The effects of actinic light (AL) intensity on the age dependence of nonphotochemical fluorescence quenching (qN) and effective quantum yield in PSII (ΦPSII) were studied in continuously illuminated wheat leaves of the upper tier. Regular changes were revealed in both age dependence of qN at elevated AL intensities and light curves of qN. These changes are related to alterations in strategies of redistribution and use of absorbed light energy by the photosynthetic apparatus at different stages of wheat leaf development. Unlike ΦPSII, qN as a parameter was more sensitive to the differences in the leaf age at a certain range of light intensities. At the same time, the stability of qN at moderate light intensities may serve as an indication of leaf maturity., T. V. Nesterenko, V. N. Shikhov, A. A. Tikhomirov., and Obsahuje seznam literatury
Different light filters affect leaf photosynthetic features and fruit quality. Consequently, selecting the appropriate covering filter for rain-shelter cultivation of peaches is a key part of successful production. We used a late-maturing peach variety ‘Xiahui 8’ to study differences in leaf photosynthetic features, chlorophyll fluorescence characteristics, and fruit quality under neutral, red, yellow, green, and blue filter, with natural light as control. The results showed that the leaf photosynthetic ability and internal quality under the neutral filter treatment were elevated compared with the control, and the appearance color was the same as the control. Leaves under neutral filter could maintain higher photosynthetic ability than other filter treatments. In addition, the fruits could also keep higher quality when treated with neutral filter. Therefore, the application of neutral filter in rain-shelter cultivation of ‘Xinhui 8’ peaches is recommended for maintaining high photosynthetic capacity and for improving fruit quality., B.-B. Zhang, J.-L. Xu, M. Zhou, D.-H. Yan, R.-J. Ma., and Obsahuje bibliografii
The effect of two elevated carbon dioxide concentrations, 700 µmol(CO2) mol-1 (C700) and 1 400 µmol(CO2) mol-1 (C1400), on photosynthetic performances of 1-year-old Prunus avium L. plant was studied. Plants grown at C700 were characterised by increased net photosynthetic rate (PN) as compared to those grown at C1400. Plant photosynthetic adjustment to C1400 resulted in 27 % higher PN than in control at atmospheric CO2 concentration (Ca) at the beginning of the experiment (3-4 weeks) with a consequent decline to the end of the experiment. Thus, 1 400 µmol(CO2) mol-1 had short-term stimulatory effect on plant PN. Both chlorophyll (Chl) a and b concentrations dramatically decreased during exposure to C1400. Compensation irradiance was increased by 57 % in C700 and by 87 % in C1400. Photochemical efficiency (φ) was affected by balloon environment, however, a clear stimulatory effect of C700 was detected. Opposite influence of both elevated CO2 concentrations on PNmax was established: slight increase by C700 (2.7 % at Ca), but considerable decrease by C1400 (63 % at Ca). Exposure to C700 enhanced compensation irradiance by 42 %, while C1400 by only 21 %. Either C700 or C1400 did not reduce stomatal conductance (gs). Leaf area per plant (LAR) was more stimulated by C700 than by C1400. High unit area leaf mass, specific leaf area, and dry matter accumulation in roots without affecting tissue density characterised plants grown in C1400. However, when considering the root : shoot ratio, these plants allocated less carbon to the roots than plants from other treatments.
