The rainy season affects the development of maize in Liaoning Province in China. Continuous, rainy weather and scant sunlight result in poor pollination, bald tips, and in an abnormally high, barren stalk. Field studies were conducted at the kernel formation stage (3-11 d after silking). Paired, near-isogenic lines of nonbarren stalk (Shennong 98B) and barren stalk (Shennong 98A) were exposed to 38, 60, and 75% shading to investigate changes in photosynthesis and chlorophyll (Chl) fluorescence characteristics under different light intensities. Net photosynthetic rate (PN), leaf maximum photochemical efficiency of PSII (Fv/Fm), photochemical quenching of Chl fluorescence (qP), and actual photochemical efficiency of PSII (ΦPSII) of Shennong 98B were always higher than those of Shennong 98A under natural light, contrary to nonphotochemical quenching (NPQ). Fv/Fm, ΦPSII, and qP increased, while PN and electron transport rate (ETR) decreased after shading, and this was aggravated with increasing shade intensity. PN, qP, ΦPSII, and ETR were lower than the values in natural light condition after seven days of shading. NPQ, Fv/Fm, ΦPSII, qP, and ETR recovered, when shading was removed. The PN of two inbred lines returned soon to the control levels after 38% shade. Under shade and natural light conditions, the PN and Chl fluorescence characteristics of Shennong 98A were both lower than those of Shennong 98B. We suggest that a poor adaptability to low light is an important physiological reason for inducing barren stalk in low light-sensitive maize., X. M. Zhong, Z.S. Shi, F.H. Li, H.J. Huang., and Obsahuje bibliografii
In the present study, photosynthetic traits and chlorophyll (Chl) fluorescence parameters of Populus sibirica grown under different irrigation regimes were investigated to estimate seedling growth and vitality for reforestation of a desertification area. According to our results, photosynthesis and Chl fluorescence were significantly affected by water deficit only under severe drought conditions., T. Y. Lee, S. Y. Woo, M. J. Kwak, K. Inkyin, K. E. Lee, J. H. Jang, I. R. Kim., and Obsahuje seznam literatury
To uncover adaptation capacities of two flooding-tolerant plant species, Pterocarya stenoptera (a native species) and Pinus elliottii (an exotic species from southeastern USA), to alternating submergence and drought, we investigated their physiological and growth responses to water stress. Water treatments, including control, continuous flooding (CF), and periodic flooding and drought (PF), were applied to seedlings in order to simulate water level fluctuation in the hydrofluctuation zone of the Three Gorges Reservoir Region. Results showed that net photosynthetic rate (P N), stomatal conductance, and intrinsic water-use efficiency of both plant species were negatively affected under CF and PF compared with the corresponding controls. The P N of both species under PF was comparable to that under CF. At the end of the experiment, the ratio of intercellular to ambient CO2 concentration was not statistically different between water treatments, while that of P. elliottii was significantly higher than that of P. stenoptera. Although P. stenoptera formed lenticels under flooding conditions, P. elliottii seedlings allocated more mass to leaves and increased the relative growth rate of height to enhance the photosynthetic efficiency. Our results illustrated that P. stenoptera and P. elliottii seedlings developed different adaptive strategies in response to flooding, both CF and PF. Therefore, both P. stenoptera and P. elliottii are promising candidates for the vegetation reconstruction of the riparian zones in the Three Gorges Reservoir Region., Y. Yang, C. Li., and Obsahuje seznam literatury
A study on photosynthetic and yield effects of waterlogging of winter wheat at four stages of growth was conducted in specially designed experimental tanks during the 2007-2008 and 2008-2009 seasons. Compared with the control, waterlogging treatments at tillering and jointing-booting stages reduced photosynthetic rate (PN) and transpiration (E) significantly, it also decreased average leaf water-use efficiency (WUE, defined as the ratio of PN to E) by 3.3% and 3.4% in both years. All parameters returned quickly to the control level after soil was drained. Damage to the photosynthetic apparatus during waterlogging resulted in a lower Fv/Fm ratio, especially at the first two stages. A strong reduction in root length, root mass, root/shoot ratio, total dry mass, and leaf area index were observed. The responses from vegetative plants at tillering and jointing-booting stages were greater than in generative plants at onset of flowering and at milky stages. The number of panicles per hectare at tillering stage and the spikelet per panicle at the stages of jointing-booting and at onset of flowering were also significantly reduced by waterlogging, giving 8.2-11.3% decrease of the grain yield relative to the control in both years. No significant difference in yield components and a grain yield was observed between the control and treatments applied at milky stages. These responses, modulated by the environmental conditions prevailing during and after waterlogging, included negative effects on the growth, photosynthetic apparatus, and the grain yield in winter wheat, but the effect was strongly stage-dependent. and G. C. Shao ... [et al.].
