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Does Leaf Position within a Canopy Affect Acclimation of
Photosynthesis to Elevated CO2?
: Analysis of a Wheat Crop under Free-Air CO2
Enrichment 总被引:1,自引:0,他引:1 下载免费PDF全文
Colin P. Osborne Julie La Roche Richard L. Garcia Bruce A. Kimball Gerard W. Wall Paul J. Pinter Jr. Robert L. La Morte George R. Hendrey Steve P. Long 《Plant physiology》1998,117(3):1037-1045
Previous studies of photosynthetic acclimation to elevated CO2 have focused on the most recently expanded, sunlit leaves in the canopy. We examined acclimation in a vertical profile of leaves through a canopy of wheat (Triticum aestivum L.). The crop was grown at an elevated CO2 partial pressure of 55 Pa within a replicated field experiment using free-air CO2 enrichment. Gas exchange was used to estimate in vivo carboxylation capacity and the maximum rate of ribulose-1,5-bisphosphate-limited photosynthesis. Net photosynthetic CO2 uptake was measured for leaves in situ within the canopy. Leaf contents of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), light-harvesting-complex (LHC) proteins, and total N were determined. Elevated CO2 did not affect carboxylation capacity in the most recently expanded leaves but led to a decrease in lower, shaded leaves during grain development. Despite this acclimation, in situ photosynthetic CO2 uptake remained higher under elevated CO2. Acclimation at elevated CO2 was accompanied by decreases in both Rubisco and total leaf N contents and an increase in LHC content. Elevated CO2 led to a larger increase in LHC/Rubisco in lower canopy leaves than in the uppermost leaf. Acclimation of leaf photosynthesis to elevated CO2 therefore depended on both vertical position within the canopy and the developmental stage. 相似文献
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Kindt KS Quast KB Giles AC De S Hendrey D Nicastro I Rankin CH Schafer WR 《Neuron》2007,55(4):662-676
Dopamine has been implicated in the modulation of diverse forms of behavioral plasticity, including appetitive learning and addiction. An important challenge is to understand how dopamine's effects at the cellular level alter the properties of neural circuits to modify behavior. In the nematode C. elegans, dopamine modulates habituation of an escape reflex triggered by body touch. In the absence of food, animals habituate more rapidly than in the presence of food; this contextual information about food availability is provided by dopaminergic mechanosensory neurons that sense the presence of bacteria. We find that dopamine alters habituation kinetics by selectively modulating the touch responses of the anterior-body mechanoreceptors; this modulation involves a D1-like dopamine receptor, a Gq/PLC-beta signaling pathway, and calcium release within the touch neurons. Interestingly, the body touch mechanoreceptors can themselves excite the dopamine neurons, forming a positive feedback loop capable of integrating context and experience to modulate mechanosensory attention. 相似文献
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Photosynthesis, light and nitrogen relationships in a young deciduous forest canopy under open-air CO2 enrichment 总被引:3,自引:0,他引:3
Y. Takeuchi M. E. Kubiske J. G. Isebrands K.S. Pregtizer G. Hendrey & D. F. Karnosky 《Plant, cell & environment》2001,24(12):1257-1268
Leaf photosynthesis (Ps), nitrogen (N) and light environment were measured on Populus tremuloides trees in a developing canopy under free‐air CO2 enrichment in Wisconsin, USA. After 2 years of growth, the trees averaged 1·5 and 1·6 m tall under ambient and elevated CO2, respectively, at the beginning of the study period in 1999. They grew to 2·6 and 2·9 m, respectively, by the end of the 1999 growing season. Daily integrated photon flux from cloud‐free days (PPFDday,sat) around the lowermost branches was 16·8 ± 0·8 and 8·7 ± 0·2% of values at the top for the ambient and elevated CO2 canopies, respectively. Elevated CO2 significantly decreased leaf N on a mass, but not on an area, basis. N per unit leaf area was related linearly to PPFDday,sat throughout the canopies, and elevated CO2 did not affect that relationship. Leaf Ps light‐response curves responded differently to elevated CO2, depending upon canopy position. Elevated CO2 increased Pssat only in the upper (unshaded) canopy, whereas characteristics that would favour photosynthesis in shade were unaffected by elevated CO2. Consequently, estimated daily integrated Ps on cloud‐free days (Psday,sat) was stimulated by elevated CO2 only in the upper canopy. Psday,sat of the lowermost branches was actually lower with elevated CO2 because of the darker light environment. The lack of CO2 stimulation at the mid‐ and lower canopy was probably related to significant down‐regulation of photosynthetic capacity; there was no down‐regulation of Ps in the upper canopy. The relationship between Psday,sat and leaf N indicated that N was not optimally allocated within the canopy in a manner that would maximize whole‐canopy Ps or photosynthetic N use efficiency. Elevated CO2 had no effect on the optimization of canopy N allocation. 相似文献