Lowering irradiance can delay the flower stalk, i.e., spike development, in order to schedule flowering time of Phalaenopsis; however, the effect on photosynthetic performance and spiking inhibition remains poorly understood. We compared light and shade treatments of Phalaenopsis aphrodite subsp. formosana in order to determine how limiting light affects day-night changes in the photosynthetic capacity of leaves and the carbon pool of leaves and stems resulting in delayed spiking. The low irradiance treatment [20 μmol(photon) m-2 s-1] for six weeks did not affect potential functions of photosynthetic apparatus estimated by chlorophyll a fluorescence analysis, but it significantly reduced the net CO2 uptake and O2 evolution rates, carbohydrate and organic acid concentrations, and amplitudes of CAM activity in new and fully expanded leaves of Phalaenopsis and delayed the spiking compared with the control kept at 150 μmol(photon) m-2 s-1. The shortened stem contained a remarkably high sucrose concentration, accounting for more than 80% of total soluble sugars for both treatments throughout the day. Moreover, the sucrose concentration was unaffected by the lowering of irradiance. The relationship between the sucrose content and spiking seemed to be loose; the major factor(s) for spiking in Phalaenopsis remained to be ascertained as the flower stalk bud is attached to the shortened stem., Y.-C. Liu, C.-H. Liu, Y.-C. Lin, C.-H. Lu, W.-H. Chen, H.-L. Wang., and Obsahuje seznam literatury
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 a greenhouse experiment, the influence of arbuscular mycorrhizal fungi (Glomus mosseae and Glomus intraradices) and water stress [100% field capacity (FC), 75% FC, 50% FC and 25% FC] on maximal quantum yield of photosystem II (PSII) photochemistry (Fv/Fm) and some other ecophysiological characteristics of two pistachio cultivar (Pistacia vera cv.
Badami-Riz-Zarand and Pistacia vera cv. Qazvini) were investigated.
No difference was found in colonization rate between the two arbuscular mycorrhizal fungi (AMF) applied. Water stress reduced the mycorrhizal colonization in both cultivars at the same rate but the difference was significant just with severe water stress level (25% FC). The Fv/Fm was also adversely affected by water stress from 75% FC downwards in Qazvini cultivar while in Badami, increase in water-stress intensity had no significant effect on this parameter. Gasexchange parameters were decreased with increasing stress intensity and chlorophyll (Chl) pigments were increased with mild water stress (75% FC) compared with control (100% FC) and then decreased with increasing stress intensity. The carotenoids (Car) content increased significantly in the stressed leaves in all water-stress levels irrespective of AMF treatment and cultivar type.
The adverse effects of water stress were significantly reduced by AM inoculation and in the most of measured parameters, both AMF had an equal influence except with the intercellular CO2 concentration (Ci), where G. intraradices was superior. Results obtained from Chl fluorescence probe indicated that inoculated AMF enhanced photochemical efficiency of light reactions of the PSII in intact pistachio leaf tissues both under irrigation and waterstress conditions. Under mild and moderate water stress, mycorrhizal pistachio plants had higher relative Chl and Car content and higher gas-exchange capacity (increased photosynthesis and transpiration rate) but under severe water-stress condition (25% FC), the effects of mycorrhizal treatments were not noticeable. Data obtained in present study emphasized that Qazvini is more tolerant to water stress than Badami because photosynthesis activity in Qazvini was more efficiently protected than in the Badami, as indicated by related parameters. and V. Bagheri ... [et al.].
The effects of NaCl (200 mM) and osmotic stress generated by polyethylene glycol (PEG) on PSII maximal quantum efficiency, photosynthetic CO2/H2O gas exchange at two CO2 concentrations, content of chlorophyll, proline, and malondialdehyde were investigated in shoots of C4 xerohalophyte Haloxylon aphyllum (Chenopodiaceae). The PEG treatment induced a low water osmotic potential (-0.4 MPa) and inhibited photosynthesis (by a factor of 2) and transpiration (by a factor of 4). The NaCl treatment, at equal osmoticity conditions, reduced transpiration (by a factor of 2) and stimulated photosynthesis (by a factor of 2.5). Only the
PEG-treated plants showed osmotic stress effects, which were demonstrated by an increase in proline and malondialdehyde contents in the shoot tissue. The data indicated that the halophilic character of this species was essential for maintaining the plant water status and photosynthesis under osmoticity induced by NaCl treatment. Herewith, the presence of C4-type photosynthesis appeared to be just an auxiliary mechanism, because this xerohalophyte did not reveal the efficiency in water use typical for C4 plants under osmotic stress, in the absence of a saline substrate., Z. F. Rakhmankulova, P. Yu. Voronin, E. V. Shuyskaya, N .A. Kuznetsova, N. V. Zhukovskaya, K. N. Toderich., and Obsahuje bibliografii
Wheat (Triticum aestivum L.) genotypes K-65 (salt tolerant) and HD 2329 (salt sensitive) were grown in pots under natural conditions and irrigated with NaCl solutions of electrical conductivity (ECe) 4.0, 6.0, and 8.0 dS m-1. Control plants were irrigated without saline water. Observations were made on the top most fully expanded leaf at tillering, anthesis, and grain filling stages. The net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) were reduced with the addition of NaCl. The reduction was higher in HD 2329 than in K-65. Salinity enhanced leaf to air temperature gradient (ΔT) in both the genotypes. NaCl increased the activities of superoxide dismutase (SOD) and peroxidase (POX); the percent increment was higher in K-65. The sodium and potassium contents were higher in the roots and leaves of K-65 over HD 2329. Thus at cellular level K-65 has imparted salt tolerance by manipulating PN, E, gs, and K accumulation in leaves along with overproduction of antioxidative enzyme activities (SOD and POX). and N. Sharma ... [et al.].
