Tomato (Lycopersicon esculentum Mill. cv. Pearson) plants were grown in growth chambers for 25 days with cadmium (Cd) and then exposed briefly to ozone (O3). Gas exchange, chlorophyll a fluorescence, and pigment composition were analysed in leaves at the end of the treatment to assess the effects of a single pollutant and their combination on photosynthesis. The CO2 assimilation rate was dramatically reduced in plants subjected to the combined treatment, while the single effect of Cd appeared less severe than that of O3. The decline of CO2 photoassimilation found in all
O3-exposed plants was attributed to both stomatal and nonstomatal limitations. Tomato plants seemed to detoxify Cd to a great extent, but this resulted in growth suppression. In response to O3 exposure, the plants protected their photosystems by heat dissipation of excess energy via the xanthophyll cycle. Cd combined with O3 affected adversely this cycle resulting in an increase in photosynthetic performance under the same experimental light conditions., E. Degl’Innocenti, A. Castagna, A. Ranieri, L. Guidi., and Obsahuje bibliografii
Geitlerinema amphibium (BA-13), mat-forming cyanobacterium from the southern Baltic Sea, was grown at three irradiances [5, 65, and 125 μmol(photon) m-2 s-1] and three temperatures (15, 22.5, and 30°C). To determine the effect of the investigated factors and their interaction on culture concentration, pigment content, and photosynthetic parameters of cyanobacterium, factorial experiments and two-way analysis of variance (ANOVA) were carried out. Both chlorophyll (Chl) a and phycobilins (PB) were influenced by the irradiance and temperature, but stronger effect was noted in the case of the former one. Chl a and PB concentration per 100 μm of filament dropped above 4-fold with the increasing irradiance. The ratios between individual carotenoids [β-carotene, zeaxanthin, and myxoxanthophyll (Myx)] and Chl a increased significantly with an increase in the irradiance. The greatest fluctuations were observed in the ratio of Myx to Chl a (above 10-fold). Thus, Myx was suggested as the main photoprotective carotenoid in G. amphibium. Based on photosynthetic light response (PI) curves, two mechanisms of photoacclimation in G. amphibium were recognized: a change of photosynthetic units (PSU) number and a change of PSU size. These two mechanisms constituted the base of significant changes in photosynthetic rate and its parameters, such as the compensation point (PC), the initial slope of photosynthetic curve (α), saturation irradiance (EK), maximal photosynthetic rate (Pmax), and dark respiration rate (RD). The greatest changes were observed in PC values (about 15-fold within the range of the factors tested). Studied parameters showed a wide range of changes, which might indicate G. amphibium ability to acclimatize well to irradiance and temperature, and indirectly might explain the successful growth of cyanobacterium in dynamically changing environmental conditions., S. Jodłowska, A. Latała., and Obsahuje bibliografii
The chilling and light stresses were experimentally created to explore photosynthesis of Fraxinus mandshurica seedlings in northeast China. Net photosynthetic rate, stomatal conductance, and transpiration rate decreased significantly with the decline of temperature and light. Significant interaction effects of light and chilling were observed on gas exchange of photosynthesis. The minimal fluorescence yield of the dark-adapted state (F0) increased with increasing light and decreasing temperature. Both high and low light stresses induced the decreases of the maximal quantum yield of PSII photochemistry (Fv/Fm), photochemical quenching coefficient (qP), nonphotochemical quenching (NPQ), and electron transport rate. Decline of Fv/Fm and increased F0 were observed under decreasing temperatures. Decreased NPQ and qP at frost temperature suggest that F. mandschurica failed to dissipate excess light energy. No interactive effects of chilling and light on chlorophyll fluorescence parameters suggests that F. mandschurica seedlings might be adapted to combined stresses of light and chilling., X. F. Li, L. Jin, C. Y. Zhu, Y. J. Wen, Y. Wang., and Obsahuje bibliografii
