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1.
Photosynthetic characteristics at high measurement irradiance were analyzed for single leaves of two C 3 and one C 4 species grown under twenty one combinations of irradiance level, irradiance duration, and air temperature in order to test the idea that photosynthetic characteristies developed by leaves in different environments are controlled by the daily amount of photosynthesis. Photosynthetic rates per unit area and mesophyll conductances at 25°C and air levels of CO 2 and O 2, and parameters for two photosynthesis models were used to characterize the photosynthetic properties of the leaves. Leaves with highest values of the photosynthetic parameters for each species were often developed in environments with irradiance levels below saturation for photosynthesis, and with only 12 hours of irradiance per day. Lower air temperature during growth increased the photosynthetic characteristics for a given irradiance regime. Photosynthetic characteristics had higher correlation coefficients with daily photosynthesis of mature leaves divided by 24-hour leaf elongation rates of young leaves, than with daily photosynthesis alone, indicating that photosynthetic characteristics may be related to a balance between photosynthesis and leaf expansion. 相似文献
2.
Summary The photosynthetic responses to light of leaves irradiated on the adaxial or abaxial surfaces, were measured for plants with contrasting leaf orientations. For vertical-leaf species of open habitats ( Eryngium yuccifolium and Silphium terebinthinaceum), photosynthetic rates were identical when irradiated on either surface. However, for horizontal-leaf species of open habitats ( Ambrosia trifida and Solidago canadensis), light-saturated rates of photosynthesis for adaxial irradiation were 19 to 37% higher than rates for abaxial irradiation. Leaves of understory plants ( Asarum canadense and Hydrophyllum canadense) were functionally symmetrical although they had horizontal orientation. Photosynthetic rates were measured at saturating CO 2, thus differences in the response to incident irradiance presumably resulted from complex interactions of light and leaf optical properties rather than from stomatal effects. Differences in absorptance (400–700 nm) among leaf surfaces were evident for horizontal-leaf species but the primary determinant of functional symmetry was leaf anatomy. Functionally symmetrical leaves had upper and lower palisade layers of equal thickness (vertical leaves of open habitats) or were composed primarily of a single layer of photosynthetic cells (horizontal leaves of understory habitats). Photosynthetic symmetry of vertical-leaf species may be an adaptation to maximize daily integrated carbon gain and water-use efficiency, whereas asymmetry of horizontal-leaf species may be an adaptation to maximize daily integrated carbon gain and photosynthetic nutrient-use efficiency. 相似文献
3.
Changes in specific leaf area (SLA, projected leaf area per unit leaf dry mass) and nitrogen partitioning between proteins within leaves occur during the acclimation of plants to their growth irradiance. In this paper, the relative importance of both of these changes in maximizing carbon gain is quantified. Photosynthesis, SLA and nitrogen partitioning within leaves was determined from 10 dicotyledonous C 3 species grown in photon irradiances of 200 and 1000 µmol m ?2 s ?1. Photosynthetic rate per unit leaf area measured under the growth irradiance was, on average, three times higher for high‐light‐grown plants than for those grown under low light, and two times higher when measured near light saturation. However, light‐saturated photosynthetic rate per unit leaf dry mass was unaltered by growth irradiance because low‐light plants had double the SLA. Nitrogen concentrations per unit leaf mass were constant between the two light treatments, but plants grown in low light partitioned a larger fraction of leaf nitrogen into light harvesting. Leaf absorptance was curvilinearly related to chlorophyll content and independent of SLA. Daily photosynthesis per unit leaf dry mass under low‐light conditions was much more responsive to changes in SLA than to nitrogen partitioning. Under high light, sensitivity to nitrogen partitioning increased, but changes in SLA were still more important. 相似文献
4.
Nuphar lutea is an amphibious plant with submerged and aerial foliage, which raises the question how do both leaf types perform photosynthetically
in two different environments. We found that the aerial leaves function like terrestrial sun-leaves in that their photosynthetic
capability was high and saturated under high irradiance (ca. 1,500 μmol photons m −2 s −1). We show that stomatal opening and Rubisco activity in these leaves co-limited photosynthesis at saturating irradiance fluctuating
in a daily rhythm. In the morning, sunlight stimulated stomatal opening, Rubisco synthesis, and the neutralization of a night-accumulated
Rubisco inhibitor. Consequently, the light-saturated quantum efficiency and rate of photosynthesis increased 10-fold by midday.
