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1.
Picea asperata is a dominant species in the subalpine coniferous forests distributed in eastern edges of Tibetan Plateau and upper reaches
of the Yangtze River. The paper mainly identified the short-term influences of experimental warming, nitrogen fertilization,
and their combination on growth and physiological performances of Picea asperata seedlings. These seedlings were subjected to two levels of temperature (ambient; infrared heater warming) and two nitrogen
levels (0; 25 g m−2 a−1 N) for 6 months. We used a free air temperature increase of overhead infrared heater to raise both air and soil temperature
by 2.1 and 2.6°C, respectively. The temperature increment induced an obvious enhancement in biomass accumulation and the maximum
net photosynthetic rate, and decreased AOS and MDA level under ambient nitrogen conditions. Whereas, negative effects of experimental
warming on growth and physiology was observed under nitrogen fertilization condition. On the other hand, nitrogen fertilization
significantly improved plant growth in unwarmed plots, by stimulating total biomass, maximum net photosynthetic rate (A
max), antioxidant compounds, as well as reducing the content of AOS and MDA. However, in warmed plots, nitrogen addition clearly
decreased A
max, antioxidant compounds, and induced higher accumulation of AOS and MDA. Obviously, the beneficial effects of sole nitrogen
on growth and physiology of Picea asperata seedlings could not be magnified by artificial warming. 相似文献
2.
The response of photosynthetic model parameters to temperature and nitrogen concentration in Pinus radiata D. Don 总被引:5,自引:4,他引:1
A. S. WALCROFT D. WHITEHEAD W. B. SILVESTER F. M. KELLIHER 《Plant, cell & environment》1997,20(11):1338-1348
Responses of photosynthesis (A) to intercellular CO2 concentration (ci) in 2-year-old Pinus radiata D. Don seedlings were measured at a range of temperatures in order to parametrize a biophysical model of leaf photosynthesis. Increasing leaf temperature from 8 to 30°C caused a 4-fold increase in Vcmax, the maximum rate of carboxylation (10.7–43.3 μol m?2 s?1 and a 3-fold increase in Jmax, the maximum electron transport rate (20.5–60.2 μmol m ?2 s?1). The temperature optimum for Jmax was lower than that for Vcmax, causing a decline in the ratio Jmax:Vcmax from 2.0 to 1.4 as leaf temperature increased from 8 to 30°C. To determine the response of photosynthesis to leaf nitrogen concentration, additional measurements were made on seedlings grown under four nitrogen treatments. Foliar N concentrations varied between 0.36 and 1.27 mol kg?1, and there were linear relationships between N concentration and both Vcmax and Jmax. Measurements made throughout the crown of a plantation forest tree, where foliar N concentrations varied from 0.83 mol kg?1 near the base to 1.54 mol kg?1 near the leader, yielded similar relationships. These results will be useful in scaling carbon assimilation models from leaves to canopies. 相似文献
3.
Qing Liu Huajun Yin Jinsong Chen Chunzhang Zhao Xinying Cheng Yunyan Wei Bo Lin 《Ecological Research》2011,26(3):637-648
The impacts of global climatic change on belowground ecological processes of terrestrial ecosystems are still not clear. We
therefore conducted an experiment in the subalpine coniferous forest ecosystem of the eastern edges of the Tibetan Plateau
to study roots of Picea asperata seedlings and rhizosphere soil responses to soil warming and nitrogen availability from April 2007 to December 2008. The
seedlings were subjected to two levels of temperature (ambient; infrared heater warming) and two nitrogen levels (0 or 25 g m−2year−1 N). We used a free air temperature increase from an overhead infrared heater to raise both air and soil temperature by 2.1
and 2.6°C, respectively. The results showed that warming alone significantly increased total biomass, coarse root biomass
and fine root biomass of P. asperata seedlings. Both total biomass and fine root biomass were increased, but coarse root biomass was significantly decreased by
nitrogen fertilization and warming combined with nitrogen fertilization. Warming induced a prominent increase in soil organic
carbon (SOC) and NO3
−-N of rhizosphere soil, while nitrogen fertilization significantly decreased SOC and NH4
+-N of rhizosphere soil. The warming, fertilization and warming × N fertilization interaction decreased soil microbial C significantly,
but substantially increased soil microbial N. These results suggest that nitrogen deposition combined with warmer temperatures
under future climatic change possibly will have no effect on fine root production of P. asperata seedlings, but could enhance the nitrification process of their rhizosphere soils in subalpine coniferous forests. 相似文献
4.
