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1.
Shin-Ichiro Katahata Masaaki Naramoto Yoshitaka Kakubari Yuzuru Mukai 《Trees - Structure and Function》2007,21(6):619-629
Seasonal changes in photosynthetic capacity, leaf nitrogen (N) content, leaf chlorophyll (Chl) content and leaf N allocation
patterns in leaves of different ages in the evergreen understory shrub, Daphniphyllum
humile Maxim, growing at a forest border and an understory site were studied. In current-year leaves at the understory site, the
N and Rubisco contents increased from spring to autumn although their light-saturated photosynthetic rate at 22°C (P
max22) remained stable, indicating that their mesophyll conductance rates declined as they completed their development and/or that
they invested increasing amounts of their resources in photosynthetic enzymes during this period. In contrast, seasonal changes
in P
max22 in current-year leaves at the forest border site were correlated with changes in Rubisco content. In 1-year old leaves at
the understory site, P
max22 and contents of Chl, leaf N, and Rubisco remained stable from spring to autumn, while these parameters decreased in 1-year-old
forest border leaves, indicating that N may have been remobilized from shaded 1-year-old leaves to sunlit current-year leaves.
When leaves senesced at the forest border site the Rubisco content decreased more rapidly than that of light-harvesting proteins
such as LHCII, suggesting that N remobilization from Rubisco may be more efficient, possibly because Rubisco has greater N
costs and is soluble, whereas the light-harvesting proteins are membrane components. 相似文献
2.
A. LAISK H. EICHELMANN V. OJA B. RASULOV E. PADU I. BICHELE H. PETTAI & O. KULL 《Plant, cell & environment》2005,28(3):375-388
The present study was performed to investigate the adjustment of the rate parameters of the light and dark reactions of photosynthesis to the natural growth light in leaves of an overstorey species, Betula pendula Roth, a subcanopy species, Tilia cordata P. Mill., and a herb, Solidago virgaurea L., growing in a natural plant community in Järvselja, Estonia. Shoots were collected from the site and individual leaves were measured in a laboratory applying a standardized routine of kinetic gas exchange, Chl fluorescence and 820 nm transmittance measurements. These measurements enabled the calculations of the quantum yield of photosynthesis and rate constants of excitation capture by photochemical and non-photochemical quenchers, rate constant for P700+ reduction via the cytochrome b6f complex with and without photosynthetic control, actual maximum and potential (uncoupled) electron transport rate, stomatal and mesophyll resistances for CO2 transport, Km(CO2) and Vm of ribulose-bisphosphate carboxylase-oxygenase (Rubisco) in vivo. In parallel, N, Chl and Rubisco contents were measured from the same leaves. No adjustment toward higher quantum yield in shade compared with sun leaves was observed, although relatively more N was partitioned to the light-harvesting machinery in shade leaves ( H. Eichelmann et al., 2004 ). The electron transport rate through the Cyt b6f complex was strongly down-regulated under saturating light compared with darkness, and this was observed under atmospheric, as well as saturating CO2 concentration. In vivo Vm measurements of Rubisco were lower than corresponding reported measurements in vitro, and the kcat per reaction site varied widely between leaves and growth sites. The correlation between Rubisco Vm and the photosystem I density was stronger than between Vm and the density of Rubisco active sites. The results showed that the capacity of the photosynthetic machinery decreases in shade-adjusted leaves, but it still remains in excess of the actual photosynthetic rate. The photosynthetic control systems that are targeted to adjust the photosynthetic rate to meet the plant's needs and to balance the partial reactions of photosynthesis, down-regulate partial processes of photosynthesis: excess harvested light is quenched non-photochemically; excess electron transport capacity of Cyt b6f is down-regulated by ΔpH-dependent photosynthetic control; Rubisco is synthesized in excess, and the number of activated Rubisco molecules is controlled by photosystem I-related processes. Consequently, the nitrogen contained in the components of the photosynthetic machinery is not used at full efficiency. The strong correlation between leaf nitrogen and photosynthetic performance is not due to the nitrogen requirements of the photosynthetic apparatus, but because a certain amount of energy must be captured through photosynthesis to maintain this nitrogen within a leaf. 相似文献
3.
