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1.
David Whitehead Kevin L. Griffin† Matthew H. Turnbull‡ David T. Tissue§ Victor C. Engel† Kim J. Brown† William S.F. Schuster¶ Adrian S. Walcroft 《Global Change Biology》2004,10(6):925-938
Measurements of photosynthesis and respiration were made on leaves in summer in a Quercus rubra L. canopy at approximately hourly intervals throughout 5 days and nights. Leaves were selected in the upper canopy in fully sunlit conditions (upper) and in the lower canopy (lower). In addition, leaves in the upper canopy were shaded (upper shaded) to decrease photosynthesis rates. The data were used to test the hypothesis that total night‐time respiration is dependent on total photosynthesis during the previous day and that the response is mediated through changes in storage in carbohydrate pools. Measurements were made on clear sunny days with similar solar irradiance and air temperature, except for the last day when temperature, especially at night, was lower than that for the previous days. Maximum rates of photosynthesis in the upper leaves (18.7 μmol m?2 s?1) were approximately four times higher than those in the lower leaves (4.3 μmol m?2 s?1) and maximum photosynthesis rates in the upper shaded leaves (8.0 μmol m?2 s?1) were about half those in the upper leaves. There was a strong linear relationship between total night‐time respiration and total photosynthesis during the previous day when rates of respiration were normalized to a fixed temperature of 20°C, removing the effects of temperature from this relationship. Measurements of specific leaf area, nitrogen and chlorophyll concentration and calculations of the maximum rate of carboxylation activity, Vcmax, were not significantly different between upper and upper shaded leaves 5 days after the shading treatment was started. There were small, but significant decreases in the rate of apparent maximum electron transport at saturating irradiance, Jmax (P>0.05), and light use efficiency, ? (P<0.05), for upper shaded leaves compared with those for upper leaves. This suggests that the duration of shading in the experiment was sufficient to initiate changes in the electron transport, but not the carboxylation processes of photosynthesis. Support for the hypothesis was provided from analysis of soluble sugar and starch concentrations in leaves. Respiration rates in the upper shaded leaves were lower than those expected from a relationship between respiration and soluble sugar concentration for fully exposed upper and lower leaves. However, there was no similar difference in starch concentrations. This suggests that shading for the duration of several days did not affect sugar concentrations but reduced starch concentrations in leaves, leading to lower rates of respiration at night. A model was used to quantify the significance of the findings on estimated canopy CO2 exchange for the full growing season. Introducing respiration as a function of total photosynthesis on the previous day resulted in a decrease in growing season night‐time respiration by 23% compared with the value when respiration was held constant. This highlights the need for a process‐based approach linking respiration to photosynthesis when modelling long‐term carbon exchange in forest ecosystems. 相似文献
2.
Tree root and soil heterotrophic respiration as revealed by girdling of boreal Scots pine forest: extending observations beyond the first year 总被引:26,自引:0,他引:26
BHUPINDERPAL-SINGH A. NORDGREN M. OTTOSSON LÖFVENIUS M. N. HÖGBERG P. -E. MELLANDER & P. HÖGBERG 《Plant, cell & environment》2003,26(8):1287-1296
Limitations in available techniques to separate autotrophic (root) and soil heterotrophic respiration have hampered the understanding of forest C cycling. The former is here defined as respiration by roots, their associated mycorrhizal fungi and other micro‐organisms in the rhizosphere directly dependent on labile C compounds leaked from roots. In order to separate the autotrophic and heterotrophic components of soil respiration, all Scots pine trees in 900 m2 plots were girdled to instantaneously terminate the supply of current photosynthates from the tree canopy to roots. Högberg et al. (Nature 411, 789–792, 2001) reported that autotrophic activity contributed up to 56% of total soil respiration during the first summer of this experiment. They also found that mobilization of stored starch (and likely also sugars) in roots after girdling caused an increased apparent heterotrophic respiration on girdled plots. Herein a transient increase in the δ13C of soil CO2 efflux after girdling, thought to be due to decomposition of 13C‐enriched ectomycorrhizal mycelium and root starch and sugar reserves, is reported. In the second year after girdling, when starch reserves of girdled tree roots were exhausted, calculated root respiration increased up to 65% of total soil CO2 efflux. It is suggested that this estimate of its contribution to soil respiration is more precise than the previous based on one year of observation. Heterotrophic respiration declined in response to a 20‐day‐long 6 °C decline in soil temperature during the second summer, whereas root respiration did not decline. This did not support the idea that root respiration should be more sensitive to variations in soil temperature. It is suggested that above‐ground photosynthetic activity and allocation patterns of recent photosynthates to roots should be considered in models of responses of forest C balances to global climate change. 相似文献
3.
