601
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Causin HF, Rufty TW, Reynolds JF. Gas exchange and carbon metabolism in two Prosopis species (Fabaceae) from semiarid habitats: effects of elevated CO2, N supply, and N source. AMERICAN JOURNAL OF BOTANY 2006; 93:716-723. [PMID: 21642135 DOI: 10.3732/ajb.93.5.716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Predicting future plant and ecosystem responses to elevated CO(2) also requires an understanding of the role of other factors, especially soil nitrogen. This is particularly challenging for global aridlands where total N and the relative amounts of nitrate and ammonia vary both spatially and seasonally. We measured gas exchange and primary and secondary C metabolites in seedlings of two dominant aridland shrub species (Prosopis flexuosa [S America] and P. glandulosa [N America]) grown at ambient (350 ppm) or elevated (650 ppm) CO(2) and nitrogen at two levels (low [0.8 mM] and high [8.0 mM]) and at either 1 : 1 or 3 : 1 nitrate to ammonia. Whereas elevated CO(2) increased assimilation rate, water use efficiency, and primary carbon metabolites in both species, these increases were strongly contingent upon nitrogen availability. Elevated CO(2) did not increase secondary metabolites (i.e., phenolics). For these important aridland species, the effects of elevated CO(2) are strongly influenced by nitrogen availability and to a lesser extent by the relative amounts of nitrate and ammonia supplied, which underscores the importance of both the amount and chemical composition of soil nitrogen in mediating the potential responses of seedling growth and establishment of aridland plants under future CO(2)-enriched atmospheres.
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Affiliation(s)
- Humberto F Causin
- Departamento de Biodiversidad y Biología Experimental, F.C.E. N., Universidad de Buenos Aires, Ciudad Universitaria, 1428 Capital Federal, Argentina
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602
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Borjigidai A, Hikosaka K, Hirose T, Hasegawa T, Okada M, Kobayashi K. Seasonal changes in temperature dependence of photosynthetic rate in rice under a free-air CO(2) enrichment. ANNALS OF BOTANY 2006; 97:549-57. [PMID: 16399793 PMCID: PMC2803663 DOI: 10.1093/aob/mcl001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2005] [Revised: 10/13/2005] [Accepted: 11/26/2005] [Indexed: 05/06/2023]
Abstract
BACKGROUND AND AIMS Influences of rising global CO(2) concentration and temperature on plant growth and ecosystem function have become major concerns, but how photosynthesis changes with CO(2) and temperature in the field is poorly understood. Therefore, studies were made of the effect of elevated CO(2) on temperature dependence of photosynthetic rates in rice (Oryza sativa) grown in a paddy field, in relation to seasons in two years. METHODS Photosynthetic rates were determined monthly for rice grown under free-air CO(2) enrichment (FACE) compared to the normal atmosphere (570 vs 370 micromol mol(-1)). Temperature dependence of the maximum rate of RuBP (ribulose-1,5-bisphosphate) carboxylation (V(cmax)) and the maximum rate of electron transport (J(max)) were analysed with the Arrhenius equation. The photosynthesis-temperature response was reconstructed to determine the optimal temperature (T(opt)) that maximizes the photosynthetic rate. KEY RESULTS AND CONCLUSIONS There was both an increase in the absolute value of the light-saturated photosynthetic rate at growth CO(2) (P(growth)) and an increase in T(opt) for P(growth) caused by elevated CO(2) in FACE conditions. Seasonal decrease in P(growth) was associated with a decrease in nitrogen content per unit leaf area (N(area)) and thus in the maximum rate of electron transport (J(max)) and the maximum rate of RuBP carboxylation (V(cmax)). At ambient CO(2), T(opt) increased with increasing growth temperature due mainly to increasing activation energy of V(cmax). At elevated CO(2), T(opt) did not show a clear seasonal trend. Temperature dependence of photosynthesis was changed by seasonal climate and plant nitrogen status, which differed between ambient and elevated CO(2).
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Affiliation(s)
- Almaz Borjigidai
- Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan.