Analysis of differences in photosynthetic nitrogen use efficiency of alpine and lowland Poa species 总被引:1,自引:0,他引:1
This study investigates factors determining variation in photosynthetic nitrogen use efficiency (φN) in seven slow- and fast-growing Poa species from altitudinally contrasting sites. The species and their environmental origin were (in order of increasing relative
growth rate): two alpine (Poa fawcettiae and P. costiniana), one sub-alpine (P. alpina) and three temperate lowland perennials (P. pratensis, P. compressa and P. trivialis), as well as one temperate lowland annual (P. annua). Plants were grown hydroponically under identical conditions with free access to nutrients in a growth room. Photosynthesis
per unit leaf area measured at growth irradiance (500 μmol m−2 s−1) was slightly higher in the slow-growing alpine species. At saturating light intensities, photosynthesis was considerably
higher in the alpine species than in the lowland species. Carboxylation capacity and Rubisco content per unit leaf area were
also greater in the alpine species. Despite variation between the species, the in vivo specific activity of Rubisco showed
little relationship to relative growth rate or photosynthetic rate. Both at light saturation and at the growth irradiance,
φN was lowest in the slow-growing alpine species P. fawcettiae, P. costiniana and P. alpina, and highest in the fast-growing P. compressa and P. annua. The proportion of leaf nitrogen that was allocated to photosynthetic capacity and the in vivo catalytic constant of Rubisco
accounted for most of the variation in φN at light saturation. Minor variations in intercellular CO2 partial pressure also contributed to some extent to the variations in φN at light saturation. The low φN values at growth irradiance exhibited by the alpine species were additionally due to a lower percentage utilisation of their
high photosynthetic capacity compared to the lowland species.
Received: 28 May 1998 / Accepted: 28 March 1999 相似文献
4.
Changes in leaf photosynthetic parameters with leaf position and nitrogen content within a rose plant canopy (Rosa hybrida) 总被引:6,自引:2,他引:4
This paper deals with changes in leaf photosynthetic capacity with depth in a rose (Rosa hybrida cv. Sonia) plant canopy. Measurements of leaf net CO2 assimilation (Al) and total nitrogen content (Nl) were performed in autumn under greenhouse conditions on mature leaves located at different layers within the plant canopy, including the flower stems and the main shoots. These leaves were subjected (i) to contrasting levels of CO2 partial pressure (pa) at saturating photosynthetic photon flux density (I about 1000 μ mol m ? 2 s ? 1) and (ii) to saturating CO2 partial pressure (pa about 100 Pa) and varying I, while conditions of temperature were those prevailing in the greenhouse (20–38 °C). A biochemical model of leaf photosynthesis relating Al to intercellular CO2 partial pressure (pi) was parameterized for each layer of leaves, supplying corresponding values of the photosynthetic Rubisco capacity (Vlm) and the maximum rate of electron transport (Jm). The results indicated that rose leaves growing at the top of the canopy had higher values of Jm and Vlm, which resulted from a higher allocation of nitrogen to the uppermost leaves. Mean values of total leaf nitrogen, Nl, decreased about 35% from the uppermost leaves of flower stem to leaves growing at the bottom of the plant. The derived values of non‐photosynthetic nitrogen, Nb, varied from 76 mmolN m ? 2leaf (layer 1) to 60 mmolN m ? 2leaf (layer 4), representing a large fraction of Nl (50 and 60% in layer 1 and 4, respectively). Comparison of leaf photosynthetic nitrogen (Np = Nl–Nb) and I profiles supports the hypothesis that rose leaves acclimate to the time‐integrated absorbed I. The relationships between I and Np, obtained during autumn, spring and summer, indicate that rose leaves seem also to acclimate their photosynthetic capacity seasonally, by allocating more photosynthetic nitrogen to leaves in autumn and spring than in summer. 相似文献
5.
Lucia R. Dillenburg Alan H. Teramura Irwin N. Forseth Dennis F. Whigham 《American journal of botany》1995,82(4):454-461
This 2-year field study examined stomatal conductance, photosynthesis, and biomass allocation of Liquidambar styraciflua saplings in response to below- and aboveground competition with the vines Lonicera japonica and Parthenocissus quinquefolia. Vine competition did not affect stomatal conductance of the host trees. The leaf photosynthetic capacity and photosynthetic nitrogen-use efficiency were significantly reduced by root competition with vines, either singly or in combination with aboveground competition, early in the second growing season. However, such differences disappeared by the end of the second growing season. Trees competing below ground with vines also had lower allocation to leaves compared with steins. Aboveground competition with vines resulted in reduced photosynthetic capacity per unit leaf area, but not per unit leaf weight, in trees. No correlation was found between single leaf photosynthetic capacity and tree growth. In contrast, a high positive correlation existed between allocation to leaves and diameter growth. Results from this study suggest that allocation patterns are more affected than leaf photosynthesis in trees competing with vines. 相似文献
6.
