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  • 1
    Electronic Resource
    Electronic Resource
    Extension of a biochemical model for the generalized stoichiometry of electron transport limited C3 photosynthesis (2004)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 27 (2004), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The widely used steady-state model of Farquhar et al. (Planta 149: 78–90, 1980) for C3 photosynthesis was developed on the basis of linear whole-chain (non-cyclic) electron transport. In this model, calculation of the RuBP-regeneration limited CO2-assimilation rate depends on whether it is insufficient ATP or NADPH that causes electron transport limitation. A new, generalized equation that allows co-limitation of NADPH and ATP on electron transport is presented herein. The model is based on the assumption that other thylakoid pathways (the Q-cycle, cyclic photophosphorylation, and pseudocyclic electron transport) interplay with the linear chain to co-contribute to a balanced production of NADPH and ATP as required by stromal metabolism. The original model assuming linear electron transport limited either by NADPH or by ATP, predicts quantum yields for CO2 uptake that represent the highest and the lowest values, respectively, of the range given by the new equation. The applicability of the new equation is illustrated for a number of C3 crop species, by curve fitting to gas exchange data in the literature. In comparison with the original model, the new model enables analysis of photosynthetic regulation via the electron transport pathways in response to environmental stresses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2004.01224.x
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  • 2
    Electronic Resource
    Electronic Resource
    Do open-top chambers overestimate the effects of rising CO2 on plants? An analysis using spring wheat (1999)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 5 (1999), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: The microclimate in facilities for studying effects of elevated CO2 on crops differs from ambient conditions. Open-top chambers (OTCs) increase temperature by 1–3 °C. If temperature and CO2 interact in their effect on crops, this would limit the value of OTC experiments. Furthermore, interaction of CO2 and temperature deserves study because increases in atmospheric CO2 concentration are expected to cause global warming.This paper describes two experiments in which a recently developed cooling system for OTCs was used to analyse the effects of temperature on photosynthesis, growth and yield of spring wheat (Triticum aestivum L., cv. Minaret). Two levels of CO2 were used (350 and 700 ppm), and two levels of temperature, with cooled OTCs being 1.6–2.4 °C colder than noncooled OTCs.Photosynthetic rates were increased by elevated CO2, but no effect of temperature was found. Cross-switching CO2 concentrations as well as determination of A–Ci curves showed that plant photosynthetic capacity after anthesis acclimated to elevated CO2. The acclimation may be related to the effects of CO2 on tissue composition: elevated CO2 decreased leaf nitrogen concentrations and increased sugar content. Calculations of the seasonal mean crop light-use efficiency (LUE) were consistent with the photosynthesis data in that CO2 increased LUE by 20% on average whereas temperature had no effect. Both elevating CO2 and cooling increased grain yield, by an average of 11% and 23%, respectively. CO2 and temperature stimulated yield via different mechanisms: CO2 increased photosynthetic rate, but decreased crop light interception capacity (LAI), whereas cooling increased grain yield by increasing LAI and extending the growing season with 10 days. The effects of CO2 and temperature were not additive: the CO2 effect was about doubled in the noncooled open-top chambers. In most cases, effects on yield were mediated through increased grain density rather than increased individual grain weights.The higher growth response to elevated CO2 in noncooled vs. cooled OTCs shows that a cooling system may remove a bias towards overestimating crop growth response to CO2 in open-top chambers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.1999.00233.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of light and gibberellic acid on photosynthesis during leaf senescence of alstroemeria cut flowers. (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 90 (1994), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The functioning of the photosynthetic apparatus during leaf senescence was investigated in alstroemeria cut flowers by a combination of gas-exchange measurements and analysis of in vivo chlorophyll fluorescence. Chlorophyll loss in leaves of alstroemeria cut flowers is delayed by light and by a treatment of the cut flowers with gibberellic acid (GA3). The maximal photosynthesis of the leaves was approximately 6 μmol CO2 m−2 s−1 at I 350 μmol m−2 s−1 (PAR) which is relatively low for intact C3 leaves. Qualitatively the gas-exchange rates followed the decline in chlorophyll content for the various treatments, i.e. light and GA3-treatment delayed the decline in photosynthetic rates. However, when chlorophyll loss could not yet be observed in the leaves, photosynthetic rates were already strongly decreased. In vivo fluorescence measurements revealed that the decrease in CO2 uptake is (partly) due to a decreased electron flow through photosystem II. Furthermore, analysis of the fluorescence data showed a high nonphotochemical quenching under all experimental conditions, indicating that the consumption of reducing power in the Calvin cycle is very low. The chlorophyll, remaining after 9 days incubation of leaves with GA3 in the dark should be considered as a ‘cosmetic’ pigment without any function in the supply of assimilates to the flowers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb00390.x
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of water stress on photosynthesis and chlorophyll fluorescence of five potato cultivars (1989)
    Springer
    Potato research 32 (1989), S. 17-32 
    Details
    ISSN: 1871-4528
