Responses of salt-tolerant and intolerant wheat genotypes to sodium chloride: Photosynthesis,antioxidants activities,and yield

Physiological responses of two wheat (Triticum aestivum L.) genotypes (salt-tolerant DK961 and salt-sensitive JN17) to increased salt concentrations (50, 100, 150 mM NaCl: NaCl⁵⁰, NaCl¹⁰⁰, NaCl¹⁵⁰) were studied. Photosynthetic capacity, irradiance response curves, contents of soluble sugars, proteins, and chlorophyll (Chl), K⁺/Na⁺ ratio, and activities of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) in flag leaves were measured on 7 d after anthesis. In control (NaCl⁰) plants, non-significant (p>0.05) differences were found in gas exchange and saturation irradiance (SI) between salt-tolerant (ST) and salt-sensitive (SS) wheat genotypes. However, we found higher soluble sugar and protein contents, K⁺/Na⁺ ratio, and antioxidant enzyme activities, but lower Chl content and yield in ST wheat. Salinity stresses remarkably increased soluble sugar and protein contents and the antioxidant activities, but decreased K⁺/Na⁺ ratio, Chl contents, SI, photosynthetic capacities, and yield, the extent being considerably larger in JN17 than DK961. Although the soluble sugar and protein contents and the antioxidant activities of JN17 elevated more evidently under salt stresses, those variables never reached the high levels of DK961. The antioxidant enzyme activities of SS wheat increased in NaCl⁵⁰ and NaCl¹⁰⁰, but decreased rapidly when the NaCl concentration reached 150 mM. Thus the ST wheat could maintain higher grain yield than the SS one by remaining higher osmoregulation and antioxidative abilities, which led to higher photosynthetic capacity. Hence the ST wheat could harmonize the relationship between CO₂ assimilation (source) and the grain yield (sink) under the experimental conditions.     

Photosynthesis, photoprotection, and growth of shade-tolerant tropical tree seedlings under full sunlight

High solar radiation in the tropics is known to cause transient reduction in photosystem II (PSII) efficiency and CO(2) assimilation in sun-exposed leaves, but little is known how these responses affect the actual growth performance of tropical plants. The present study addresses this question. Seedlings of five woody neotropical forest species were cultivated under full sunlight and shaded conditions. In full sunlight, strong photoinhibition of PSII at midday was documented for the late-successional tree species Ormosia macrocalyx and Tetragastris panamensis and the understory/forest gap species, Piper reticulatum. In leaves of O. macrocalyx, PSII inhibition was accompanied by substantial midday depression of net CO(2) assimilation. Leaves of all species had increased pools of violaxanthin-cycle pigments. Other features of photoacclimation, such as increased Chl a/b ratio and contents of lutein, β-carotene and tocopherol varied. High light caused strong increase of tocopherol in leaves of T. panamensis and another late-successional species, Virola surinamensis. O. macrocalyx had low contents of tocopherol and UV-absorbing substances. Under full sunlight, biomass accumulation was not reduced in seedlings of T. panamensis, P. reticulatum, and V. surinamensis, but O. macrocalyx exhibited substantial growth inhibition. In the highly shade-tolerant understory species Psychotria marginata, full sunlight caused strongly reduced growth of most individuals. However, some plants showed relatively high growth rates under full sun approaching those of seedlings at 40?% ambient irradiance. It is concluded that shade-tolerant tropical tree seedlings can achieve efficient photoacclimation and high growth rates in full sunlight.     

The role of chloride channels and chloride ions in steroidogenesis regulation in the gonads of amphibians,birds and mammals

The paper represents the first review of data on the involvement of chloride channels (their inhibitors and media, in which chloride ions are substituted for anions that poorly penetrate in the cell) in the regulation of basal and gonadotropin-stimulated steroidogenesis in the gonads of amphibians, birds, and mammals. Possible causes are considered for different reactions of the gonad steroidogenic cells in representatives of different vertebrate classes to a decreased medium concentration of chloride and the involvement of chloride channels and/or chloride ions in the regulation of steroidogenesis is discussed.     

Photosynthesis,carbon allocation,and growth of sulfur dioxide ecotypes ofGeranium carolinianum L.

