Cuttings of Populus cathayana Rehd, originating from three triploid and one diploid populations with the same parents but different gamete origins, were used to examine physiological responses to drought stress and rewatering by exposure to three progressive water regimes. Progressive drought stress significantly decreased the leaf relative water content (RWC), photosynthesis, and chlorophyll fluorescence parameters, and increased the relative electrolyte leakage, malondialdehyde (MDA), free proline (Pro), and antioxidant enzymes, such as superoxide dismutase, peroxidase, and catalase, in the four populations evaluated. However, compared to the diploid population, triploid populations showed lower relative electrolyte leakage and MDA, higher RWC and Pro content, and more efficient photosynthesis and antioxidant systems under the same water regime. Our data indicated that triploid populations possessed more efficient protective mechanisms than that of diploid population with gradually increasing drought stress. Moreover, some triploid genotypes were less tolerant to water stress than that of diploids due to large intrapopulation overlap., T. Liao, Y. Wang, C. P. Xu, Y. Li, X. Y. Kang., and Obsahuje bibliografii
Benzoxazolin-2-(3H)-one (BOA) has been tested in many plants species, but not in soybean (Glycine max). Thus, a hydroponic experiment was conducted to assess the effects of BOA on soybean photosynthesis. BOA reduced net photosynthetic rate, stomatal conductance, and effective quantum yield of PSII photochemistry without affecting intercellular CO2 concentration or maximal quantum yield of PSII photochemistry. Results revealed that the reduced stomatal conductance restricted entry of CO2 into substomatal spaces, thus limiting CO2 assimilation. No change found in intercellular CO2 concentration and reduced effective quantum yield of PSII photochemistry revealed that CO2 was not efficiently consumed by the plants. Our data indicated that the effects of BOA on soybean photosynthesis occurred due to the reduced stomatal conductance and decreased efficiency of carbon assimilation. The accumulation of BOA in soybean leaves reinforced these findings. and Obsahuje bibliografii
The effect of ectomycorrhizal Pisolithus tinctorius (Pt) infection was studied on the growth and photosynthetic characteristics of Pinus densiflora seedlings grown at ambient (360 µmol mol-1, AC) and elevated (720 µmol mol-1, EC) CO2 concentrations. After 18 weeks, Pt inoculation had led to significantly increased dry mass and stem diameter of P. densiflora at both CO2 concentrations, relative to non-inoculated seedlings. Moreover, EC significantly increased the ectomycorrhizal development. The phosphate content in needles inoculated with Pt was about three times higher than without inoculation at both CO2 concentrations. The PAR saturated net photosynthetic rates (Psat) of P. densiflora inoculated with Pt were clearly higher than for control seedlings at both CO2 concentrations, and the maximum net photosynthetic rate (PN) at saturated CO2 concentration (Pmax) was higher than in controls. Moreover, the carboxylation efficiency (CE) and RuBP regeneration rate of the PN/Ci curve for P. densiflora inoculated with Pt were significantly higher than for non-inoculated seedlings at both CO2 concentrations, especially at EC. The water use efficiency (WUE) of seedlings inoculated with Pt grown at EC was significantly raised. Allocation of photosynthates to roots was greater in Pt inoculated pine seedlings, because of the enhanced activity of ectomycorrhiza associated with seedlings at EC. Moreover, PN of non-inoculated seedlings grown for 18 weeks at EC tended to be down regulated; in contrast, Pt inoculated seedlings showed no down-regulation at EC. The activity of ectomycorrhiza may therefore be enhanced physiological function related to water and phosphate absorption in P. densiflora seedlings at EC. and D. S. Choi ... [et al.].
Water availability is an important factor for plant growth in arid environments. In recent decades, vermicompost (VC) fertilizer has been used in agriculture as a safe and effective fertilizer with high water-holding capacity. The aim of the present study was to characterize effects of VC fertilizer on photosynthetic activity of chickpea (Cicer arietinum L. cv. Karaj) under drought conditions at three different growth stages. Tests were carried out with four volumetric ratios of VC to soil, i.e., 0:100, 10:90, 20:80, and 30:70, and three levels of drought stress, i.e., no stress (NS), moderate drought (MS), and severe drought (SS) (100, 75, and 25% of field capacity, respectively). Evaluations were performed at the seedling, flowering, and podding stage. We found that the VC treatment under NS conditions significantly increased total chlorophyll content [Chl (a+b)], intercellular CO2 concentration (C i), net photosynthetic rate (P N), transpiration rate (E), and maximal quantum yield of PSII photochemistry (Fv/Fm) at all three stages. The VC addition of 10 and 20% significantly enhanced the Chl content and Fv/Fm under MS and Fv/Fm, C i, and P N under SS at the flowering stage. In conclusion, our results proved a positive effect of the VC fertilizer on photosynthesis of chickpea under NS conditions, but it was not found under MS and SS., S. R. Hosseinzadeh, H. Amiri, A. Ismaili., and Obsahuje seznam literatury
Two greenhouse experiments were conducted in order to investigate the effects of different levels of water stress on gas exchange, chlorophyll fluorescence, chlorophyll content, antioxidant enzyme activities, lipid peroxidation, and yield of tomato plants (Solanum lycopersicum cv. Jinfen 2). Four levels of soil water content were used: control (75 to 80% of field water capacity), mild water stress (55 to 60%), moderate water stress (45 to 50%), and severe water stress (35 to 40%). The controlled irrigation was initiated from the third leaf stage until maturity. The results of
