The effect of drought stress on energy dissipation and antioxidant enzyme system in two sweet sorghum inbred lines (M-81E and Roma) was investigated. Results showed that the germination indicator increased more in M-81E than that in Roma under rehydration. Under drought stress, both the maximal photochemical efficiency of PSII (Fv/Fm) and oxidoreductive activity (ΔI/I0) of Roma decreased more than those in M-81E. Relative to Fv/Fm, the ΔI/I0 decreased markedly, which indicated that PSI was more sensitive to drought stress than PSII. Increases in the reduction state of QA (1-qp), nonphotochemical quenching (NPQ) and minimal fluorescence yield of the dark-adapted state (F0) were greater in Roma than those in M-81E; meanwhile, the H2O2 content was lower in M-81E than that in Roma. Our results suggested that the photoinhibition might be related to the accumulation of reactive oxygen species (ROS). The antioxidant enzyme system and energy dissipation of M-81E could respectively increase drought tolerance by eliminating ROS and excess energy more efficiently than that of Roma., Y. Y. Guo, S. S. Tian, S. S. Liu, W. Q. Wang, N. Sui., and Obsahuje bibliografii
Significant linear relationships between photosynthetic capacity and principal components loaded by phloem cell numbers and tracheary elements per minor vein as well as the latter two normalized for vein density (proxy for apoplastic phloem loading capacity involving membrane transporters) were revealed for all apoplastic loaders (summer annuals and winter annual Arabidopsis thaliana). In addition, significant linear relationships between photosynthetic capacity and a principal component loaded by tracheary element cross-sectional areas and volumes per unit of leaf area (water flux capacity proxy) was present for symplastic and apoplastic loaders. Lastly, a significant linear relationship between photosynthetic capacity and a principal component loaded by phloem cell cross-sectional areas and volumes per unit of leaf area (proxy for symplastic loading capacity involving cytosolic enzymes for companion cells) was revealed for summer annual symplastic loaders as well as for A. thaliana (in the case of sieve elements, a proxy for sugar export capacity from the leaves)., S. K. Polutchko, J. J. Stewart, B. Demmig-Adams, W. W. Adams., and Obsahuje bibliografické odkazy
The changes in growth and photosynthetic performance of two wheat (Triticum aestivum L.) cultivars (Bolal-2973 and Atay-85) differing in their sensitivity to boron (B) toxicity were investigated under toxic B conditions. Eight-day old seedlings were exposed to highly toxic B concentrations (5, 7.5, and 10 mM H3BO3) for 5 and 9 days. Fast chlorophyll a fluorescence kinetics was determined and analysed using JIP test. Growth parameters, tissue B contents, and membrane damage were measured at two stress durations. The photochemical performance of PSII was hindered more in the sensitive cultivar (Atay-85) than that of the tolerant one (Bolal-2973) under B toxicity. The increase in the B concentration and stress duration caused membrane leakage in both cultivars. However, higher membrane damage was observed in Atay-85 compared to Bolal-2973. Additionally, significant reduction of growth parameters was observed in both cultivars at toxic B concentrations. The accumulation of B was higher in shoots than in roots of both cultivars. Nevertheless, Atay-85 translocated more B from roots to leaves compared to Bolal-2973. The advantages of certain JIP test parameters were demonstrated for evaluation of PSII activity in plants exposed to B stress. Evaluation of photosynthetic performance by JIP test as well as assessment of growth and tissue B content might be used to determine the effects of B toxicity in wheat. The results indicated lesser sensitivity to B toxicity in Bolal-2973 compared to Atay-85., M. T. Öz, Ö. Turan, C. Kayihan, F. Eyidoğan, Y. Ekmekçi, M. Yücel, H. A. Öktem., and Obsahuje bibliografii
Water availability is one of the most important limiting factors in agriculture worldwide, particularly in arid and semiarid regions. Six spring wheat genotypes, i.e. three UK cultivars Cadenza, Paragon, and Xi-19 and three synthetic-derived lines L-22, L-24, and L-38, were grown in a phytotron under well-watered (until 40 days after sowing) and drought conditions. The aim of the study was to evaluate the traits related to photosynthetic capacity (net photosynthesis rate, stomatal conductance, internal CO2 concentration, transpiration rate, carboxylation capacity, instantaneous and intrinsic water-use efficiency) and plant biomass production in the cultivars and synthetic derivatives of wheat genotypes under well-watered and water-limited conditions. Genotypic variations in gas-exchange traits including net photosynthetic rate, carboxylation capacity, instantaneous water-use efficiency, and biomass yield were found amongst genotypes. Drought significantly reduced the total dry matter per plant. The synthetic derivatives L-22 and L-24 showed higher performance of stomata for most of the stomatal aperture characteristics. Total dry matter was positively related to net photosynthetic rate and to instantaneous and intrinsic water-use efficiencies. Finally, net photosynthetic rate was also positively related to stomatal conductance and transpiration rate under both the well-watered and water-limited drought conditions., S. Sikder, J. Foulkes, H. West, J. De Silva, O. Gaju, A. Greenland, P. Howell., and Obsahuje bibliografii
Wild Arachis genotypes were analysed for chlorophyll a fluorescence, carbon isotope discrimination (ΔC), specific leaf area (SLA), and SPAD readings. Associations between different traits, i.e., SLA and SPAD readings (r =-0.76), SLA and ΔC (r = 0.42), and ΔC and SPAD readings (r = 0.30) were established. The ratio of maximal quantum yield of PSII photochemistry (Fv/Fm) showed a wider variability under water deficit (WD) than that after irrigation (IR). Genotypes were grouped according to the Fv/Fm ratio as: efficient, values between 0.80 and 0.85; moderately efficient, the values from 0.79 to 0.75; inefficient, the values < 0.74. Selected Selected genotypes were evaluated also for their green fodder yield: the efficient genotypes ranged between 3.0 and 3.8, the moderately efficient were 2.6 and 2.7, the inefficient genotypes were of 2.3 and 2.5 t ha-1 per year in 2008 and 2009, respectively. Leaf
