Anthropogenic activities are changing global precipitation regimes and result in many middle latitude arid and semiarid regions experiencing less precipitation and more extreme weather events. However, little is known about the response of active ingredient accumulation in the medicinal herb Plantago depressa Willd. Therefore, we carried out a greenhouse experiment in order to study effect of control (CK, normal water supply equal to 309 mm per four months), -30 (-WS) and +30% (+WS) of the control water supply on the photosynthesis (PN), C/N ratio, and plantamajoside accumulation in P. depressa. Our results showed that compared with the-WS and CK treatments, the +WS treatment significantly enhanced biomass, the C/N ratio, plantamajoside concentration, yield in shoots and roots, and PN, but declined the N concentration in shoots and roots. The plantamajoside concentration was positively correlated with PN, the soluble sugar content, and the C/N ratio, but negatively correlated with the N concentration. Our results suggested that, under experimental conditions, +WS increased the C/N ratio and promoted the plantamajoside accumulation of P. depressa., Z. Li, W. Bai, L. Zhang, L. Li., 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
We studied the effect of arbuscular mycorrhizal (AM) fungus, Glomus constrictum (Trappe), and soil phosphorus (P) on
gas-exchange parameters, growth, and nutrition of soybean plants grown in pots with sterilized soil. Two contrasting concentrations of KH2PO4, i.e. no added and 0.5 g(P) kg-1(soil), were used. Addition of soluble phosphate increased all growth parameters, P and N concentrations, and most of the studied photosynthetic parameters of both the mycorrhizal and nonmycorrhizal plants. The mycorrhizal inoculation significantly increased plant growth responses, P and N concentrations in shoot and root tissues, acid and alkaline phosphatase activities, and total soluble proteins in root tissues compared with the nonmycorrhizal plants. The stimulations were related to the level of the mycorrhizal colonization in the root tissues. The mycorrhizal plants showed significantly higher net photosynthetic rate, stomatal conductance, and transpiration rate than those of nonmycorrhizal plants, especially in soil without added P. The phosphate addition to soil reduced generally the percentage of the mycorrhizal colonization in the root tissues, and consequently the mycorrhizal benefits. In general, growth, nutrition, and photosynthetic parameters of the soybean plants showed a high degree of dependency on the mycorrhizal fungus in nonfertilized soil when compared with the soil fertilized with P. This study confirmed that AM colonization could improve growth and nutrition of the soybean plant through increasing photosynthesis in leaves, particularly at low P in soil., G. M. Abdel-Fattah, A. A. Asrar, S. M. Al-Amri, E. M. Abdel-Salam., and Obsahuje bibliografii
In order to elucidate the drought resistance and high-yield mechanism of hybrid millet, we studied the influence of drought stress on the photosynthetic characteristics and dry matter accumulation. Our results revealed that drought stress caused lesser reduction in the net photosynthetic rate, maximal quantum yield of PSII photochemistry, excitation energy capture efficiency of PSII reaction centers and in the yield of hybrid millet compared to normal millet. When drought stress occurred in the jointing stage, the percentage decrease of PN, Fv/Fm, Fv′/Fm′, and the yield of Zhangzagu3 cultivar compared to control were 27.9%, 2.6%, 25. 5%, and 1.9%, respectively, the percentage decrease of Zhangzagu5 were 37.6%, 3.9%, 28.3%, and 16.7%, respectively, the decrease percentage of Datong29 were 60.1%, 6.4%, 4%, and 23.4%, respectively. Hybrid millet showed the similar reduction in the parameters referred above, when drought stress occurred at the heading stage, but the percentage decrease was much higher than that at the jointing stage. We concluded that hybrid millet showed higher drought resistance than normal millet., H. B. Lu, Y. M. Qiao, X. C. Gong, H. Q. Li, Q. Zhang, Z. H. Zhao, L. L. Meng., and Obsahuje bibliografii