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603
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Fouad WM, Rathinasabapathi B. Expression of bacterial L-aspartate-alpha-decarboxylase in tobacco increases beta-alanine and pantothenate levels and improves thermotolerance. PLANT MOLECULAR BIOLOGY 2006; 60:495-505. [PMID: 16525887 DOI: 10.1007/s11103-005-4844-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2005] [Accepted: 11/07/2005] [Indexed: 05/07/2023]
Abstract
L- Aspartate-alpha-decarboxylase catalyzes the decarboxylation of L -aspartate to generate Beta-alanine and carbon dioxide. This is an unusual pyruvoyl-dependent enzyme unique to prokaryotes that undergoes limited self-processing. The Escherichia coli pan D gene encoding L- aspartate-alpha-decarboxylase was expressed under a constitutive promoter in transgenic tobacco. Transgene expression was verified by assays based on RNA blots, immunoblots and enzyme activity in vitro. The pan D lines had increased levels of leaf Beta-alanine (1.2- to 4-fold), pantothenate (3.2- to 4.1-fold) and total free amino acids (up to 3.7-fold) compared to wild-type and vector controls. Growth of homozygous lines expressing E. coli L- aspartate-alpha-decarboxylase was less affected than that of the control lines when the plants were stressed for 1 week at 35 degrees C. When transferred from 35 to 30 degrees C for 3 weeks, the Pan D transgenic lines recovered significantly (P
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Affiliation(s)
- Walid M Fouad
- Plant Molecular and Cellular Biology Program, Horticultural Sciences Department, University of Florida, Gainesville, FL 32611-0690, USA
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604
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Schurr U, Walter A, Rascher U. Functional dynamics of plant growth and photosynthesis--from steady-state to dynamics--from homogeneity to heterogeneity. PLANT, CELL & ENVIRONMENT 2006; 29:340-52. [PMID: 17080590 DOI: 10.1111/j.1365-3040.2005.01490.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Plants are much more dynamic than we usually expect them to be. This dynamic behaviour is of paramount importance for their performance under natural conditions, when resources are distributed heterogeneously in space and time. However, plants are not only the cue ball of their physical and chemical environment. Endogenous rhythms and networks controlling photosynthesis and growth buffer plant processes from external fluctuations. This review highlights recent evidence of the importance of dynamic temporal and spatial organization of photosynthesis and of growth in leaves and roots. These central processes for plant performance differ strongly in their dependence on environmental impact and endogenous properties, respectively. Growth involves a wealth of processes ranging from the supply of resources from external and internal sources to the growth processes themselves. In contrast, photosynthesis can only take place when light and CO2 are present and thus clearly requires 'input from the environment'. Nevertheless, growth and photosynthesis are connected to each other via mechanisms that are still not fully understood. Recent advances in imaging technology have provided new insights into the dynamics of plant-environment interactions. Such processes do not only play a crucial role in understanding stress response of plants under extreme environmental conditions. Dynamics of plants under modest growth conditions rise from endogenous mechanisms as well as exogenous impact too. It is thus an important task for future research to identify how dynamic external conditions interact with plant-internal signalling networks to optimize plant behaviour in real time and to understand how plants have adapted to characteristic spatial and temporal properties of the resources from their environment, on which they depend on.
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Affiliation(s)
- U Schurr
- ICG-III (Phytosphere), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
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605
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Long SP, Zhu XG, Naidu SL, Ort DR. Can improvement in photosynthesis increase crop yields? PLANT, CELL & ENVIRONMENT 2006; 29:315-30. [PMID: 17080588 DOI: 10.1111/j.1365-3040.2005.01493.x] [Citation(s) in RCA: 602] [Impact Index Per Article: 33.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The yield potential (Yp) of a grain crop is the seed mass per unit ground area obtained under optimum growing conditions without weeds, pests and diseases. It is determined by the product of the available light energy and by the genetically determined properties: efficiency of light capture (epsilon i), the efficiency of conversion of the intercepted light into biomass (epsilon c) and the proportion of biomass partitioned into grain (eta). Plant breeding brings eta7 and epsilon i close to their theoretical maxima, leaving epsilon c, primarily determined by photosynthesis, as the only remaining major prospect for improving Yp. Leaf photosynthetic rate, however, is poorly correlated with yield when different genotypes of a crop species are compared. This led to the viewpoint that improvement of leaf photosynthesis has little value for improving Yp. By contrast, the many recent experiments that compare the growth of a genotype in current and future projected elevated [CO2] environments show that increase in leaf photosynthesis is closely associated with similar increases in yield. Are there opportunities to achieve similar increases by genetic manipulation? Six potential routes of increasing epsilon c by improving photosynthetic efficiency were explored, ranging from altered canopy architecture to improved regeneration of the acceptor molecule for CO2. Collectively, these changes could improve epsilon c and, therefore, Y p by c. 50%. Because some changes could be achieved by transgenic technology, the time of the development of commercial cultivars could be considerably less than by conventional breeding and potentially, within 10-15 years.
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Affiliation(s)
- Stephen P Long
- Department of Crop Science, University of Illinois, Urbana, IL 61801, USA.