The relative impacts of daytime and night-time warming on photosynthetic capacity in Populus deltoides 总被引:2,自引:1,他引:1
In order to investigate the relative impacts of increases in day and night temperature on tree carbon relations, we measured night‐time respiration and daytime photosynthesis of leaves in canopies of 4‐m‐tall cottonwood (Populus deltoides Bartr. ex Marsh) trees experiencing three daytime temperatures (25, 28 or 31 °C) and either (i) a constant nocturnal temperature of 20 °C or (ii) increasing nocturnal temperatures (15, 20 or 25 °C). In the first (day warming only) experiment, rates of night‐time leaf dark respiration (Rdark) remained constant and leaves displayed a modest increase (11%) in light‐saturated photosynthetic capacity (Amax) during the day (1000–1300 h) over the 6 °C range. In the second (dual night and day warming) experiment, Rdark increased by 77% when nocturnal temperatures were increased from 15 °C (0·36 µmol m?2 s?1) to 25 °C (0·64 µmol m?2 s?1). Amax responded positively to the additional nocturnal warming, and increased by 38 and 64% in the 20/28 and 25/31 °C treatments, respectively, compared with the 15/25 °C treatment. These increases in photosynthetic capacity were associated with strong increases in the maximum carboxylation rate of rubisco (Vcmax) and ribulose‐1,5‐bisphosphate (RuBP) regeneration capacity mediated by maximum electron transport rate (Jmax). Leaf soluble sugar and starch concentration, measured at sunrise, declined significantly as nocturnal temperature increased. The nocturnal temperature manipulation resulted in a significant inverse relationship between Amax and pre‐dawn leaf carbohydrate status. Independent measurements of the temperature response of photosynthesis indicated that the optimum temperature (Topt) acclimated fully to the 6 °C range of temperature imposed in the daytime warming. Our findings are consistent with the hypothesis that elevated night‐time temperature increases photosynthetic capacity during the following light period through a respiratory‐driven reduction in leaf carbohydrate concentration. These responses indicate that predicted increases in night‐time minimum temperatures may have a significant influence on net plant carbon uptake. 相似文献
4.
ERIC A. HOBBIE JILLIAN GREGG† DAVID M. OLSZYK† PAUL T. RYGIEWICZ† DAVID T. TINGEY† 《Global Change Biology》2002,8(11):1072-1084
Models of photosynthesis, respiration, and export predict that foliar labile carbon (C) should increase with elevated CO2 but decrease with elevated temperature. Sugars, starch, and protein can be compared between treatments, but these compounds make up only a fraction of the total labile pool. Moreover, it is difficult to assess the turnover of labile carbon between years for evergreen foliage. Here, we combined changes in foliar Carea (C concentration on an areal basis) as needles aged with changes in foliar isotopic composition (δ13C) caused by inputs of 13C‐depleted CO2 to estimate labile and structural C in needles of different ages in a four‐year, closed‐chamber mesocosm experiment in which Douglas‐fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were exposed to elevated temperature (ambient + 3.5 °C) and CO2 (ambient + 179 ppm). Declines in δ 13C of needle cohorts as they aged indicated incorporation of newly fixed labile or structural carbon. The δ 13C calculations showed that new C was 41 ± 2% and 28 ± 3% of total needle carbon in second‐ and third‐year needles, respectively, with higher proportions of new C in elevated than ambient CO2 chambers (e.g. 42 ± 2% vs. 37 ± 6%, respectively, for second‐year needles). Relative to ambient CO2, elevated CO2 increased labile C in both first‐ and second‐year needles. Relative to ambient temperature, elevated temperature diminished labile C in second‐year needles but not in first‐year needles, perhaps because of differences in sink strength between the two needle age classes. We hypothesize that plant‐soil feedbacks on nitrogen supply contributed to higher photosynthetic rates under elevated temperatures that partly compensated for higher turnover rates of labile C. Strong positive correlations between labile C and sugar concentrations suggested that labile C was primarily determined by carbohydrates. Labile C was negatively correlated with concentrations of cellulose and protein. Elevated temperature increased foliar %C, possibly due to a shift of labile constituents from low %C carbohydrates to relatively high %C protein. Decreased sugar concentrations and increased nitrogen concentrations with elevated temperature were consistent with this explanation. Because foliar constituents that vary in isotopic signature also vary in concentrations with leaf age or environmental conditions, inferences of ci/ca values from δ 13C of bulk leaf tissue should be done cautiously. Tracing of 13C through foliar carbon pools may provide new insight into foliar C constituents and turnover. 相似文献
5.
