This work aimed to study the effects of commercial doses of the fungicide, Mancozeb, on the photosynthetic apparatus of lettuce young leaves (YL) and expanded leaves (EL). Seven days after Mancozeb application, chlorophyll a fluorescence, pigment contents, lipid peroxidation, and proline content were evaluated. Independently of leaf age, Mancozeb treatment reduced the efficiency of photosystem II photochemistry, increased the nonphotochemical quenching and proline content, decreased pigment contents, and induced lipid peroxidation. Moreover, EL showed a more stable photosynthetic apparatus, less prone to oxidative damages compared with YL. The parameters measured proved to be good markers for the rapid and preliminary diagnosis of fungicide toxicity., M. C. Dias, P. Figueiredo, I. F. Duarte, A. M. Gil, C. Santos., and Obsahuje bibliografii
Responses of the photosynthetic electron transport system of chloroplasts to exogenous proline application were evaluated in young and mature leaves of Arabidopsis thaliana plants under optimal growth conditions. Exogenous proline application (10 mM) during the 4th week of growth increased proline accumulation in young leaves more than in mature leaves, and possibly due to its degradation producing NADPH, decreased significantly the ratio of NADP+/NADPH in both leaf types compared with controls (without proline). However, the ratio of NADP+/NADPH remained significantly higher in the young leaves, suggesting lower proline degradation which resulted in less reduced plastoquinone pool than that in the mature leaves, under both low light [130 μmol(photon) m-2 s-1] and high light [1,200 μmol(photon) m-2 s-1] treatments. The young leaves seemed to adjust nonphotochemical fluorescence quenching in order to maintain a better PSII quantum yield. We concluded that under optimal growth conditions exogenous proline results in overreduction of the plastoquinone pool and blockage of photosynthetic electron flow due to accumulation of NADPH. We suggest that optimum concentrations of proline are required for optimal PSII photochemistry., I. Sperdouli, M. Moustakas., and Obsahuje seznam literatury
Nostoc muscorum cells showed metal-induced decrease in the relative growth, pigment contents, O2 evolution, and Hill activity in response to lead (Pb2+) and cadmium (Cd2+) treatment, which was further accentuated with increase in metal exposure time and metal concentration. I50 concentrations (50% growth inhibitory concentrations) of Pb2+ and Cd2+ for growth of N. muscorum were 55 and 21 μg mL-1, respectively. These results indicated that the cells of N. muscorum were more susceptible to Cd2+ in comparison to Pb2+. The O2 production was relatively more sensitive to both heavy metals (I50: 16 and 10 μg mL-1 of Pb2+ and Cd2+, respectively) than the Hill activity (I50: 61 and 39 μg mL-1 of Pb2+ and Cd2+, respectively). Further, measurement of Hill activity in the presence of metals and electron donors showed that inhibition sites of both Pb2+ and Cd2+ were located on the oxidizing site of PSII. The chlorophyll a (Chl a) and phycobilisome (PB) fluorescence emission spectra showed that energy transfer from Chl a and PB to PSII reaction center was more susceptible to Cd2+ than Pb2+., S. Dixit, D. P. Singh., and Obsahuje bibliografii
In eukaryotic oxygenic photosynthetic organisms (both plants and algae), the maximum fluorescence is at peak P, with peak M lying much lower, or being even absent. Thus, the PSMT phase, where S is semisteady state, and T is terminal state, is replaced by a monotonous P→T fluorescence decay. In the present study, we found that dimethoate-treated wheat plant leaves showed SM transient, whereas in the case of control plants monotonous P→T fluorescence decay occured. We suggest that this was partly due to quenching of fluorescence due to [H+], responsible for P to S (T) decay in control plants (Briantais et al. 1979) being replaced by state transition (state 2 to state 1) in dimethoate-treated plants (Kaňa et al. 2012)., J. K. Pandey, R. Gopal., and Obsahuje bibliografii
The photosynthetic responses to elevated CO2 concentration (EC) at ambient and ambient +4°C temperature were aßsessed in the second leaf of rice (Oryza sativa L.) seedlings. The duration of different leaf developmental phases, as characterised by changes in photosynthetic pigment contents and photochemical potential, was protracted in the seedlings grown under EC. On the other hand, a temporal shift in the phases of development with an early onset of senescence was observed in the seedlings grown under EC at ambient +4°C temperature. The contents of carotenoids, ß-carotene, and xanthophyll cycle pigments revealed that EC downregulated the protective mechanism of photosynthetic apparatus against oxidative damages, whereas this mechanism assumed higher significance under EC at ambient +4°C temperature. We observed an enhancement in electron transport activity, photochemical potential, and net photosynthesis in spite of a loss in photostasis of photosynthesis under EC. On the other hand, the loss in photostasis of photosynthesis was exacerbated under EC at ambient +4°C temperature due to the decline in electron transport activity, photochemical potential, and net photosynthesis., S. Panigrahi, M. K. Pradhan, D. K. Panda, S. K. Panda, P. N. Joshi., and Seznam literatury