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606
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Raines CA. Transgenic approaches to manipulate the environmental responses of the C3 carbon fixation cycle. PLANT, CELL & ENVIRONMENT 2006; 29:331-9. [PMID: 17080589 DOI: 10.1111/j.1365-3040.2005.01488.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The limitation to photosynthetic CO2 assimilation in C3 plants in hot, dry environments is dominated by ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco) because CO2 availability is restricted and photorespiration is stimulated. Using a combination of genetic engineering and transgenic technology, three approaches to reduce photorespiration have been taken; two of these focused on increasing the carboxylation efficiency of Rubisco either by reducing the oxygenase reaction directly or by manipulating the Rubisco enzyme by concentrating CO2 in the region of Rubisco through the introduction of enzymes of the C4 pathway. The third approach attempted to reduce photorespiration directly by manipulation of enzymes in this pathway. The progress in each of these areas is discussed, and the most promising approaches are highlighted. Under saturating CO2 conditions, Rubisco did not limit photosynthesis, and limitation shifted to ribulose bisphosphate (RuBP) regeneration capacity of the C3 cycle. Transgenic analysis was used to identify the specific enzymes that may be targets for improving carbon fixation, and the way this may be exploited in the high CO2 future is considered.
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Affiliation(s)
- Christine A Raines
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex, CO4 3SQ, UK.
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607
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Usuda H. Effects of Elevated CO2 on the Capacity for Photosynthesis of a Single Leaf and a Whole Plant, and on Growth in a Radish. ACTA ACUST UNITED AC 2006; 47:262-9. [PMID: 16357037 DOI: 10.1093/pcp/pci244] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The atmospheric concentration of CO2 will probably rise to about 700 micromol mol(-1) by the end of this century. The effects of elevated growth CO2 on photosynthesis are still not fully understood. Effects of elevated growth CO2 on the capacity for photosynthesis of a single leaf and a whole plant were investigated with the radish cultivar White Cherish. The plants were grown under ambient ( approximately 400 micromol mol(-1)) or elevated CO2 ( approximately 750 micromol mol(-1)). The rates of net photosynthesis per leaf area with a whole plant and a single leaf of plants of various ages (15-26 d after planting) were measured under ambient and elevated CO2. The rates of photosynthesis were increased by 20-28% by elevated CO2. There was no effect of elevated growth CO2 on the rate of photosynthesis, clearly indicating no downward acclimation of photosynthesis to elevated CO2. Elevated CO2 increased dry weight accumulation by >27%. The effect of elevated CO2 on other growth characteristics will also be shown.
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Affiliation(s)
- Hideaki Usuda
- School of Medicine, Teikyo University, 359 Ohtsuka, Hachioji, 192-0395 Japan.
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608
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Sage RF, McKown AD. Is C4 photosynthesis less phenotypically plastic than C3 photosynthesis? JOURNAL OF EXPERIMENTAL BOTANY 2006; 57:303-17. [PMID: 16364950 DOI: 10.1093/jxb/erj040] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
C4 photosynthesis is a complex specialization that enhances carbon gain in hot, often arid habitats where photorespiration rates can be high. Certain features unique to C4 photosynthesis may reduce the potential for phenotypic plasticity and photosynthetic acclimation to environmental change relative to what is possible with C3 photosynthesis. During acclimation, the structural and physiological integrity of the mesophyll-bundle sheath (M-BS) complex has to be maintained if C4 photosynthesis is to function efficiently in the new environment. Disruption of the M-BS structure could interfere with metabolic co-ordination between the C3 and C4 cycles, decrease metabolite flow rate between the tissues, increase CO2 leakage from the bundle sheath, and slow enzyme activity. C4 plants have substantial acclimation potential, but in most cases lag behind the acclimation responses in C3 plants. For example, some C4 species are unable to maintain high quantum yields when grown in low-light conditions. Others fail to reduce carboxylase content in shade, leaving substantial over-capacity of Rubisco and PEP carboxylase in place. Shade-tolerant C4 grasses lack the capacity for maintaining a high state of photosynthetic induction following sunflecks, and thus may be poorly suited to exploit subsequent sunflecks compared with C3 species. In total, the evidence indicates that C4 photosynthesis is less phenotypically plastic than C3 photosynthesis, and this may contribute to the more restricted ecological and geographical distribution of C4 plants across the Earth.
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Affiliation(s)
- Rowan F Sage
- Department of Botany, University of Toronto, 25 Willcocks Street, Toronto, ON M5S3B2 Canada.
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609
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Augusti A, Betson TR, Schleucher J. Hydrogen exchange during cellulose synthesis distinguishes climatic and biochemical isotope fractionations in tree rings. THE NEW PHYTOLOGIST 2006; 172:490-9. [PMID: 17083679 DOI: 10.1111/j.1469-8137.2006.01843.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The abundance of the hydrogen isotope deuterium (D) in tree rings is an attractive record of climate; however, use of this record has proved difficult so far, presumably because climatic and physiological influences on D abundance are difficult to distinguish. Using D labelling, we created a D gradient in trees. Leaf soluble sugars of relatively low D abundance entered cellulose synthesis in stems containing strongly D-labelled water. We used nuclear magnetic resonance (NMR) spectroscopy to quantify D in the C-H groups of leaf glucose and of tree-ring cellulose. Ratios of D abundances of individual C-H groups of leaf glucose depended only weakly on leaf D labelling, indicating that the D abundance pattern was determined by physiological influences. The D abundance pattern of tree-ring cellulose revealed C-H groups that exchanged strongly (C(2)-H) or weakly (C(6)-H2) with water during cellulose synthesis. We propose that strongly exchanging C-H groups of tree-ring cellulose adopt a climate signal stemming from the D abundance of source water. C-H groups that exchange weakly retain their D abundance established in leaf glucose, which reflects physiological influences. Combining both types of groups may allow simultaneous reconstruction of climate and physiology from tree rings.