Summary This study investigated ways in which genetically determined differences in SO₂ susceptibility resulting from ecotypic differentiation inGeranium carolinianum were expressed physiologically. The SO₂-resistant and SO₂-sensitive ecotypes were exposed to a combination of short- and long-term SO₂ exposures to evaluate the responses of photosynthesis, H₂S efflux from foliage (sulfur detoxification), photoassimilate retention, leaf-diffusive resistance to CO₂, and growth. When exposed to SO₂, both ecotypes re-emit sulfur in a volatile, reduced form, presumably as H₂S. Because H₂S efflux rates at various SO₂ concentrations were comparable between ecotypes, genetic differences inG. carolinianum could not be attributed to a re-emission of excess sulfur as H₂S. Incipient SO₂ effects on photosynthesis were observed as cumulative SO₂ flux into the leaf interior excecded 0.40 nmol·m^–2 in the resistant ecotype and 0.26 nmol·m^–2 in the sensitive ecotype. Although initial SO₂-induced changes in photosynthesis in both ecotypes were mediated through an increase in stomatal resistance to CO₂, the ecotype-specific patterns as a function of pollutant concentration and exposure time were associated with marked increases in residual resistance to CO₂. Patterns in photosynthesis, photoassimilate retention, and growth following long-term SO₂ exposures were also ecotype-specific. Although physiological accommodation of SO₂ stress was observed in both ecotypes, it was more pronounced in the resistant ecotype. The physiological mechanisms underlying genetic differences inG. carolinianum in response to SO₂ stress were concluded to be (1) dissimilar threshold levels of response to SO₂ and/or its toxic derivatives and (2) differences in homeostatic processes governing the rate of repair or compensation for physiological injury.Research sponsored by the Office of Health and Environmental Research, U.S. Department of Energy, under contract No. DEAC05-840R21400 with Martin Marietta, Energy Systems, Inc. and the U.S. Environmental Protection AgencyPublication No. 2610, Environmental Sciences Division, Oak Ridge National Laboratory     

Photosynthesis,growth, and decay traits in Sphagnum – a multispecies comparison

Peat mosses (Sphagnum) largely govern carbon sequestration in Northern Hemisphere peatlands. We investigated functional traits related to growth and decomposition in Sphagnum species. We tested the importance of environment and phylogeny in driving species traits and investigated trade‐offs among them. We selected 15 globally important Sphagnum species, representing four sections (subgenera) and a range of peatland habitats. We measured rates of photosynthesis and decomposition in standard laboratory conditions as measures of innate growth and decay potential, and related this to realized growth, production, and decomposition in their natural habitats. In general, we found support for a trade‐off between measures of growth and decomposition. However, the relationships are not strong, with r ranging between 0.24 and 0.45 for different measures of growth versus decomposition. Using photosynthetic rate to predict decomposition in standard conditions yielded R² = 0.20. Habitat and section (phylogeny) affected the traits and the trade‐offs. In a wet year, species from sections Cuspidata and Sphagnum had the highest production, but in a dry year, differences among species, sections, and habitats evened out. Cuspidata species in general produced easily decomposable litter, but their decay in the field was hampered, probably due to near‐surface anoxia in their wet habitats. In a principal components analysis, PCA, photosynthetic capacity, production, and laboratory decomposition acted in the same direction. The species were imperfectly clustered according to vegetation type and phylogeny, so that some species clustered with others in the same section, whereas others clustered more clearly with others from similar vegetation types. Our study includes a wider range of species and habitats than previous trait analyses in Sphagnum and shows that while the previously described growth–decay trade‐off exists, it is far from perfect. We therefore suggest that our species‐specific trait measures offer opportunities for improvements of peatland ecosystem models. Innate qualities measured in laboratory conditions translate differently to field responses. Most dramatically, fast‐growing species could only realize their potential in a wet year. The same species decompose fast in laboratory, but their decomposition was more retarded in the field than that of other species. These relationships are crucial for understanding the long‐term dynamics of peatland communities.     

Photosynthesis and growth of winter wheat in response to waterlogging at different growth stages

A study on photosynthetic and yield effects of waterlogging of winter wheat at four stages of growth was conducted in specially designed experimental tanks during the 2007–2008 and 2008–2009 seasons. Compared with the control, waterlogging treatments at tillering and jointing-booting stages reduced photosynthetic rate (P _N) and transpiration (E) significantly, it also decreased average leaf water-use efficiency (WUE, defined as the ratio of P _N to E) by 3.3% and 3.4% in both years. All parameters returned quickly to the control level after soil was drained. Damage to the photosynthetic apparatus during waterlogging resulted in a lower F_v/F_m ratio, especially at the first two stages. A strong reduction in root length, root mass, root/shoot ratio, total dry mass, and leaf area index were observed. The responses from vegetative plants at tillering and jointing-booting stages were greater than in generative plants at onset of flowering and at milky stages. The number of panicles per hectare at tillering stage and the spikelet per panicle at the stages of jointing-booting and at onset of flowering were also significantly reduced by waterlogging, giving 8.2–11.3% decrease of the grain yield relative to the control in both years. No significant difference in yield components and a grain yield was observed between the control and treatments applied at milky stages. These responses, modulated by the environmental conditions prevailing during and after waterlogging, included negative effects on the growth, photosynthetic apparatus, and the grain yield in winter wheat, but the effect was strongly stage-dependent.     