    Keywords: drought tolerance ; stomatal behaviour ; breeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Reduction of leaf photosynthesis due to water stress has been analyzed into various components and genetic variation in these components has been evaluated. Five potato cultivars were grown on nutrient solution in a conditioned glasshouse. Water stress was imposed by adding polyethylene glycol to the nutrient solution. Photosynthesis, transpiration and chlorophyll fluorescence were measured on intact leaves during the stress period and after recovery from the stress. Water stress reduced photosynthesis, initially as a consequence of stomatal closure, but after 3 days increasingly by inhibiting directly the photosynthetic capacity (mesophyll limitation). Stomatal closure correlated with the reduction in photosynthesis, but it was not the sole cause of this reduction because the internal CO2 concentration in the leaves was not affected by water stress, indicative of inhibitory factors other than stomatal ones. Chlorophyll fluorescence emission suggested that the Calvin cycle was inhibited, while quantum efficiency was not affected at 17°C. Increasing the temperature to 27°C reduced quantum efficiency but only in the stress environment. The recovery of young leaves after relief of the stress was associated with a lower stomatal conductance but a higher mesophyll conductance compared with the control, which caused a low internal CO2 concentration and probably invoked photo-inhibition and leaf damage. Cultivar differences in photosynthetic rate were highly significant under both optimal and stress conditions, and corresponded with differences in mesophyll conductance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02365814
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  • 5
    Electronic Resource
    Electronic Resource
    Evaluation of breeding strategies for drought tolerance in potato by means of crop growth simulation (1990)
    Springer
    Plant and soil 123 (1990), S. 193-203 
    Details
    ISSN: 1573-5036
    Keywords: breeding ; drought tolerance ; potato ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Breeding strategies for drought tolerance in potato were evaluated by means of a crop growth model, in which seasonal courses of crop dry matter accumulation and soil moisture availability were simulated in dependence of plant characteristics and weather and soil data. Several plant characteristics substantially influenced the simulated instantaneous water consumption of the genotype. However, effects of genotypic differences on final tuber yield were much smaller because of the close relationship between transpiration and growth. Hence, a lower water consumption not only saved water for later use, but was also at the expense of the actual growth rate. Selection for low-transpiration types, at unchanged water use efficiency, would result in lower yields under optimum conditions. Short periods of drought, in general, reduced tuber yield of late genotypes less than that of early genotypes. Late genotypes had a surplus of leaf area for full light interception giving a lower impact of leaf area reduction. Late drought affected early genotypes less because of escape. The simulation results emphasized the complexity of selection for drought tranrance caused by the many plant processes involved, the contrast between instantaneous and cumulative reactions and the strong genotype × environment interaction for drought tolerance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00011268
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  • 6
    Electronic Resource
    Electronic Resource
    Comparative response of wheat and oilseed rape to nitrogen supply: absorption and utilisation efficiency of radiation and nitrogen during the reproductive stages determining yield (2000)
    Springer
    Plant and soil 220 (2000), S. 189-205 
    Details
    ISSN: 1573-5036
    Keywords: biomass ; intercepted radiation ; nitrogen nutrition ; oilseed rape ; radiation use efficiency ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We investigated the response of spring wheat and oilseed rape to nitrogen (N) supply, focusing on the critical period for grain number definition and grain filling. Crops were grown in containers under a shelter and treated with five combinations of applied N. Wheat and oilseed rape produced comparable amounts of biomass and yield when corrected for the costs of biomass synthesis (SC). From the responses of biomass and yield to late N applications and the apparent contribution of mobilised biomass to yield, it seems that the yield of oilseed rape was more source-limited during grain filling than that of wheat, particularly at the medium and high N levels. Both species recovered equal amounts of N from the total available N in the soil and had similar N use efficiencies, expressed as yield per unit of N absorbed. However, oilseed rape had higher efficiency to convert absorbed N in biomass, but lower harvest index of N than wheat. Oilseed rape had similar or lower root biomass than wheat, depending on N level, but higher root length per unit soil volume and specific root length. The specific uptake rate of N per unit root dry weight during the critical period for grain number determination was higher in oilseed rape than in wheat. In wheat, N limitation affected growth through a similar or lower reduction in radiation use efficiency corrected for synthesis costs (RUESC) than in the cumulative amount of intercepted photosynthetically active radiation (IPARc). In oilseed rape, lower growth due to N shortage was associated more with RUESC than IPARc, during flowering while during grain filling both components contributed similarly to decreased growth. RUESC and the concentration of N in leaves and inflorescence (LIN%) decreased from flowering to maturity and were curvilinearly related. Oilseed rape tended to have higher RUESC than wheat at high N supply during the critical period for grain number determination, and generally lower during grain filling. The reasons for these differences and possibilities to increase yield potential are discussed in terms of the photosynthetic efficiency of the different organs and changes in source–sink ratio during reproductive stages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004757124939