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Affiliation(s)
- Angela Augusti
- Department of Medical Biochemistry and Biophysics, Umea University, Sweden
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610
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Morgan PB, Mies TA, Bollero GA, Nelson RL, Long SP. Season-long elevation of ozone concentration to projected 2050 levels under fully open-air conditions substantially decreases the growth and production of soybean. THE NEW PHYTOLOGIST 2006; 170:333-43. [PMID: 16608458 DOI: 10.1111/j.1469-8137.2006.01679.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Mean surface ozone concentration is predicted to increase 23% by 2050. Previous chamber studies of crops report large yield losses caused by elevation of tropospheric ozone, and have been the basis for projecting economic loss. This is the first study with a food crop (soybean, Glycine max) using free-air gas concentration enrichment (FACE) technology for ozone fumigation. A 23% increase in ozone concentration from an average daytime ambient 56 p.p.b. to a treatment 69 p.p.b. over two growing seasons decreased seed yield by 20%. Total above-ground net primary production decreased by 17% without altering dry mass allocation among shoot organs, except seed. Fewer live leaves and decreased photosynthesis in late grain filling appear to drive the ozone-induced losses in production and yield. These results validate previous chamber studies suggesting that soybean yields will decrease under increasing ozone exposure. In fact, these results suggest that when treated under open-air conditions yield losses may be even greater than the large losses already reported in earlier chamber studies. Yield losses with elevated ozone were greater in the second year following a severe hailstorm, suggesting that losses caused by ozone might be exacerbated by extreme climatic events.
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Affiliation(s)
- Patrick B Morgan
- Department of Plant Biology, University of Illinois, 379 Edwin R. Madigan Laboratory, 1201 West Gregory, Urbana, IL 61801, USA
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611
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Driscoll SP, Prins A, Olmos E, Kunert KJ, Foyer CH. Specification of adaxial and abaxial stomata, epidermal structure and photosynthesis to CO2 enrichment in maize leaves. JOURNAL OF EXPERIMENTAL BOTANY 2006; 57:381-90. [PMID: 16371401 DOI: 10.1093/jxb/erj030] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Acclimation to CO2 enrichment was studied in maize plants grown to maturity in either 350 or 700 microl l-1 CO2. Plants grown with CO2 enrichment were significantly taller than those grown at 350 microl l-1 CO2 but they had the same number of leaves. High CO2 concentration led to a marked decrease in whole leaf chlorophyll and protein. The ratio of stomata on the adaxial and abaxial leaf surfaces was similar in all growth conditions, but the stomatal index was considerably increased in plants grown at 700 microl l-1 CO2. Doubling the atmospheric CO2 content altered epidermal cell size leading to fewer, much larger cells on both leaf surfaces. The photosynthesis and transpiration rates were always higher on the abaxial surface than the adaxial surface. CO2 uptake rates increased as atmospheric CO2 was increased up to the growth concentrations on both leaf surfaces. Above these values, CO2 uptake on the abaxial surface was either stable or increased as CO2 concentration increased. In marked contrast, CO2 uptake rates on the adaxial surface were progressively inhibited at concentrations above the growth CO2 value, whether light was supplied directly to this or the abaxial surface. These results show that maize leaves adjust their stomatal densities through changes in epidermal cell numbers rather than stomatal numbers. Moreover, the CO2-response curve of photosynthesis on the adaxial surface is specifically determined by growth CO2 abundance and tracks transpiration. Conversely, photosynthesis on the abaxial surface is largely independent of CO2 concentration and rather independent of stomatal function.