Photosynthesis, temperature and radial growth of Scots pine in northern Finland: identifying the influential time intervals

We analyzed the statistical dependence between temperature, the state of functional substances (S), estimated photosynthetic production and the radial growth of Scots pine in northern Finland. Annual sums of these variables were calculated for intervals consisting of consecutive calendar days. For daily mean temperature, all possible intervals between 1 April of the previous year and 31 August of the current year were tested. For S and the daily photosynthetic production, the tested range included days from April to October of the previous year and from April to August of the current year. These sums were compared with tree-ring indices using the Pearson correlation coefficient over the period 1906–2002. The highest correlations (r = 0.64) between daily mean temperature and growth indices were obtained for current-year periods starting 22 June and ending 28 July. For S, a temperature-derived variable describing the instantaneous photosynthetic capacity of Scots pine, the respective interval was from 5 July to 31 July (r = 0.63). The daily photosynthetic production of Scots pine was estimated for 1906–2002 using the PhenPhoto model. The interval during which the estimated daily photosynthetic production of Scots pine produced the highest correlation with growth indices (r = 0.56) was from 5 July to 27 July. Previous-year values of each variable were also significantly correlated to annual growth indices. The intervals with highest correlations were in May–June for each variable, and the correlations were rather low—between 0.3 and 0.4. We also tested selection criteria based on intervals that do not consist of consecutive calendar days, but results did not show notable improvements over the customarily used continuous intervals.     

Effects of sodium chloride stress and calcium supply on growth, potassium uptake, and internal chloride and sodium levels of winter wheat seedlings

The effects of saline conditions on the K+ (86Rb), Na+ and Cl- uptake and growth of 6-day-old wheat (Triticum aestivum L. cv. GK Szeged) seedlings were studied in the absence and presence of Ca2+. It was found that on direct NaCl treatment the K+ uptake of the roots in the absence of Ca2+ declined significantly with increasing salinity. The reverse was true, however, in the case of NaCl pretreatment: seedlings grown under highly saline conditions (50 mM NaCl) absorbed more K+ than those pretreated with low levels of NaCl (1 or 10 mM NaCl). The data indicate a definite Na(+)-induced K+ uptake inhibition and/or feed-back regulation in the K+ uptake of roots under the above-mentioned growth conditions. As regards the Ca2+ effect, it was established that supplemental Ca2+ counteracts the unfavourable effect of saline conditions as concerns both the K+ uptake of the roots and the dry matter yield of the seedlings. The internal concentrations of Na+ and Cl- in the seedlings increased in proportion to increasing salinity. Marked differences were experienced, however, in the internal concentrations of Na+ and Cl- in the roots and shoots, respectively. It was concluded that under these experimental conditions the salt tolerance of wheat could be related to its capability of restricting the transport of Na+ at low and moderate levels to the shoots, where it is highly toxic.     

Photosynthesis for Food, Fuel and the Future

<正>Photosynthesis is a process that converts solar energy to chemical energy in many different organisms,ranging from plants to bacteria.Photosynthesis provides all the food we eat and all the fossil fuel we use.Photosynthesis has long been studied in order to understand its underlying mechanisms a     

Photosynthesis in sugar beet depends on root growth

Summary Sugar-beet plants, germinated in growth cabinets at 20°C and transplanted into the field after 3 weeks, developed much larger roots than plants grown from seed drilled directly into the soil. At the end of the season, the roots of transplants were 39% greater than from drilled seed—an increase of 14 m tons per hectare. The increased yield was mainly due to a sustained increase in photosynthesis because of the larger sink for carbohydrates provided by plants from the growth cabinets.     

Photosynthesis,growth and hydrocarbon production ofBotryococcus braunii immobilized by entrapment and adsorption in polyurethane foams

Summary Direct entrapment of the hydrocarbonrich algaBotryococcus braunii was examined using eleven polyurethane prepolymers. A high toxicity was observed in several foams. With five of the tested prepolymers, nevertheless, a large part of the algal population can survive entrapment and substantial photosynthetic capacity, ca. 40–60% relative to free controls, was retained one day after immobilization. However, prolonged batches under standard conditions revealed a long-term toxicity; as a result the photosynthetic capacity and hydrocarbon production of the entrapped cultures were strongly reduced relative to free controls. Immobilization ofB. braunii was also achieved, with a loading yield of ca. 70%, via adsorption on FHP 4000 and FHP 5000 foams. Subsequent batch cultures under shaken and airlift conditions revealed a substantial release, ca. 30% of free cells, at the end of the cultures. However, the release from these adsorbed cultures was no higher than from directly entrappedB. braunii. Furthermore, no toxic effects were noted in the adsorbed cultures; the showed active growth, high photosynthetic capacity and produced quite large amounts of hydrocarbons, the chemical structure and the relative abundance of which were not altered by immobilization. Taking into account cell leakage, it appears that adsorbed cultures exhibit a similar, and sometimes even higher metabolic activity than free controls; thus, under air-lift conditions, high biomass and hydrocarbon productivities can be achieved.     