夜间变暖提高荫香叶片的光合能力 总被引:3,自引:0,他引:3
研究了不同氮供应的条件下夜间变暖对荫香叶片光合能力的影响。当植株生长在相同的日间温度(25℃),而夜间温度从18℃增至20℃时,叶片的光合速率增高(p<0.05)。高氮供应的植株,夜间变暖下其叶片光合速率较低氮供应的高,氮供应增高能促进夜间变暖提高叶片光合速率的效应。在低氮供给和夜间变暖下,植株叶片的光下呼吸和暗呼吸的增高显著(p<0.05)。无论在高氮或低氮供应下,生长在夜间变暖下的植物,其叶片的R ub isco最大羧化速率(Vcm ax)和光合电子传递最大速率(Jm ax)增高(p<0.05),氮供应能增强夜间变暖对Vcm ax和Jm ax的正向效应。夜间变暖降低植株叶片的比叶重,而增加单位叶干重的氮含量(Nm),单位叶面积的氮含量(Na)没发生明显变化。随着全球气候变化,夜间趋暖将有利于树木叶片光合能力的提高,结合高氮供给将会明显地增高植物的碳固定。 相似文献
7.
Involvement of nitrogen and cytokinins in photosynthetic acclimation to elevated CO2 of spring wheat
Diego Gutiérrez Rosa Morcuende Alejandro Del Pozo Rafael Martínez-Carrasco Pilar Pérez 《Journal of plant physiology》2013
Acclimation of photosynthetic capacity to elevated CO2 involves a decrease of the leaf Rubisco content. In the present study, it was hypothesized that nitrogen uptake and partitioning within the leaf and among different aboveground organs affects the down-regulation of Rubisco. Given the interdependence of nitrogen and cytokinin signals at the whole plant level, it is also proposed that cytokinins affect the nitrogen economy of plants under elevated CO2, and therefore the acclimatory responses. Spring wheat received varying levels of nitrogen and cytokinin in field chambers with ambient (370 μmol mol−1) or elevated (700 μmol mol−1) atmospheric CO2. Gas exchange, Rubisco, soluble protein and nitrogen contents were determined in the top three leaves in the canopy, together with total nitrogen contents per shoot. Growth in elevated CO2 induced decreases in photosynthetic capacity only when nitrogen supply was low. However, the leaf contents of Rubisco, soluble protein and total nitrogen on an area basis declined in elevated CO2 regardless of nitrogen supply. Total nitrogen in the shoot was no lower in elevated than ambient CO2, but the fraction of this nitrogen located in flag and penultimate leaves was lower in elevated CO2. Decreased Rubisco: chlorophyll ratios accompanied losses of leaf Rubisco with CO2 enrichment. Cytokinin applications increased nitrogen content in all leaves and nitrogen allocation to senescing leaves, but decreased Rubisco contents in flag leaves at anthesis and in all leaves 20 days later, together with the amount of Rubisco relative to soluble protein in all leaves at both growth stages. The results suggest that down regulation of Rubisco in leaves at elevated CO2 is linked with decreased allocation of nitrogen to the younger leaves and that cytokinins cause a fractional decrease of Rubisco and therefore do not alleviate acclimation to elevated CO2. 相似文献
8.