Understanding the effects of nitrogen (N) fertilization on Miscanthus × giganteus greenhouse gas emissions, nitrate leaching, and biomass production is an important consideration when using this grass as a biomass feedstock. The objective of this study was to determine the effect of three N fertilization rates (0, 60, and 120?kg?N?ha?1 using urea as the N source) on nitrous oxide (N2O) and carbon dioxide (CO2) emissions, nitrogen leaching, and the biomass yields and N content of M. × giganteus planted in July 2008, and evaluated from 2009 through early 2011 in Urbana, Illinois, USA. While there was no biomass yield response to N fertilization rates in 2009 and 2010, the amount of N in the harvested biomass in 2010 was significantly greater at the 60 and 120?kg?N?ha?1?N rates. There was no significant CO2 emission response to N rates in 2009 or 2010. Similarly, N fertilization did not increase cumulative N2O emissions in 2009, but cumulative N2O emissions did increase in 2010 with N fertilization. During 2009, nitrate (NO 3 ? ) leaching at the 50-cm soil depth was not related to fertilization rate, but there was a significant increase in NO 3 ? leaching between the 0 and 120?kg?N?ha?1 treatments in 2010 (8.9 and 28.9?kg?NO3?CN?ha?1?year?1, respectively). Overall, N fertilization of M. × giganteus led to N2O releases, increased fluxes of inorganic N (primarily NO 3 ? ) through the soil profile; and increased harvested N without a significant increase in biomass production. 相似文献
5.
S. Shimoda 《Photosynthetica》2012,50(3):387-394
Photosynthetic parameters and leaf carbon isotope composition (??13C) in contrasting rice genotypes in relation to supplemental nitrogen (N) application and water management during the grain-filling period were compared. The changes in stomatal conductance (g s) and ratio of intercellular to ambient CO2 mole fraction (C i/C a) depended on the leaf nitrogen concentration (leaf N) in both ??Hinohikari?? (temperate japonica genotype) and ??IR36?? (indica genotype). In ??Hinohikari??, ??13C reflects photosynthetic gas exchange during the grain-filling period, which is indicated by the significant response of ??13C to leaf N. In contrast, in ??IR36?? ??13C did not depend on leaf N. This varietal difference in ??13C to leaf N can be attributed to a difference in the timing of leaf senescence. In ??IR36??, leaf N and photosynthetic parameters decreased more rapidly, indicating earlier senescence and a shorter grain-filling period in comparison with ??Hinohikari??. The significant increase in shoot dry mass in ??Hinohikari?? resulting from supplemental N application, compared with nonsignificant effect observed in ??IR36??, suggests that the timing of senescence in relation to the grainfilling period has a preponderant influence on productivity. 相似文献
6.
Sexual dimorphisms of dioecious plants are important in controlling and maintaining sex ratios under changing climate environments. Yet, little is known about sex-specific responses to elevated CO2 with soil nitrogen (N) deposition. To investigate sex-related physiological and biochemical responses to elevated CO2 with N deposition, Populus cathayana Rehd. was employed as a model species. The cuttings were subjected to two CO2 regimes (350 and 700???mol?mol?1) with two N levels (0 and 5?g?N?m?2?year?1). Our results showed that elevated CO2 and N deposition separately increased the total number of leaves, leaf area (LA), leaf mass, net photosynthetic rate (P n), light saturated photosynthetic rate (P max), chlorophyll a (Chl a), and chlorophyll a to chlorophyll b ratio (Chl a/b) in both males and females of P. cathayana. However, the effects on LA, leaf mass, P n, P max, Chl a and Chl a/b were weakened under the combined treatment of elevated CO2 and N deposition. Males had higher leaf mass, P n, P max, apparent quantum yield (??), carboxylation efficiency (CE), Chl a, Chl a/b, leaf N, and root carbon to N ratio (C/N) than did females under elevated CO2 with N deposition. In contrast to males, females had significantly higher levels of soluble sugars in leaves and greater starch accumulation in roots and stems under the same condition. The results of the present work imply that P. cathayana females are more responsive and suffer from greater negative effects on growth and photosynthetic capacity than do males when grown under elevated CO2 with soil N deposition. 相似文献
7.
