a1_The photosynthetic and chlorophyll fluorescence parameters were studied in Ziziphus jujuba var. spinosus under different soil water gradients obtained by irrigation and natural water consumption. We used the rectangular hyperbola model, the nonrectangular hyperbola model, the exponential model, and the modified rectangular hyperbola model to fit our data and evaluate them quantitatively. Based on the relationship among the parameters, the effects of the availability of soil water on photosynthesis were elucidated. The results showed that: (1) The relationship between water content and photosynthetic parameters were fitted best by the modified rectangular hyperbola model, followed by the nonrectangular hyperbola model, the exponential model, and the rectangular hyperbola model. The modified rectangular hyperbola model fitted best the maximum net photosynthetic rate (PNmax) and the light-saturation point (LSP), while the nonrectangular hyperbola model fitted best the dark respiration rate (RD), the apparent quantum yield (AQY), and the light-compensation point (LCP)., a2_(2) The main reason for the net photosynthetic rate (PN) decline was that it reached a stomatal limit when the soil relative water content (RWC) was greater than 25% and it reached a nonstomatal limit when the RWC was lesser than 25%. Under these conditions, the photosynthetic apparatus of Z. jujuba was irreversibly damaged. (3) Pmax, RD, AQY, and LSP increased first and then decreased, while LCP increased contrary to the RWC. The P N light-response parameters reached optimum when the RWC was 56-73%. (4) The quantum yield of PSII photochemistry reached a maximum when RWC was 80%. Nonphotochemical quenching decreased rapidly, and the minimum fluorescence in the dark-adapted state increased rapidly when RWC was lesser than 25%. Under these conditions, PSII was irreversibly damaged. (5) The RWC range of 11-25% resulted in low productivity and low water use efficiency (WUE). The RWC range of 25-56% resulted in moderate productivity and moderate WUE, and the RWC range of 56-80% resulted in high productivity and high WUE. The RWC range of 80-95% resulted in moderate productivity and low WUE. In summary, photosynthesis of Z. jujuba was physiologically adaptable in response to water stress in sand formed from seashells. The photosynthetic and physiological activity was maintained relatively high when the RWC was between 56 and 80%; Z. jujuba seedlings grew well under these conditions., J. B. Xia, G. C. Zhang, R. R. Wang, S. Y. Zhang., and Obsahuje bibliografii
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