Seasonal response of photosynthesis to elevated CO2 in loblolly pine (Pinus taeda L.) over two growing seasons 总被引:1,自引:0,他引:1
Trees growing in natural systems undergo seasonal changes in environmental factors that generate seasonal differences in net photosynthetic rates. To examine how seasonal changes in the environment affect the response of net photosynthetic rates to elevated CO2, we grew Pinus taeda L. seedlings for three growing seasons in open-top chambers continuously maintained at either ambient or ambient + 30 Pa CO2. Seedlings were grown in the ground, under natural conditions of light, temperature nd nutrient and water availability. Photosynthetic capacity was measured bimonthly using net photosynthetic rate vs. intercellular CO2 partial pressure (A-Ci) curves. Maximum Rubisco activity (Vcmax) and ribulose 1,5-bisphosphate regeneration capacity mediated by electron transport (Jmax) and phosphate regeneration (PiRC) were calculated from A-Ci curves using a biochemically based model. Rubisco activity, activation state and content, and leaf carbohydrate, chlorophyll and nitrogen concentrations were measured concurrently with photosynthesis measurements. This paper presents results from the second and third years of treatment. Mean leaf nitrogen concentrations ranged from 13.7 to 23.8 mg g?1, indicating that seedlings were not nitrogen deficient. Relative to ambient CO2 seedlings, elevated CO2 increased light-saturated net photosynthetic rates 60–110% during the summer, but < 30% during the winter. A relatively strong correlation between leaf temperature and the relative response of net photosynthetic rates to elevated CO2 suggests a strong effect of leaf temperature. During the third growing season, elevated CO2 reduced Rubisco activity 30% relative to ambient CO2 seedlings, nearly completely balancing Rubisco and RuBP-regeneration regulation of photosynthesis. However, reductions in Rubisco activity did not eliminate the seasonal pattern in the relative response of net photosynthetic rates to elevated CO2. These results indicate that seasonal differences in the relative response of net photosynthetic rates to elevated CO2 are likely to occur in natural systems. 相似文献
9.
Background and Aims
Understorey evergreen species commonly have a higher leaf nitrogen content in winter than in summer. Tested here is a hypothesis that such changes in leaf nitrogen content maximize nitrogen-use efficiency, defined as the daily carbon gain per unit nitrogen, under given temperature and irradiance levels.Methods
The evergreen shrub Aucuba japonica growing naturally at three sites with different irradiance regimes in Japan was studied. Leaf photosynthetic characteristics, Rubisco and leaf nitrogen with measurements of temperature and irradiance monthly at each site were determined. Daily carbon gain was determined as a function of leaf nitrogen content to calculate the optimal leaf nitrogen content that maximized daily nitrogen-use efficiency.Key Results
As is known, the optimal leaf nitrogen content increased with increasing irradiance. The optimal leaf nitrogen content also increased with decreasing temperature because the photosynthetic capacity per Rubisco decreased. Across sites and months, the optimal leaf nitrogen content was close to the actual leaf nitrogen content and explained the variation in actual leaf nitrogen by 64 %. Sensitivity analysis showed that the effect of temperature on optimal nitrogen content was similar in magnitude to that of irradiance.Conclusions
Understorey evergreen species regulate leaf nitrogen content so as to maximize nitrogen-use efficiency in daily carbon gain under changing irradiance and temperature conditions. 相似文献10.
Non-destructive and rapid method for assessment of leaf photosynthetic characteristics is needed to support photosynthesis
modelling and growth monitoring in crop plants. We determined the quantitative relationships between leaf photosynthetic characteristics
and canopy spectral reflectance under different water supply and nitrogen application rates. The responses of reflectance
at red radiation (wavelength 680 nm) to different water contents and nitrogen rates were parallel to those of leaf net photosynthetic
rate (P
N). The relationships of reflectance at 680 nm and ratio index of R(810,680) (near infrared/red, NIR/R) to P
N of different leaf positions and leaf layers in rice indicated that the top two full leaves were the best leaf positions for
quantitative monitoring of leaf P
N with remote sensing technique, and the ratio index R(810,680) was the best ratio index for evaluating leaf photosynthetic
characteristics in rice. Testing of the models with independent data sets indicated that R(810,680) could well estimate P
N of top two leaves and canopy leaf photosynthetic potential in rice, with the root mean square error of 0.25, 0.16, and 4.38,
respectively. Hence R(810,680) can be used to monitor leaf photosynthetic characteristics at different growth stages of rice
under diverse growing conditions. 相似文献
11.