Direct and indirect effects of elevated CO2 on leaf respiration in a forest ecosystem 总被引:1,自引:0,他引:1
We measured the short‐term direct and long‐term indirect effects of elevated CO2 on leaf dark respiration of loblolly pine (Pinus taeda) and sweetgum (Liquidambar styraciflua) in an intact forest ecosystem. Trees were exposed to ambient or ambient + 200 µmol mol?1 atmospheric CO2 using free‐air carbon dioxide enrichment (FACE) technology. After correcting for measurement artefacts, a short‐term 200 µmol mol?1 increase in CO2 reduced leaf respiration by 7–14% for sweetgum and had essentially no effect on loblolly pine. This direct suppression of respiration was independent of the CO2 concentration under which the trees were grown. Growth under elevated CO2 did not appear to have any long‐term indirect effects on leaf maintenance respiration rates or the response of respiration to changes in temperature (Q10, R0). Also, we found no relationship between mass‐based respiration rates and leaf total nitrogen concentrations. Leaf construction costs were unaffected by growth CO2 concentration, although leaf construction respiration decreased at elevated CO2 in both species for leaves at the top of the canopy. We conclude that elevated CO2 has little effect on leaf tissue respiration, and that the influence of elevated CO2 on plant respiratory carbon flux is primarily through increased biomass. 相似文献
6.
In water-stressed leaves, accumulation of neutral osmotica enhances the heat tolerance of photosynthetic electron transport. There are large diurnal and day-to-day changes in leaf sugar content because of variations in net photosynthetic production, respiration and retranslocation. To test the hypothesis that diurnal and day-to-day variations in leaf sugar content and osmotic potential significantly modify the responses to temperature of photosynthetic electron transport rate, we studied chlorophyll fluorescence rise temperatures (i.e. critical temperatures at break-points in fluorescence versus temperature response curves, corresponding to enhanced damage of PSII centers and detachment of pigment-binding complexes) in the dark at a background of weak far-red light (T(FR)) and under actinic light (T(L)), and responses of foliar photosynthetic electron transport rate to temperature using gas-exchange and chlorophyll fluorescence techniques in the temperate tree Populus tremula L. Sucrose and sorbitol feeding experiments demonstrated strong increases of fluorescence rise temperatures T(FR) and T(L) with decreasing leaf osmotic potential and increasing internal sugar concentration. Similar T(FR) and T(L) changes were observed in response to natural variation in leaf sugar concentration throughout the day. Increases in leaf sugar concentration led to an overall down-regulation of the rate of photosynthetic electron transport (J), but increases in the optimum temperature (Topt) of J. For the entire dataset, Topt varied from 33.8 degrees C to 43 degrees C due to natural variation in sugars and from 33.8 degrees C to 52.6 degrees C in the sugar feeding experiments, underscoring the importance of sugars in modifying the response of J to temperature. However, the correlations between the sugar concentration and fluorescence rise temperature varied between the days. This variation in fluorescence rise temperature was best explained by the average temperature of the preceding 5 or 6 days. In addition, there was a significant year-to-year variation in heat sensitivity of photosynthetic electron transport that was associated with year-to-year differences in endogenous sugar content. Our data demonstrate a diurnal variation in leaf heat tolerance due to changes in sugar concentration, but they also show that this short-term modification in heat tolerance is super-imposed by long-term changes in heat resistance driven by average temperature of preceding days. 相似文献
7.
