Excessive cadmium (Cd) content in soil leads to a number of phytotoxic effects and challenges agricultural production. Aim of this study was to investigate different responses of two maize inbreds and their hybrid to an elevated Cd content in soil by measuring photosynthetic and biochemical activity and to identify a Cd tolerance mechanism. Antioxidant statusrelated parameters varied significantly between inbreds and treatments. Dry mass increased in both inbreds, but remained unchanged in hybrid. After the Cd treatment, parameters of chlorophyll a fluorescence varied between inbreds and hybrid performance was similar to inbred B84. We concluded that inbred B84 is Cd-sensitive compared to Os6-2, which did not appear to be negatively affected by Cd treatment at this growth stage studied. We suspect that due to a dilution effect in the hybrid, there was no or very weak Cd stress detected by biochemical parameters, although stress was detected by chlorophyll a fluorescence., M. Franić, V. Galić, M. Mazur, D. Šimić., and Obsahuje bibliografii
Ginseng (Panax ginseng) is a typical perennial shade plant. Aim of this study was to investigate the effects of exogenous hormones on photosynthesis of P. ginseng. At different growth stages, the aerial parts of P. ginseng plants were cut at the stem base and they were inserted into the nutrient solutions containing different exogenous hormones. Then the leaf photosynthesis and water absorbing capacity (absorbing water mass) of the excised plants were measured. The results showed that exogenous abscisic acid (ABA) decreased significantly net photosynthetic rate (PN), stomatal conductance, transpiration rate, and absorbed water mass of excised P. ginseng at all growth stages, while both cytokinin (CTK) and indole-3-acetic acid (IAA) enhanced those parameters. Comparing different growth stages, ABA caused more severe inhibition of leaf photosynthesis at the early growth stage, while CTK and IAA showed significant enhancement of leaf photosynthesis at later growth stage. ABA reduced highly intercellular CO2 concentration of P. ginseng at the flowering and green fruit stages, but it had only a small effect at red fruit early and red fruit stages. During the early growth stage, the inhibitory effect of ABA on leaf PN might be caused mainly due to the stomatal limitation. However, the reason for this reduction was complex at the later growth stage and it included stomatal and other factors., X. Li, K. Xu., and Obsahuje bibliografii
Nitric oxide (NO) is an important signalling molecule with diverse physiological functions in plants. In plant cell, it is synthesised in several metabolic ways either enzymatically or nonenzymatically. Due to its high reactivity, it could be also cytotoxic in dependence on concentration. Such effects could be also mediated by NO-derived compounds. However, the role of NO in photosynthetic apparatus arrangement and in photosynthetic performance is poorly understood as indicated by a number of studies in this field with often conflicting results. This review brings a short survey of the role of exogenous NO in photosynthesis under physiological and stressful conditions, particularly of its effect on parameters of chlorophyll fluorescence. and D. Procházková ... [et al.].