The present study was undertaken to test for the hypothesis that the rate of development in the capacity for photosynthetic electron transport per unit area (Jmax;A), and maximum carboxylase activity of Rubisco (Vcmax;A) is proportional to average integrated daily quantum flux density (Qint) in a mixed deciduous forest dominated by the shade‐intolerant species Populus tremula L., and the shade‐tolerant species Tilia cordata Mill. We distinguished between the age‐dependent changes in net assimilation rates due to modifications in leaf dry mass per unit area (MA), foliar nitrogen content per unit dry mass (NM), and fractional partitioning of foliar nitrogen in the proteins of photosynthetic electron transport (FB), Rubisco (FR) and in light‐harvesting chlorophyll‐protein complexes (Vcmax;A ∝ MANMFR; Jmax;A ∝ MANMFB). In both species, increases in Jmax;A and Vcmax;A during leaf development were primarily determined by nitrogen allocation to growing leaves, increases in leaf nitrogen partitioning in photosynthetic machinery, and increases in MA. Canopy differences in the rate of development of leaf photosynthetic capacity were mainly controlled by the rate of change in MA. There was only small within‐canopy variation in the initial rate of biomass accumulation per unit Qint (slope of MA versus leaf age relationship per unit Qint), suggesting that canopy differences in the rate of development of Jmax;A and Vcmax;A are directly proportional to Qint. Nevertheless, MA, nitrogen, Jmax;A and Vcmax;A of mature leaves were not proportional to Qint because of a finite MA in leaves immediately after bud‐burst (light‐independent component of MA). MA, leaf chlorophyll contents and chlorophyll : N ratio of mature leaves were best correlated with the integrated average quantum flux density during leaf development, suggesting that foliar photosynthetic apparatus, once developed, is not affected by day‐to‐day fluctuations in Qint. However, for the upper canopy leaves of P. tremula and for the entire canopy of T. cordata, there was a continuous decline in N contents per unit dry mass in mature non‐senescent leaves on the order of 15–20% for a change of leaf age from 40 to 120 d, possibly manifesting nitrogen reallocation to bud formation. The decline in N contents led to similar decreases in leaf photosynthetic capacity and foliar chlorophyll contents. These data demonstrate that light‐dependent variation in the rate of developmental changes in MA determines canopy differences in photosynthetic capacity, whereas foliar photosynthetic apparatus is essentially constant in fully developed leaves. 相似文献
12.
The objectives of this work using Phaseolus vulgaris were to examine whether the light spectrum incident on mature primary leaves (PLs) is related to leaf‐to‐leaf systemic regulation of developing trifoliate leaves (TLs) in photosynthetic characteristics, and to investigate the relative importance of spectrum and photosynthetic photon flux density (PPFD) in light‐induced systemic regulation. Systemic regulation was induced by altering PPFD and the spectrum of light incident on PLs using a shading treatment and lighting treatments including either white, blue, green or red light‐emitting diodes (LEDs). Photosynthetic characteristics were evaluated by measuring the light‐limited and light‐saturated net photosynthetic rates and the amounts of nitrogen (N), chlorophyll (Chl) and ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39). Shading treatment on PLs decreased the amounts of N, Chl and Rubisco of TLs and tended to decrease the photosynthetic rates. However, we observed no systemic effects induced by the light spectrum on PLs in this study, except that a higher amount of Rubisco of TLs was observed when the PLs were irradiated with blue LEDs. Our results imply that photoreceptors in mature leaves have little influence on photosynthetic rates and amounts of N and Chl of developing leaves through systemic regulation, although the possibility of the action of blue light irradiation on the amount of Rubisco cannot be ruled out. Based on these results, we concluded that the light spectrum incident on mature leaves has little systemic effect on developing leaves in terms of photosynthetic characteristics and that the light‐induced systemic regulation was largely accounted for by PPFD. 相似文献
13.