Photosynthetic and gas exchange characteristics of dominant woody plants on a moisture gradient in an African savanna 总被引:4,自引:0,他引:4
Guy Franklin Midgley Julieta Nelida Aranibar† Khanyisa Brian Mantlana‡ Stephen Macko† 《Global Change Biology》2004,10(3):309-317
We determined key photosynthetic gas exchange parameters, and their temperature dependence, in dominant woody plants at four savanna sites on a moisture gradient in Botswana, southern Africa. Leaf stable carbon and nitrogen (N) isotope and morphological measures were made concurrently. Sampling of these predominantly non‐N‐fixing species took place during an exceptional rainfall season, representing near‐optimum conditions for primary production at these sites. The mean specific leaf area and leaf size were positively related to mean annual rainfall (MAR); species with larger leaves of lower density were more abundant in wetter sites. Almost all species at all sites showed high net light‐saturated photosynthetic rates (Amax?10 μmol CO2 m?2 s?1) due both to high CO2 carboxylation (Vc,max) and RubP‐regeneration capacity (Jmax). These high rates were associated with high values of leaf [N]. Across all sites, the temperature response of Amax showed no clear optimum, and a gradual drop from 25°C to 35°C, without notable temperature limitation at leaf temperatures in excess of 35°C. Dark respiration rate (Rday) across all species and sites increased exponentially with increasing leaf temperature. Species sampled at selected sites revealed a negative relationship between leaf δ13C (stable carbon isotope ratio) and MAR, suggesting higher leaf‐level water‐use efficiency at drier sites when integrated over the life of the leaf. At wetter sites, specific leaf [N] was lower and photosynthetic nitrogen‐use efficiency increased, a pattern reflected at the ecosystem level by less 15N enrichment of leaves at these sites. Taken together, the results suggest a switch from water‐use to nitrogen‐use efficiency constraints with increasing moisture availability. These constraints impact leaf form and function significantly, and may emerge at the ecosystem level in aspects of water and N cycling. 相似文献
8.
Ecophysiological responses of Abies fabri seedlings to drought stress and nitrogen supply 总被引:1,自引:0,他引:1
Jianying Guo Yan Yang Genxu Wang Liudong Yang Xiangyang Sun 《Physiologia plantarum》2010,139(4):335-347
Abies fabri (Mast.) Craib. (A. fabri) is an endemic and dominant species in typical subalpine dark coniferous forests distributed in mountainous regions of Western Sichuan, China. We investigated the ecophysiological responses of A. fabri seedlings to short‐term experimental drought, nitrogen supply and their interaction. Drought stress was created by excluding natural precipitation with automatically controlled plastic roof that covered the seedlings. Nitrogen fertilization was applied weekly by spraying over seedlings ammonium nitrate solution (50 kg N ha?1 year?1) during the growing season of 2009. The results showed that drought stress decreased leaf relative water content (RWC), whereas it caused marked increases in root mass ratio (RMR) and root/shoot mass ratio by 6.19 and 10.39%, respectively, as compared with the control. Drought stress increased malondialdehyde (MDA) content, electrolyte leakage, proline content, soluble sugars content and the activities of antioxidant enzymes, whereas nitrogen supply decreased MDA content, but enhanced activities of some antioxidant enzymes [especially peroxidase (POD)]. In the drought stressed plots, nitrogen supply increased RWC and decreased the content of MDA. The combination of drought stress and nitrogen supply also decreased the activities of antioxidant enzymes. These results indicated that the negative effects of drought stress on A. fabri seedlings might be alleviated by nitrogen supply. 相似文献
9.