5-aminolevulinic acid (ALA) is an essential precursor for the biosynthesis of tetrapyrrols such as heme and chlorophyll (Chl). Previous studies have focused mainly on promotive effects of exogenous ALA on plant growth, while regulatory mechanisms affecting Chl biosynthesis have been only partially discussed. In the present study, the ameliorative role of exogenous ALA was investigated on Chl and endogenous ALA biosynthesis in six-day-old etiolated oilseed rape (Brassica napus L.) cotyledons during the de-etiolation stage. We showed that exogenously applied ALA of a low dosage enhanced Chl and ALA accumulation in cotyledons, while 600 µM ALA treatment inhibited the accumulation of Chl and ALA severely. However, the gene expression levels of glutamyl-tRNA reductase (HEMA) and glutamate-1-semialdehyde aminotransferase (GSA) were not affected under either low or high ALA concentrations. Furthermore, water deficit induced by polyethylene glycol 6000 (PEG) suppressed the Chl and ALA accumulation in cotyledons, while the inhibition was partially alleviated in the cotyledons pretreated with ALA. The decrease in Chl biosynthesis induced by PEG stress was assumed to be related to downregulation of HEMA and Mg-chelatase ChlH (ChlH), and upregulation of ferrochelatase (FC) genes. Moreover, exogenously applied ALA did not show any effect on the expression of Chl synthesis-related genes under the PEG treatment. These results showed a difference in suppressing ALA synthesis due to the high concentration of ALA and PEG. Exogenously applied ALA did not affect the expression of HEMA and GSA, thus exogenous ALA regulated Chl synthesis not via the regulation of transcriptional level in ALA biosynthesis. However, the inhibition in Chl and endogenous ALA accumulation by the PEG treatment may be attributed to downregulation of HEMA and ChlH, and upregulation of FC., D. Liu, D. D. Kong, X. K. Fu, B. Ali, L. Xu, W. J. Zhou., and Seznam literatury
The effects of polyamines (PAs) on salt stress in Bakraii (Citrus reticulata × Citrus limetta) seedlings were studied. Foliar treatments by putrescine (Put), spermidine (Spd), and spermine (Spm) (0, 0.5, and 1 mM) were applied during the salinity period
(0 and 75 mM of NaCl). PA-treated seedlings showed a lower content of Na+ and Cl- in leaves. Application of PAs increased net photosynthetic rate in salt-stressed plants and it contributed to the enhanced growth parameters. PAs application considerably induced growth improvement in Bakraii seedlings which was found to be associated with reduced electrolyte leakage, increased relative water content, chlorophyll fluorescence parameters, activities of key antioxidant enzymes, as well as increased photosynthetic pigment concentration under saline regime. These results showed the promising use of PAs, especially of Spd and Spm, for reducing the negative effects of salinity stress and improving the growth of citrus seedlings., D. Khoshbakht, M. R. Asghari, M. Haghighi., and Obsahuje bibliografii
Salicylic acid (SA) is a common, plant-produced signal molecule that is responsible for inducing tolerance to a number of biotic and abiotic stresses. Our experiment was therefore conducted to test whether the application of SA at various concentrations (0, 0.10, 0.50, and 1.00 mM) as a foliar spray would protect citrus seedlings (Valencia orange/Bakraii) subjected to salt stress (0, 25, 50, and 75 mM NaCl). Growth parameters, leaf chlorophyll (Chl) content, relative water content (RWC), maximal quantum yield of PSII photochemistry (Fv/Fm), and gas-exchange variables were negatively affected by salinity. In addition, leaf electrolyte leakage (EL) and proline content increased by salinity treatments. Application of SA increased net photosynthetic rate and proline content in salt stressed plants and may have contributed to the enhanced growth parameters. SA treated plants had greater Chl content and RWC compared with untreated plants when exposed to salt stress. Fv/Fm ratio and stomatal conductance were also significantly higher in SA treated plants under saline stress conditions. SA application reduced EL compared to untreated plants, indicating possible protection of integrity of the cellular membrane. It appeared that the best ameliorative remedies of SA were obtained when Valencia orange/Bakraii seedlings were sprayed by 0.50 and 1.00 mM solutions. Overall, the adverse effects of salt stress could be alleviated by exogenous application of SA., D. Khoshbakht, M. R. Asgharei., and Obsahuje seznam literatury
