Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Pure stands of Ryegrass were in their third year of growth in the field, exposed to either ambient (355[mu]mol mol[sup -1]), or elevated (600[mu]mol mol[sup -1]) atmospheric CO[sub 2] concentration. A Free-Air CO[sub 2] Enrichment (FACE) system was used to maintain the elevated CO[sub 2] concentration whilst limiting experimental constraints on the field conditions. The theoretically predicted increase in the net rates of CO[sub 2] uptake per unit leaf area (A[mu]mol mol[sup -1]) as a consequence, primarily, of the suppression of photorespiration by CO[sub 2] a competitive inhibitor of RubP oxygenation by Rubisco, was observed for the Lolium perenne studied. Also observed was a general decline in leaf evapotranspiration (E) consistent with observations of increased water use efficiency of crops grown in elevated CO[sub 2]. Enhancement of leaf A in the FACE grown L. perenne ranged from 26.5 1% to 44.95% over the course of a diurnal set of measurements. Whilst reductions in leaf E reached a maximum of 16.61% over the same diurnal course of-measurements. The increase in A was reconciled with an absence of the commonly observed decline in V[sub c][sub max] as a measure of the maximum in vivo carboxylation capacity of the primary carboxylasing enzyme Rubisco and J[sub max] a measure of the maximum rate of electron transport. The manipulation of the source sink balance of the crop, stage of canopy regrowth or height in the canopy had no effect on the observation of a lack of response. The findings of this study will be interpreted with respect to the long term implications of C[sub 3] crops being able to adapt physiologically to maximize the potential benefits conferred by growth in elevated CO[sub 2].
Author: Publisher: ISBN: Category : Languages : en Pages : 87
Book Description
In this study, the photosynthetic responses of field grown Lolium perenne to ambient (354?mol mol−1) and elevated (600?mol mol−1) C{sub a} were measured. The experiment utilized the FACE facility at Eschikon, Switzerland; here the L. Perenne swards had been grown at two nitrogen treatments, with six cuts per year, for 4 years. The study revealed a significant decrease in Rubisco activity (Vcmax) in the low nitrogen FACE plots; this is consistent with the theories of source-sink imbalance resulting in feedback inhibition and down-regulation. Such negative acclimation was not wholly supported by diurnal investigations which revealed an average stimulation of 53.38% and 52.78% in the low and high nitrogen, respectively. However, light response curves and AI investigations also suggested down-regulation, especially in the low nitrogen. SI is expected to decrease in response to elevated C{sub a}, if any change is seen. This was indeed observed in the high nitrogen plots but for the low nitrogen a significant increase was found. Conclusions drawn from this project center around the implications of negative acclimation to future crop productivity. For instance, inter-specific differences in response to elevated C{sub a} may result in ecosystem changes and new management techniques may be necessary. However, real predictions cannot be made from leaf level studies alone as these may not represent the overall changes at the whole plant level.
Author: Publisher: ISBN: Category : Languages : en Pages : 87
Book Description
In this study, the photosynthetic responses of field grown Lolium perenne to ambient (354 [mu]mol mol−1) and elevated (600 [mu]mol mol−1) C{sub a} were measured. The experiment utilized the FACE facility at Eschikon, Switzerland; here the L. Perenne swards had been grown at two nitrogen treatments, with six cuts per year, for 4 years. The study revealed a significant decrease in Rubisco activity (Vcmax) in the low nitrogen FACE plots; this is consistent with the theories of source-sink imbalance resulting in feedback inhibition and down-regulation. Such negative acclimation was not wholly supported by diurnal investigations which revealed an average stimulation of 53.38% and 52.78% in the low and high nitrogen, respectively. However, light response curves and AI investigations also suggested down-regulation, especially in the low nitrogen. SI is expected to decrease in response to elevated C{sub a}, if any change is seen. This was indeed observed in the high nitrogen plots but for the low nitrogen a significant increase was found. Conclusions drawn from this project center around the implications of negative acclimation to future crop productivity. For instance, inter-specific differences in response to elevated C{sub a} may result in ecosystem changes and new management techniques may be necessary. However, real predictions cannot be made from leaf level studies alone as these may not represent the overall changes at the whole plant level.
Author: Publisher: ISBN: Category : Languages : en Pages : 31
Book Description
Stands of Ryegrass (Lolium perenne L. cv. Bastion) were grown in the field at ambient or elevated (600[mu]mol/mol) CO2 concentration, high (560Kg/ha) or low (140Kg/ha) nitrogen addition and with a frequent (every 4 weeks) or infrequent (every 8 weeks) cutting regime. Plants were in the second year of a 3 year experiment. Exposure to elevated CO2 was carried out with a Free-Air CO2 Enrichment (FACE) system which provides the most {open_quote}realistic{close_quote} system of CO2 fumigation currently available. Elevated CO2 increased diurnal CO2 assimilation by between 34 and 88% whilst reducing rates of stomatal conductance by between 1 and 42%. However, analysis of the A vs. Ci response showed considerable acclimation of the photosynthetic apparatus in response to elevated CO2 - Vc{sub max} as an in vivo measure of RubisCO activity, decreased by between 29 and 35% in high CO2, whilst J{sub max}, as a measure of the RubP regeneration capacity, showed no significant change. Two out of three additional perennial grassland species studied showed similar acclamatory behavior to Ryegrass. Diurnal assimilation rate, J{sub max} and, in most cases, Vc{sub max}, increased significantly directly after cutting of Ryegrass stands, but nitrogen treatment had little effect on any of these parameters. Neither stomatal density, stomatal index nor stomatal pore length of Ryegrass were significantly altered by growth in elevated CO2. The results are discussed in terms of the limitation imposed on maximizing photosynthetic and growth responses of Ryegrass at elevated CO2, by the ability of perennial species to increase long-term sink capacity under these conditions.