In tropical mountains, trees are the dominant life form from sea level to above 4,000-m altitude under highly variable thermal conditions (range of mean annual temperatures: <8 to >28°C). How light-saturated net photosynthesis of tropical trees adapts to variation in temperature, atmospheric CO2 concentration, and further environmental factors, that change along elevation gradients, is not precisely known. With gas exchange measurements in mature trees, we determined light-saturated net photosynthesis at ambient temperature (T) and [CO2] (A sat) of 40 tree species from 21 families in tropical mountain forests at 1000-, 2000-, and 3000-m elevation in southern Ecuador. We tested the hypothesis that stand-level averages of A sat and leaf dark respiration (R D) per leaf area remain constant with elevation. Stand-level means of A sat were 8.8, 11.3, and 7.2?μmol?CO2?m?2?s?1; those of R D 0.8, 0.6, and 0.7?μmol?CO2?m?2?s?1 at 1000-, 2000-, and 3000-m elevation, respectively, with no significant altitudinal trend. We obtained coefficients of among-species variation in A sat and R D of 20–53% (n?=?10–16 tree species per stand). Examining our data in the context of a pan-tropical A sat data base for mature tropical trees (c. 170 species from 18 sites at variable elevation) revealed that area-based A sat decreases in tropical mountains by, on average, 1.3?μmol?CO2?m?2?s?1?per?km altitude increase (or by 0.2?μmol?CO2?m?2?s?1 per K temperature decrease). The A sat decrease occurred despite an increase in leaf mass per area with altitude. Local geological and soil fertility conditions and related foliar N and P concentrations considerably influenced the altitudinal A sat patterns. We conclude that elevation is an important influencing factor of the photosynthetic activity of tropical trees. Lowered A sat together with a reduced stand leaf area decrease canopy C gain with elevation in tropical mountains. 相似文献
10.
Fertilization commonly increases biomass production in loblolly pine (Pinus taeda L.). However, the sequence of short‐term physiological adjustments allowing for the establishment of leaf area and enhanced growth is not well understood. The effects of fertilization on photosynthetic parameters, root respiration, and growth for over 200 d following the application of diammonium phosphate were intensively investigated in an effort to establish a relative sequence of events associated with improved growth. Root respiration, foliar nitrogen concentration [N]f, and light‐saturated net photosynthesis (Asat) temporarily increased following fertilization. Asat was correlated positively with [N]f when non‐fertilized and fertilized treatments were pooled (R2 = 0.47). Increased photosynthetic capacity following fertilization was due to both improved photochemical efficiency and capacity and enhanced carboxylation capacity of Rubisco. Positive effects of fertilization on growth were observed shortly after Asat increased. Fertilized seedlings had 36.5% more leaf area and 36.5% greater total dry weight biomass at 211 d following fertilization. It is concluded that fertilization temporarily increased photosynthetic capacity, which resulted in a pool of photo‐assimilate used to build leaf area. The N from fertilizer initially invested in photosynthetic structures and enzymes probably re‐translocated to newly developing foliage, explaining the reduction in [N]f and Asat that was observed after peak levels were achieved following fertilization. 相似文献
11.
The ecophysiological linkage of leaf phosphorus (P) to photosynthetic capacity (A
max) and to the A
max–nitrogen relation remains poorly understood. To address this issue we compiled published and unpublished field data for mass-based
A
max, nitrogen (N) and P (n = 517 observations) from 314 species at 42 sites in 14 countries. Data were from four biomes: arctic, cold temperate, subtropical
(including Mediterranean), and tropical. We asked whether plants with low P levels have low A
max, a shallower slope of the A
max–N relationship, and whether these patterns have a geographic signature. On average, leaf P was substantially lower in the
two warmer than in the two colder biomes, with the reverse true for N:P ratios. The evidence indicates that the response of
A
max to leaf N is constrained by low leaf P. Using a full factorial model for all data, A
max was related to leaf N, but not to leaf P on its own, with a significant leaf N × leaf P interaction indicating that the
response of A
max to N increased with increasing leaf P. This was also found in analyses using one value per species per site, or by comparing
only angiosperms or only woody plants. Additionally, the slope of the A
max–N relationship was higher in the colder arctic and temperate than warmer tropical and subtropical biomes. Sorting data into
low, medium, and high leaf P groupings also showed that the A
max–N slope increases with leaf P. These analyses support claims that in P-limited ecosystems the A
max–N relationship may be constrained by low P, and are consistent with laboratory studies that show P-deficient plants have
limited ribulose-1,5-bisphosphate regeneration, a likely mechanism for the P influence upon the A
max–N relation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
12.