a1_Perennial organ functions of trees living in seasonal environments exhibit temporal changes that can be classified as long-term interannual changes and seasonal fluctuations within single years. However, few studies have separately quantified these changes from longitudinal measurement data or analyzed the relationships between them. We developed a hierarchical Bayesian statistical model consisting of three parts: a long-term interannual change expressed by consecutive annual linear trends, seasonal fluctuations with 26 values for two-week periods in a year, and a random effect for repeated measurements. The model can extract long-term interannual changes and seasonal fluctuations from longitudinal repeated measure data. The pattern of seasonal fluctuation, the amount of seasonal fluctuation, and the net annual change are expressed by the estimated model parameters. We applied our model to foliar chlorophyll (Chl) and nitrogen (N) content measured repeatedly on more than 1-year-old leaves of saplings in four evergreen broad-leaved tree species using nondestructive optical methods. The model successfully explained large variations in the Chl and N content. In general, seasonal fluctuations corresponded to the phenology of current-year leaves; Chl and N tended to decrease from the opening to maturation of new leaves and increased during the rest period. The magnitude of the decrease in the Chl and N content in the growth period of current-year leaves (Δγ) did not decrease noticeably as leaves aged. For the Chl content, Δγ was positively correlated with the maximum value before leaf opening across species. For the N content, Δγ and the maximum value before leaf opening were not clearly correlated across species, but were positively correlated within some species., a2_A model parameter for annual linear trends in Chl and N varied from positive (indicating increasing trends) to negative values (indicating decrease) depending on species and leaf age in years., D. Mizusaki, K. Umeki, T. Honjo., and Obsahuje seznam literatury
In order to use rationally switchgrass (Panicum virgatum L.) introduced in a large scale in semiarid regions on the Loess Plateau of China, we investigated and compared soil water storage dynamics, diurnal and seasonal changes in leaf photosynthetic characteristics, and biomass production of switchgrass grown under three different row spacing (20, 40, and 60 cm). Results indicated that photosynthetic parameters showed a pronounced seasonality. Diurnal course of net photosynthetic rate (P N) was bimodal, showing obvious midday depression, which was mainly due to stomatal limitation in May and June, by nonstomatal limitation in August, and both stomatal and nonstomatal factors in September. Generally, P N, stomatal conductance, instantaneous water-use efficiency, light-saturated net photosynthetic rate, saturation irradiance, and compensation irradiance increased with increasing row spacing. Plant height, leaf width, and a relative growth rate of biomass accumulation were significantly higher at the row spacing of 60 cm, while 20 cm spacing showed significantly higher aboveground biomass production and the biomass water-use efficiency. All these confirmed that soil water is the key limiting factor influencing switchgrass photosynthesis, and suggested that the wide row plantation (i.e., 60 cm) was more beneficial to switchgrass growth, while narrow spacing was in favor of improving switchgrass productivity and water-use efficiency., Z. J. Gao, B. C. Xu, J. Wang, L. J. Huo, S. Li., and Obsahuje seznam literatury
Diurnal dynamics of photosynthetic character of Angelica sinensis, as well as effect of continuous cropping on leaf photosynthetic character, antioxidant enzyme activity and growth of A. sinensis were investigated under field condition. The results showed that the diurnal net photosynthetic rate of A. sinensis in sunny day exhibited a double-peak pattern, and the peaks occurred at 9:45 and 16:45 h, respectively. There was a significant midday depression with A. sinensis, which was caused principally by stomatal factors such as stomatal conductance. The results also showed that net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), intercellular CO2 concentration (Ci), and chlorophyll content (Chl) of A. sinensis plants under continuous cropping were significantly lower than those of the control. The activity of total superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and growth parameters of A. sinensis plants were significantly decreased under continuous cropping condition. This study provides evidence of continuous cropping obstacle effect on photosynthesis, antioxidant enzyme activity, and growth parameters of A. sinensis in a field experiment, which partly explained the yield reduction of A. sinensis in the field, when it was cultivated continuously on the same soil., X. H. Zhang ... [et al.]., and Obsahuje bibliografii
The effects of the diurnal variations in ambient temperature on some C3 and C4 enzymes in the Salsola dendroides and Suaeda altissima species of Chenopodiaceae family were studied during the intensive vegetation period. Activities of phosphoenolpyruvate carboxylase (PEPC) and cytosolic aspartate aminotransferase (AsAT) were shown to decrease in both species in the afternoon and evening. The activity of the mitochondrial AsAT decreased in S. altissima, remained relatively constant in S. dendroides during the day. The activity of alanine aminotransferase was high in the S. dendroides species in the morning and evening and decreased in the S. altissima species by the evening. Glucose-6-phosphate activated PEPC in both species throughout the day. The study of the redox status-regulated C3 enzymes showed temperature-related increases in NADP-glyceraldehyde 3-phosphate dehydrogenase activity in both plants, in fructose-2,6-bisphosphatase activity in the S. altissima species, and in NADP-MDH activity in the S. dendroides species in the afternoon., T. Y. Orujova, S. M. Bayramov, U. A. Gurbanova, H. G. Babayev, M. N. Aliyeva, N. M. Guliyev, Y. M. Feyziyev., and Obsahuje bibliografii
We hypothesized that decreased stomatal conductance (gs) at elevated CO2 might decrease transpiration (E), increase leaf water potential (ΨW), and thereby protect net photosynthesis rate (PN) from heat damage in maize (Zea mays L) seedlings. To separate long-term effects of elevated CO2, plants grew at either ambient CO2 or elevated CO2. During high-temperature treatment (HT) at 45°C for 15 min, leaves were exposed either to ambient CO2 (380 μmol mol-1) or to elevated CO2 (560 μmol mol-1). HT reduced PN by 25 to 38% across four CO2 combinations. However, the gs and E did not differ among all CO2 treatments during HT. After returning the leaf temperature to 35°C within 30 min, gs and E were the same or higher than the initial values. Leaf water potential (ΨW) was slightly lower at ambient CO2, but not at elevated CO2. This study highlighted that elevated CO2 failed in protecting PN from 45°C via decreasing gs and ΨW., M. N. Qu, J. A. Bunce, Z. S. Shi., and Obsahuje bibliografii