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Affiliation(s)
- S P Driscoll
- Crop Performance and Improvement Division, Rothamsted Research, Harpenden, Herts AL5 2JQ, UK
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612
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Wingler A, Purdy S, MacLean JA, Pourtau N. The role of sugars in integrating environmental signals during the regulation of leaf senescence. JOURNAL OF EXPERIMENTAL BOTANY 2006; 57:391-9. [PMID: 16157653 DOI: 10.1093/jxb/eri279] [Citation(s) in RCA: 216] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Although leaf senescence results in a loss of photosynthetic carbon fixation, the senescence-dependent release of nutrients, especially of nitrogen, is important for the growth of young leaves and for reproduction. Environmental regulation of senescence is therefore a vital factor in the carbon and nitrogen economy of plants. Leaf senescence is a highly plastic trait that is affected by a range of different environmental factors including light, nutrient supply, CO2 concentration, and abiotic and biotic stress. In this review, the focus is on the impact of environmental conditions on sugar accumulation and sugar signalling during senescence. By signalling a high availability of carbon relative to nitrogen in the old leaves, sugar accumulation can trigger leaf senescence. Sugar-induced senescence is therefore particularly important under low nitrogen availability and may also play a role in light signalling. Whether or not sugars are involved in regulating the senescence response of plants to elevated CO2 remains unresolved. Senescence can be delayed or accelerated in elevated CO2 and no clear relationship between sugar accumulation and senescence has been found. Plasticity in the response to environmental factors, such as daylength and sugar accumulation, varies between different Arabidopsis accessions. This natural variation can be exploited to analyse the genetic basis of the regulation of senescence and the consequences for growth and fecundity. Different evolutionary strategies, i.e. early senescence combined with a high reproductive effort or late senescence combined with a low reproductive effort, may be an important adaptation of Arabidopsis accessions to their natural habitat.
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Affiliation(s)
- Astrid Wingler
- Department of Biology, University College London, Gower Street, London WC1E 6BT, UK.
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613
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Matros A, Amme S, Kettig B, Buck-Sorlin GH, Sonnewald U, Mock HP. Growth at elevated CO2 concentrations leads to modified profiles of secondary metabolites in tobacco cv. SamsunNN and to increased resistance against infection with potato virus Y. PLANT, CELL & ENVIRONMENT 2006; 29:126-37. [PMID: 17086759 DOI: 10.1111/j.1365-3040.2005.01406.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The effect of elevated CO2 concentrations on the levels of secondary metabolites was investigated in tobacco plants grown under two nitrogen supply (5 and 8 mM NH4NO3) and CO2 conditions (350 and 1000 p.p.m.) each. High CO2 resulted in a dramatic increase of phenylpropanoids in the leaves, including the major carbon-rich compound chlorogenic acid (CGA) and the coumarins scopolin and scopoletin at both nitrogen fertilizations. This was accompanied by increased PAL activity in leaves and roots, which was even higher at the lower nitrogen supply. Hardly any change was observed for the structural phenolic polymer lignin and the sesquiterpenoid capsidiol. In contrast, elevated CO2 led to clearly decreased levels of the main nitrogen-rich constituent nicotine at the lower N-supply (5 mM NH4NO3) but not when plants were grown at the higher N-supply (8 mM NH4NO3). Inoculation experiments with potato virus Y (PVY) were used to evaluate possible ecological consequences of elevated CO2. The titre of viral coat-protein was markedly reduced in leaves under these conditions at both nitrogen levels. Since PR-gene expression and free salicylic acid (SA) levels remained unchanged at elevated CO2, we suggest that the accumulation of phenylpropanoids, for example, the major compound CGA and the coumarins scopolin and scopoletin may result in an earlier confinement of the virus at high CO2. Based on our results two final conclusions emerge. First, elevated CO2 leads to a shift in secondary metabolite composition that is dependent on the availability of nitrogen. Second, changes in the pool of secondary metabolites have important consequences for plant-pathogen interactions as shown for PVY as a test organism.
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Affiliation(s)
- Andrea Matros
- Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstr. 3, D-06466 Gatersleben, Germany
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614
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Sakai H, Hasegawa T, Kobayashi K. Enhancement of rice canopy carbon gain by elevated CO(2) is sensitive to growth stage and leaf nitrogen concentration. THE NEW PHYTOLOGIST 2006; 170:321-32. [PMID: 16608457 DOI: 10.1111/j.1469-8137.2006.01688.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Increasing our understanding of the factors regulating seasonal changes in rice canopy carbon gain (C(gain): daily net photosynthesis -- night respiration) under elevated CO(2) concentrations ([CO(2)]) will reduce our uncertainty in predicting future rice yields and assist in the development of adaptation strategies. In this study we measured CO(2) exchange from rice (Oryza sativa) canopies grown at c. 360 and 690 micromol mol(-1)[CO(2)] in growth chambers continuously over three growing seasons. Stimulation of C(gain) by elevated [CO(2)] was 22-79% during vegetative growth, but decreased to between -12 and 5% after the grain-filling stage, resulting in a 7-22% net enhancement for the whole season. The decreased stimulation of C(gain) resulted mainly from decreased canopy net photosynthesis and partially from increased respiration. A decrease in canopy photosynthetic capacity was noted where leaf nitrogen (N) decreased. The effect of elevated [CO(2)] on leaf area was generally small, but most dramatic under ample N conditions; this increased the stimulation of whole-season C(gain). These results suggest that a decrease in C(gain) enhancement following elevated CO(2) levels is difficult to avoid, but that careful management of nitrogen levels can alter the whole-season C(gain) enhancement.