During the afternoon, gradual closure of the stomata and a decrease in Rubisco content reduced the light-saturated photosynthetic
rate. However, at limited irradiance, stomatal behavior and Rubisco content had only a marginal effect on the photosynthetic
rate, which did not change during the day. In contrast to the aerial leaves, the photosynthesis rate of the submerged leaves,
adapted to a shaded environment, was saturated under lower irradiance. The light-saturated quantum efficiency of these leaves
was much lower and did not change during the day. Due to their low photosynthetic affinity for CO 2 (35 μM) and inability to utilize other inorganic carbon species, their photosynthetic rate at air-equilibrated water was
CO 2-limited. These results reveal differences in the photosynthetic performance of the two types of Nuphar leaves and unravel how photosynthetic daily rhythm in the aerial leaves is controlled. 相似文献
5.
The response of apparent photosynthesis to N nutrition was studied in the C 3 grass, tall fescue ( Festuca arundinacea Schreb.), in the C 4 species Panicum maximum Jacq., and in Panicum milioides Nees ex Trin., a species with characteristics intermediate between C 3 and C 4 photosynthetic types. Plants were grown in culture solution containing 1, 5, 50, and 200 milligrams N per liter. Apparent photosynthesis was measured on the youngest fully expanded leaves at 320 microliters of CO 2 per liter of air and 21% O 2. Leaf conductance was calculated from transpiration measurements, and CO 2 compensation concentrations were also estimated. Several leaf anatomical characteristics were studied on plastic-embedded material. Leaf N content was determined on leaves which were used in photosynthesis measurements. 相似文献
6.
The azimuth of vertical leaves of Silphium terebinthinaceum profoundly influenced total daily irradiance as well as the proportion of direct versus diffuse light incident on the adaxial and abaxial leaf surface. These differences caused structural and physiological adjustments in leaves that affected photosynthetic performance. Leaves with the adaxial surface facing East received equal daily integrated irradiance on each surface, and these leaves had similar photosynthetic rates when irradiated on either the adaxial or abaxial surface. The adaxial surface of East-facing leaves was also the only surface to receive more direct than diffuse irradiance and this was the only leaf side which had a clearly defined columnar palisade layer. A potential cost of constructing East-facing leaves with symmetrical photosynthetic capcity was a 25% higher specific leaf mass and increased leaf thickness in comparison to asymmetrical South-facing leaves. The adaxial surface of South-facing leaves received approximately three times more daily integrated irradiance than the abaxial surface. When measured at saturating CO 2 and irradiance, these leaves had 42% higher photosynthetic rates when irradiated on the adaxial surface than when irradiated on the abaxial surface. However, there was no difference in photosynthesis for these leaves when irradiated on either surface when measurements were made at ambient CO 2. Stomatal distribution (mean adaxial/abaxial stomatal density = 0.61) was unaffected by leaf orientation. Thus, the potential for high photosynthetic rates of adaxial palisade cells in South-facing leaves at ambient CO 2 concentrations may have been constrained by stomatal limitations to gas exchange. The distribution of soluble protein and chlorophyll within leaves suggests that palisade and spongy mesophyll cells acclimated to their local light environment. The protein/chlorophyll ratio was high in the palisade layers and decreased in the spongy mesophyll cells, presumably corresponding to the attentuation of light as it penetrates leaves. Unlike some species, the chlorophyll a/b ratio and the degree of thylakoid stacking was uniform throughout the thickness of the leaf. It appears that sun-shade acclimation among cell layers of Silphium terebinthinaceum leaves is accomplished without adjustment to the chlorophyll a/b ratio or to thylakoid membrane structure. 相似文献
7.
Photosynthetic responses of intact leaves of the desert shrub Encelia farinosa were measured during a long term drought cycle in order to understand the responses of stomatal and nonstomatal components to water stress. Photosynthetic rate at high irradiance and leaf conductance to water vapor both decreased linearly with declining leaf water potential. The intercellular CO 2 concentration (c i) remained fairly constant as a function of leaf water potential in plants subjected to a slow drought cycle of 25 days, but decreased in plants exposed to a 12-day drought cycle. With increasing water stress, the slope of the dependence of photosynthesis on c i (carboxylation efficiency) decreased, the maximum photosynthetic rates at high c i became saturated at lower values, and water use efficiency increased. Both the carboxylation efficiency and photosynthetic rates were positively correlated with leaf nitrogen content. Associated with lower leaf conductances, the calculated stomatal limitation to photosynthesis increased with water stress. However, because of simultaneous changes in the dependence of photosynthesis on c i with water stress, increased leaf conductance alone in water-stressed leaves would not result in an increase in photosynthetic rates to prestressed levels. Both active osmotic adjustment and changes in specific leaf mass occurred during the drought cycle. In response to increased water stress, leaf specific mass increased. However, the increases in specific leaf mass were associated with the production of a reflective pubescence and there were no changes in specific mass of the photosynthetic tissues. The significance of these responses for carbon gain and water loss under arid conditions are discussed. 相似文献
8.
