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
Melatonin has different functions in plant growth and development, especially in the protection of plants suffering from various forms of abiotic stress. We explored the effect of melatonin priming on photosynthetic activity of tomato (Lycopersicon esculentum L.) leaves. Our results showed that 100 µM is the optimal concentration used for alleviation of the damage to photosynthetic apparatus. Melatonin priming both in the form of leaf spray and direct root application was found to reduce the damage to photosynthetic apparatus, and increase the electron transfer rate and quantum yield of PSI and PSII photochemistry, to protect the thylakoid membrane from damage caused by low-temperature stress. Our study provides fundamental information for further research on the molecular mechanism of melatonin function in regulating photosynthesis., X. L. Yang, H. Xu, D. Li, X. Gao, T. L. Li, R. Wang., and Obsahuje bibliografii
In order to evaluate effect of weedy rice on the photosynthesis and grain filling of cultivated rice, cultivated rice ‘Nanjing 44‘ was planted in the field under different densities of weedy rice ‘JS-Y1‘ for two years. The results showed that net photosynthetic rate (PN), net assimilation rate, grain filling rate, and the grain yield of cultivated rice all decreased with increasing weedy rice density. Furthermore, yield component analysis revealed that increasing weedy rice density had the most significant effect on the percentage of filled grains and the number of rice panicles. The correlation analyses indicated that the yield of cultivated rice was highly correlated with the net photosynthetic rate and the net assimilation rate. Our results illustrated that high density of weedy rice might cause yield losses in cultivated rice by inhibition of photosynthesis and grain filling., X. M. Xu, G. Li, Y. Su, X. L. Wang., and Obsahuje bibliografii
Our study investigated the physiological and biochemical basis for the effects of exogenous phenolic acids on the function of the photosynthetic apparatus and photosynthetic electron transport rate in strawberry seedlings. Potted seedlings of the strawberry (Fragaria × ananassa Duch.) were used. Syringic acid inhibited net photosynthetic rate and water-use efficiency decreased. Additionally, primary quinone electron acceptor of the PSII reaction centre, the PSII reaction centre and the oxygen evolving complex were also impaired. Both the maximum quantum yield of the PSII primary photochemistry and the performance index on absorption basis were depressed, resulting in reduced function of the photosynthetic electron transport chain. Otherwise, low phthalic acid concentrations enhanced photosynthetic capacity, while high concentrations showed opposite effects. Syringic acid exhibited a higher toxic effect than that of phthalic acid which was more evident at higher concentrations., X. F. Lu, H. Zhang, S. S. Lyu, G. D. Du, X. Q. Wang, C. H. Wu, D. G. Lyu., and Obsahuje bibliografii
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
Our experiment was carried out in order to explore effects of plant growth regulators (PGR; thidiazuron, paclobutrazol, and ascorbic acid) on physiological traits of wheat genotypes under water surplus and deficit conditions. Study revealed that relative water content, membrane stability index, chlorophyll content, photosynthetic rate (PN), and maximal quantum yield of PSII improved with PGRs application across the genotypes both under irrigation and water stress. The response of HD 2733 genotype was more positive toward PGRs treatment as compared to other genotypes under water stress. Higher PN and chlorophyll contents were observed in HD 2987 followed by C 306 genotype under water-stress conditions. Moreover, Rubisco small subunit (SSU) expression was lower in wheat genotypes under water stress as compared to irrigated conditions. Application of PGRs led to upregulation of SSU under water stress, while no significant change was found in Rubisco level and activity under irrigated condition in dependence on PGRs treatments. Yield-related traits showed also significant reduction under water-stress conditions, while application of PGRs enhanced the yield and its components. Results indicated that the PGRs exhibited a positive interaction and synergetic effect on water stressed wheat plants in terms of photosynthetic machinery and yield., S. K. Dwivedi, A. Arora, V. P. Singh, G. P. Singh., and Obsahuje bibliografii