The impact of drought stress (DS) on eight Eurasian and North African genotypes of wild barley (Hordeum spontaneum) was evaluated by analysis of chlorophyll (Chl) a fluorescence fast induction curves using the JIP-test. Three-week-old, pot-grown plants were exposed to a DS treatment by withholding water for nine days. The genotype-specific impairment of the functionality of the photosynthetic electron transport chain was quantified using the relative decline of the performance indices (PIabs and PItot), two key parameters of the JIP-test. The genotypes showing the highest (HOR10164) and lowest (HOR10710) relative PIs under DS were subjected to additional experiments, including measurements of leaf gas exchange, water status, pigment content, key enzyme activity, and protein abundance. The genotypes showed a specific profile of DS-mediated inhibition of photosynthesis, associated with higher relative leaf water contents in HOR10164 at the end of the treatment. Whereas decreased photosynthetic rate in HOR10164 was mainly caused by stomatal closure, nonstomatal limitations (decreased Rubisco content and activity) were detected in HOR10710. Additional genotype specific features were the upregulation of the NADP-malate dehydrogenase in HOR10164 and a decreased fraction of QA-reducing reaction centers in HOR10710., C. Jedmowski, S. Bayramov, W. Brüggemann., and Obsahuje bibliografii
The rare and endangered plant, Begonia fimbristipula, shows red and green phenotypes, differentiated by a coloration of the abaxial leaf surface. In this study, we compared morphological and physiological traits of both phenotypes. The results showed that the red phenotype contained a significantly higher chlorophyll content, closer arrangement of chloroplasts, and a more developed grana. In addition, the red phenotype transferred significantly more light energy into the electron transport during the photoreaction. Similarly, the maximum photosynthetic rate, instantaneous water-use and light-use efficiencies of the red B. fimbristipula were all significantly higher than those of the green individuals. The differentiation between these two phenotypes could be caused by their different survival strategies under the same conditions; epigenetic variations may be in some correlation with this kind of phenotype plasticity. Red B. fimbristipula has an advantage in resource acquisition and utilization and possesses a better self-protection mechanism against changes in environmental conditions, therefore, it might adapt better to global climate change compared to the green phenotype. Further studies on the possible epigenetic regulation of those phenotypic differentiations are needed., Y. Wang, L. Shao, J. Wang, H. Ren, H. Liu, Q. M. Zhang, Q. F. Guo, X. W. Chen., and Seznam literatury
The pericarp of cereal crops is considered a photosynthetically active tissue. Although extensive studies have been performed on green leaves, the photosynthetic role of the pericarp in cereal caryopsis development has not been well investigated. In the present study, we investigated the anatomy, ultrastructure, chlorophyll (Chl) fluorescence, and oxygen evolution of the pericarp during caryopsis ontogenesis in field wheat (Triticum aestivum L.). The results showed that wheat pericarp cross-cells contained Chl; the grana stacks and thylakoid membranes in the cross-cells were more distinct in the pericarp than those in the flag leaves as shown by transmission electron microscopy. Chl fluorescence revealed that the photosynthetic efficiency, which was indicated by values of maximum efficiency of PSII photochemistry and effective PSII quantum yield, was lower in the pericarp compared to that of the flag leaf eight days after anthesis (DAA), whereas similar values were subsequently observed. The nonphotochemical quenching values were lower from 8-16 DAA but significantly increased in the pericarp from 24-32 DAA compared to the flag leaf. The oxygen evolution rate of the flag leaves was consistently higher than that of pericarp; notably, isolated pericarps released more oxygen than intact pericarps during caryopsis development. These results suggest that the pericarp plays a key role in caryopsis development by performing photosynthesis as well as by supplying oxygen to the endosperm and dissipating excessive energy during the
grain-filling stages., L. A. Kong , Y. Xie, M. Z. Sun, J. S. Si, L. Hu., and Obsahuje seznam literatury
The diurnal trends of gas exchange and chlorophyll fluorescence parameters in four Lycoris species (L. houdyshelii, L. aurea, L. radiata var. pumila and L. albiflora) were determined and compared with a portable photosynthesis analysis system. Our study revealed that L. houdyshelii had the lowest light compensation point (LCP), while the other three species had higher LCP (12.37-14.99 μmol m-2 s-1); L. aurea had the highest light saturation point (LSP) (1,189 μmol m-2 s-1), and L. houdyshelii and L. albiflora had lower LSP with the values being 322 and 345 μmol m-2 s-1, respectively, and L. radiata var. pumila showed the intermediate LSP. Both the species L. houdyshelii and L. albiflora exhibited a typical and obvious decline in net photosynthetic rate (PN) during midday, which was not observed in L. aurea. This indicated a possible photoinhibition in L. houdyshelii and L. albiflora as the ratio of variable to maximum fluorescence (Fv/Fm) values were higher in these two species. The minimal fluorescence (F0) values were lower in L. aurea and L. radiata var. pumila. The diurnal changes of transpiration rate (E) in all four species presented only one peak, appearing between 11:00 h or 13:00 h. By using simple correlation analyses, it was observed that the environmental factors affecting