We carried out a field experiment in order to study effects of fertilization in juvenile plants of three coffee (Coffea arabica) cultivars in Yunnan, SW China. Fertilization treatments included a control without fertilizer (CK), combinations of three NPK fertilization rates [high fertilization (FH), medium fertilization (FM), and low fertilization (FL) with 135, 90, and 45 g per plant per year, respectively], and at two N:P2O5:K2O ratios (R1, 1:0.5:0.8; R2, 1:0.8:0.5). The growth in juvenile plants was not altered by fertilization, with two clear growth peaks being observed in both the height and stem growth rates (RGRs) throughout a year. Both FM and FH resulted in significantly higher RGRs in both height and stem diameter compared to FL and CK in all three cultivars. At the same fertilization rate, the leaf area, branch number, longest branch length, internode number, and biomass of R2 were higher than those of R1, and P significantly affected the root biomass and root to shoot ratio. Compared to the FL treatment, both FM and FH treatments resulted in higher net photosynthetic rates and stomatal conductance across seasons, and in higher intrinsic water-use efficiency during the dry season and at the middle of the wet season. Photosynthetic nitrogen-use efficiency at R2 was higher than that at R1, but no significant differences were observed between the different fertilization rates. Among the three coffee cultivars, Caturra exhibited the highest height, stem diameter, longest branch length, and internode number. Our results indicated that the optimal N:P2O5:K2O ratio was 1:0.8:0.5 for the juvenile growth of coffee plants. Both FM and FH could help optimize the growth and photosynthetic rate of coffee plants, but FM is suitable for the ecological friendly agriculture and economic sustainability at coffee plantations., Z. X. Zhang, Z. Q. Cai, G. Z. Liu, H. Wang, L. Huang, C. T. Cai., and Obsahuje bibliografii
The ecophysiological function(s) and consequences of guttation, a phenomenon by which water is exuded by and accumulated as droplets along the leaf margins under high humidity in many plants that grow in wet soil, has been poorly studied and remains largely unknown. Thus, leaf gas exchange and chlorophyll fluorescence were examined, using two experimental approaches, in Alchemilla mollis plants under conditions that promoted guttation and those that prevented this phenomenon. Although results were variable, depending on the experimental approach, prevention of guttation effected reductions in photosynthesis and transpiration, as well as photochemical activity measured with fluorescence techniques. These findings lend partial support for a previously hypothesized function of guttation: prevention of excess water in leaves, yet they contradict those of several other studies. More work is required in order to adequately understand the function of guttation., Y.-C. Chen, T.-C. Lin, C. E. Martin., and Obsahuje bibliografii
Water is a limited resource and is likely to become even more restricted with climate change. The aim of this study was to evaluate the effect of humic acid (HA) applications on photosynthesis efficiency of rapeseed plants under different watering conditions. Water stress strongly increased electron transport flux, probability that trapped excitation can move an electron into the electron transport chain beyond QA, and quantum yield of reduction of end electron acceptors at the PSI acceptor side. Application of HA decreased the values of these parameters to be similar to those of non-stress conditions. We found that, the application of HA improved plants net photosynthesis under water stress via increasing the rate of gas exchange and electron transport flux in plants., R. Lotfi, H. M. Kalaji, G. R. Valizadeh, E. Khalilvand Behrozyar, A. Hemati, P. Gharavi-Kochebagh, A. Ghassemi., and Obsahuje bibliografii
Chrococcoid cyanobacteria of the genus Synechococcus are the important component of marine and freshwater ecosystems. Picocyanobacteria comprise even 80% of total cyanobacterial biomass and contribute to 50% of total primary cyanobacterial bloom production. Chlorophyll (Chl) fluorescence and photosynthetic light response (P-I) curves are commonly used to characterize photoacclimation of Synechococcus strains. Three brackish, picocyanobacterial strains of Synechococcus (BA-132, BA-124, BA-120) were studied. They were grown under 4 irradiances [10, 55, 100, and 145 μmol(photon) m-2 s-1] and at 3 temperatures (15, 22.5, and 30°C). Photosynthetic rate was measured by Clark oxygen electrode, whereas the Chl fluorescence was measured using Pulse Amplitude Modulation fluorometer. Based on P-I, two mechanisms of photoacclimation were recognized in Synechococcus. The maximum value of maximum rate of photosynthesis (Pmax) expressed per biomass unit at 10 μmol(photon) m-2 s-1 indicated a change in the number of photosynthetic units (PSU). The constant values of initial slope of photosynthetic light response curve (α) and the maximum value of Pmax expressed per Chl unit at 145 μmol(photon) m-2 s-1 indicated another mechanism, i.e. a change in PSU size. These two mechanisms caused changes in photosynthetic rate and its parameters (compensation point, α, saturation irradiance, dark respiration, Pmax) upon the influence of different irradiance and temperature. High irradiance had a negative effect on fluorescence parameters, such as the maximum quantum yield and effective quantum yield of PSII photochemistry (φPSII), but it was higher in case of φPSII., S. Jodłowska, S. Śliwińska., and Obsahuje bibliografii
