The photosynthesis was investigated 30 d after Pb treatment in Myrica rubra seedlings. The Pb treatment resulted in significantly increased Pb concentrations in shoots. Low Pb concentration exposure (≤2 mM) reduced the net photosynthetic rate (PN), transpiration rate (E), and stomatal conductance (gs) without affecting the intercellular CO2 concentration (Ci), chlorophyll (Chl) content, and Chl fluorescence parameters. At 10 d after severe Pb treatment (≥4 mM), PN was inhibited and accompanied by Chl damage, while at 30 d, the inhibition of PN was followed by an increase of Ci and a decrease of gs, E, Chl content, and Chl fluorescence parameters. M. rubra showed a promising prospect for use in the soil phytoremediation, when Pb concentration is low, but the remediation efficiency of M. rubra is limited if Pb exceeds 2 mM., B. He, M. Gu, X. Wang, X. He., and Obsahuje bibliografii
The effects of 0, 30, 60, and 90 mM NaCl, and 0 and 5 mM CaCl2 on certain parameters of photosynthesis and growth in alfalfa (Medicago sativa L. cv. Ghara yonjeh) plants were studied. The increasing NaCl concentration in the Hoagland nutrient solution decreased the contents of chlorophylls and the net photosynthetic rate, and increased the rate of respiration (RD) and CO2 compensation concentration in the leaves of treated plants. The contents of carotenoids (Car) were not significantly affected. The addition of 5 mM CaCl2 enhanced the RD and increased the Car contents in treated leaves. With the NaCl concentration in the culture medium increasing, the dry matter production in both root and shoot decreased, as well as the relative growth rate (RGR), net assimilation rate (NAR), and leaf area ratio (LAR). The addition of CaCl2 caused a partial elimination of the NaCl effects on the root and shoot, RGR and NAR, and it decreased the LAR. and R. A. Khavari-Nejad, N. Chaparzadeh.
Populus x euramericana cv. ‘Neva’ is an important tree species in northern China. In the study, we used its potted oneyear- old seedlings as experimental material and established three treatments (CK, 0.5X, and 1.0X) according to the concentrations of phenolic acids in order to examine the effects of different concentrations on the photosynthetic characteristics and growth of poplar. With increasing concentrations of phenolic acids, the net photosynthetic rate, stomatal limitation, transpiration rate, apparent quantum yield, photochemical quenching coefficient, electron transport rate, chlorophyll content, and total biomass decreased significantly. The intercellular CO2 concentration, light-compensation point, nonphotochemical quenching, malondialdehyde content, and root/shoot ratio increased significantly. Peroxidase and superoxide dismutase activities initially decreased and then increased. We concluded that phenolic acids significantly inhibited poplar’s photosynthesis and the higher phenolic acid concentration, the greater inhibition of photosynthesis occurred. This inhibition effect was mainly caused by nonstomatal factors. Phenolic acids induced noticeable photoinhibition, resulted in the irreversible damage of membrane structure, and then changed intracellular metabolic processes. To cope with phenolic acid stress, poplar seedlings increased dissipation of excess light energy and distributed relatively more biomass to underground parts within carbon allocation., D. F. Xie, G. C. Zhang, X. X. Xia, Y. Lang, S. Y. Zhang., and Obsahuje bibliografii
As a common waterfront and wet environment tree species, Salix babylonica shows a great potential for restoration of contaminated water or soil environments, such as phenol-polluted water. However, studies on such remediation effects have not been carried out yet. The objective of this study was to investigate the effects of phenols on photosynthesis of S. babylonica. Photosynthetic and chlorophyll fluorescence parameters of S. babylonica cuttings were determined in hydroponic experiment, where six phenol concentrations was used (0, 50, 100, 200, 400, and 800 mg L-1). Phenol presence inhibited photosynthesis of S. babylonica significantly, as the net photosynthetic rate (PN),