Leaf senescence of Quercus myrtifolia as affected by long-term CO2 enrichment in its native environment 总被引:1,自引:0,他引:1
J. -H. Li P. Dijkstra § G. J. Hymus § R. M. Wheeler † W. C. Piastuch ‡ C. R. Hinkle‡ B. G. Drake§ 《Global Change Biology》2000,6(7):727-733
The long‐term effects of elevated (ambient plus 350 μmol mol?1) atmospheric CO2 concentration (Ca) on the leaf senescence of Quercus myrtifolia Willd was studied in a scrub‐oak community during the transition from autumn (December 1997) to spring (April 1998). Plants were grown in large open‐top chambers at the Smithsonian CO2 Research Site, Merritt Island Wildlife Refuge, Cape Canaveral, Florida. Chlorophyll (a + b) concentration, Rubisco activity and N concentration decreased by 75%, 82%, and 52%, respectively, from December (1997) to April (1998) in the leaves grown at ambient Ca. In contrast, the leaves of plants grown at elevated Ca showed no significant decrease in chlorophyll (a + b) concentration or Rubisco activity, and only a 25% reduction in nitrogen. These results indicate that leaf senescence was delayed during this period at elevated Ca. Delayed leaf senescence in elevated Ca had important consequences for leaf photosynthesis. In elevated Ca the net photosynthetic rate of leaves that flushed in Spring 1997 (last year's leaves) and were 13 months old was not different from fully‐expanded leaves that flushed in 1998, and were approximately 1 month old (current year's leaves). In ambient Ca the net photosynthetic rate of last year's leaves was 54% lower than for current year's leaves. When leaves were fully senesced, nitrogen concentration decreased to about 40% of the concentration in non‐senesced leaves, in both CO2 treatments. In April, net photosynthesis was 97% greater in leaves grown in elevated Ca than in those grown at ambient. During the period when elevated Ca delayed leaf senescence, more leaves operating at higher photosynthetic rate would allow the ecosystem dominated by Q. myrtifolia to gain more carbon at elevated Ca than at ambient Ca. 相似文献
14.
苗圃科学施氮(N)作为提高苗木N贮存水平与质量的核心手段,能否提高干旱立地苗木造林效果仍存在争议;N贮存水平与干旱如何协同作用影响叶片光合N分配及苗木生物量积累尚不明确。阐明上述问题,能够为干旱立地下的森林植被恢复以及造林苗木科学精准施N提供科学依据。选择栓皮栎(Quercus variabilis Blume)为研究对象,对一年生苗木设置2个苗圃木质化期N加载水平(0、24 mg N/株),翌年春苗木移栽后设置2个灌溉水平(85%、40%田间持水量),取样测定苗木生物量、叶片N、叶绿素与脯氨酸水平、以及气体交换参数,计算光合N分配及光合N利用效率(PNUE)。结果表明,叶片发育完成后,干旱抑制N向光合系统分配,但N加载处理提高了干旱下的光合N含量,从而在一定程度上抵消干旱对生物量积累的抑制;无N加载苗木则向光合系统投入更少的N,而提高脯氨酸水平,生物量积累受抑制更为显著。无N加载苗木在遭受干旱后将N向羧化组分分配,而N加载苗木遭遇干旱后则显著抑制叶片将N向羧化系统以及电子传递系统分配,捕光组分N的分配则不受植物体内N贮存或外部水分状况的影响,栓皮栎苗木通过调整不同功能组分光合N含量和... 相似文献
15.
Plants grown at elevated CO2 often acclimate such that their photosynthetic capacities are reduced relative to ambient CO2-grown plants. Reductions in synthesis of photosynthetic enzymes could result either from reduced photosynthetic gene expression or from reduced availability of nitrogen-containing substrates for enzyme synthesis. Increased carbohydrate concentrations resulting from increased photosynthetic carbon fixation at elevated CO2 concentrations have been suggested to reduce the expression of photosynthetic genes. However, recent studies have also suggested that nitrogen uptake may be depressed by elevated CO2, or at least that it is not increased enough to keep pace with increased carbohydrate production. This response could induce a nitrogen limitation in elevated-CO2 plants that might account for the reduction in photosynthetic enzyme synthesis. If CO2 acclimation were a response to limited nitrogen uptake, the effects of elevated CO2 and limiting nitrogen supply on photosynthesis and nitrogen allocation should be similar. To test this hypothesis we grew non-nodulating soybeans at two levels each of nitrogen and CO2 concentration and measured leaf nitrogen contents, photosynthetic capacities and Rubisco contents. Both low nitrogen and elevated CO2 reduced nitrogen as a percentage of total leaf dry mass but only low nitrogen supply produced significant decreases in nitrogen as a percentage of leaf structural dry mass. The primary effect of elevated CO2 was to increase non-structural carbohydrate storage rather than to decrease nitrogen content. Both low nitrogen supply and elevated CO2 also decreased carboxylation capacity (Vcmax) and Rubisco content per unit leaf area. However, when Vcmax and Rubisco content were expressed per unit nitrogen, low nitrogen supply generally caused them to increase whereas elevated CO2 generally caused them to decrease. Finally, elevated CO2 significantly increased the ratio of RuBP regeneration capacity to Vcmax whereas neither nitrogen supply nor plant age had a significant effect on this parameter. We conclude that reductions in photosynthetic enzyme synthesis in elevated CO2 appear not to result from limited nitrogen supply but instead may result from feedback inhibition by increased carbohydrate contents. 相似文献
16.
