Soil salinization and alkalinization frequently co-occur in naturally saline and alkaline soils. To understand the characteristics of mixed salt-alkali stress and adaptive response of Medicago ruthenica seedlings to salt-alkali stress, water content of shoots, growth and photosynthetic characteristics of seedlings under 30 salt-alkaline combinations (salinity 24-120 mM and pH 7.03-10.32) with mixed salts (NaCl, Na2SO4, NaHCO3, and Na2CO3) were examined. The indices were significantly affected by both salinity and pH. The interactive effects between salt and alkali stresses were significant, except for photosynthetic pigments. Water content of shoots, relative growth rates of shoots and roots and pigment concentrations showed decreasing trends with increasing salinity and alkalinity. The root activity under high alkalinity and salinity treatments gradually decreased, but was stimulated by the combined effects of low alkalinity and salinity. The survival rate decreased with increased salinity, except at pH 7.03-7.26 when all plants survived. Net photosynthetic rate, stomatal conductance and intercellular CO2 concentration decreased with increased salinity and pH. M. ruthenica tolerated the stress of high salt concentration when alkali concentration was low, and the synergistic effects of high alkali and high salt concentrations lead to the death of some or all seedlings. M. ruthenica appeared to be salt-alkali tolerant. Reducing the salt concentration or pH based on the salt components in the soil may be helpful to abate damage from mixed salt-alkaline stress. and J. Y. Yang ... [et al.].
Chlorophyll (Chl) content, dry mass, relative water content (RWC), leaf mass per area (LMA), proline (Pro) content, malondialdehyde (MDA) content, superoxide dismutase (SOD) and peroxidase (POD) activity, PN-PAR response curves and gas exchange were studied to determine the effects of water stress on photosynthetic activity, dry mass partitioning and metabolic changes in four provenances of neem (Azadirachta indica A. Juss). The results indicated that provenance differences existed in the adaptation response to water stress that included changes to growth strategies coupled with ecophysiological and metabolic adjustments. As water stress increased, stomatal conductance (gs), net photosynthetic rate (PN), transpiration rate (E), and leaf RWC decreased while LMA increased in all provenances. Dry mass was reduced in droughted plants and the percentage increased in dry mass allocated to roots, and enzyme activities of SOD and POD were highest in neem originating from Kalyani (KA) provenance and lowest in neem originating from New Dehli (ND) provenance. In contrast, water stress increased MDA content least in KA and most in ND. Furthermore, neem originating from ND also had the greatest decrease in Chl a/b ratio while the ratio was least affected in neem originating from KA. These findings suggest neem originating from KA may have more drought resistance than neem originating from ND. The data from PN-PAR response curves are less clear. While these curves showed that drought stress increased compensation irradiance (Ic) and dark respiration (RD) and decreased saturation irradiance (Is) and maximum net photosynthetic rate (Pmax), the extent of decline in P max was provenance dependent. P max under non-waterlimiting conditions was higher in neem originating from Jodhpur (MA) (about 14 μmol m-2 s-1) than in the other three provenances (all about 10 μmol m-2 s-1), but mild water stress had minimal effect on Pmax of these three provenances whereas Pmax of MA provenance declined to 10 μmol m-2 s-1, i.e. a similar value. However, under severe water stress P max of MA and KA provenances had declined to 40% of non-stressed values (about 6 and 4 μmol m-2 s-1, respectively) whereas the decline in Pmax of neem originating from Kulapachta (KU) and ND provenances was about 50% of nonstressed values (about 5 μmol m-2 s-1). These data suggest the PN responses of KU and ND provenances are most tolerant, and KA and MA least tolerant to increasing water stress, but also suggest MA provenance could be the most desired under both non-water-limiting and water-limiting conditions due to highest Pmax in all conditions. and Y. X. Zheng ... [et al.].