light-saturated net photosynthetic rate, apparent quantum yield, maximal quantum yield of PSII photochemistry, and effective quantum yield of PSII photochemistry declined significantly. The higher the concentration of phenol solution, the greater inhibition of photosynthesis occurred. Our data indicated that nonstomatal limitation was responsible for the reduction of PN. S. babylonica should be used to remediate phenol-contaminated water, when the concentration of phenol solution is lower than 200 mg L-1. Otherwise, the efficiency of photosynthesis of S. babylonica would decrease markedly. However, further study is needed to determine the maximum concentration of phenol that S. babylonica can tolerate to maintain normal photosynthetic activity., H. Li, G. C. Zhang, H. C. Xie, K. Li, S. Y. Zhang., and Obsahuje seznam literatury
The response of selected photosynthetic and morphological parameters of plants to drought was examined in 5 inbred lines of maize (Zea mays L.) and their 10 F1 hybrids. The aim of the study was to establish whether the photosynthetic performance of parental genotypes under drought conditions correlates with the performance of their progeny and whether the net photosynthetic rate, the chlorophyll fluorescence parameters or the content of photosynthetic pigments could be used as reliable physiological markers for early breeding generations. The relative importance of the additive and the nonadditive (dominance, maternal) genetic effects in the inheritance of these parameters was also assessed by means of the quantitative genetics analysis. The results showed that the nonadditive genetic effects associated with a particular combination of genotypes or a particular direction of crossing are at least equally and often even more important as the additivity and that these genetic effects almost totally change with the exposure of plants to drought conditions. This was reflected in the inability to predict the response of F1 hybrids to drought on the basis of the photosynthetic performance of their parents, which indicates that the practical usability of such parameters in maize breeding programs is rather limited. and D. Holá ... [et al.].
Differences in ultrastructural parameters of mesophyll cell (MC) chloroplasts, contents of photosynthetic pigments, and photochemical activities of isolated MC chloroplasts were studied in the basal, middle, and apical part of mature or senescing leaf blade of two maize genotypes. A distinct heterogeneity of leaf blade was observed both for structural and functional characteristics of chloroplasts. In both mature and senescing leaves the shape of MC chloroplasts changed from flat one in basal part of leaf to nearly spherical one in leaf apex. The volume density of granal thylakoids decreased from leaf base to apex in both types of leaves examined, while the amount of intergranal thylakoids increased in mature leaves but decreased in senescing leaves. The most striking heterogeneity was found for the quantity of plastoglobuli, which strongly increased with the increasing distance from leaf base. The differences in chloroplast ultrastructure were accompanied by differences in other photosynthetic characteristics. The Hill reaction activity and activity of photosystem 1 of isolated MC chloroplasts decreased from leaf base to apex in mature leaves. Apical part of senescing leaf blade was characterised by low contents of chlorophyll (Chl) a and Chl b, whereas in mature leaves, the content of Chls as well as the content of total carotenoids (Car) slightly increased from basal to apical leaf part. This was reflected also in the ratio Chl (a+b)/total Car; the ratio of Chl a/b did not significantly differ between individual parts of leaf blade. Both genotypes examined differed in the character of developmental gradient observed along whole length of leaf blade. and J. Kutík ... [et al.].