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Biotic, abiotic and performance aspects of the Nevada Desert Free-Air CO2 Enrichment (FACE) Facility 总被引:3,自引:0,他引:3
DeaN. N. Jordan Stephen F. Zitzer † George R. Hendrey ‡ Keith F. Lewin ‡ JohN. Nagy ‡ Robert S. Nowak § Stanley D. Smith James S. Coleman¶ Jeffrey R. Seemann§ 《Global Change Biology》1999,5(6):659-668
Arid and semiarid climates comprise roughly 40% of the earth’s terrestrial surface. Deserts are predicted to be extremely responsive to global change because they are stressful environments where small absolute changes in water availability or use represent large proportional changes. Water and carbon dioxide fluxes are inherently coupled in plant growth. No documented global change has been more substantial or more rapid than the increase in atmospheric CO2. Free Air CO2 Enrichment (FACE) technology permits manipulation of CO2 in intact communities without altering factors such as light intensity or quality, humidity or wind. The Nevada Desert FACE Facility (NDFF) consists of three 491 m2 plots in the Mojave Desert receiving 550 μL L–1 CO2, and six ambient plots to assess both CO2 and fan effects. The shrub community was characterized as a Larrea–Ambrosia–Lycium species complex. Data are reported through 12 months of operation. 相似文献
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Carlo Calfapietra Elizabeth A. Ainsworth Claus Beier Paolo De Angelis David S. Ellsworth Douglas L. Godbold George R. Hendrey Thomas Hickler Marcel R. Hoosbeek David F. Karnosky John King Christian Körner Andrew D.B. Leakey Keith F. Lewin Marion Liberloo Stephen P. Long Martin Lukac Rainer Matyssek Franco Miglietta Reinhart Ceulemans 《Trends in plant science》2010,15(1):5-10
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A free-air enrichment system for exposing tall forest vegetation to elevated atmospheric CO2 总被引:7,自引:0,他引:7
George R. Hendrey David S. Ellsworth Keith F. Lewin JohN. Nagy 《Global Change Biology》1999,5(3):293-309
A free-air CO2 enrichment (FACE) system was designed to permit the experimental exposure of tall vegetation such as stands of forest trees to elevated atmospheric CO2 concentrations ([CO2]a) without enclosures that alter tree microenvironment. We describe a prototype FACE system currently in operation in forest plots in a maturing loblolly pine (Pinus taeda L.) stand in North Carolina, USA. The system uses feedback control technology to control [CO2] in a 26 m diameter forest plot that is over 10 m tall, while monitoring the 3D plot volume to characterize the whole-stand CO2 regime achieved during enrichment. In the second summer season of operation of the FACE system, atmospheric CO2 enrichment was conducted in the forest during all daylight hours for 96.7% of the scheduled running time from 23 May to 14 October with a preset target [CO2] of 550 μmol mol–1, ≈ 200 μmol mol–1 above ambient [CO2]. The system provided spatial and temporal control of [CO2] similar to that reported for open-top chambers over trees, but without enclosing the vegetation. The daily average daytime [CO2] within the upper forest canopy at the centre of the FACE plot was 552 ± 9 μmol mol–1 (mean ± SD). The FACE system maintained 1-minute average [CO2] to within ± 110 μmol mol–1 of the target [CO2] for 92% of the operating time. Deviations of [CO2] outside of this range were short-lived (most lasting < 60 s) and rare, with fewer than 4 excursion events of a minute or longer per day. Acceptable spatial control of [CO2] by the system was achieved, with over 90% of the entire canopy volume within ± 10% of the target [CO2] over the exposure season. CO2 consumption by the FACE system was much higher than for open-top chambers on an absolute basis, but similar to that of open-top chambers and branch bag chambers on a per unit volume basis. CO2 consumption by the FACE system was strongly related to windspeed, averaging 50 g CO2 m–3 h–1 for the stand for an average windspeed of 1.5 m s–1 during summer. The [CO2] control results show that the free-air approach is a tractable way to study long-term and short-term alterations in trace gases, even within entire tall forest ecosystems. The FACE approach permits the study of a wide range of forest stand and ecosystem processes under manipulated [CO2]a that were previously impossible or intractable to study in true forest ecosystems. 相似文献
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