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  • 7
    Electronic Resource
    Electronic Resource
    Implications of selecting for persistency on hydroponics in timothy (Phleum pratense L.) (1988)
    Springer
    Euphytica 39 (1988), S. 131-139 
    Details
    ISSN: 1573-5060
    Keywords: Phleum pratense L. ; timothy ; breeding ; hydroponics ; persistency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Twenty four populations of timothy (Phleum pratense L.) with varying persistency were grown on a nutrient flow system and in soil. Growth analyses showed that seedlings grew faster on nutrient solution than in soil but this was only temporary. After the fourth cutting, regrowth of plants in soil was faster than on hydroponics, probably because the optimal growth conditions and the relatively high temperatures in the nutrient solution led to a depleted storage carbohydrate pool, necessary for regrowth. Non-destructive growth analyses were carried out by monitoring the amount of acid needed to compensate for carbohydrate extrusion by the roots in exchange for nitrate uptake. It was assumed that regrowth was proportional to the NO3 - incorporated in the plants. The calculated growth efficiency on hydroponics, averaged over all populations, ranged between 4.4 and 5.4 gram dry matter per megajoule photosynthetic radiation absorbed. The populations responded significantly differently to a frequent cutting regime. As a function of harvest number, the competitive ability of some populations decreased compared with the mean of all populations, while that of others increased or remained stable. The coefficients of genetic variation for shoot regrowth ranged between 0.16–0.22 for different harvests. For root regrowth and tillering the coefficients of genetic variation were even higher: 0.21–0.25 for the roots and 0.18–0.35 for the tiller number. Dry matter production was closely correlated with tiller formation (r=0.95). The application of nitrogen to the nutrient solution was controlled by a simple computer model, which was based on the incoming radiation and which calculated momentaneous growth of the plants on a minutes time base. Thus an equilibrium between nitrogen application and the demand of the plants was maintained. During the last regrowth period, the nitrogen supply was limited to 30% of the optimal addition rate. The production of different populations under limited supply (sixth harvest) was closely correlated with that under optimal supply (fifth harvest), (r=0.7).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00043376
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  • 8
    Electronic Resource
    Electronic Resource
    Genetic variation for resistance to low-temperature photoinhibition of photosynthesis in maize (Zea mays L.) (1994)
    Springer
    Euphytica 80 (1994), S. 85-93 
    Details
    ISSN: 1573-5060
    Keywords: maize ; Zea mays ; photoinhibition ; photosynthesis ; low-temperature adaptation ; breeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Sixty-seven inbred lines of maize were evaluated for resistance to low-temperature photoinhibition of photosynthesis, using a pulse-modulated chlorophyll fluorescence technique. The evaluation procedure was based on leaf discs, which were exposed to a high irradiance (1000 µmol/m2/s) at 7°C. The efficiency of open PSII reaction centres as a reflection of overall photosynthesis was measured before and after a photoinhibition-inducing treatment. Exposure of leaf discs to photoinhibitory condition for 2, 4, and 8 hours resulted in an efficiency reduction of 30, 53 and 83%, respectively. Testing of inbred lines showed large differences for photoinhibition susceptibility. The difference in photosynthetic efficiency between the most extreme lines after a treatment of eight hours was 39%. Resistance to photoinhibition was shown to be relevant under cool field conditions. It proved to be a trait strongly amenable to selection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00039302
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  • 9
    Electronic Resource
    Electronic Resource
    The use of chlorophyll fluorescence as a screening method for cold tolerance in maize (1989)
    Springer
    Photosynthesis research 20 (1989), S. 235-247 
    Details
    ISSN: 1573-5079
    Keywords: breeding ; chlorophyll fluorescence ; chlorosis ; cold tolerance ; maize ; Zea mays L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chlorosis in maize (Zea mays L.) is a common phenomenon in the 12 to 17°C temperature range. A newly developed chlorophyll-fluorescence technique was used to elucidate the underlying subcellular processes of resistance to chlorosis. Four populations were used that were developed by divergent mass selection for contrasting resistance to chlorosis in a cold-tolerant dent and a cold-tolerant flint population. Young plants from the four populations were kept for six days at 17/10, 15/10 and 13/10°C (day/night). After 1, 3 and 6 days various chlorophyll-fluorescence parameters were determined. The measurements were done on leaf 4. Differences were not uniform for all fluorescence properties. The resistant and susceptible populations of the two sets differed for the Q-quenching which is related to the electron transport rate in the chloroplast. For the E-quenching which is related to the Calvin cycle activity, the resistant dent differed significantly from the other three populations. The ratio Fm/Fo (related to the transfer of absorbed light-energy from antennae pigments to reaction centers in the chloroplast) was higher for the resistant dent population than for the susceptible one. The flint types did not differ for this property. Apparently, divergent mass selection for chlorosis resistance resulted in various changes at the subcellular level that are not necessarily comparable for flint and dent types. When after 6 days the temperature was raised from 13°C to 17°C, the fluorescence signals led to the conclusion that there was a full recovery of various processes after two days, except for the metabolic activity of the susceptible flint.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034067
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