Rising atmospheric carbon dioxide has the potential to alter leaf litter chemistry, potentially affecting decomposition and rates of carbon and nitrogen cycling in forest ecosystems. This study was conducted to determine whether growth under elevated atmospheric CO2 altered the quality and microbial decomposition of leaf litter of a widely distributed northern hardwood species at sites of low and high soil nitrogen availability. In addition, we assessed whether the carbon–nutrient balance (CNB) and growth differentiation balance (GDB) hypotheses could be extended to predict changes in litter quality in response to resource availability. Sugar maple (Acer saccharum) was grown in the field in open‐top chambers at 36 and 55 Pa partial pressure CO2, and initial soil mineralization rates of 45 and 348 μg N g?1 d?1. Naturally senesced leaf litter was assessed for chemical composition and incubated in the laboratory for 111 d. Microbial respiration and the production of dissolved organic carbon (DOC) were quantified as estimates of decomposition. Elevated CO2 and low soil nitrogen resulted in higher litter concentrations of nonstructural carbohydrates and condensed tannins, higher C/N ratios and lower N concentrations. Soil N availability appears to have had a greater effect on litter quality than did atmospheric CO2, although the treatments were additive, with highest concentrations of nonstructural carbohydrates and condensed tannins occurring under elevated CO2–low soil N. Rates of microbial respiration and the production of DOC were insensitive to differences in litter quality. In general, concentrations of litter constituents, except for starch, were highly correlated to those in live foliage, and the CNB/GDB hypotheses proved useful in predicting changes in litter quality. We conclude the chemical composition of sugar maple litter will change in the future in response to rising atmospheric CO2, and that soil N availability will exert a major control. It appears that microbial metabolism will not be directly affected by changes in litter quality, although conclusions regarding decomposition as a whole must consider the entire soil food web. 相似文献
8.
Effects of decreased net carbon exchange on carbohydrate metabolism in sugar beet source leaves 总被引:3,自引:2,他引:1
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The relationship between CO2 concentration and starch synthesis and degradation was studied by measuring leaf starch content and disappearance of 14C-starch. At a concentration of 340 microliters CO2 per liter, starch accumulated without degradation of previously synthesized starch. Degradation of starch began when CO2 concentration was lowered, but its synthesis continued. At 120 microliters CO2 per liter rates of synthesis and degradation were equal. Even at the CO2 compensation point, synthesis of starch continued. Concomitant starch synthesis and mobilization supported export from the leaf. Changes in starch metabolism that occur when photosynthesis is CO2-limited provide a means to study regulation of starch metabolism and carbon allocation in translocating leaves. 相似文献
9.
Leaf respiration is differentially affected by leaf vs. stand-level night-time warming 总被引:5,自引:0,他引:5
Kevin L. Griffin Matthew Turnbull† Ramesh Murthy‡ Guanghui Lin‡ John Adams‡ Blake Farnsworth‡ Tilak Mahato‡ Guerric Bazin§ Mark Potasnak Joe A. Berry¶ 《Global Change Biology》2002,8(5):479-485
Plant respiration is an important physiological process in the global carbon cycle serving as a major carbon flux from the biosphere to the atmosphere. Respiration is sensitive to temperature providing a link between environmental variability, climate change and the global carbon cycle. We measured leaf respiration in Populus deltoides after manipulating the air temperature surrounding part of a single leaf, and compared this to the temperature response of the same leaves after manipulating the temperature of the stand. The short‐term temperature response of respiration (Q10– change in the respiration rate with a 10 °C increase in leaf temperature) was 1.7 when the leaf temperature was manipulated, but 2.1 when the stand‐level temperature was changed. As a result, total night‐time carbon release during the five‐day experiment was 21% lower when using the Q10 estimates from the tradition leaf manipulation compared to the stand‐level manipulation. We conclude that the temperature response of leaf respiration is related to whole plant carbon and energy demands, and that appropriate experimental procedures are required in examining respiratory CO2 release under variable temperature conditions. 相似文献
10.