E. Ögren 《Photosynthesis research》1988,18(3):263-275
The response to drought was compared for willow plants of optimal leaf nitrogen content (100 N) and those of 86% of this content (86 N). Gas exchange measurements revealed that the carboxylation efficiency (CE) of photosynthesis was more sensitive to drought than the photosynthetic capacity in both N regimes. Since the leaf content of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was found to be much more resistant it is suggested that a decreased specific activity of Rubisco underlies the decreased CE. Although the rate of water consumption was the same for 86 N and 100 N plants the photosynthetic apparatus responded much more rapidly in the 86 N leaves. This increased sensitivity of 86 N leaves was not due to accelerated senescence as judged by comparison with parallel plants subjected to discontinued fertilization; the two categories of treatments resulted in the same loss of leaf nitrogen and Rubisco but drought induced a much more rapid photosynthetic depression. In contrast to the drought situation, 86 N and 100 N plants behaved similarly when compared under short term water stress. First, when single attached leaves were exposed to a sudden drop in air humidity the capacity of CO2 uptake in both N regimes decreased about 20% over 10 min while the leaf water potential remained high. Second, in freely transpiring leaf discs cut from 86 N and 100 N leaves the same relationship between capacity of O2 evolution and extent of dehydration was observed. The possible mechanisms underlying the increased susceptibility of 86 N leaves to drought is discussed; the water status of the roots not the leaves is suggested to be the determining factor.Abbreviations CE
carboxylation efficiency
- 100 N
optimal nitrogen regime
- 86 N
suboptimal nitrogen regime with 86% of the optimal leaf nitrogen content, Rubisco ribulose-1,5-bisphosphate carboxylase/oxygenase 相似文献
17.
The role of Rubisco and cell walls in the interspecific variation in photosynthetic capacity 总被引:2,自引:0,他引:2
Photosynthetic capacity is known to vary considerably among species. Its physiological cause and ecological significance have
been one of the most fundamental questions in plant ecophysiology. We studied the contents of Rubisco (a key enzyme of photosynthesis)
and cell walls in leaves of 26 species with a large variation in photosynthetic rates. We focused on photosynthetic nitrogen-use
efficiency (PNUE, photosynthetic rate per nitrogen), which can be expressed as the product of Rubisco-use efficiency (RBUE,
photosynthetic rate per Rubisco) and Rubisco nitrogen fraction (RNF, Rubisco nitrogen per total leaf nitrogen). RBUE accounted
for 70% of the interspecific variation in PNUE. The variation in RBUE was ascribed partly to stomatal conductance, and other
factors such as mesophyll conductance and Rubisco kinetics might also be involved. RNF was also significantly related to PNUE
but the correlation was relatively weak. Cell wall nitrogen fraction (WNF, cell wall nitrogen per total leaf nitrogen) increased
with increasing leaf mass per area, but there was no correlation between RNF and WNF. These results suggest that nitrogen
allocation to cell walls does not explain the variation in PNUE. The difference in PNUE was not caused by a sole factor that
was markedly different among species but by several factors each of which was slightly disadvantageous in low PNUE species.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
We examined temporal changes in the amount of nitrogenous compounds in leaves from the outer and inner parts of the crown
of Quercus myrsinaefolia growing in a seasonal climate. Throughout the leaf life span, metabolic protein and Rubisco content closely correlated with
total nitrogen content, while structural protein content was relatively stable after full leaf expansion. Chlorophyll content
was affected by shading as well as total nitrogen content in outer leaves that were overtopped by new shoots in the second
year. Outer leaves showed a large seasonal variation in photosynthetic nitrogen-use efficiency (PNUE; the light-saturated
photosynthetic rate per unit leaf nitrogen content) during the first year of their life, with PNUE decreasing from the peak
in summer towards winter. Outer and inner leaves both showed age-related decline in PNUE in the second year. There were no
such drastic changes in leaf nitrogen partitioning that could explain seasonal and yearly variations in PNUE. Nitrogen resorption
occurred in overwintering leaves in spring. Metabolic protein explained the majority of nitrogen being resorbed, whereas structural
protein, which was low in degradability, contributed little to nitrogen resorption. 相似文献
19.