Assessing the influence of warming on leaf traits, carbon, and nutrient concentrations above and below ground to understand how the dominant sedge Kobresia pygmaea (C. B. Clarke) C. B. Clarke may respond and adapt to extant and future climate in the alpine meadow of the Qinghai-Tibetan Plateau. A warming experiment was conducted in the permafrost region of the Qinghai-Tibetan Plateau from 2008 to 2009. Two 2-year warming treatments (T1, annual warming of 2.1°C; T2, annual warming of 4.4°C) were used, and responses of leaf traits and above- and belowground carbon, nitrogen, and phosphorus concentrations of K. pygmaea were examined. The results show that both moderate (T1) and more extensive (T2) warming decreased leaf mass, leaf thickness, and vascular bundle size, and increased the mass-based photosynthetic rate (Amass) and photosynthetic nitrogen use efficiency (PNUE). A moderate warming significantly decreased leaf carbon (C), nitrogen (N), and phosphorus (P), and root C and N concentrations of K. pygmaea. These decreases were even more pronounced under the more extensive warming. The decreases in leaf N and P were significantly larger than the decrease in leaf C concentration. Root P concentration increased more under the extensive than the moderate warming. The observed increase in leaf C:N ratio in the warming treatment indicates that enhanced temperature may increase the long-term nitrogen use efficiency of K. pygmaea leaves. This again suggests that K. pygmaea might adapt well to future climate warming, and that nitrogen might be a more important factor for K. pygmaea dominated alpine meadows under future climate warming. 相似文献
13.
Effect of biochar amendment on maize yield and greenhouse gas emissions from a soil organic carbon poor calcareous loamy soil from Central China Plain 总被引:30,自引:0,他引:30
Afeng Zhang Yuming Liu Genxing Pan Qaiser Hussain Lianqing Li Jinwei Zheng Xuhui Zhang 《Plant and Soil》2012,351(1-2):263-275
Aims
A field experiment was conducted to investigate the effect of biochar on maize yield and greenhouse gases (GHGs) in a calcareous loamy soil poor in organic carbon from Henan, central great plain, China.Methods
Biochar was applied at rates of 0, 20 and 40?t?ha?1 with or without N fertilization. With N fertilization, urea was applied at 300?kg?N ha?1, of which 60% was applied as basal fertilizer and 40% as supplementary fertilizer during crop growth. Soil emissions of CO2, CH4 and N2O were monitored using closed chambers at 7?days intervals throughout the whole maize growing season (WMGS).Results
Biochar amendments significantly increased maize production but decreased GHGs. Maize yield was increased by 15.8% and 7.3% without N fertilization, and by 8.8% and 12.1% with N fertilization under biochar amendment at 20?t?ha?1 and 40?t?ha?1, respectively. Total N2O emission was decreased by 10.7% and by 41.8% under biochar amendment at 20?t?ha?1 and 40?t?ha?1 compared to no biochar amendment with N fertilization. The high rate of biochar (40?t?ha?1) increased the total CO2 emission by 12% without N fertilization. Overall, biochar amendments of 20?t?ha?1 and 40?t?ha?1 decreased the total global warming potential (GWP) of CH4 and N2O by 9.8% and by 41.5% without N fertilization, and by 23.8% and 47.6% with N fertilization, respectively. Biochar amendments also decreased soil bulk density and increased soil total N contents but had no effect on soil mineral N.Conclusions
These results suggest that application of biochar to calcareous and infertile dry croplands poor in soil organic carbon will enhance crop productivity and reduce GHGs emissions. 相似文献14.