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Affiliation(s)
- H Sakai
- National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba 305-8604, Japan.
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615
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Dermody O, Long SP, DeLucia EH. How does elevated CO2 or ozone affect the leaf-area index of soybean when applied independently? THE NEW PHYTOLOGIST 2006; 169:145-55. [PMID: 16390426 DOI: 10.1111/j.1469-8137.2005.01565.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Changes in leaf-area index (LAI) may alter ecosystem productivity in elevated [CO2] or [O3]. By increasing the apparent quantum yield of photosynthesis (phi(c,max)), elevated [CO2] may increase maximum LAI. However, [O3] when elevated independently accelerates senescence and may reduce LAI. Large plots (20 m diameter) of soybean (Glycine max) were exposed to ambient (approx. 370 micromol mol(-1)) or elevated (approx. 550 micromol mol(-1)) CO2 or 1.2 times ambient [O3] using soybean free-air concentration enrichment (SoyFACE). In 2001 elevated CO2 had no detectable effect on maximum LAI, but in 2002 maximum LAI increased by 10% relative to ambient air. Elevated [CO2] also increased the phi(c,max) of shade leaves in both years. Elevated [CO2] delayed LAI loss to senescence by approx. 54% and also increased leaf-area duration. Elevated [O3] accelerated senescence, reducing LAI by 40% near the end of the growing season. No effect of elevated [O3] on photosynthesis was detected. Elevated [CO2] or [O3] affected LAI primarily by altering the rate of senescence; knowledge of this may aid in optimizing future soybean productivity.
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Affiliation(s)
- Orla Dermody
- Program in Ecology and Evolutionary Biology, University of Illinois, Urbana, IL 61801, USA
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616
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Abstract
Plants are subject to a wide range of abiotic stresses, and their cuticular wax layer provides a protective barrier, which consists predominantly of long-chain hydrocarbon compounds, including alkanes, primary alcohols, aldehydes, secondary alcohols, ketones, esters and other derived compounds. This article discusses current knowledge relating to the effects of stress on cuticular waxes and the ways in which the wax provides protection against the deleterious effects of light, temperature, osmotic stress, physical damage, altitude and pollution. Topics covered here include biosynthesis, morphology, composition and function of cuticular waxes in relation to the effects of stress, and some recent findings concerning the effects of stress on regulation of wax biosynthesis are described.
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Affiliation(s)
- Tom Shepherd
- Quality Health & Nutrition, Scottish Crop Research Institute, Mylnefield, Invergowrie, Dundee DD2 5DA.
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617
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Norby RJ, Delucia EH, Gielen B, Calfapietra C, Giardina CP, King JS, Ledford J, McCarthy HR, Moore DJP, Ceulemans R, De Angelis P, Finzi AC, Karnosky DF, Kubiske ME, Lukac M, Pregitzer KS, Scarascia-Mugnozza GE, Schlesinger WH, Oren R. Forest response to elevated CO2 is conserved across a broad range of productivity. Proc Natl Acad Sci U S A 2005; 102:18052-6. [PMID: 16330779 PMCID: PMC1312431 DOI: 10.1073/pnas.0509478102] [Citation(s) in RCA: 337] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Climate change predictions derived from coupled carbon-climate models are highly dependent on assumptions about feedbacks between the biosphere and atmosphere. One critical feedback occurs if C uptake by the biosphere increases in response to the fossil-fuel driven increase in atmospheric [CO(2)] ("CO(2) fertilization"), thereby slowing the rate of increase in atmospheric [CO(2)]. Carbon exchanges between the terrestrial biosphere and atmosphere are often first represented in models as net primary productivity (NPP). However, the contribution of CO(2) fertilization to the future global C cycle has been uncertain, especially in forest ecosystems that dominate global NPP, and models that include a feedback between terrestrial biosphere metabolism and atmospheric [CO(2)] are poorly constrained by experimental evidence. We analyzed the response of NPP to elevated CO(2) ( approximately 550 ppm) in four free-air CO(2) enrichment experiments in forest stands. We show that the response of forest NPP to elevated [CO(2)] is highly conserved across a broad range of productivity, with a stimulation at the median of 23 +/- 2%. At low leaf area indices, a large portion of the response was attributable to increased light absorption, but as leaf area indices increased, the response to elevated [CO(2)] was wholly caused by increased light-use efficiency. The surprising consistency of response across diverse sites provides a benchmark to evaluate predictions of ecosystem and global models and allows us now to focus on unresolved questions about carbon partitioning and retention, and spatial variation in NPP response caused by availability of other growth limiting resources.