Y. Yasumura 《Photosynthetica》2009,47(2):263-270
Annual plants transport a large portion of carbohydrates and nitrogenous compounds from leaves to seeds during the phase of
reproductive growth. This study aimed to clarify how reproductive growth affects photosynthetic traits in leaves and matter
transport within the plant in the annual herb Chenopodium album L. Plants were grown in pots and either reproductive tissues or axillary leaves were removed at anthesis. Matter transport
was evaluated as temporal changes in dry mass (as a substitute of carbohydrates) and nitrogen content of aboveground organs:
leaves, axillary leaves, stems and reproductive tissues. Photosynthetic capacity (light-saturated photosynthetic rate under
ambient CO2 concentration), nitrogen, chlorophyll and soluble protein content were followed in the 20th leaf that was mature at the start of the experiment. Removal of reproductive tissues resulted in accumulation of dry mass
in leaves and axillary leaves, and accumulation of nitrogen in stem as nitrogen resorption from leaves and axillary leaves
proceeded with time. Removal of axillary leaves proportionally reduced dry mass and nitrogen allocation to reproductive tissues,
thus affecting the quantity but not quality of seeds. Removal treatments did not alter the time course of photosynthetic capacity,
nitrogen, chlorophyll or soluble protein content during senescence in the 20th leaf, but changed the photosynthetic capacity per unit of leaf nitrogen according to demand from reproductive tissues. Together,
the results indicate that reproductive tissues affected carbon and nitrogen economy separately. The amount of carbon was adjusted
in leaves through photosynthetic capacity and carbohydrate export from them, and the amount of nitrogen was adjusted by transport
from stem to reproductive tissues. The plant’s ability to independently regulate carbon and nitrogen economy should be important
in natural habitats where the plant carbon-nitrogen balance can easily be disturbed by external factors. 相似文献
20.
Acclimation of photosynthesis and respiration to elevated atmospheric CO2 in two Scrub Oaks 总被引:1,自引:0,他引:1
Graham J.Hymus Tom G. Snead David P. Johnson Bruce A. Hungate Bert G. Drake 《Global Change Biology》2002,8(4):317-328
Abstract For two species of oak, we determined whether increasing atmospheric CO2 concentration (Ca) would decrease leaf mitochondrial respiration (R) directly, or indirectly owing to their growth in elevated Ca, or both. In particular, we tested whether acclimatory decreases in leaf‐Rubisco content in elevated Ca would decrease R associated with its maintenance. This hypothesis was tested in summer 2000 on sun and shade leaves of Quercus myrtifolia Willd. and Quercus geminata Small. We also measured R on five occasions between summer 1999 and 2000 on leaves of Q. myrtifolia. The oaks were grown in the field for 4 years, in either current ambient or elevated (current ambient + 350 µmol mol?1) Ca, in open‐top chambers (OTCs). For Q. myrtifolia, an increase in Ca from 360 to 710 µmol mol?1 had no direct effect on R at any time during the year. In April 1999, R in young Q. myrtifolia leaves was significantly higher in elevated Ca—the only evidence for an indirect effect of growth in elevated Ca. Leaf R was significantly correlated with leaf nitrogen (N) concentration for the sun and shade leaves of both the species of oak. Acclimation of photosynthesis in elevated Ca significantly reduced maximum RuBP‐saturated carboxylation capacity (Vc max) for both the sun and shade leaves of only Q. geminata. However, we estimated that only 11–12% of total leaf N was invested in Rubisco; consequently, acclimation in this plant resulted in a small effect on N and an insignificant effect on R. In this study measurements of respiration and photosynthesis were made on material removed from the field; this procedure had no effect on gas exchange properties. The findings of this study were applicable to R expressed either per unit leaf area or unit dry weight, and did not support the hypothesis that elevated Ca decreases R directly, or indirectly owing to acclimatory decreases in Rubisco content. 相似文献