In order to investigate the effects of low irradiation (LI) on cucumber (Cucumis sativus L. cv. Jinyou 35) during a ripening stage, our experiment was carried out in a climate chamber. Two levels of PAR were set for plants: normal irradiation [NI, 600 μmol(photon) m-2 s-1] and low irradiation [LI, 100 μmol(photon) m-2 s-1], respectively. The experiments lasted for 9 d; then both groups of plants were transferred under NI to recover for 16 d. The plants showed severe chlorosis after the LI treatment. Chlorophyll (Chl) a, initial slope, photosynthetic rate at saturating irradiation (P max), light saturation point, maximal photochemical efficiency of PSII (Fv/Fm), electron transport rate of PSII (ETR), soluble protein content, and catalase (CAT) activity in cucumber leaves decreased under LI stress, while Chl b, carotenoids, light compensation point, nonphotochemical quenching (qN), superoxide dismutase (SOD), and malondialdehyde (MDA) exhibited an increasing trend under LI. After 16 d of recovery, values of P max, Fv/Fm, ETR, qN, SOD, CAT, MDA, and soluble protein were close to those of the control after one, three, and five days of the LI treatment, while those kept under LI for 7 and 9 d could not return to the control level. Therefore, 7 d of LI stress was a meteorological disaster index for LI in cucumber at the fruit stage., Z. Q. Yang, C. H. Yuan, W. Han, Y. X. Li, F. Xiao., and Obsahuje seznam literatury
Pepper is a thermophilous and heliophilic vegetable. In China, pepper is grown in greenhouse during winter and spring under lower temperature and irradiation. In this study, we investigated the effects of low temperature and low irradiance (LTLI) on the physiological characteristics and the expression of related genes in five pepper species, Capsicum annuum L. (CA), C. baccatum L. (CB), C. chinense Jacquin (CC), C. frutescens L. (CF), and C. pubescens Ruiz & Pavon (CP) in order to screen for greenhouse species that is resistant to such adverse conditions. We observed significant reductions not only in photosynthetic pigments and stomatal conductance but also in proline, total soluble sugar, enzyme activity, and root activity; disordered arrangements of leaf palisade and spongy tissues; and first rising and then falling expression of C-repeat binding factor (CBF3) and cold-regulated genes (CORc410). These results indicate that pepper is not resistant to LTLI. We also found that CP showed significantly higher photosynthetic activity, more proline and total soluble sugar, higher enzyme activity, higher root activity, higher CBF3 and CORc410 expression levels, more tightly packed leaf palisade and spongy tissues, and thicker bundle sheath than the other four species did under LTLI, while CF exhibited the lowest values for these indicators. It demonstrated significant differences in the ability to resist to LTLI among different species, with CP showing the strongest resistance, followed by CB. Therefore, we recommend the introduction of CP and CB to greenhouse cultivation to further screen for low temperature and low light-resistant pepper varieties to increase pepper production by strengthening intervariety hybridization., L. J. Ou, G. Wei, Z.Q. Zhang, X. Z. Dai, X. X. Zou., and Obsahuje bibliografii
The effects of NaCl stress on the growth and photosynthetic characters of Ulmus pumila L. seedlings were investigated under sand culture condition. With increasing NaCl concentration, main stem height, branch number, leaf number, and leaf area declined, while Na+ content and the Na+/K+ ratio in both expanded and expanding leaves increased. Na+ content was significantly higher in expanded leaves than in those just expanding. Chlorophyll (Chl) a and Chl b contents declined as NaCl concentration increased. The net photosynthetic rate, intercellular CO2 concentration, stomatal conductance, and transpiration rate also declined, but stomatal limitation value increased as NaCl concentration increased. Both the maximal quantum yield of PSII photochemistry and the effective quantum yield of PSII photochemistry declined as NaCl concentration rose. These results suggest that the accumulation of Na+ in already expanded leaves might reduce damage to the expanding leaves and help U. pumila endure high salinity. The reduced photosynthesis in response to salt stress was mainly caused by stomatal limitation., Z. T. Feng, Y. Q. Deng, H. Fan, Q. J. Sun, N. Sui, B. S. Wang., and Obsahuje bibliografii