96.2%. CO2 compensation points and photorespiration rate exhibited a trend opposite to that of Pmax,c and Vc, indicating that moderate water stress was beneficial for increasing plant assimilation, decreasing photorespiration, and increasing production of photosynthates. gs declined significantly with increasing [CO2] under different water supplies, but the RWC range maintaining high gs increased. gs reached its maximum, when RWC was approximately 73% and then decreased with declining RWC. The maximal gs was found with increasing RWC. Thus, based on photosynthetic characteristics in artificial, vegetation construction in semiarid loess hill and gully area, F. rhynchophylla could be planted in habitats of low soil water content. and S. Y. Zhang ... [et al.].
Changes in the temperature dependence of the maximum carboxylation capacity (VCmax) of Rubisco during thermal acclimation of PN remain controversial. I tested for acclimation of the temperature dependence of VCmax in quinoa, wheat, and alfalfa. Plants were grown with day/night temperatures of 12/6, 20/14, and 28/22°C. Responses of PN to substomatal CO2 (Ci) and CO2 at Rubisco (Cc) were measured at leaf temperatures of 10-30°C. VCmax was determined from the initial slope of the PNvs. Ci or Cc curve. Slopes of linear regressions of 1/VCmaxvs. 1/T [K] provided estimates the activation energy. In wheat and alfalfa the increases in activation energy with growth temperature calculated using Ci did not always occur when using Cc, indicating the importance of mesophyll conductance when estimating the activation energy. However, in quinoa, the mean activation energy approximately doubled between the lowest and highest growth temperatures, whether based on Ci or Cc., J. A. Bunce., and Obsahuje bibliografii
This study investigated whether gas exchange and the present content of antioxidant compounds can contribute to the survival of Euterpe oleracea plants in environments of frequent waterlogging. A factorial randomised, experimental design included two distinct water conditions (waterlogging and control) and five evaluation times (0, 6, 12, 18, and 24 d). Gasexchange parameters, leaf temperature, electrolyte leakage, and contents of antioxidant compounds were measured. Waterlogging did not promote significant alterations in net photosynthetic rate and transpiration, and stomatal conductance was reduced only after 18 d. Malondialdehyde and glutathione contents did not significantly change during waterlogging. Additionally, electrolyte leakage was significant only after 18 d of waterlogging. Thus, this study revealed that maintenance in gas exchange and antioxidant compounds might contribute to the survival of E. oleracea plants in environments exposed to waterlogging., T. S. Pereira, A. K. S. Lobato, G.A.R. Alves, R.N. Ferreira, O.N. Silva, A. P. Martins Filho, E.S. Pereira, L.S. Sampaio., and Obsahuje bibliografii
Intercropping is a sustainable agricultural practice used worldwide for highly efficient utilization of resources. However, short crops often grow under the shade of the canopy of tall crops in intercropping systems. Plants evolved two main strategies to deal with shade: avoidance and tolerance. Soybean (Glycine max), a legume crop, is often planted in intercropping. But little is known about a strategy that soybean may employ to deal with shade at seedling stage. Therefore, we determined morphological and physiological traits related to shade tolerance and shade avoidance in seedlings of two varieties. Generally, both varieties showed similar shade tolerance traits, such as increased specific leaf area and chlorophyll (Chl) content, and reduced photosynthetic capacity and the Chl a/b ratio. The light-limiting environment eliminated the benefits of shade tolerance traits for the carbon gain, which led to similar real-time photosynthesis and biomass in intercropping. By contrast, two varieties expressed different changes in shade avoidance traits. The variety Guixia 3 exhibited clear preference of shade avoidance that resulted in a high main stem, hypocotyl elongation, and biomass allocation towards the stem. The variety Gongxuan 1 showed those traits less. We suggested that the genetic variation occurs within soybean, thus the shade avoidance related traits might be important for variety selection for intercropping. Hence, the evaluation of performance should focus on shade avoidance in soybean genotypes in future experiments., W. Z. Gong, C. D. Jiang, Y. S. Wu, H. H. Chen, W. Y. Liu, W. Y. Yang., and Obsahuje bibliografii