KRISTINE Y. CROUS JOANA ZARAGOZA‐CASTELLS MARKUS LÖW DAVID S. ELLSWORTH DAVID T. TISSUE MARK G. TJOELKER CRAIG V. M. BARTON TERESA E. GIMENO OWEN K. ATKIN 《Global Change Biology》2011,17(4):1560-1576
Understanding the impacts of atmospheric [CO2] and drought on leaf respiration (R) and its response to changes in temperature is critical to improve predictions of plant carbon‐exchange with the atmosphere, especially at higher temperatures. We quantified the effects of [CO2]‐enrichment (+240 ppm) on seasonal shifts in the diel temperature response of R during a moderate summer drought in Eucalyptus saligna growing in whole‐tree chambers in SE Australia. Seasonal temperature acclimation of R was marked, as illustrated by: (1) a downward shift in daily temperature response curves of R in summer (relative to spring); (2)≈60% lower R measured at 20oC (R20) in summer compared with spring; and (3) homeostasis over 12 months of R measured at prevailing nighttime temperatures. R20, measured during the day, was on average 30–40% higher under elevated [CO2] compared with ambient [CO2] across both watered and droughted trees. Drought reduced R20 by≈30% in both [CO2] treatments resulting in additive treatment effects. Although [CO2] had no effect on seasonal acclimation, summer drought exacerbated the seasonal downward shift in temperature response curves of R. Overall, these results highlight the importance of seasonal acclimation of leaf R in trees grown under ambient‐ and elevated [CO2] as well as under moderate drought. Hence, respiration rates may be overestimated if seasonal changes in temperature and drought are not considered when predicting future rates of forest net CO2 exchange. 相似文献
11.
12.
Chiaki Matsukura Shin-ichi Itoh Keisuke Nemoto Eiichi Tanimoto Junji Yamaguchi 《Planta》1998,205(2):145-152
The mechanism of gibberellin (GA)-induced leaf sheath growth was examined using a dwarf mutant of rice (Oryza sativa L. cv. Tan-ginbozu) treated in advance with an inhibitor of GA biosynthesis. Gibberellic acid (GA3) enhanced the growth of the second leaf sheath, but auxins did not. Measurement of the mitotic index and cell size revealed
that cell elongation rather than cell division is promoted by GA3. Gibberellic acid increased the extensibility of cell walls in the elongation zone of the leaf sheath. It also increased
the total amount of osmotic solutes including sugars in the leaf sheath, but did not increase the osmotic concentration of
the cell sap, due to an accompanying increase in cell volume by water absorption. In the later stage of GA3-induced growth, starch granules completely disappeared from leaf sheath cells, whereas dense granules remained in control
plants. These findings indicate that GA enhances cell elongation by increasing wall extensibility, osmotic concentration being
kept unchanged by starch degradation.
Received: 28 August 1997 / Accepted: 16 October 1997 相似文献
13.
Ons Talbi Zribi Nehla Labidi Inès Slama Ahmed Debez Riadh Ksouri Mokded Rabhi Abderrazak Smaoui Chedly Abdelly 《Plant Growth Regulation》2012,66(1):75-85
Hordeum maritimum (Poacea) is a facultative halophyte potentially useful for forage production in saline zones. Here, we assessed whether moderate
NaCl-salinity can modify the plant response to phosphorus (P) shortage. Plants were cultivated for 55 days under low or sufficient
P supply (5 or 60 μmol plant−1 week−1 KH2PO4, respectively), with or without 100 mM NaCl. When individually applied, salinity and P deficiency significantly restricted
whole-plant growth, with a more marked effect of the latter stress. Plants subjected to P deficiency showed a significant
increase in root growth (as length and dry weight) and root/shoot DW ratio. Enhanced root growth and elongation presumably
correspond to the well-known root adaptive response to mineral deficiency. However, leaf relative water content, leaf P concentration,
and leaf gas exchange parameters were significantly restricted. The interactive effects of salinity and P deficiency were
not added one to another neither on whole plant biomass nor on plant nutrient uptake. Indeed, 100 mM NaCl-addition to P-deficient
plants significantly restored the plant growth and improved CO2 assimilation rate, root growth, K+/Na+ ratio and leaf proline and soluble sugar concentrations. It also significantly enhanced leaf total antioxidant capacity and
leaf anthocyanin concentration. This was associated with significantly lower leaf osmotic potential, leaf Na+ and malondialdehyde (MDA) concentration. Taken together, these results suggest that mild salinity may mitigate the adverse
effects of phosphorus deficiency on H. maritimum by notably improving the plant photosynthetic activity, the osmotic adjustment capacity, the selective absorption of K+ over Na+ and antioxidant defence. 相似文献
14.
