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Photosynthesis in Climatic Races of Mimulus. II. Effect of Time and CO2 Concentration on Rate

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... Measurement of the net CO 2 exchange of plants, through uptake by photosynthesis and release by respiration, provides a convenient method of determining how plants respond to various environmental influences. CO 2 exchange is one of the primary growth processes and the literature shows that it is influenced by many factors, for example: light intensity (Tailing, 1961; Hesketh and Baker, 1967); temperature (Kramer and Kozlowski, I960); CO 2 concentration (Gaastra, 1962); O 2 concentration (Bjorkman, 1968); air movement (Decker, 1947); nutrient levels, particularly potassium (Ozbun et al., 1965); vapour pressure (Pallas et al., 1967); internal moisture stress (Klickoff, 1965); age of leaf (Elmore et al., 1967); leaf arrangement (Pearce et al., 1967); assimilate utilisation (King et al., 1967); and intensityXduration effects (Milner and Hiesey, 1964; Hesketh, 1968). This series of papers aims to provide a body of data on the CO a exchange pattern of a number of species relevant to the New Zealand environment. ...
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The apparatus is described and measurements are given of net CO 2 exchange of shoots of Lolium perenne, Trifolium repens, Lycopersicon esculentum, Cucurbitu maxima, Xanthium orientale, Chionochloa rubra, and Celmisia spectabilis at various light intensities. The maximum rates at a photosynthetic irradiance of 300 W.m— 2 ranged from 35 mg CO 2 .g dry weight—' .hr-1 for the first three species down to 5 mg.g— 1 .hr— x for the last two, which are indigenous alpine species. The relationship between the species was altered when rates of exchange were expressed per unit leaf area or unit projected leaf area. INTRODUCTION
... Factors such as stomatal closure, photoinhibition and endogenous rhythms do not seem to be involved in these responses. Similar observations have been reported in other species (4,13,15,18). In contrast, Geiger (7) chilled the primary leaf petiole and node of a bean plant but no effect on the rate of net photosynthesis of that leaf . ...
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The rate of net CO(2) assimilation of mature wheat (Triticum aestivum L.) leaves in ambient air (21% O(2), 340 microbars CO(2)) declined with time of illumination at temperatures lower than 25 degrees C, but not at higher temperatures, and the rate of decline increased when maintained in air with higher CO(2) concentration (700-825 microbars). In this latter case, the decline in the rate of net CO(2) assimilation also occurred at high temperatures. Stomatal conductance also declined with time in some cases and stomata became more sensitive to CO(2), but this was not the primary cause of the decrease in CO(2) assimilation because internal partial pressure of CO(2) remained constant. Treatments which reduced the rate of translocation (e.g. lower temperatures, chilling the base of the leaf) produced a marked decline in CO(2) assimilation of leaves in atmospheric and high CO(2) concentrations. The decreased net CO(2) assimilation was correlated with carbohydrate accumulation in each case, suggesting end product inhibition of photosynthesis. Analysis of CO(2) assimilation in high carbohydrate leaves as a function of intercellular CO(2) partial pressure showed reduction in the upper part of the curve. The initial slope of this curve, however, was not affected. Photosynthetic rates in the upper part of this curve generally recovered after a short period in darkness in which carbohydrates were removed from the leaf. The stimulation of net CO(2) assimilation by 2% O(2) (Warburg effect), and the apparent quantum yield, decreased after several hours of light.
... In the present experiment, genotypes with the slowest rates of apparent photosynthesis per unit leaf area {6/1^, 6/19) responded to increasing CO2 to the highest level in the same way as did the genotype that had the fastest rate (5/19) at lower concentrations (Table i). Differences in degree of response to increasing CO2 have also been noted by Milner and Hiesey (1964b) in Mimulus cardinalis. ...
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A manometric technique was used to examine the effect of light intensity and CO2 on the relative photosynthetic activity of ten contrasting Lolium genotypes grown in a common environment. Relationships between leaf anatomy and photosynthesis were examined. At a given CO2 concentration, apparent photosynthesis increased with increasing light intensity until ‘light saturation’was reached. The saturating light intensity increased with increasing CO2 concentration. There were significant differences in photosynthetic rate between genotypes where light or CO2 respectively were limiting, but the relative order of the genotypes differed in these two cases. There was also independent variation in response to increasing CO2 to very high concentrations. At approximately 300 ppm CO2 and at light saturation, apparent photosynthesis was negatively correlated with mesophyll cell size. The most efficient leaves under these conditions were smaller and thinner than the less efficient. When light was limiting, apparent photosynthesis was not related to any anatomical feature. There was no indication of a stomatal effect under any conditions. The association between light-saturated photosynthesis and mesophyll cell size was similar to that between cell size and the estimated cell surface: volume ratio.
