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
We summarize the contemporary understanding of the effects of metal stress on various photosynthetic processes in photoautotrophic organisms and of the defence strategies employed by these organisms to avoid such stress. Cadmium is in the centre of interest of this review, as a non-essential element and important environmental pollutant, but Al, Pb, Hg, As, Cu, and Zn are also considered. Toxic metal ions pollute the environment through anthropogenic activities and affect the quality of plant crop. They represent one of the main abiotic stress factors influencing the health of plants and, as a secondary effect, of animals including man. The review summarizes the generally accepted answers to the questions: How do the toxic metal ions enter the photosynthetic organisms? How are they accumulated in plants? Which mechanisms do plants develop to tolerate metal stress and protect themselves? and T. Kučera, H. Horáková, A. Šonská.
A trace amount of chlorophyll (Chl) a was found in addition to protochlorophyllide (PChlide) a and protochlorophylls (PChls) a in acetone extracts of etiolated cucumber cotyledons by HPLC. There was, however, no chlorophyllide (Chlide) a, which was present in extracts from illuminated cotyledons. After 10 min exposure of cotyledons to light, all PChlide a was photoreduced to Chlide a. Hence, the whole pool of PChlide seems to be photoactive. The "photoinactive" spectral form PChl(ide) F633 was identified as a mixture of monovinyl-PChls a esterified by different alcohols.
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
Sparse-elm grassland is the remarkable landscape of Hunshandak Sandland in Inner Mongolia Autonomic Region of China. Maximum quantum efficiency (Fv/Fm) of 99 native plant species (85 grasses, 11 shrubs, and 3 trees) of different plant functional Types (PFTs) distributed in fixed sand dune, lowland, and wetland was investigated. Deep-rooted plant species (tree, shrub, and perennial grass) had higher Fv/Fm values than the shallow-rooted species (annual grasses), suggesting that soil drought is the major environmental stress. Annual C4 grasses had higher Fv/Fm values than annual C3 or CAM ones, indicating that C4 photosynthesis is more ecologically adaptive than CAM and C3 grasses. According to the habitats with annual C3 grass distribution, Fv/Fm values were in the order of fixed dune>lowland>wetland, suggesting that salt and pH value may enhance irradiance or heat stress for those distributed in pickled and watery habitats. Based on such characteristics, Ulmus pumila, Salix gordejevii, Caragana microphylla, Agriophyllum pungens, and Agropyron cristatum are recommended as ideal species for ecological restoration in degraded sand-land ecosystems. and Yong-Geng Li ... [et al.].
High salt concentration is a major abiotic stress limiting plant growth and productivity in many areas of the world. Elaeagnus angustifolia L. adapts to adverse environments and is widely planted in the western region of China as a windbreaker and for landscape and soil stabilization. High salt concentrations inhibited photosynthesis of E. angustifolia, but the mechanism is not known. In this paper, RNA-sequencing was used to investigate effects of salt stress on the photosynthetic characteristics of the species. In total, 584 genes were identified and involved in photosynthetic pathways. The downregulation of genes that encode key enzymes involved in photosynthesis and genes correlated to important structures in photosystem and light-harvesting complexes might be the main reason, particularly, the downregulation of the gene that encodes magnesium chelatase. This would decrease the activity of enzymes involved in chlorophyll synthesis and the downregulation of the key gene that encodes Rubisco, and thereby decreases enzyme activity and the protein content of Rubisco., J. Lin, J. P. Li, F. Yuan, Z. Yang, B. S. Wang, M. Chen., and Obsahuje bibliografii
Rice being the major food crop for more than half of the world population is severely affected by drought stress starting from the establishment of the seedling. We focused on the UV-B priming mediated transgenerational drought tolerance of a drought-tolerant rice variety (Vaisakh) towards polyethylene glycol (PEG) 6,000 (20%)-induced drought. Results showed that priming in F0 generation and re-priming in F1 generation with UV-B enhanced the PEG stress tolerance potential of rice seedlings with increased expression of genes encoding antioxidant enzymes and stress-related proteins offering better protection to primed plants. UV-B priming maintained oxidative homeostasis of the plant cell thus ensuring uninterrupted mitochondrial and photosynthetic activities. Cumulatively, our results suggest that the transgenerational priming memory retained in the seeds is transferred to offspring without any loss. Moreover, re-priming in F1 generation further boosted the innate tolerance potential of a tolerant variety resulting in stable cellular redox homeostasis.
RNA gel hybridization showed that the expression of monodehydroascorbate reductase (MDHAR) in the wild type (WT) tomato was decreased firstly and then increased under salt- and polyethylene glycol (PEG)-induced osmotic stress, and the maximum level was observed after treatment for 12 h. WT, sense transgenic and antisense transgenic tomato plants were used to analyze the antioxidative ability to cope with osmotic stresses. After salt stress, the fresh mass (FM) and height of sense transgenic lines were greater than those of antisense lines and WT plants. Under salt and PEG treatments, sense transgenic plants showed a lower level of hydrogen peroxide (H2O2) and malondialdehyde (MDA), a higher net photosynthetic rate (PN), and the maximal photochemical efficiency of PSII (Fv/Fm) compared with WT and antisense transgenic plants. Moreover, sense lines maintained higher ascorbate peroxidase (APX) activity than WT and antisense plants under salt- and PEG-induced osmotic stress. These results indicate that chloroplastic MDHAR plays an important role in alleviating photoinhibition of PSII by elevating ascorbate (AsA) level under salt- and PEG-induced osmotic stress., F. Li ... [et al.]., and Obsahuje bibliografii
Chlorophyll (Chl) fluorescence temperature cinve (FTC) of primary leaves of spring barley (Hordeum vulgare L.), cultivated imder a low irradiance, was studied at low actinic radiation excitation (436 nm, 2 W m'^) under a heating regime consisting of a linear increase of temperature (0.083 °C s’*), followed by a period of constant temperature. After prompt cooling of the sample to 77 K, Chl fluorescence spectra at defined points of the temperature regime were measured. Two distinct temperature and kinetic regions expressed by two discemible temperature maxima were observed for ťhis type of the FTC. Two triggering temperatures of successive irreversible changes are postulated at 45-48 “C and 53-55 °C temperature intervals, respectively; they may correlate with the heat inactivation of photosystem 2 and with changes of the chloroplast and cytoplasmic membrane integrity.
At various intervals after inoculation of the roots of groundnut plants with the fungus Macrophomina phaseoli, 14CO2 was administered to branch 2 (from the base) of the plants in the light. The effects of the disease on the translocation of 14C-photosynthates out of the source branch to the rest of the plant were studied 24 h after labelling. As the plant aged and the disease symptom development became more evident, an increasing percentage of the fixed 14C-photosynthates was exported from branch 2 of the inoculated plants (IP) compared to the non-inoculated plants (NIP). The apex, main stem, and branch 1 of NIP imported more of the total fixed 14C throughout the developmental stages of the plant except for day 10 after inoculation when branch 1 of IP imported almost 76 % of the total fixed 14C. The roots of IP were the major sink and imported higher percent of the total fixed 14C than the roots of NIP.