The effects of kinetin on starch and sugar levels and on 14CO2 and 32P-orthophosphate labeling patterns of floated Chinese cabbage (Brassica pekinensis) leaf discs were investigated. Kinetin caused gross starch degradation. Neutral sugars were depressed by 30 to 40% in leaf tissue treated with kinetin for 24 hours. 14CO2 labeling of leaf discs pretreated with kinetin for 24 hours showed increased radioactivity in chloroform-soluble material and most sugar phosphates, and a 35 to 40% decrease in radioactivity in the neutral sugars, glucose, sucrose, and fructose. Incorporation into ATP was increased by 40% by kinetin. 32P-Orthophosphate uptake was inhibited 30% by kinetin. When corrected for uptake, kinetin stimulated incorporation into chloroform-soluble material but had little effect on other cell fractions. These results indicate that kinetin mobilizes starch reserves and increases the flow of sugars required for the synthesis of lipids and structural materials in floated discs. 相似文献
15.
A study was conducted in the Lower Laurentians of southern Quebec to test the hypothesis that base cation fertilization would improve the nutrient status of declining sugar maples (Acer saccharum Marsh.) and alter the partitioning of leaf C and N. Six 40×40 m plots were delineated in an 80 year old stand of sugar maple. Three plots received a mixture of fertilizer and liming materials (500 kg ha–1 of K2SO4, 250 kg ha–1 of CaCO3 and 250 kg ha–1 of CaMg(CO2)2) in the spring of 1989. Leaves from mid crown of dominant or co-dominant maples were sampled monthly during the 1990 growing season. Trees were cored in 1992 to measure their response in diameter growth. Fertilization increased diameter growth and foliar K concentration of trees but reduced foliar Ca concentration. Fertilization resulted in lower starch concentrations and higher ratios of soluble sugars to starch in June and September, and in higher free amino acid concentrations but lower ratio of total non-structural carbohydrates to free amino acids in September. Leaf proline concentration was correlated with leaf starch concentration (r=0.39). The results suggest that amelioration of K deficiencies in sugar maple through fertilization with a mixture of base cations can increase tree growth and affect the seasonal dynamics of foliar C and N pools.Abbreviations FAA
free amino acids
- TNC
total non-structural carbohydrates 相似文献
16.