Atmospheric CO2 concentration continues to rise and is predicted to reach approximately 700 ppm by 2100. Some predictions suggest that the dry season in West Africa could be extended with climate change. This study examined the effects of elevated CO2 concentration and water deficit on growth and photosynthesis of juvenile cacao. Light-saturated photosynthesis (Pmax), quantum efficiency, and intrinsic water-use efficiency increased significantly in response to elevated CO2, as did a range of growth and development responses (e.g. leaf area and leaf number), but the magnitude of the increase was dependent on the water treatment. Stomatal index was significantly greater in the elevated CO2 treatment; an atypical response which may be a reflection of the environment in which cacao evolved. This study shows a positive effect of elevated CO2 on juvenile cacao which may help to alleviate some of the negative impacts of water deficit stress., F. Lahive, P. Hadley, A. J. Daymond., and Obsahuje bibliografii
The objective of this study was to evaluate the significance of blue light (B) in the growth and photosynthetic capacity of cucumber. Gas exchange, chlorophyll (Chl) fluorescence kinetics, chloroplast ultrastructure, and leaf growth were investigated to explore the influence of three different light qualities of light emitting diodes (LEDs) on plant morphogenesis and the development of photosynthetic apparatus in cucumber (Cucumis sativus) leaves from emergence to full expansion under weak light [50 μmol(photon) m-2 s-1]. We found that B could significantly increase the leaf area (LA), shoot elongation, Chl a/b, net photosynthetic rate, and stomatal conductance (g s). In addition, the comparisons of maximal quantum yield of PSII photochemistry and the photosynthetic performance index between B-, W (white light)-, and R (red light)-grown leaves suggested that B was essential for the development of photosynthetic apparatus under weak light. B-grown leaves had the lowest Chl content under weak light, however, they had well-developed chloroplasts with the highest degree of stacked lamellae and the lowest starch accumulation. This could explain to a considerable extent the highest net photosynthetic rate per Chl unit. The results demonstrated that B optimized photosynthetic performance by improving the photosynthetic rate, increasing LA, and prolonging active photosynthesis duration under low irradiance. Therefore B is necessary to ensure healthy development of chloroplasts and highly efficient photosynthetic functions in cucumbers under a weak light environment. More importantly, our study also provided theoretical and technical support for the development of light environmental control technology., X. Y. Wang, X. M. Xu, J. Cui., and Obsahuje bibliografii
Four fluorescence parameters [Fv/Fm = the intrinsic efficiency of energy conversion via photosystem 2 (PS2); Fv'/Fm'= the efficiency of energy conversion via PS2 in the light; P = fraction of absorbed radiant energy utilized for photosynthesis; and D = fraction of absorbed radiant energy dissipated as heat] were measured on leaves of seven species of succulents having epidermal windows. While the function of leaf windows has reportedly been to increase absorption of radiant energy and, hence, the rate of photosynthesis in these species, recent evidence indicates that this translucent portion of epidermal tissue, lacking chlorophyll, may also result in photoinhibition in these species, especially for those with growth habits aboveground. Species with aboveground and belowground growth habits were compared with their leaf windows covered with reflective tape and with windows unobstructed. Results showed no increase in photoinhibition for these species resulting from the radiant energy penetrating the window tissue. Although the efficiency of the photosynthetic mechanism was not significantly influenced by the additional radiant energy provided by the window for individual species, there were significant differences in the efficiencies of radiant energy capture (Fv'/Fm') and utilization (P) between the two growth habits. Species with an aboveground growth habit were less efficient in radiant energy utilization compared with the species having a belowground growth habit. and K. J. Egbert, C. E. Martin.
Low temperature (LT) is one of the major factors that limit crop production and reduce yield. To better understand the cold-tolerance mechanism in the plantains, a sensitive cultivar Williams (Musa acuminata AAA cv. Williams) and a tolerant cultivar Cachaco (Musa paradisiaca ABB cv. Dajiao) were used. LT resulted in increased malondialdehyde (MDA) content, elevated contents of hydrogen peroxide (H2O2) and superoxide radical (O2.-), and decreased photochemical efficiency (Fv/Fm) and net photosynthetic rate (PN), but cv. Cachaco showed better LT tolerance than cv. Williams. After LT treatment for 120 h, total scavenging capability (DPPH. scavenging capability) in Williams showed a significant decrease but no significant alternations was found in Cachaco. Ascorbate peroxidase (APX) and peroxidase (POD) displayed a significant increase but superoxide dismutase (SOD) showed no significant alternations and catalase (CAT) showed a significant decrease in Cachaco after 120 h of LT treatment. All the four antioxidant enzymes above showed a significant decrease in Williams after 120 h of LT treatment. Our results suggest that higher activities of APX, POD, SOD, and DPPH. scavenging capability to a certain extent can be used to explain the higher cold tolerance in the plantain, which would provide a theoretical guidance for bananas production and screening cold-resistant variety. and Q. Zhang ... [et al.].