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Affiliation(s)
- Richard J Norby
- Environmental Sciences Division, Oak Ridge National Laboratory, TN 37831-6422, USA
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618
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Long SP, Ainsworth EA, Leakey ADB, Morgan PB. Global food insecurity. treatment of major food crops with elevated carbon dioxide or ozone under large-scale fully open-air conditions suggests recent models may have overestimated future yields. Philos Trans R Soc Lond B Biol Sci 2005; 360:2011-20. [PMID: 16433090 PMCID: PMC1569581 DOI: 10.1098/rstb.2005.1749] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Predictions of yield for the globe's major grain and legume arable crops suggest that, with a moderate temperature increase, production may increase in the temperate zone, but decline in the tropics. In total, global food supply may show little change. This security comes from inclusion of the direct effect of rising carbon dioxide (CO2) concentration, [CO2], which significantly stimulates yield by decreasing photorespiration in C3 crops and transpiration in all crops. Evidence for a large response to [CO2] is largely based on studies made within chambers at small scales, which would be considered unacceptable for standard agronomic trials of new cultivars or agrochemicals. Yet, predictions of the globe's future food security are based on such inadequate information. Free-Air Concentration Enrichment (FACE) technology now allows investigation of the effects of rising [CO2] and ozone on field crops under fully open-air conditions at an agronomic scale. Experiments with rice, wheat, maize and soybean show smaller increases in yield than anticipated from studies in chambers. Experiments with increased ozone show large yield losses (20%), which are not accounted for in projections of global food security. These findings suggest that current projections of global food security are overoptimistic. The fertilization effect of CO2 is less than that used in many models, while rising ozone will cause large yield losses in the Northern Hemisphere. Unfortunately, FACE studies have been limited in geographical extent and interactive effects of CO2, ozone and temperature have yet to be studied. Without more extensive study of the effects of these changes at an agronomic scale in the open air, our ever-more sophisticated models will continue to have feet of clay.
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Affiliation(s)
- Stephen P Long
- Department of Plant Biology, University of Illinois, 379 Edward R. Madigan Laboratory, 1201 West Gregory, Urbana, IL 61801, USA.
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619
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Abstract
The yield and quality of food crops is central to the well being of humans and is directly affected by climate and weather. Initial studies of climate change on crops focussed on effects of increased carbon dioxide (CO2) level and/or global mean temperature and/or rainfall and nutrition on crop production. However, crops can respond nonlinearly to changes in their growing conditions, exhibit threshold responses and are subject to combinations of stress factors that affect their growth, development and yield. Thus, climate variability and changes in the frequency of extreme events are important for yield, its stability and quality. In this context, threshold temperatures for crop processes are found not to differ greatly for different crops and are important to define for the major food crops, to assist climate modellers predict the occurrence of crop critical temperatures and their temporal resolution. This paper demonstrates the impacts of climate variability for crop production in a number of crops. Increasing temperature and precipitation variability increases the risks to yield, as shown via computer simulation and experimental studies. The issue of food quality has not been given sufficient importance when assessing the impact of climate change for food and this is addressed. Using simulation models of wheat, the concentration of grain protein is shown to respond to changes in the mean and variability of temperature and precipitation events. The paper concludes with discussion of adaptation possibilities for crops in response to drought and argues that characters that enable better exploration of the soil and slower leaf canopy expansion could lead to crop higher transpiration efficiency.
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Affiliation(s)
- John R Porter
- Environment, Resources and Technology Group, Royal Veterinary and Agricultural University, 2630 Taastrup, Denmark.
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620
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621
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Taylor G, Street NR, Tricker PJ, Sjödin A, Graham L, Skogström O, Calfapietra C, Scarascia-Mugnozza G, Jansson S. The transcriptome of Populus in elevated CO2. THE NEW PHYTOLOGIST 2005; 167:143-54. [PMID: 15948837 DOI: 10.1111/j.1469-8137.2005.01450.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The consequences of increasing atmospheric carbon dioxide for long-term adaptation of forest ecosystems remain uncertain, with virtually no studies undertaken at the genetic level. A global analysis using cDNA microarrays was conducted following 6 yr exposure of Populus x euramericana (clone I-214) to elevated [CO(2)] in a FACE (free-air CO(2) enrichment) experiment. Gene expression was sensitive to elevated [CO(2)] but the response depended on the developmental age of the leaves, and < 50 transcripts differed significantly between different CO(2) environments. For young leaves most differentially expressed genes were upregulated in elevated [CO(2)], while in semimature leaves most were downregulated in elevated [CO(2)]. For transcripts related only to the small subunit of Rubisco, upregulation in LPI 3 and downregulation in LPI 6 leaves in elevated CO(2) was confirmed by anova. Similar patterns of gene expression for young leaves were also confirmed independently across year 3 and year 6 microarray data, and using real-time RT-PCR. This study provides the first clues to the long-term genetic expression changes that may occur during long-term plant response to elevated CO(2).