We studied how tomato (Lycopersicon esculentum Mill.) chloroplast omega-3 fatty acid desaturase gene (Lefad7) overexpression enhanced low-temperature (LT) tolerance in transgenic tomato plants. In these plants, the content of linolenic acid (18:3) markedly increased and, correspondingly, the content of linoleic acid (18:2) decreased. Similar changes were found after 6 h under LT (4°C) treatment. Under LT stress, wild type (WT) tomato plants showed a much greater increase in relative electrolyte leakage and malondialdehyde (MDA) contents compared with transgenic plants. Transgenic plants exhibited higher activities of antioxidative enzymes and a lower content of reactive oxygen species (ROS). Transgenic plants maintained a relatively higher level of the net photosynthetic rate (PN) and chlorophyll (Chl) content than WT plants under LT stress. Taken together, we suggested that overexpression of Lefad7 enhanced LT tolerance by changing the composition of membrane lipids in tomato plants, with the increased content of trienoic fatty acids and reduced content of dienoic fatty acids that led to series of physiological alterations., X. Y. Liu ... [et al.]., and Obsahuje bibliografii
Článek přináší poznatky o vznikajících mezidruhových vztazích v ekosystémech po zavlečení nového invazního druhu rostliny – netýkavky žláznaté (Impatiens glandulifera) – a uvádí některé entomologické aspekty jejího masového výskytu v novém prostředí., The impact of aphids on the invasive plant Impatiens glandulifera in the Czech Republic is shown and some entomological aspects of I. glandulifera distribution in local ecosystems are discussed., and Petr Starý, Jan Havelka.
Industrial chicory, Cichorium intybus L., has rather poor early vigour under the typical early spring morning conditions of low temperatures and high light intensity. Screening tools are being developed to assess the cold tolerance/sensitivity of young industrial chicory plants under these conditions. Refinement of such tools requires better understanding of the plants' physiological responses. In this paper we discuss the effects of growth temperature (GT), measurement temperature (MT), and measuring light intensity (ML) on the relaxation of the Kautsky curve. We chose the chicory variety 'Hera', as it is known to possess a good average early vigour. Young plants of the variety 'Hera' were grown at three temperatures (GT): 16°C (reference), 8°C (intermediate), and 4°C (cold stress). The dark relaxation kinetics were analyzed at different light intensities (ML) in combination with different measurement temperatures (MT). The three components of the nonphotochemical quenching process (NPQE, NPQT, and NPQI) were determined. NPQE was not affected by GT but was significantly affected by MT and ML. NPQT and NPQI were affected by all factors and their interactions. An acclimation effect for plants grown at low GT was detected. Acclimation resulted in lower NPQT and NPQI values. The halftime of the inhibition depending on NPQ (NPQI) was not affected by any of the factors investigated. Based on the data generated, we conclude that NPQI is a valuable parameter for screening the cold sensitivity of young industrial chicory plants. and P. Lootens ... [et al.].
Industrial chicory, Cichorium intybus L., is cultivated for the production of inulin. Most varieties of industrial chicory exhibit rather poor early growth, which limits further yield improvements in their European cultivation area. The poor early growth could be due to suboptimum adaptation of the gene pool to growth at low temperatures, sometimes in combination with high light intensities, which is typical of early-spring mornings. We have used chlorophyll (Chl) a fluorescence to evaluate the response of young plants of the cultivar 'Hera' to low temperatures and high light intensities. Plants were grown at three temperatures: 16°C (reference), 8°C (intermediate), and 4°C (cold stress). Light-response measurements were carried out at different light intensities in combination with different measurement temperatures. Parameters that quantify the photosystem II (PSII) operating efficiency (including PSII maximum efficiency and PSII efficiency factor) and nonphotochemical quenching (NPQ) are important to evaluate the stress in terms of severity, the photosynthetics processes affected, and acclimation to lower growth temperatures. The results clearly demonstrate that in young industrial chicory plants the photosynthetic system adapts to lower growth temperatures. However, to fully understand the plant response to the stresses studied and to evaluate the long-term effect of the stress applied on the growth dynamics, the subsequent dark relaxation dynamics should also be investigated. and S. Devacht ... [et al.].