Author: Publisher: ISBN: Category : Languages : en Pages : 31
Book Description
Stands of Ryegrass (Lolium perenne L. cv. Bastion) were grown in the field at ambient or elevated (600?mol/mol) CO2 concentration, high (560Kg/ha) or low (140Kg/ha) nitrogen addition and with a frequent (every 4 weeks) or infrequent (every 8 weeks) cutting regime. Plants were in the second year of a 3 year experiment. Exposure to elevated CO2 was carried out with a Free-Air CO2 Enrichment (FACE) system which provides the most {open_quote}realistic{close_quote} system of CO2 fumigation currently available. Elevated CO2 increased diurnal CO2 assimilation by between 34 and 88% whilst reducing rates of stomatal conductance by between 1 and 42%. However, analysis of the A vs. Ci response showed considerable acclimation of the photosynthetic apparatus in response to elevated CO2 - Vc{sub max} as an in vivo measure of RubisCO activity, decreased by between 29 and 35% in high CO2, whilst J{sub max}, as a measure of the RubP regeneration capacity, showed no significant change. Two out of three additional perennial grassland species studied showed similar acclamatory behavior to Ryegrass. Diurnal assimilation rate, J{sub max} and, in most cases, Vc{sub max}, increased significantly directly after cutting of Ryegrass stands, but nitrogen treatment had little effect on any of these parameters. Neither stomatal density, stomatal index nor stomatal pore length of Ryegrass were significantly altered by growth in elevated CO2. The results are discussed in terms of the limitation imposed on maximizing photosynthetic and growth responses of Ryegrass at elevated CO2, by the ability of perennial species to increase long-term sink capacity under these conditions.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The response of intra and interspecific variation in photosynthetic acclimation to growth at elevated atmospheric CO[sub 2] concentration (600[micro]mol mol-l) in six important grassland species was investigated. Plants were grown in a background sward of Lolium perenne and measurements were made after four years of growth at elevated C[sub a]. Elevated CO[sub 2] was maintained using a FACE (Free-Air Carbon Enrichment) system. Significant intra and interspecific variation in acclimation response was demonstrated. The response of adaxial and abaxial stomatal conductance to elevated CO[sub 2] was also investigated. The stomatal conductance of both the adaxial and abaxial leaf surfaces was found to be reduced by elevated C[sub a]. Significant asymmetric responses in stomatal conductance was demonstrated in D. glomerata and T. pratense. Analysis of stomatal indices and densities indicated that the observed reductions in stomatal conductance were probably the result of changes in stomatal aperture.
Author: Publisher: ISBN: Category : Languages : en Pages : 70
Book Description
Plots of Medicago sativa cv. saranac were grown in the field at ambient (355 [mu]mol CO2 mol−1 air) or elevated (600[mu]mol CO2 mol−1 air) CO2 concentrations. High (200kg yr−1) or low (20kg yr−1) nitrogen levels were applied to two isogeneic lines, one able and one unable to use nitrogen fixing bacteria. Plants were in the second year of field growth. Exposure to elevated CO2 was via a Free-Air CO2 Enrichment System (FACE). Elevated CO2 increased diurnal assimilation by between 12% and 92%. Analysis of A/C{sub i} responses showed that effective nitrogen fertilisation was more important to rubisCO and RuBP activity than elevated CO2. No acclimation was consistently observed. Leaves lower down the canopy were found to have lower Vc{sub max} and J{sub max} values, though age may be the cause of the latter effect. FACE conditions have only a small effect on these responses. There was some evidence found for the down-regulation of photosynthesis in the late afternoon. The FACE conditions had no affect on stomatal density but did increase epidermal cell density.
Author: Yunpu Zheng Publisher: Frontiers Media SA ISBN: 2832549411 Category : Science Languages : en Pages : 137
Book Description
It is well known that agricultural and forest ecosystems are the most important carbon sinks in terrestrial ecosystems, and therefore understanding the key processes and potential mechanisms of agricultural and forest ecosystems in response to climate change is critical for accurately estimating the carbon sinks in agriculture and forests. However, the response and adaptation of carbon-water-nitrogen processes in agricultural and forest ecosystems to climate change remain unclear. These knowledge gaps create significant uncertainties in future projections, and fully exploring the potential mechanisms and processes of agriculture and forests to climate change is pivotal to projecting the potential risk of climate change on global grain yield and forest carbon sequestrations.
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Author: Yunpu Zheng