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Affiliation(s)
- Gail Taylor
- School of Biological Sciences, Bassett Crescent East, University of Southampton, SO16 7PX, UK.
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622
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Ainsworth EA, Long SP. What have we learned from 15 years of free-air CO2 enrichment (FACE)? A meta-analytic review of the responses of photosynthesis, canopy properties and plant production to rising CO2. THE NEW PHYTOLOGIST 2005; 165:351-71. [PMID: 15720649 DOI: 10.1111/j.1469-8137.2004.01224.x] [Citation(s) in RCA: 1337] [Impact Index Per Article: 70.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Free-air CO(2) enrichment (FACE) experiments allow study of the effects of elevated [CO(2)] on plants and ecosystems grown under natural conditions without enclosure. Data from 120 primary, peer-reviewed articles describing physiology and production in the 12 large-scale FACE experiments (475-600 ppm) were collected and summarized using meta-analytic techniques. The results confirm some results from previous chamber experiments: light-saturated carbon uptake, diurnal C assimilation, growth and above-ground production increased, while specific leaf area and stomatal conductance decreased in elevated [CO(2)]. There were differences in FACE. Trees were more responsive than herbaceous species to elevated [CO(2)]. Grain crop yields increased far less than anticipated from prior enclosure studies. The broad direction of change in photosynthesis and production in elevated [CO(2)] may be similar in FACE and enclosure studies, but there are major quantitative differences: trees were more responsive than other functional types; C(4) species showed little response; and the reduction in plant nitrogen was small and largely accounted for by decreased Rubisco. The results from this review may provide the most plausible estimates of how plants in their native environments and field-grown crops will respond to rising atmospheric [CO(2)]; but even with FACE there are limitations, which are also discussed.
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Affiliation(s)
- Elizabeth A Ainsworth
- Department of Crop Sciences, University of Illinois, 190 Edward R. Madigan Laboratory, 1201 W. Gregory Drive, Urbana, IL 61801, USA
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623
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Bernacchi CJ, Morgan PB, Ort DR, Long SP. The growth of soybean under free air [CO(2)] enrichment (FACE) stimulates photosynthesis while decreasing in vivo Rubisco capacity. PLANTA 2005; 220:434-46. [PMID: 15252734 DOI: 10.1007/s00425-004-1320-8] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2004] [Accepted: 05/28/2004] [Indexed: 05/22/2023]
Abstract
Down-regulation of light-saturated photosynthesis (A(sat)) at elevated atmospheric CO(2) concentration, [CO(2)], has been demonstrated for many C(3) species and is often associated with inability to utilize additional photosynthate and/or nitrogen limitation. In soybean, a nitrogen-fixing species, both limitations are less likely than in crops lacking an N-fixing symbiont. Prior studies have used controlled environment or field enclosures where the artificial environment can modify responses to [CO(2)]. A soybean free air [CO(2)] enrichment (FACE) facility has provided the first opportunity to analyze the effects of elevated [CO(2)] on photosynthesis under fully open-air conditions. Potential ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylation (V(c,max)) and electron transport through photosystem II (J(max)) were determined from the responses of A(sat) to intercellular [CO(2)] (C(i)) throughout two growing seasons. Mesophyll conductance to CO(2) (g(m)) was determined from the responses of A(sat) and whole chain electron transport (J) to light. Elevated [CO(2)] increased A(sat) by 15-20% even though there was a small, statistically significant, decrease in V(c,max). This differs from previous studies in that V(c,max)/J(max) decreased, inferring a shift in resource investment away from Rubisco. This raised the C(i) at which the transition from Rubisco-limited to ribulose-1,5-bisphosphate regeneration-limited photosynthesis occurred. The decrease in V(c,max) was not the result of a change in g(m), which was unchanged by elevated [CO(2)]. This first analysis of limitations to soybean photosynthesis under fully open-air conditions reveals important differences to prior studies that have used enclosures to elevate [CO(2)], most significantly a smaller response of A(sat) and an apparent shift in resources away from Rubisco relative to capacity for electron transport.
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Affiliation(s)
- Carl J Bernacchi
- Atmospheric Environment Section, Illinois State Water Survey, 2204 Griffith Drive, Champaign, IL 61820, USA.
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624
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Gifford RM. The CO 2 fertilising effect - does it occur in the real world? THE NEW PHYTOLOGIST 2004; 163:221-225. [PMID: 33873623 DOI: 10.1111/j.1469-8137.2004.01133.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Affiliation(s)
- Roger M Gifford
- CSIRO Plant Industry GPO Box 1600, Canberra, ACT 2601, Australia (tel +61 26246 5441; fax +61 26246 5000; email )
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