Effect of sodium chloride on the growth ofLolium perenne

Summary Under the conditions of these experiments sodium chloride in the rooting medium does not have the same effect on the growth ofLolium perenne as does water stress.     

Structural-functional role of chloride in photosystem II

Chloride binding in photosystem II (PSII) is essential for photosynthetic water oxidation. However, the functional roles of chloride and possible binding sites, during oxygen evolution, remain controversial. This paper examines the functions of chloride based on its binding site revealed in the X-ray crystal structure of PSII at 1.9 ? resolution. We find that chloride depletion induces formation of a salt bridge between D2-K317 and D1-D61 that could suppress the transfer of protons to the lumen.     

Photosynthesis, photorespiration and nitrogen metabolism

Abstract. The ATP and reduced ferredoxin generated in photosynthetic reactions in the chloroplast are utilized for a large number of reactions other than CO₂-fixation. Quantitatively the most important reaction is the reassimilation of ammonia liberated during photorespiration in C₃ plants via the glutamate synthase cycle. Chloroplasts are also able to reduce nitrite to ammonia, sulphate to sulphide, and synthesize a number of amino acids. The amino acids essential for human nutrition are all synthesized in the chloroplast and evidence is presented to suggest that they may be the sole site of such biosynthetic reactions.     

Potential role of tryptophan and chloride in the inhibition of human myeloperoxidase

Myeloperoxidase (MPO) binds H2O2 in the absence and presence of chloride (Cl-) and catalyzes the formation of potent oxidants through 1e(-) and 2e(-) oxidation pathways. These potent oxidants have been implicated in the pathogenesis of various diseases including atherosclerosis, asthma, arthritis, and cancer. Thus, inhibition of MPO and its by-products may have a wide application in biological systems. Using direct rapid kinetic measurements and H2O2-selective electrodes, we show that tryptophan (Trp), an essential amino acid, is linked kinetically to the inhibition of MPO catalysis under physiological conditions. Trp inactivated MPO in the absence and presence of plasma levels of Cl(-), to various degrees, through binding to MPO, forming the inactive complexes Trp-MPO and Trp-MPO-Cl, and accelerating formation of MPO Compound II, an inactive form of MPO. Inactivation of MPO was mirrored by the direct conversion of MPO-Fe(III) to MPO Compound II without any sign of Compound I accumulation. This behavior indicates that Trp binding modulates the formation of MPO intermediates and their decay rates. Importantly, Trp is a poor substrate for MPO Compound II and has no role in destabilizing complex formation. Thus, the overall MPO catalytic activity will be limited by: (1) the dissociation of Trp from Trp-MPO and Trp-MPO-Cl complexes, (2) the affinity of MPO Compound I toward Cl(-) versus Trp, and (3) the slow conversion of MPO Compound II to MPO-Fe(III). Importantly, Trp-dependent inhibition of MPO occurred at a wide range of concentrations that span various physiological and supplemental ranges.     

Microclimate, Canopy Structure and Photosynthesis in Canopies of Three Contrasting Temperate Forage Grasses: III. Canopy Photosynthesis, Individual Leaf Photosynthesis and the Distribution of Current Assimilate

The rates of canopy and individual leaf photosynthesis and ¹⁴Cdistribution for three temperate forage grasses Lolium perennecv. S24, L. perenne cv. Reveille and Festuc'a arundinacea cv.SI70 were determined in the field during a summer growth period.Canopy photosynthesis declined as the growth period progressed,reflecting a decline in the photosynthetic capacity of successiveyoungest fully expanded leaves. The decline in the maximum photosyntheticcapacity of the canopies was correlated with a decline in theirquantum efficiencies at low irradiance. Changes in canopy structureresulted in changes in canopy net photosynthesis and dark respiration.No clear relationships between changes in the environment andchanges in canopy net photosynthesis and dark respiration wereestablished. The relative distributions of ¹⁴C in the shootsof the varieties gave a good indication of the amount of drymatter per ground area in the varieties.