Abstract Net nitrate uptake rates were measured and the kinetics calculated in non-nodulated Pisum sativum L. cv. Marma and Lemna gibba L. adapted to constant relative rates of nitrate-N additions (RA), ranging from 0.03 to 0.27 d?1 for Pisum and from 0.05 to 0.40 d?1 for Lemna, Vmax of net nitrate uptake (measured in the range 10 to 100 mmol m?3 nitrate, i.e. ‘system I’) increased with RA in the growth limiting range but decreased when RA exceeded the relative growth rate (RGR), Km was not significantly related to changes in RA. On the basis of previous 13N-flux experiments, it is concluded that the differences in Vmax at growth limiting RA are attributable to differences in influx rates. Linear relationships between Vmax and tissue nitrogen concentrations were obtained in the growth limiting range for both species, and extrapolated intercepts relate well with the previously defined minimal nitrogen concentrations for plant growth (Oscarson, Ingemarsson & Larsson, 1989). Analysis of Vmax for net nitrate uptake on intact plant basis in relation to nitrogen demand during stable, nitrogen limited, growth shows an increased overcapacity at lower RA values in both species, which is largely explained by the increased relative root size at low RA. A balancing nitrate concentration, defined as the steady state concentration needed to sustain the relative rate of increase in plant nitrogen (RN), predicted by RA, was calculated for both species. In the growth limiting range, this value ranges from 3.5 mmol m?3 (RA 0.03 d?1) to 44 mmol m?3 (RA 0.21 d?1) for Pisum and from 0.2 mmol m?3 (RA 0.05 d?1) to 5.4 mmol m?3 (RA 0.03 d?1) for Lemna. It is suggested that this value can be used as a unifying measure of the affinity for nitrate, integrating the performance of the nitrate uptake system with nitrate flux and long term growth and demand for nitrogen. 相似文献
15.
《Saudi Journal of Biological Sciences》2022,29(4):2238-2246
Spinach (Spinacia oleracea L.) is considered a nitrogen (N) intensive plant with high nitrate (NO3?) accumulation in its leaves. The current study via a two-year field trial introduced an approach by combining N fertilization from different sources (e.g., ammonium nitrate; 33.5 % N, and urea; 48 % N) at different rates (180, and 360 kg N ha?1) with the foliar spraying of molybdenum (Mo) as sodium molybdate, and/or manganese (Mn) as manganese sulphate at rates of 50 and 100 mgL?1 of each or with a mixture of Mo and Mn at rates of 50 and 50 mg L?1, respectively on growth, chemical constituents, and NO3? accumulation in spinach leaves. Our findings revealed that the highest rate of N fertilization (360 kg N ha?1) significantly increased most of the measured parameters e.g., plant length, fresh and dry weight plant?1, number of leaves plant?1, leaf area plant?1, leaf pigments (chlorophyll a, b and carotenoids), nutrients (N, P, K, Fe, Mn, Zn), total soluble carbohydrates, protein content, net assimilation rate, and NO3? accumulation, but decreased leaf area ratio and relative growth rate. Moreover, plants received urea-N fertilizer gave the highest values of all previous attributes when compared with ammonium nitrate –N fertilizers, and the lowest values of NO3? accumulation. The co-fertilization of N-Mo-Mn gave the highest values in all studied attributes and the lowest NO3? accumulation. The best treatment was recorded under the treatment of 360 kg N-urea ha?1 in parallel with the combined foliar application of Mo and Mn (50 + 50 mg L?1). Our findings proposed that the co-fertilization of N-Mo-Mn could enhance spinach yield and its quality, while reducing NO3? accumulation in leaves, resulting agronomical, environmental and economic benefits. 相似文献
16.
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
17.