To clarify relationships between leaf size and the environment variables, we constructed an energy balance model for a single
leaf incorporating Leuning’s stomatal conductance model and Farquhar’s leaf photosynthesis model. We ran this model for various
environmental conditions paying particular attention to the leaf boundary layer. The leaf size maximizing the rate of photosynthesis
per unit leaf area ( A) at a high irradiance differed depending on the air temperature. In warm environments, A increased with decrease in leaf size, whereas in cool environments, there was the leaf size maximizing A. With the increase in leaf size, the CO 2 concentration inside the leaf ( C
i) decreased and the leaf temperature increased, both due to lower boundary layer conductance. At low air temperatures, the
negative effect of low C
i on A in large leaves was compensated by the increase in leaf temperature towards the optimum temperature for A. This balance determined the optimum leaf size for A at low air temperatures. With respect to water use efficiency, large leaves tended to be advantageous, especially in cool
environments at low-to-medium irradiances. Some temperature-dependent trends in leaf size observed in nature are discussed
based on the present results. 相似文献
9.
Potatoes (Solanum tuberosum L., cv. Bintje) were grown in a naturally lit glasshouse. Laboratory measurements on leaves at three insertion levels showed a decline with leaf age in photosynthetic capacity and in stomatal conductance at near saturating irradiance. Conductance declined somewhat more with age than photosynthesis, resulting in a smaller internal CO 2 concentration in older relative to younger leaves. Leaves with different insertion number behaved similarly. The changes in photosynthesis rate and in nitrogen content with leaf age were closely correlated. When PAR exceeded circa 100 W m –2 the rate of photosynthesis and stomatal conductance changed proportionally as indicated by a constant internal CO 2 concentration. The photosynthesis-irradiance data were fitted to an asymptotic exponential model. The parameters of the model are AMAX, the rate of photosynthesis at infinite irradiance, and EFF, the slope at low light levels. AMAX declined strongly with leaf age, as did EFF, but to a smaller extent. During drought stress photosynthetic capacity declined directly with decreasing water potential (range –0.6 to –1.1 MPa). Initially, stomatal conductance declined faster than photosynthetic capacity.Abbreviations LNx
leaf number x, counted in acropetal direction
- DAP
days after planting
- DALA
days after leaf appearance
- C i
CO 2 concentration in the leaf
- C a
CO 2 concentration in ambient air
- LWP
leaf water potential
- OP
osmotic potential
- PAR
photosynthetically active radiation 相似文献
10.
Some ecophysiological features in sun and shade leaves of tall European beech trees (Fagus sylvatica L.) growing in a natural
forest stand were investigated. Quantitative leaf characteristics were followed in the field and under controlled conditions.
In the sun leaves significantly higher rates of photosynthesis, photorespiration and dark respiration, and also photosynthetic
CO 2 fixation capacity, photosynthetic productivity, and saturating, adaptation and compensating irradiances were found. Specific
leaf mass, mean leaf area, stomata density and size as well as the chlorophyll content per unit dry mass were also significantly
different in both types of the leaves. Higher photosynthetic efficiency in the shade leaves allows them a better utilization
of the lower irradiance for carbon dioxide uptake. The importance of these findings for annual carbon gain of the shade tolerant
European beech species is also discussed. 相似文献
11.