树干呼吸(E_s)是森林生态系统碳循环过程的重要组成部分,深入理解树干呼吸过程对未来气候变暖的响应及反馈机制有助于更加精确地估算森林生态系统碳储量。为揭示毛白杨树干呼吸及其温度敏感性的昼夜变化和季节动态规律,利用Li-Cor6400便携式光合作用测定系统及其配套使用的土壤呼吸测量气室(LI-6400-09)对冀南平原区毛白杨的树干呼吸和树干温度实施为期1年的连续监测。结果表明:(1)在生长季,毛白杨树干呼吸与树干温度之间在晚上呈现正相关的关系(R~2=0.88);相反,两者在白天为负相关的关系(R~2=0.96)。(2)整个观测期内,毛白杨树干呼吸和树干温度均呈现"钟形"的变化曲线,树干呼吸与树干温度之间存在着较好的指数函数关系(R~2=0.93),且树干呼吸的温度敏感性系数(Q_(10))为2.62;不同季节毛白杨树干呼吸的Q_(10)存在差异,生长季的Q_(10)(1.95)明显低于非生长季(3.00),表明生长呼吸和维持呼吸对温度的响应也并不相同。(3)温度矫正后的毛白杨树干呼吸(R_(15))在昼夜和季节尺度上均存在明显的变异,即夜晚的R_(15)显著高于白天(P0.01),生长季的R_(15)明显高于非生长季(P0.05);树干可溶性糖含量与生长季的R_(15)存在较好的相关性(R~2=0.52),而非生长季的R_(15)却主要受到树干淀粉含量的影响。研究结果表明,在生长季,毛白杨树干呼吸的在日变化主要受到温度的影响,而在季节尺度上Q_(10)的变异则与树干呼吸中维持呼吸所占比例及树干中非结构性碳水化合物(可溶性糖和淀粉)的含量及类型紧密相关。 相似文献
17.
The dependence of respiration on photosynthetic substrate supply and temperature: integrating leaf, soil and ecosystem measurements 总被引:5,自引:0,他引:5
IAIN P. HARTLEY ANNA F. ARMSTRONG RAMESH MURTHY† GREG BARRON-GAFFORD‡ PHIL INESON OWEN K. ATKIN 《Global Change Biology》2006,12(10):1954-1968
Interactions between photosynthetic substrate supply and temperature in determining the rate of three respiration components (leaf, belowground and ecosystem respiration) were investigated within three environmentally controlled, Populus deltoides forest bays at Biosphere 2, Arizona. Over 2 months, the atmospheric CO2 concentration and air temperature were manipulated to test the following hypotheses: (1) the responses of the three respiration components to changes in the rate of photosynthesis would differ both in speed and magnitude; (2) the temperature sensitivity of leaf and belowground respiration would increase in response to a rise in substrate availability; and, (3) at the ecosystem level, the ratio of respiration to photosynthesis would be conserved despite week‐to‐week changes in temperature. All three respiration rates responded to the CO2 concentration‐induced changes in photosynthesis. However, the proportional change in the rate of leaf respiration was more than twice that of belowground respiration and, when photosynthesis was reduced, was also more rapid. The results suggest that aboveground respiration plays a key role in the overall response of ecosystem respiration to short‐term changes in canopy photosynthesis. The short‐term temperature sensitivity of leaf respiration, measured within a single night, was found to be affected more by developmental conditions than photosynthetic substrate availability, as the Q10 was lower in leaves that developed at high CO2, irrespective of substrate availability. However, the temperature sensitivity of belowground respiration, calculated between periods of differing air temperature, appeared to be positively correlated with photosynthetic substrate availability. At the ecosystem level, respiration and photosynthesis were positively correlated but the relationship was affected by temperature; for a given rate of daytime photosynthesis, the rate of respiration the following night was greater at 25 than 20°C. This result suggests that net ecosystem exchange did not acclimate to temperature changes lasting up to 3 weeks. Overall, the results of this study demonstrate that the three respiration terms differ in their dependence on photosynthesis and that, short‐ and medium‐term changes in temperature may affect net carbon storage in terrestrial ecosystems. 相似文献
18.