The inhibition of photorespiration can be used to improve plant carbon fixation. In order to compare the effects of three photorespiration inhibitors [glycine, NaHSO3, and isonicotinyl hydrazide (INH)], photosynthetic parameters of leaves sprayed respectively with these chemicals were examined and their inhibiting efficiency was evaluated in Caragana korshinskii. Our results showed that 5 mM glycine could reduce the photorespiratory rate (PR) effectively, while the net photosynthetic rate (PN), stomatal conductance (gs), and intercellular CO2 concentration (Ci) significantly increased. The ratio of electron flow for ribulose-1,5-bisphosphate (RuBP) carboxylation to RuBP oxygenation was elevated markedly. NaHSO3 and INH could also suppress the PR in some cases, whereas PN was not improved. The glyoxylate content increased considerably after application of low concentrations of glycine. These results suggested that low concentrations of glycine could suppress photorespiration by
feed-back inhibition of glyoxylate and enhance photosynthesis by regulating gs, Ci, and the distribution of electron flow in C. korshinskii., T. Kang, H. D. Wu, B. Y. Lu, X. J. Luo, C. M. Gong, J. Bai., and Obsahuje bibliografii
This study was performed to evaluate the ecophysiological acclimation of Catalpa bungei plantlets to different light conditions. We hypothesized that the acclimation of old and newly developed leaves to both increasing and decreasing irradiance should follow different patterns. The growth, photosynthesis, chlorophyll (Chl) content, and Chl fluorescence response were examined over a range of light treatments. The plants were grown under fixed light intensities of 80% (HH), 50% (MM), 30% (LL) of sun light and transferring irradiance of 80% to 50% (HM), 80% to 30% (HL), 30% to 50% (LM) and 30% to 80% (LH). For old leaves, light-saturation point, photosynthetic capacity, dark respiration rate of LH were lower than that of HH, while HL were higher than LL, indicating that light-response parameters were affected by the original growth light environment. Initial fluorescence increased and variable fluorescence decreased in LH and LM after transfer, and the PSII damage was more serious in LH than that in LM, and could not recover within 30 d. It suggested that the photoinhibition damage and recovery time in old leaves was related to the intensity of light after transfer. For the newly emerged leaves with leaf primordia formed under the same light environment, a significant difference was observed in leaf morphology and pigment contents, suggesting that previous light environment exhibited carry-over effect on the acclimation capacity to a new light environment. Our result showed that thinning and pruning intensity should be considered in plantation management, because great changes in light intensity may cause photoinhibition in shade-adapted leaves., J. W. Wu, Y. Su, J. H. Wang, Q. He, Q. Qiu, J. W. Ma, J. Y. Li., and Obsahuje bibliografii
In order to assess its response to the herbicide, sethoxydim (SEY), seedlings of two foxtail millet (Setaria italica) hybrids were exposed to 0.75, 1.5, 3, and 6 L(SEY active ingredient, ai) ha-1 for 7 and 15 d. Our results showed that SEY reduced photosynthesis and oxidative stress in the hybrid millet (Zhangza) at the dosage below 1.5 L(ai) ha-1 (i.e., recommended dosage), whereas it caused death of Jingu 21 at all treatment dosages. In addition, we further explored the effect of SEY on PSI and PSII; the hybrid millet showed a greater tolerance to SEY and also the ability to recover. In conclusion, the hybrid millet seems to possess certain photosynthetic protection mechanisms which could reduce or eliminate the herbicide stress by increasing nonphotochemical quenching for dissipating excessive light energy under SEY-induced oxidative stress., M. J. Guo, Y. G. Wang, S. Q. Dong, Y. Y. Wen, X. E. Song, P. Y. Guo., and Obsahuje bibliografii
WN6 (a stay-green wheat cultivar) and JM20 (control) were used to evaluate the effects of exogenous cytokinin on photosynthetic capacity and antioxidant enzymes activities in flag leaves. Results showed that WN6 reached the higher grain mass, which was mainly due to the higher photosynthetic rate resulting from the higher maximal quantum yield of PSII photochemistry (ΦPSII) and probability that a trapped exaction transfers an electron into the electron transport chain beyond QA (Ψo), and lower relative variable fluorescence intensity at the J-step (Vj). Exogenous 6-benzylaminopurine (6-BA) enhanced antioxidant enzymes activities and decreased malondialdehyde (MDA) content. Enhanced Ψo and electron transport rate (ETR), and decreased Vj contributed to improved photosynthetic rate in the 6-BA treatment. In addition, exogenous 6-BA significantly increased endogenous zeatin (Zt) content, which was significantly and positively correlated with the antioxidant enzyme activity and ΦPSII, implying that higher Zt content was responsible for the improved antioxidant status and photosynthetic performance., D. Q. Yang, Y. L. Luo, W. H. Dong, Y. P. Yin, Y. Li, Z. L. Wang., and Obsahuje bibliografii