The purpose of this study was to clarify effects of anthocyanins on photosynthesis and photoinhibition in green and red leaves of Oxalis triangularis. Gas analysis indicated that green plants had the highest apparent quantum yield for CO2 assimilation [0.051 vs. 0.031 μmol(CO2) μmol-1(photon)] and the highest maximum photosynthesis [10.07 vs. 7.24 μmol(CO2) m-2 s-1], while fluorescence measurements indicated that red plants had the highest PSII quantum yield [0.200 vs. 0.143 μmol(e-) μmol-1(photon)] and ETRmax [66.27 vs. 44.34 μmol(e-) m-2 s-1]. Red plants had high contents of anthocyanins [20.11 mg g-1(DM)], while green plants had low and undetectable levels of anthocyanin. Red plants also had statistically significantly (0.05>p>0.01) lower contents of xanthophyll cycle components [0.63 vs. 0.76 mg g-1(DM)] and higher activities of the reactive oxygen scavenging enzyme ascorbate peroxidase [41.2 vs. 10.0 nkat g-1(DM)]. Anthocyanins act as a sunscreen, protecting the chloroplasts from high light intensities. This shading effect causes a lower photosynthetic CO2 assimilation in red plants compared to green plants, but a higher quantum efficiency of photosystem II (PSII). Anthocyanins contribute to photoprotection, compensating for lower xanthophyll content in red plants, and red plants are less photoinhibited than green plants, as illustrated by the Fv/Fm ratio. and S. L. Nielsen, A.-M. Simonsen
Anastatica hierochuntica is an annual desert plant, which was recently shown to have unusually low nonphotochemical quenching (NPQ) and a high PSII electron transport rate (ETR). In the current study, we examined how these unusual characteristics are related to a lack of CO2 and inhibition of net photosynthetic rate (P N). We compared the photosynthetic and photoprotective response of A. hierochuntica and sunflower (Helianthus annuus), under conditions of photosynthetic inhibition, with either low CO2 or drought. We found that under nonsteady state conditions of low CO2 availability, A. hierochuntica exhibited about half of the NPQ values and almost twice of the ETR values of H. annuus. However, the long-term inhibition of P N under drought caused a similar increase in NPQ and a decrease in ETR in both A. hierochuntica and H. annuus. These results suggest that the unusually low NPQ and high ETR in A. hierochuntica are not directly related to a response to drought conditions., A. Eppel, S. Rachmilevitch., and Obsahuje seznam literatury
Nicosulfuron is a post-emergence herbicide used for weed control in fields of maize (Zea mays L.). We used a pair of nearly isogenic inbred lines, SN509-R (nicosulfuron-resistant) and SN509-S (nicosulfuron-sensitive), to study the effect of nicosulfuron on waxy maize seedling. After the nicosulfuron treatment, net photosynthetic rate, stomatal conductance, transpiration rate, leaf maximum photochemical efficiency of PSII, photochemical quenching of chlorophyll fluorescence, and the actual photochemical efficiency of PSII were significantly lower in SN509-S than those of SN509-R, contrary to intercellular CO2 concentration, stomatal limitation, and nonphotochemical quenching. Compared to SN509-R, antioxidant enzyme activities in SN509-S decreased significantly in response to the nicosulfuron treatment, while SN509-S exhibited an increased malondialdehyde content, which was associated with lower antioxidant enzyme activities. These results collectively suggest that the nicosulfuron-resistance mechanism was associated with photosynthetic rate, reactive oxygen species metabolism, and protective mechanisms., J. Wang, X. M. Zhong, X. L. Lv, Z. S. Shi, F. H. Li., and Obsahuje bibliografii