H. WAYNE POLLEY PATRICIA C. MIELNICK† WILLIAM A. DUGAS† HYRUM B. JOHNSON JOAQUIN SANABRIA† 《Global Change Biology》2006,12(8):1390-1399
Respiration (carbon efflux) by terrestrial ecosystems is a major component of the global carbon (C) cycle, but the response of C efflux to atmospheric CO2 enrichment remains uncertain. Respiration may respond directly to an increase in the availability of C substrates at high CO2, but also may be affected indirectly by a CO2‐mediated alteration in the amount by which respiration changes per unit of change in temperature or C uptake (sensitivity of respiration to temperature or C uptake). We measured CO2 fluxes continuously during the final 2 years of a 4‐year experiment on C3/C4 grassland that was exposed to a 200–560 μmol mol?1 CO2 gradient. Flux measurements were used to determine whether CO2 treatment affected nighttime respiration rates and the response of ecosystem respiration to seasonal changes in net C uptake and air temperature. Increasing CO2 from subambient to elevated concentrations stimulated grassland respiration at night by increasing the net amount of C fixed during daylight and by increasing either the sensitivity of C efflux to daily changes in C fixation or the respiration rate in the absence of C uptake (basal ecosystem respiration rate). These latter two changes contributed to a 30–47% increase in the ratio of nighttime respiration to daytime net C influx as CO2 increased from subamient to elevated concentrations. Daily changes in net C uptake were highly correlated with variation in temperature, meaning that the shared contribution of C uptake and temperature in explaining variance in respiration rates was large. Statistically controlling for collinearity between temperature and C uptake reduced the effect of a given change in C influx on respiration. Conversely, CO2 treatment did not affect the response of grassland respiration to seasonal variation in temperature. Elevating CO2 concentration increased grassland respiration rates by increasing both net C input and respiration per unit of C input. A better understanding of how C efflux varies with substrate supply thus may be required to accurately assess the C balance of terrestrial ecosystems. 相似文献
19.
Diel variations in carbon isotopic composition and concentration of organic acids and their impact on plant dark respiration in different species
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M. M. Lehmann F. Wegener R. A. Werner C. Werner 《Plant biology (Stuttgart, Germany)》2016,18(5):776-784
Leaf respiration in the dark and its C isotopic composition (δ13CR) contain information about internal metabolic processes and respiratory substrates. δ13CR is known to be less negative compared to potential respiratory substrates, in particular shortly after darkening during light enhanced dark respiration (LEDR). This phenomenon might be driven by respiration of accumulated 13C‐enriched organic acids, however, studies simultaneously measuring δ13CR during LEDR and potential respiratory substrates are rare. We determined δ13CR and respiration rates (R) during LEDR, as well as δ13C and concentrations of potential respiratory substrates using compound‐specific isotope analyses. The measurements were conducted throughout the diel cycle in several plant species under different environmental conditions. δ13CR and R patterns during LEDR were strongly species‐specific and showed an initial peak, which was followed by a progressive decrease in both values. The species‐specific differences in δ13CR and R during LEDR may be partially explained by the isotopic composition of organic acids (e.g., oxalate, isocitrate, quinate, shikimate, malate), which were 13C‐enriched compared to other respiratory substrates (e.g., sugars and amino acids). However, the diel variations in both δ13C and concentrations of the organic acids were generally low. Thus, additional factors such as the heterogeneous isotope distribution in organic acids and the relative contribution of the organic acids to respiration are required to explain the strong 13C enrichment in leaf dark‐respired CO2. 相似文献
20.
Interactive effects of elevated CO2 and soil fertility on isoprene emissions from Quercus robur 总被引:2,自引:0,他引:2
Malcolm Possell James Heath† C. Nicholas Hewitt Edward Ayres† Gerhard Kerstiens† 《Global Change Biology》2004,10(11):1835-1843
The effects of global change on the emission rates of isoprene from plants are not clear. A factor that can influence the response of isoprene emission to elevated CO2 concentrations is the availability of nutrients. Isoprene emission rate under standard conditions (leaf temperature: 30°C, photosynthetically active radiation (PAR): 1000 μmol photons m?2 s?1), photosynthesis, photosynthetic capacity, and leaf nitrogen (N) content were measured in Quercus robur grown in well‐ventilated greenhouses at ambient and elevated CO2 (ambient plus 300 ppm) and two different soil fertilities. The results show that elevated CO2 enhanced photosynthesis but leaf respiration rates were not affected by either the CO2 or nutrient treatments. Isoprene emission rates and photosynthetic capacity were found to decrease with elevated CO2, but an increase in nutrient availability had the converse effect. Leaf N content was significantly greater with increased nutrient availability, but unaffected by CO2. Isoprene emission rates measured under these conditions were strongly correlated with photosynthetic capacity across the range of different treatments. This suggests that the effects of CO2 and nutrient levels on allocation of carbon to isoprene production and emission under near‐saturating light largely depend on the effects on photosynthetic electron transport capacity. 相似文献