PN were different among four species and the main factors were photosynthetic photon flux density (PPFD) and relative humidity especially for L. aurea and L. radiata. The results of studying indicated that the four species could be divided into two groups. The species L. radiata var. pumila and L. aurea were more adapted to a relatively high irradiance, and L. houdyshelii and L. albiflora could be grown in moderate-shade environment in order to scale up their growth and productivity., K. Liu ... [et al.]., and Obsahuje bibliografii
Competition plays an important role in the replacement of native species by alien plants. A greenhouse experiment was conducted to investigate whether the competition pattern of alien Robinia pseudoacacia L. and native Quercus acutissima Carr. is affected by soil sterilization. Physiological traits, such as gas-exchange parameters and chlorophyll (Chl) content, and growth traits, such as the biomass accumulation of the two species, were examined in natural soil or in soil sterilized with benomyl. The results show that native Q. acutissima inhibits the growth of R. pseudoacacia in natural soil. When the two plants coexisted and competed under sterilization treatment, R. pseudoacacia was less inhibited by Q. acutissima and the competition of R. pseudoacacia decreased the growth of Q. acutissima in terms of biomass, Chl a, Chl b, total Chl, and Chl a/b. These results suggest that soil sterilization benefits the growth of R. pseudoacacia and changes the competition pattern by the changed soil biota. Soil sterilization increased the biomass of root nodules, which ultimately benefits the growth of R. pseudoacacia and root nodule bacteria may be important in the dispersal and invasion process of nitrogen-fixing alien plants such as R. pseudoacacia., H. Chen ... [et al.]., and Obsahuje bibliografii
In many plant species that remain leafless part of the year, CO2 fixation occurring in green stems represents an important carbon gain. Traditionally, a distinction has been made between stem photosynthesis and corticular photosynthesis. All stem photosynthesis is, sensu stricto, cortical, since it is carried out largely by the stem cortex. We proposed the following nomenclature: stem net photosynthesis (SNP), which includes net CO2 fixation by stems with stomata in the epidermis and net corticular CO2 fixation in suberized stems, and stem recycling photosynthesis (SRP), which defines CO2 ling in suberized stems. The proposed terms should reflect differences in anatomical and physiological traits. SNP takes place in the chlorenchyma below the epidermis with stomata, where the net CO2 uptake occurs, and it resembles leaf photosynthesis in many characteristics. SRP is found in species where the chlorenchyma is beneath a
well-developed stomata-free periderm and where reassimilation of internally respired CO2 occurs. SNP is common in plants from desert ecosystems, rates reaching up to 60% of the leaf photosynthetic rate. SRP has been demonstrated in trees from temperate forests and it offsets partially a carbon loss by respiration of stem nonphotosynthetic tissues. Reassimilation can vary between 7 and 123% of respired CO2, the latter figure implying net CO2 uptake from the atmosphere. Both types of stem photosynthesis contribute positively to the carbon economy of the species, in which they occur; they are advantageous to the plant because they allow the maintenance of physiological activity during stress, an increase of integrated water use efficiency, and they provide the carbon source used in the production of new organs., E. Ávila, A. Herrera, W. Tezara., and Obsahuje bibliografii
Differences in maximal yields of chlorophyll variable fluorescence (Fm) induced by single turnover (ST) and multiple turnover (MT) excitation are as great as 40%. Using mutants of Chlamydomonas reinhardtii we investigated potential mechanisms controlling Fm above and beyond the QA redox level. Fm was low when the QB binding site was occupied by PQ and high when the QB binding site was empty or occupied by a PSII herbicide. Furthermore, in mutants with impaired rates of plastoquinol reoxidation, Fm was reached rapidly during MT excitation. In PSII particles with no mobile PQ pool, Fm was virtually identical to that obtained in the presence of PSII herbicides. We have developed a model to account for the variations in maximal fluorescence yields based on the occupancy of the QB binding site. The model predicts that the variations in maximal fluorescence yields are caused by the capacity of secondary electron acceptors to reoxidize QA-., O. Prášil, Z. S. Kolber, P. G. Falkowski., and Obsahuje bibliografické odkazy