Due to emerging high spectral resolution, remote sensing techniques and ongoing developments to retrieve the spectrally resolved vegetation fluorescence spectrum from several scales, the light reactions of photosynthesis are receiving a boost of attention for the monitoring of the Earth's carbon balance. Sensor-retrieved vegetation fluorescence (from leaf, tower, airborne or satellite scale) originating from the excited antenna chlorophyll a molecule has become a new quantitative biophysical vegetation parameter retrievable from space using global imaging techniques. However, to retrieve the actual quantum efficiencies, and hence a true photosynthetic status of the observed vegetation, all signal distortions must be accounted for, and a high-precision true vegetation reflectance must be resolved. ESA's upcoming Fluorescence Explorer aims to deliver such novel products thanks to technological and instrumental advances, and by sophisticated approaches that will enable a deeper understanding of the mechanics of energy transfer underlying the photosynthetic process in plant canopies and ecosystems., S. Van Wittenberghe, N. Sabater, M. P. Cendrero-Mateo, C. Tenjo, A. Moncholi, L. Alonso, J. Moreno., and Obsahuje bibliografické odkazy
Environmental pollution by antibiotics poses a potential ecological risk to aquatic photosynthetic organisms. In the present study, toxic effects of erythromycin on PSI and PSII were investigated in cyanobacteria culture medium of Microcystis aeruginosa. The activity and electron transport of both photosystems were affected by erythromycin in a concentrationdependent manner. The quantum yield of PSII (YII) was reduced at 0.1 mg L-1 of erythromycin, while the quantum yield of PSI (YI) significantly decreased at concentration of 5-25 mg L-1. The decline of YII was accompanied by an increase of nonregulated energy dissipation (YNO). At 10 mg L-1 of erythromycin, YII decreased by 55%, while YNO increased by 18%. The decrease of YI induced by erythromycin was caused by donor-side limitation of PSI (YND). YND was markedly enhanced with elevated erythromycin concentration. At 10 mg L-1 of erythromycin, YI and YNA (PSI acceptor-side limitation) decreased by 8 and 82%, respectively, while YND rose by 314%. The quantum yield of cyclic electron flow increased significantly at 0.1-1 mg L-1 of erythromycin; it decreased but remained higher than that of the control at 5-25 mg L-1 of erythromycin. The contribution of cyclic electron flow to YI, and to linear electron flow rose significantly with the increasing erythromycin concentration. The maximum values of electron transport rates in PSII and PSI decreased by 71 and 24.3%, respectively, at 25 mg L-1 of erythromycin. Compared with the untreated control, the light saturation of PSII and PSI decreased significantly with increasing erythromycin concentration. We showed that concentrations of erythromycin >- 5 mg L-1 could exert acute toxicity to cyanobacteria, whereas the chronic toxicity caused by concentrations of ng or μg L-1 needs further research., C.-N. Deng, D.-Y. Zhang, X.-L. Pan., and Obsahuje bibliografii
The aim of this study was to determine the impact of increased copper contents on selected physiological processes in oneyear-old Pinus sylvestris L. needles from a former German timber storage area in Warcino Forest District, a subject to an environmental quality survey. Samples were collected from the area with the high copper content in the soil. The control area was a nearby pine tree stand showing unimpeded growth. The significant growth inhibition was found in dwarf shoots and whole needles, increased water content, and reduced dry mass were also observed. The chlorophyll content was lowered, while 20% higher electrolyte leakage was found. Chlorophyll a fluorescence indicated only higher values of the nonphotochemical quenching in P. sylvestris from the Cu-site. Significant differences were shown in the rate of gas exchange measured by changes in carbon dioxide or oxygen concentration. The intensity of photosynthesis in needles of P. sylvestris from the Cu-site measured by CO2 uptake was considerably higher than that of oxygen production. The rate of respiration in the needles from the Cu-site measured by the amount of released CO2 was higher only by 15%, while according to O2 consumed, the rate increased by 30% in relation to the control. Our results suggest that the copper accumulation in P. sylvestris needles affected the morphology and physiology of the studied organs., K. Możdżeń, T. Wanic, G. Rut, T. Łaciak, A. Rzepka., and Obsahuje bibliografii