water-relation traits studied in WD and IR showed that the efficient genotypes were superior in maintenance of leaf water-relation traits, especially, under WD. Potential genotypes identified in this study may enhance biomass productivity in the semiarid tropic regions., P. C. Nautiyal, A. L. Rathnakumar, G. Kulkarni, M. S. Sheshshayee., and Obsahuje bibliografii
Changes in photosynthetic attributes related to genetic improvement of cotton yield were studied in seven Chinese cotton cultivars widely grown in Xinjiang during the past 30 years. Our results showed that a chlorophyll (Chl) content and net photosynthetic rate (PN) of the 1980s cultivar was the highest among all after 60 days from planting (DAP). However, after 75 DAP, the Chl content, PN, and actual photochemical efficiency of PSII of the old cultivars declined gradually, whereas those of the new cultivars remained relatively high. Compared to the old cultivars, leaves of the new cultivars endured a longer period and their senescence was slower, shoot and boll dry mass was higher, but the root to shoot ratio was lower. The lint yield of the 2000s cultivars was 14.7 and 21.4% higher than that of 1990s and 1980s cultivars, respectively. The high yield of the new cultivars was attributed to a greater number of bolls per unit of area with high lint percentage. We suggested that the improved photosynthetic capacity and the increased ability to deliver photosynthates to reproductive sites during the peak boll-setting stage to boll-opening stage were the key physiological basis in the evolution process of cotton cultivars from 1980s to 2000s for the cotton yield improvement within a short growing period., H. H. Luo, H. L. Zhang, Y. L. Zhang, W. F. Zhang., and Obsahuje bibliografii
Ca2+ has been considered as a necessary ion for alleviation of stress-induced damages in plants. We investigated effects of exogenous Ca2+ on waterlogging-induced damage to pepper and its underlying mechanisms. Pepper seedlings under stress were treated by spraying of 10 mM CaCl2. Applying exogenous Ca2+ increased the biomass of pepper leaves and roots, improved photosynthetic characteristics, membrane permeability, root activity, osmotic substance contents, antioxidant enzyme and alcohol dehydrogenase activities, while it reduced lactate dehydrogenase activity. It maintained hydroxide radical contents and activities of malate dehydrogenase and succinate dehydrogenase relatively high. Our results suggested that applying exogenous Ca2+ could regulate osmotic substance contents, antioxidant system activity, root respiration, and metabolism, and subsequently alleviate waterlogging-induced damages to pepper plants., B. Z. Yang, Z. B. Liu, S. D. Zhou, L. J. Ou, X. Z. Dai, Y. Q. Ma, Z. Q. Zhang, W. C. Chen, X. F. Li, C. L. Liang, S. Yang, X. X. Zou., and Obsahuje bibliografii
Melatonin mediates many physiological processes in animals and plants. To examine the potential roles of melatonin in salinity tolerance, we investigated the effects of exogenous melatonin on growth and antioxidant system in cucumber under 200 mM NaCl stress conditions. The results showed that the melatonin-treated plants significantly increased growth mass and antioxidant protection. Under salinity stress, the addition of melatonin effectively alleviated the decrease in the net photosynthetic rate, the maximum quantum efficiency of PSII, and the total chlorophyll content. Our data also suggested that melatonin and the resistance of plants exhibited a concentration effect. The application of 50-150 μM melatonin significantly improved the photosynthetic capacity. Additionally, the pretreatment with melatonin reduced the oxidative damage under salinity stress by scavenging directly H2O2 or enhancing activity of antioxidant enzymes (including superoxide dismutase, peroxidase, catalase, ascorbate peroxidase) and concentrations of antioxidants (ascorbic acid and glutathione). Therefore, the melatonin-treated plants could effectively enhance their salinity tolerance., L. Y. Wang, J. L. Liu, W. X. Wang, Y. Sun., and Obsahuje seznam literatury
Water deficit is one of the major limiting factors in vegetation recovery and restoration in loess, hilly-gully regions of China. The light responses of photosynthesis in leaves of two-year old Prunus sibirica L., Hippophae rhamnoides L., and Pinus tabulaeformis Carr. under various soil water contents were studied using the CIRAS-2 portable photosynthesis system. Light-response curves and photosynthetic parameters were analyzed and fitted using the rectangular hyperbola model, the exponential model, the nonrectangular hyperbola model, and the modified rectangular hyperbola model. Under high light, photosynthetic rate (PN) and stomatal conductance (gs) were steady and photoinhibition was not significant, when the relative soil water content (RWC) varied from 56.3-80.9%, 47.9-82.9%, and 33.4-92.6% for P. sibirica, H. rhamnoides, and P. tabulaeformis, respectively. The light-response curves of PN, the light compensation point (LCP), and the dark respiration rate (RD) were well fitted using the above four models. The nonrectangular hyperbola was the best model in fitting the data; the modified rectangular hyperbola model was the second, and the rectangular hyperbola model was the poorest one. When RWC was higher or lower than the optimal range, the obvious photoinhibition and significant decrease in PN with increasing photosynthetic photon flux density (PPFD) were observed in all three species under high light. The light saturation point (LSP) and apparent quantum yield also decreased significantly, when the upper limit of PPFD was 200 μmol m-2 s-1. Under these circumstances, only the modified rectangular hyperbola model was able to fit well the curves of the light response, LCP, LSP, RD, and light-saturated PN. and Y. Lang ... [et al.].