Simultaneous measurements of leaf gas exchange and chlorophyll fluorescence for Koelreuteria paniculata Laxm. at 380 ± 5.6 and 600 ± 8.5 μmol mol-1 were conducted, and the photosynthetic electron flow via photosystem II (PSII) to photosynthesis, photorespiration, and other electron-consuming processes were calculated. The results showed that the photosynthetic electron flow associated with carboxylation (Jc), oxygenation (Jo), and other
electron-consuming processes (Jr) were 72.7, 45.7, and 29.4 μmol(e-) m-2 s-1 at 380 μmol mol-1, respectively; and 86.1, 35.3, and 48.2 μmol(e-) m-2 s-1 at 600 μmol mol-1, respectively. Our results revealed that other aspects associated with electronconsuming processes, except for photosynthesis and respiration, were neither negligible nor constant under photorespiratory conditions. Using maximum net photosynthetic rate (Pmax), day respiration (R), photorespiration rate (Rl), and maximum electron flow via PSII
(Jmax), the use efficiency of electrons via PSII at saturation irradiance to fix CO2 was calculated. The calculated results showed that the use efficiency of electrons via PSII to fix CO2 at 600 μmol mol-1 was almost as effective as that at 380 μmol mol-1, even though more electrons passed through PSII at 600 μmol mol-1 than at 380 μmol mol-1., Z. P. Ye, Q. Yu, H. J. Kang., and Obsahuje bibliografii
The effectiveness of eight spectral reflectance indices for estimating chlorophyll (Chl) content in leaves of Eugenia uniflora L., a tropical tree species widely distributed throughout the world and a key species for ecosystem restoration projects, was evaluated. Spectral reflectance indices were tested using sun and shade leaves with a broad variation in leaf mass per area (LMA). Shortly after plants were exposed to chilling temperatures, there was a dramatic visible change in some sun leaves from green to red. Prior to testing Chl-related reflectance indices, the green and red leaves were separated according to the anthocyanin reflectance index (ARI). Slightly green to dark green leaves corresponded to an ARI value less than 0.11 (n = 107), whereas slightly red to red leaves corresponded to an ARI value greater than 0.11 (n = 35). To estimate leaf Chl, two simple reflectance indices (SR680 and SR705), two normalized difference indices (ND680 and ND705), two modified reflectance indices (mSR705 and mND705), a modified Chl absorption ratio index (mCARI705) and an index insensitive to the presence of anthocyanins (CIre) were evaluated. Good estimates of leaf Chl content were obtained using the reflectance indices tested regardless of the presence of anthocyanins and changes in LMA. Based on the coefficients of determination (r2) and the root mean square errors (RMSɛc) the best results were obtained with reflectance indices measured at wavelengths of 750 and 705 nm. Considering the performance of the models the best reflectance indices to estimate Chl contents in E. uniflora leaves with a broad variation in LMA and anthocyanin contents was SR705 and mCARI705., M. S. Mielke, B. Schaffer, A. C. Schilling., and Obsahuje bibliografii
Epigenetická regulace aktivity genů může významnou měrou ovlivňovat fenotypovou variabilitu organismů. Vzhledem k tomu, že některá indukovaná epigenetická variabilita může být děděna po mnoho generací, je možné, že epigenetická variabilita ovlivňuje jak ekologii, tak i evoluční trajektorie organismů. V článku popisuji některé poslední poznatky úlohy epigenetické variability v ekologii a evoluci rostlin., Phenotypic variation can be driven by epigenetic regulation of genes' activity. It is possible that induced epigenetic variation can alter the ecology and evolutionary trajectories of organisms because some induced epigenetic variation can be faithfully heritable among several generations. In the article, I discuss some recent information about the role of epigenetic variation in the ecology and evolution of plants., and Vít Latzel.
Excitation kinetics based on feedback regulation of chlorophyll (Chl) fluorescence of leaves measured with the chlorophyll fluorometer, FluoroMeter Modul (FMM), are presented. These kinetics showed the variation of excitation light (laser power, LP) regulated by the feedback mechanism of the FMM, an intelligent Chl fluorometer with embedded computer, which maintains the fluorescence response constant during the 300-s transient between the dark- and light-adapted state of photosynthesis. The excitation kinetics exhibited a rise of LP with different time constants and fluctuations leading to a type of steady state. The variation of excitation kinetics were demonstrated using the example of primary leaves of etiolated barley seedlings (Hordeum vulgare L. cv. Barke) during 48 h of greening in the light with gradual accumulation of Chl and development of photosynthetic activity. The excitation kinetics showed a fast rise followed by a short plateau at ca. 30 s and finally a slow constant increase up to 300 s. Only in the case of 2 h of greening in the light, the curve reached a stable steady state after 75 s followed by a slight decline. The final LP value (at 300 s of illumination) increased up to 12 h of greening and decreased with longer greening times. The active feedback mechanism of the FMM adjusted the excitation light during the measurement to the actual photosynthetic capacity of the individual leaf sample. In this way, the illumination with excessive light was avoided. The novel excitation kinetics can be used to characterize health, stress, disease, and/or product quality of plant material., C. Buschmann ... [et al.]., and Obsahuje bibliografii