Photosynthesis has walked into the path of evolution for over millions of years. Organisms relying directly on photosynthesis, when subjected to adverse environments for a long duration, experience retardation in their growth and development. Salinity stress is perceived as one of the major threats to agriculture as it can cause an irreversible damage to the photosynthetic apparatus at any developmental stage of the plant. However, halophytes, a special category of plants, carry out all life processes, including photosynthesis, without showing any compromise even under high saline environments. The fascinating mechanism for Na+ exclusion from cytosol besides retaining photosynthetic efficiency in halophytes can provide a valuable genetic resource for improving salt stress tolerance in glycophytes. Understanding how plants stabilize their photosynthetic machinery and maintain the carbon balance under saline conditions can be extremely useful in designing crops for saline and dry lands., S. Wungrampha, R. Joshi, S. L. Singla-Pareek, A. Pareek., and Obsahuje bibliografické odkazy
The microstructure of leaves and ultrastructure of chloroplasts were examined in tomato (Lycopersicon esculentum L.) plants treated with elevated temperature. Plants were exposed to 35°C for 30 d after florescence. The plants grown continuously under 25°C served as controls. Compared with the controls, the net photosynthetic rate (PN) in stressed plants decreased significantly. Stomatal conductance, intercellular CO2 concentrations, the rate of transpiration, and the limitation of stomatal conductance showed that the decrease in PN was caused mainly by nonstomatal restrictions. Meanwhile, stomata density increased significantly in the stressed plants. The stomata status of opening and closing became disorganized with a prolonged 35°C exposure. The damage of chloroplast membrane occurred earlier and was more serious in the plants under elevated temperature. At the same time, the thylakoids were loosely distributed with lesser grana, but the number of lipid droplets increased in chloroplasts. The number of starch grains in chloroplasts increased first and then decreased. In addition, the length of the main nerve in leaves increased and the main vein showed distortion in the plants stressed by 35°C. An increase was observed in the number of cells on the abaxial side of the main vein and these cells were overly congregated. The thickness of a vertical section became thinner in the stressed leaves. The cells of the upper epidermis thinned, and the ratio of palisade tissue to spongy tissue decreased. Generally, the photosynthetic apparatus of tomato changed significantly and the changed chloroplast ultrastructure might be one of the important reasons that caused the decrease of PN under 35°C., J. Zhang, X. D. Jiang, T. L. Li, X. J. Cao., and Obsahuje bibliografii
The objectives of the study were to characterize photosynthesis of temperate fallow C3 herbaceous species and examine the performance of a simple photosynthesis model (based on the Farquhar's equations) to simulate carbon fluxes at the leaf and canopy levels. The maximum rate of carboxylation at 25°C (V m0) was estimated for sunlit leaves using in situ gas exchange data under saturating irradiance. Throughout the seasons, leaf measurements indicate that values of V m0 were similar for the four major species of the fallow. The rate declined from March (100 µmol m-2 s-1) to July (50 µmol m-2 s-1) and remained almost constant until November. The maximum quantum yield estimated for Potentilla reptans L. (dominant species) was 0.082 mol(CO2) mol-1(photon absorbed), similar to values already published for C3 species. Leaf area index (LAI) increased from winter (less than 0.2 m2 m-2) to spring (up to 4 m2 m-2). Rates of canopy photosynthesis (measured with a canopy chamber) strongly depended on LAI and temperature, in addition to irradiance. They reached a maximum of 25 µmol m-2 s-1 and were intermediate between those published for C4 grassland or cultivated species, and on woody species. At leaf level, simulations gave realistic predictions. At canopy level, the model had the ability to reproduce the effects of environmental and seasonal conditions. However, simulations underestimated the photosynthetic activity of the fallow canopy. and M. Gouasmi ... [et al.].