Calligonum caput-medusae is known to grow well when irrigated with water containing NaCl. The aim of this study was to investigate ecophysiological responses of C. caput-medusae to different NaCl concentrations. In our study, we examined the effect of 0, 50, 100, 200, and 400 mM NaCl. Our results demonstrated that maximum seedling growth occurred at 50 mM NaCl. Photosynthetic parameters, such as the photosynthetic pigment content and gas exchange parameters, correlated with growth response. High salinity (≥ 100 mM NaCl) resulted in a significant reduction of the plant growth. Similarly, marked declines in the pigment content, maximal efficiency of PSII photochemistry, net photosynthetic rate, transpiration rate, and stomatal conductance were also detected. However, intercellular CO2 concentration showed a biphasic response, decreasing with water containing less than 200 mM NaCl and increasing with NaCl concentration up to 400 mM. Water-use efficiency and intrinsic water-use efficiency exhibited the opposite response. The reduction of photosynthesis at the high NaCl concentration could be caused by nonstomatal factors. High salinity led also to a decrease in the relative water content and water potential. Correspondingly, an accumulation of soluble sugars and proline was also observed. Na+ and
Cl- concentrations increased in all tissues and K+ concentrations were maintained high during exposure to NaCl compared with the control. High salinity caused oxidative stress, which was evidenced by high malondialdehyde and hydrogen peroxide contents. In order to cope with oxidative stress, the activity of antioxidative enzymes increased to maximum after 50 mM NaCl treatment. The data reported in this study indicate that C. caput-medusae can be utilized in mild salinity-prone environments., Y. Lu, J.-Q. Lei, F.-J. Zeng, B. Zhang, G.-J. Liu, B. Liu, X.-Y. Li., and Obsahuje bibliografii
Nitrogen (N) availability is a critical factor affecting photosynthetic acclimation of C3 plants under elevated atmospheric CO2 concentration ([CO2]e). However, current understanding of N effects on photosynthetic electron transport rate and partitioning, as well as its impact on photosynthesis under [CO2]e, is inadequate. Using controlled environment open-top chambers, wheat (Triticum aestivum L.) was grown at two N levels (0 and 200 mg(N) kg-1 soil) and two atmospheric CO2 concentrations of 400 ([CO2]a) and 760 μmol mol-1([CO2]e) during 2009 and 2010. Under [CO2]e high N availability increased stomatal conductance and transpiration rate, reduced limitations on the activity of triose phosphate isomerase, a Calvin cycle enzyme, and increased the rate of net photosynthesis (PN). Considering photosynthetic electron transport rate and partitioning aspects, we suggest that greater N availability increased PN under [CO2]e due to four following reasons: (1) higher N availability enhanced foliar N and chlorophyll concentrations, and the actual photochemical efficiency of photosystem (PS) II reaction centers under irradiance increased, (2) increase of total electron transport rate and proportion of open PSII reaction centers, (3) enhancement of the electron transport rate of the photochemical and carboxylation processes, and (4) reduced limitations of the Calvin cycle enzymes on the photosynthetic electron transport rate. Consequently, sufficient N improved light energy utilization in wheat flag leaves under [CO2]e, thus benefiting to photosynthetic assimilation. and X. C. Zhang, X. F. Yu, Y. F. Ma.