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The rate of apparent photosynthesis of the lowbush blueberry was determined in Warburg flasks using Pardee's CO2 buffers. A marked increase in rate of O2 evolution occurred as the temperature was raised from 13.0 to 29.5 °C. With a constant temperature of 25.0 °C the rate of O2 evolution increased as the CO2 concentration increased from 0.2 to 0.8%. The young and middle-aged leaves had a higher rate of apparent photosynthesis than the older leaves. The rate was higher at a light intensity of 1000 ft-c than at 650 ft-c at a CO2 concentration of 0.4%. At the higher light intensity a lowbush blueberry clone selected on the basis of superior agronomic characteristics had a significantly higher rate of apparent pholosynthesis than an average clone.
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Panicum virgatum is considered a relatively cold-tolerant C4 species to low night temperature from analysis of top growth, photosynthesis, dark respiration, and day–night fluctuation of nonstructural carbohydrate concentration in leaf blades grown under temperature regimes of 30–30, 30–20, and 30–10 °C. There was little influence of night temperature of 10 to 30 °C on top growth, although 20 °C night temperature was optimum. Plants grown under low night temperature (10 °C) showed a slightly reduced rate of photosynthesis early in the photoperiod, while plants at 30 °C night temperature had the highest rates of dark respiration. The time required for the plants to reach maximal photosynthetic rate from the beginning of the photoperiod was prolonged with decreased night temperature, being 1.0, 1.5, and 2.5 h for plants grown at 30–30, 30–20, and 30–10 °C regimes, respectively. Photosynthetic rates progressively declined during the rest of the photoperiod. The change in photosynthetic rate during the photoperiod and influence of night temperature on photosynthesis was highly correlated with the change in stomatal resistance to CO2 transfer (r = −0.9). Starch and total sugars in leaves accumulated slightly with time after initiation of the photoperiod and then were reduced to low levels during the night at all temperatures. Night temperature had no effect on the accumulation of these nonstructural carbohydrates during the day or on depletion from the leaves during the night.
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Sugar maple seeds were collected from populations spaced along two altitudinal gradients in the White Mountains of New Hampshire. When grown in a uniform environment, progeny of stands less than 0.8 km apart differed significantly in photosynthesis, respiration, and leaf characteristics, despite a lack of physical barriers to gene migration. Sugar maple is a long-lived (200–300 yr) species with continuous distribution, but adaptive adjustment along the altitudinal gradient has occurred in only 8,000 yr, the time since colonization of the White Mountains in the wake of glacial melting. Photosynthesis was highest in progeny from high-altitude populations, representing the species' ecological margin. High-altitude populations also had the lowest specific leaf weight (SWL), the ratio of leaf weight to leaf area, providing a highly cost-effective photosynthetic system, probably the result of natural selection in a short growing season. Respiration rates were also highest in populations native to high altitudes and constitute the cost of maintaining the photosynthetic machinery at high capacity. Photosynthesis tended toward a minimum and SLW to a maximum at mid-elevations. There were parallel patterns on both gradients, suggesting parallel evolution. There were no differences among sugar maple populations in photosynthetic response to temperature, in contrast to observations on balsam fir in the same locality.
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Acer saccharum seeds were collected from populations spaced along 2 altitudinal gradients in the White Mountains of New Hampshire. When grown in a uniform environment, progeny of stands less than 0.8 km apart differed significantly in photosynthesis, respiration, and leaf characteristics, despite a lack of physical barriers to gene migration. Sugar maple is a long-lived (200-300 yr) species with continuous distribution, but adaptive adjustment along the altitudinal gradient has occurred in only 8000 yr, the time since colonization of the White Mountains in the wake of glacial melting. Photosynthesis was highest in progeny from high-altitude populations, representing the species' ecological margin. High-altitude populations also had the lowest specific leaf weight (SLW), the ratio of leaf weight to leaf area, providing a highly cost-effective photosynthetic machinery at high capacity. Photosynthesis tended toward a minimum and SLW to a maximum at mid-elevations. There were parallel patterns on both gradients, suggesting parallel evolution. -from Authors
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Zea mays, Trifolium repens, and Celmisia angustifolia were grown at 30°, 20°, and 10°c and then the CO 2 exchange of their shoots was measured over a range of temperatures. CO 2 uptake in the light was greatest for Zea mays plants grown at 30°c and least for plants grown at 10°c. In Trifolium repens the maximum rates were for plants grown at 20°c, while plants grown at 10° and 30°c had similar rates. Plants of the alpine species Celmisia angustifolia had maximum CO: uptake when grown at 30°c and minimum at 10°c. These effects of growing temperature on CO 2 exchange did not appear to be related to leaf structure. In the second experiment, whole plants of Trifolium repens grown at 20°c, and then subjected to a sudden lowering in temperature, showed a brief (1-1 hr) increase in rate of CO 2 uptake in the light due to decrease in respiration. This was followed by a fall to a level slightly below the rate at 20°c which it then maintained for several days. By contrast Zea mays subjected to the same condi-tions showed an initial rapid drop in CCK exchange and a continued decrease over several days. INTRODUCTION
Chapter
This chapter highlights the evolutionary and ecophysiological responses of mountain plants to the growing season environment. The responses of mountain plants to their environment are due to a complex mixture of genetic and environmental influences. Plants growing on mountains experience reduced temperatures and vapor pressures with altitude, as well as a reduction in the partial pressure of air. There are many morphological, physiological, and biochemical features of plants that change with altitude, such as decrease in stature. Model simulations of canopy energy balance and CO2 fixation indicate that canopy structure and leaf area index (LAI) strongly influence both photosynthetic rate (A) and the ratio of 13C to 12C (δ13C) in leaves. δ13C measurements on expanded leaves provide a time integral of CO2 discrimination during the photosynthetic life of the leaf; they also include some unknown δ13C contribution from photosynthate exported or remobilized from other leaves and organs. The model simulations, for just the period of peak irradiance during the day, indicate that the energy balance and gas exchange of a leaf are dependent on its aerodynamic coupling with other leaves in the plant canopy, and with the air at some reference height above the canopy.