Seedling recruitment is a critical developmental stage in regeneration of plant populations under Mediterranean conditions that strongly depends on water availability. Seed mass and relative growth rate (RGR) may affect the early establishment of seedlings through different physiological processes. Here, we examined the effects of the seed mass and carbon balance on seedling growth under two water regimes in Rhamnus alaternus L. and Rhamnus ludovici-salvatoris, two Mediterranean shrubs, showing a different ability to recruit seedlings. Plant water consumption and biomass accumulation (ΔB) were measured during three periods of the growth in order to estimate water use efficiency (WUE), RGR, and its components. Additionally, net photosynthesis and leaf, stem, and root respiration were measured in plants grown in pots well watered and under progressive drought. Rhamnus alaternus showed the higher seed mass, ΔB, and plant WUE than that of R. ludovici-salvatoris in all periods and water regimes. The higher RGR of R. alaternus was observed during the first and the second period, but the reverse trend was registered during the third period as a consequence of the higher initial biomass of R. alaternus. Also, R. alaternus showed a higher specific leaf area and estimated carbon balance than that of R. ludovicisalvatoris. The observed differences in ΔB, estimated carbon balance, seed mass, and WUE between both species could explain their different distribution and ability to recruit seedlings under natural conditions., H. El Aou-Ouad, I. Florez-Sarasa, M. Ribas-Carbó, J. Flexas, H. Medrano, J. Gulías., and Obsahuje seznam literatury
The present study attempts to determine how some physiological and reproductive functions of olive tree (Olea europaea L., cv. Koroneiki) respond to enhanced UV-B radiation or heat. Enhanced UV-B radiation was applied to (1) three-year-old potted plants in an open nursery (corresponded to ca. 16% ozone depletion), and (2) in vitro cultured pollen samples (220 μmol m-2 s-1, PAR = 400-700 nm + UV-B at 7.5, 15.0, or 22.5 kJ m-2 d-1). Potted olive plants were also subjected to high temperature (38 +- 4°C) for 28 h to mimic heat levels regularly measured in olive growing areas. A significant effect of UV-B on photosynthetic rate was observed. However, enhanced UV-B radiation did affect neither chlorophyll nor carotenoid content, supporting previous reports on hardiness of the photosynthetic apparatus in olive. Increased superoxide dismutase activity was observed in UV-B-treated olive plants (+ 225%), whereas no effect was found in the plants under heat stress. Neither UV-B and nor heat did affect H2O2 accumulation in the plant tissues. However, the same treatments resulted in enhanced lipid peroxidation (+ 18% for UV-B and + 15% for heat), which is likely linked to other reactive oxygen species. The increased guaiacol peroxidase activity observed in both treatments (+ 32% for UV-B and + 49% for heat) is related to the defense against oxidative membrane damage. The observed reduction in pollen germination (20-39%) and tube length (11-44%) could have serious implications on olive yields, especially for low fruit-setting cultivars or in years and environments with additional unfavorable conditions. UV-B and heat effects described here support the hypothesis that plant response to a given stressor is affected by the overall context and that a holistic approach is necessary to determine plant strategies for climate change adaptation., G. C. Koubouris, N. Kavroulakis, I. T. Metzidakis, M. D. Vasilakakis, A. Sofo., and Obsahuje bibliografii
At present, chlorophyll meters are widely used for a quick and nondestructive estimate of chlorophyll (Chl) contents in plant leaves. Chl meters allow to estimate the Chl content in relative units - the Chl index (CI). However, using such meters, one can face a problem of converting CI into absolute values of the pigment content and comparing data acquired with different devices and for different plant species. Many Chl meters (SPAD-502, CL-01, CCM-200) demonstrated a high degree of correlation between the CI and the absolute pigment content. A number of formulas have been deduced for different plant species to convert the CI into the absolute value of the photosynthetic pigment content. However, such data have not been yet acquired for the atLEAF+ Chl meter. The purpose of the present study was to assess the applicability of the atLEAF+ Chl meter for estimating the Chl content. A significant species-specific exponential relationships between the atLEAF value (corresponding to CI) and extractable Chl a, Chl b, Chl (a+b) for Calamus dioicus and Cleistanthus sp. were shown. The correlations between the atLEAF values and the content of Chl a, Chl b, and Chl (a+b) per unit of leaf area was stronger than that per unit of dry leaf mass. The atLEAF value- Chl b correlation was weaker than that of atLEAF value-Chl a and atLEAF value-Chl (a+b) correlations. The influence of light conditions (Chl a/b ratio) on the atLEAF value has been also shown. The obtained results indicated that the atLEAF+ Chl meter is a cheap and convenient tool for a quick nondestructive estimate of the Chl content, if properly calibrated, and can be used for this purpose along with other Chl meters., E. V. Novichonok, A. O. Novichonok, J. A. Kurbatova, E. F. Markovskaya., and Obsahuje seznam literatury