A greenhouse experiment was conducted to examine the effect of foliar application of triacontanol (TRIA) on two cultivars (cv. S-24 and MH-97) of wheat (Triticum aestivum L.) at different growth stages. Plants were grown in full strength Hoagland’s nutrient solution under salt stress (150 mM NaCl) or control (0 mM NaCl) conditions. Three TRIA concentrations (0, 10, and 20 μM) were sprayed over leaves at three different growth stages, i.e. vegetative (V), boot (B), and vegetative + boot (VB) stages (two sprays on same plants, i.e., the first at 30-d-old plants and the second 78-d-old plants). Salt stress decreased significantly growth, net photosynthetic rate (PN), transpiration rate (E), chlorophyll contents (Chl a and b), and electron transport rate (ETR), while membrane permeability increased in both wheat cultivars. Stomatal conductance (gs) decreased only in salt-sensitive cv. MH-97 under saline conditions. Foliar application of TRIA at different growth stages enhanced significantly the growth, PN, gs, Chl a and b contents, and ETR, while membrane permeability was reduced in both cultivars under salt stress. Of various growth stages, foliar-applied TRIA was comparatively more effective when it was applied at V and VB stages. Overall, 10 μM TRIA concentration was the most efficient in reducing negative effects of salinity stress in both wheat cultivars. The cv. S-24 showed the better growth and ETR, while cv. MH-97 exhibited higher nonphotochemical quenching. and S. Perveen, M. Shahbaz, M. Ashraf.
Influence of different phosphorus concentrations was studied in four rice varieties (Akhanphou, MTU1010, RP BIO 226, and Swarna) differing in their tolerance to low phosphorus. There was an increase in shoot and root dry mass with the increase in phosphorus concentration. At the low phosphorus concentration at both tillering and reproductive stages, Swarna, followed by Akhanphou, recorded maximum biomass for both roots and shoots, while the minimum was observed in RP BIO 226. Reduction in photosynthetic rate, stomatal conductance, transpiration rate, and internal CO2 concentration at low phosphorus concentrations were observed at both tillering and reproductive stages in all the genotypes. In low phosphorus, maximum photosynthetic rate was found in Swarna followed by Akhanphou. Phosphorus deficiency did not alter the maximum efficiency of PSII photochemistry, however, there was a reduction in effective PSII quantum yield, electron transport rate, and coefficient of photochemical quenching, while the coefficient of nonphotochemical quenching was higher in the low phosphorus-treated plants. Prolonged exposure to excessive energy and failure to utilize the energy in carbon-reduction cycle induced the generation of reactive oxygen species, which affected PSII as indicated by the fluorescence traits. The reduction was less severe in case of Swarna and Akhanphou. The activities of superoxide dismutase, peroxidase, and catalase increased in roots under low phosphorus concentration indicating that photoprotective mechanisms have been initiated in rice plants in response to phosphorus deficiency. Comparatively, Swarna and Akhanphou exhibited a higher biomass, higher photosynthetic rate, and better reactive oxygen species-scavenging ability which conferred tolerance under low phosphorus conditions., N. Veronica, D. Subrahmanyam, T. Vishnu Kiran, P. Yugandhar, V. P. Bhadana, V. Padma, G. Jayasree, S. R. Voleti., and Obsahuje bibliografii
The steady-state oxygen evolution rate was previously shown to be stimulated by the disaccharide trehalose in PSII suspension. Here we showed a similar increase in the rate of oxygen evolution in PSII core complexes from spinach in solution and in proteoliposomes in the presence of trehalose. Using direct electrometrical technique, we also revealed that trehalose had no effect on the kinetics of electron transfer from Mn to redox-active-tyrosyl radical, YZ (S1 - S2 transition), while it accelerated the kinetics of electrogenic proton transport during S2 - S3 and S4 - S0 transitions of the wateroxidizing complex (WOC) induced by the first, second, and third laser flashes in dark-adapted PSII samples. These observations imply that the effect of trehalose occurrs due to its interaction with the WOC., M. D. Mamedov, E. S. Nosikova, L. A. Vitukhnovskaya, A. A. Zaspa, A. Yu. Semenov., and Obsahuje bibliografické odkazy