Chapter
Evidence has been examined in this work showing that large amounts of non-structural carbohydrates often accumulate in leaves during photosynthesis under several conditions: under high light and/or high carbon dioxide levels, under several stresses (e.g. low temperature, reduced water supply, flooding) and under situations of low sink demand. In wheat leaves, large carbohydrate build-up often occurs when photosynthesis rate is high, and this build-up is responsible for a reduction in the rate of photosynthesis and in the stomatal conductance observed under these conditions, and is also responsible for an increment in the rate of mitochondrial respiration in the light and in the dark. The decline of the rate of photosynthesis was not apparently due to photoinhibition, stomatal or timing effects. The increase in respiration in the light, which can be attributed to the higher substrate availability from recently fixed carbon, was not sufficiently large to account for all the observed inhibition of photosynthesis. Rather, the responses were consistent with the occurrence of end product inhibition of photosynthesis by a mechanism involving a decrease in metabolically available phosphate levels upon soluble sugar accumulation. Starch also accumulated in wheat leaves, but to a much less extent than soluble sugars. However, accumulation of starch in leaves of other species has also been negatively correlated with the rate of photosynthesis at ambient and high CO2 concentrations. In this case, inhibition of photosynthesis could occur by a different mechanism involving direct effects of starch on chloroplast metabolism or structure (e.g. mechanical damage to the thylakoids, etc).
Chapter
Wenn man die Literatur der Berichtsjahre überblickt und dabei Vor allem auch die Ergebnisse des Internationalen Botanischen Kongresses in Edinburgh 1964 [Burtt (2)] und anderer Tagungen (z. B. Meeting Bot. Soc. America 1964, Boulder: Amer. J. Bot. 51, 684–689), das große Lehr- und Handbuch der Angiospermen-Taxonomie von P. H. Davis u. Heywood (S. 351) sowie Sammelwerke [etwa Turrill (2); Maheshwari- Vol., J. Ind. Bot. Soc. 42 A, 1963] und Übersichtsreferate [z.B. von Constance (3); Heywood (3); W. Robyns (2)] berücksichtigt, dann lassen sich recht bemerkenswerte neue Entwicklungen und Schwerpunktverschiebungen in der Systematik der Samenpflanzen erkennen: 1. Über die Grundlagen der Systematik, besonders über das Verhältnis zwischen phylogenetischer und phänetischer Klassifikation, ist eine heftige Diskussion in Gang gekommen (S. 349ff.). 2. Die vergleichende Phytochemie („Chemotaxonomy“) und auch die Palynologie (u. a. mit elektronenmikroskopischen Methoden) gewinnen fortwährend an Bedeutung für die Systematik (S. 357 u. S. 373ff.). 3. Die Anwendung mathematischstatistischer Methoden und elektronischer Rechenmaschinen zur Messung von Affinitätsbeziehungen („Numerical Taxonomy“) und die Möglichkeiten der automatischen Datenverarbeitung rücken immer mehr in Griffweite des praktischen Systematikers (S. 376 u. S. 352).
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Plants pass through a succession of growth phases at a rate largely controlled by environmental factors. The spatial arrangement and efficiency of plant organs are influenced by the fluxes of energy and matter in their environments. Thus, the successful integration of processes, such as photosynthesis and nitrogen fixation, occurring in the very different environments of the soil and the air requires a complex functional balance. Such a balance is particularly complex for legumes in which the genetic expressions of the host plant and Rhizobium influence the nitrogen economy. Progress towards improvements in symbiotic nitrogen fixation has been severely limited by the difficulty of distinguishing between the metabolic activities of the roots and nodules in whole plant studies. Recent improvements in experimental precision have revealed processes which govern gaseous diffusion in nodules and control their carbohydrate use. Furthermore, the application of quantitative models to problems of carbon and nitrogen nutrition is improving the understanding of plant growth.
Article
Alpine plants of Oxyria digyna have higher apparent photosynthesis rates at various carbon dioxide concentrations than arctic, sea-level plants of the same species. The ability to utilize carbon dioxide effectively at low concentrations may be involved in the survival of plants at high elevations.
Effect of CO2 concentration on photosynthetic intensity
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