The effects of varying nitrogen supply on canopy leaf area, response of leaf net photosynthesis (An) to quantum flux density (Q), and fruit yields of kiwifruit vines (Actinidia deliciosa var. deliciosa) were examined in a two-year field experiment. Vines were grown with 0, 250 or 750 kg N ha?1 year?1. The responses to nitrogen supply were compared with responses to shade, to examine the impact of reduced carbon assimilation on canopy leaf area and fruit yields. Nitrogen supply did not affect significantly any of the measured variables during the first season of the experiment. In the second season, canopy leaf area was reduced significantly where nitrogen supply was limited. The quantum efficiency of photosynthesis (φq) increased from 0. 03 mol CO2 mol?1 Q soon after leaf emergence to more than 0. 05 mol CO2 mol?1 Q during the middle of the growing season. The quantum saturated rate of An (Asat) also increased during the season, from 7–10 μmol CO2 m?2 s?1 soon after leaf emergence, to 15–20 (μmol CO2 m?2 s?1 during the middle of the growing season. φq and Asat increased significantly with nitrogen supply at all measurement times during the second season. For vines with high nitrogen, fruit yields in both seasons were similar, averaging 3. 05 kg m?2. Fruit yields in the second season were reduced significantly where nitrogen supply was limited, due to reduced fruit numbers. The relative effects of reduced leaf area and reduced leaf photosynthesis for carbon assimilation by nitrogen deficient vines were examined using a mathematical model of canopy photosynthesis for kiwifruit vines. Simulations of canopy photosynthesis indicated that effects on leaf area and on leaf photosynthesis were of similar importance in the overall effects of nitrogen deficiency on carbon assimilation. The effects of nitrogen supply on fruit numbers (i. e. flower development) preceded the measured effects on carbon assimilation, indicating that the nitrogen supply affected carbon partitioning to reserves in the first season. 相似文献
18.
Christopher E. Doughty 《Biotropica》2011,43(6):658-665
Leaves and branches of mature trees, lianas, and gap species were warmed in an Amazonian forest for 4 mo to observe the effect of warming on photosynthesis, stomatal conductance, and transpiration. Electric resistance heaters increased air temperatures near the leaves by approximately 2°C. Sunlit leaf temperatures increased by 2–3°C on average, but during some periods leaf temperatures increased by >5°C. Maximum photosynthesis (Amax) decreased significantly in the warmed leaves vs. the control leaves over the 13‐wk study period with an average decrease in Amax of 1.4 μmol/m2s (19% decrease from a mean Amax of 7.2 μmol/m2s) when measured at 30°C and there were no signs of acclimation to higher temperatures within existing leaves. The decline in Amax was likely due to irreversible temperature damage caused by very high leaf temperatures and not due to Ci limitation of carboxylation. Warming had a larger negative impact on Amax in canopy level tree species than other tested functional groups such as lianas or gap species. Transpiration did not significantly increase in the warmed leaves compared with the control group. This study indicates that increased temperatures due to global warming could potentially decrease future tropical forest carbon uptake by a significant amount. Abstract in Portuguese is available at http://www.blackwell‐synergy.com/loi/btp . 相似文献
19.
Dan Wang Mathew W. Maughan Jindong Sun Xiaohui Feng Fernando Miguez DoKyoung Lee Michael C. Dietze 《Global Change Biology Bioenergy》2012,4(6):688-697
Nitrogen (N) addition typically increases overall plant growth, but the nature of this response depends upon patterns of plant nitrogen allocation that vary throughout the growing season and depend upon canopy position. In this study seasonal variations in leaf traits were investigated across a canopy profile in Miscanthus (Miscanthus × giganteus) under two N treatments (0 and 224 kg ha?1) to determine whether the growth response of Miscanthus to N fertilization was related to the response of photosynthetic capacity and nitrogen allocation. Miscanthus yielded 24.1 Mg ha?1 in fertilized plots, a 40% increase compared to control plots. Photosynthetic properties, such as net photosynthesis (A), maximum rate of rubisco carboxylation (Vcmax), stomatal conductance (gs) and PSII efficiency (Fv'/Fm'), all decreased significantly from the top of the canopy to the bottom, but were not affected by N fertilization. N fertilization increased specific leaf area (SLA) and leaf area index (LAI). Leaf N concentration in different canopy layers was increased by N fertilization and the distribution of N concentration within canopy followed irradiance gradients. These results show that the positive effect of N fertilization on the yield of Miscanthus was unrelated to changes in photosynthetic rates but was achieved mainly by increased canopy leaf area. Vertical measurements through the canopy demonstrated that Miscanthus adapted to the light environment by adjusting leaf morphological and biochemical properties independent of nitrogen treatments. GPP estimated using big leaf and multilayer models varied considerably, suggesting a multilayer model in which Vcmax changes both through time and canopy layer could be adopted into agricultural models to more accurately predict biomass production in biomass crop ecosystems. 相似文献