two-year trials indicated that the stomatal conductance, net photosynthetic rate, light-saturated photosynthetic rate, and saturation radiation decreased generally under all levels of water stress during all developmental stages, while compensation radiation and dark respiration rate increased generally. Water stress also declined maximum quantum yield of PSII photochemistry, electron transfer rate, and effective quantum yield of PSII photochemistry, while nonphotochemical quenching increased in all developmental stages. All levels of water stress also caused a marked reduction of chlorophyll a, chlorophyll b, and total chlorophyll content in all developmental stages, while activities of antioxidant enzymes, such as superoxide dismutase, peroxidase, and catalase, and lipid peroxidation increased., X. K. Yuan, Z. Q. Yang , Y. X. Li, Q. Liu, W. Han., and Obsahuje seznam literatury
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
The photosynthetic characterization of Populus euphratica and their response to increasing groundwater depth and temperature were analyzed based on net photosynthetic rate (PN), stomatal conductance (gs), intercellular CO2 concentration (Ci), transpiration rate (E), water use efficiency (WUE) and stomatal limitation (Ls) measured by a portable gas-exchange system (LI-6400) in the lower reaches of the Tarim River. Light-response curves were constructed to obtain light-compensation and light-saturation points (LCP and LSP), maximum photosynthetic rates (Pmax), quantum yields (AQY), and dark respiration rates (RD). The growth condition of P. euphratica, soil moisture, and groundwater depth in the plots were analyzed by field investigation. The results showed that the growth condition and photosynthetic characterization of P. euphratica were closely related to groundwater depth. The rational groundwater depth for the normal growth and photosynthesis was 3-5 m, the stress groundwater depth for mild drought was more than 5 m, for moderate drought was more than 6 m, for severe drought was more than 7 m. However, P. euphratica could keep normal growth through a strong drought resistance depended on the stomatal limitation and osmotic adjustment when it faced mild or moderate drought stress, respectively, at a normal temperature (25°C). High temperature (40°C) significantly reduced PN and drought stress exacerbated the damage of high temperature to the photosynthesis. Moreover, P. euphratica would prioritize the resistance of high temperature when it encountered the interaction between heat shock and water deficit through the stomata open unequally to improve the transpiration of leaves to dissipate overheating at the cost of low WUE, and then resist water stress through the osmotic adjustment or the stomatal limitation. and H. H. Zhou ... [et al.].
We tested the hypotheses that a reduction of incident light of 50 % over sun-acclimated leaves of water stressed kiwifruit (Actinidia deliciosa var. deliciosa) would (1) reduce stomatal limitations to carbon supply and (2) mitigate the inactivation of the primary photochemistry associated with photosystem (PS) II, thereby this increases carbon gain and water-use efficiency (WUE). Groups of field-grown vines were either shaded or left naturally exposed and subjected to progressive water stress in order to study moderately and severely droughted vines, while other groups were well irrigated. Daily variations in leaf gas exchange and midday chlorophyll (Chl) a fluorescence were determined once plants had -0.6 MPa (moderate stress) and -1.0 MPa pre-down leaf water potential (severe stress). Variations in Chl pigment content and specific leaf area (SLA) are also discussed. Results reveal that 50 % shade application maintained efficiency of PSII close to 0.8 even under severe drought so that to prevent its large decline (0.65) recorded in sunlit leaves. Under moderate stress level stomata behaviour dominated upon metabolic impairments of PSII. Reduction of irradiance increased WUE (15-20 %) in droughted vines, representing a valuable intervention to save photosynthetic apparatus and improve WUE in vines experiencing typical Mediterranean summer stresses. and G. Montanaro, B. Dichio, C. Xiloyannis.
Four plant species, Elymus mollis Trin., Carex kobomugi Ohwi, Glehnia littoralis F. Schmidt ex Miq., and Vitex rotundifolia L.f., are dominant perennial species in coastal sand dunes of Korea. We examined a physiological adaptation of these species by measurements of diurnal variation in photosynthesis and chlorophyll (Chl) fluorescence and solute patterns in leaves during one season (June), which is favorable for plant growth of all four species. All four species adopted different strategies in order to utilize radiation and to maintain water status under a fluctuating microclimate. Although the lowest water contents among four plant species was found, E. mollis with a high Chl and K+ content showed better photosynthetic performance, with high stomatal conductance (gs), net photosynthetic rate (PN), instantaneous carboxylation efficiency (CE), and water-use efficiency. Midday depression of PN in E. mollis and G. littoralis, without a reduction of gs, was associated with a reduction in CE and maximum photochemical efficiency of PSII, indicating nonstomatal limitation. Photosynthesis depression in both C. kobomugi and V. rotundifolia, with relatively low gs values, could be attributed to both stomatal and nonstomatal limitations. The high storage capacity for inorganic ions in E. molli, C. kobomugi, and G. littoralis may play an efficient role in regulating photosynthesis and maintaining leaf water status through stomatal control, and can also play an important role in osmotic adjustment., J.-S. Hwang, Y.-S. Choo., and Obsahuje bibliografii