In polyploid plants the photosynthetic rate per cell is correlated with the amount of DNA per cell. The photosynthetic rate per unit leaf area is the product of the rate per cell times the number of photosynthetic cells per unit area. Therefore, the photosynthetic rate per unit leaf area will increase if there is a less than proportional increase in cell volume at higher ploidal levels, or if cell packing is altered to allow more cells per unit leaf area. In autopolyploids ( Medicago sativa, C 3 species, and Pennisetum americanum, C 4 species) there is a doubling of photosynthesis per cell and of cell volume in the tetraploid compared to the diploid. However, there is a proportional decrease in number of cells per unit leaf area with this increase in ploidy such that the rate of photosynthesis per leaf area does not change. There is more diversity in the relationship between ploidal level (gene dosage) and photosynthetic rates per unit leaf area in allopolyploids. This is likely to reflect the effects of natural selection on leaf anatomy, and novel genetic interactions from contributed genomes which can occur with allopolyploidy. In allopolyploid wheat (C 3 species) a higher cell volume per unit DNA at the higher ploidal level is negatively correlated with photosynthesis rate per unit leaf area. Although photosynthesis per cell increases with ploidy, photosynthesis per leaf area decreases, being lowest in the allohexaploid, cultivated bread wheat ( Triticum aestivum). Alternatively, doubling of photosynthetic rate per cell with doubling of DNA, with apparent natural selection for decreased cell volume per unit DNA, results in higher rates of photosynthesis per leaf area in octaploid compared to tetraploid Panicum virgatum (C 4) which may be a case of allopolyploidy. Similar responses probably occur in Festuca arundinacea. Therefore, in some systems anatomical factors affecting photosynthesis are also affected by ploidal level. It is important to evaluate that component as well as determining the effect on biochemical processes. Current information on polyploidy and photosynthesis in several species is discussed with respect to anatomy, biochemistry and bases for expressing photosynthetic rates.Abbreviations Chl
chlorophyll
- RuBPC
ribulose-1,5-bisphosphate carboxylase 相似文献
12.
Summary The effects of irradiance during growth on biomass allocation, growth rates, leaf chlorophyll and protein contents, and on gas exchange responses to irradiance and CO 2 partial pressures of the evergreen, sclerophyllous, chaparral shrub, Ceanothus megacarpus were determined. Plants were grown at 4 irradiances for the growth experiments, 8, 17, 25, 41 nE cm -2 sec -1, and at 2 irradiances, 9 and 50 nE cm -2 sec -1, for the other comparisons.At higher irradiances root/shoot ratios were somewhat greater and specific leaf weights were much greater, while leaf area ratios were much lower and leaf weight ratios were slightly lower than at lower irradiances. Relative growth rates increased with increasing irradiance up to 25 nE cm -2 sec -1 and then leveled off, while unit leaf area rates increased steeply and unit leaf weight rates increased more gradually up to the highest growth irradiance.Leaves grown at 9 nE cm -2 sec -1 had less total chlorophyll per unit leaf area and more per unit leaf weight than those grown at 50 nE cm -2 sec -1. In a reverse of what is commonly found, low irradiance grown leaves had significantly higher chlorophyll a/b than high irradiance grown leaves. High irradiance grown leaves had much more total soluble protein per unit leaf area and per unit dry weight, and they had much higher soluble protein/chlorophyll than low irradiance grown leaves.High irradiance grown leaves had higher rates of respiration in very dim light, required higher irradiances for photosynthetic saturation and had higher irradiance saturated rates of photosynthesis than low irradiance grown leaves. CO 2 compensation irradiances for leaves of both treatments were very low, <5 nE cm -2 sec -1. Leaves grown under low and those grown under high irradiances reached 95% of their saturated photosynthetic rates at 65 and 85 nE cm -2 sec -1, respectively. Irradiance saturated rates of photosynthesis were high compared to other chaparral shrubs, 1.3 for low and 1.9 nmol CO 2 cm -2 sec -1 for high irradiance grown leaves. A very unusual finding was that leaf conductances to H 2O were significantly lower in the high irradiance grown leaves than in the low irradiance grown leaves. This, plus the differences in photosynthetic rates, resulted in higher water use efficiencies by the high irradiance grown leaves. High irradiance grown leaves had higher rates of photosynthesis at any particular intercellular CO 2 partial pressure and also responded more steeply to increasing CO 2 partial pressure than did low irradiance grown leaves. Leaves from both treatments showed reduced photosynthetic capability after being subjected to low CO 2 partial pressures (100 bars) under high irradiances. This treatment was more detrimental to leaves grown under low irradiances.The ecological implications of these findings are discussed in terms of chaparral shrub community structure. We suggest that light availability may be an important determinant of chaparral community structure through its effects on water use efficiencies rather than on net carbon gain. 相似文献
13.
The relationship between single leaf photosynthesis and conductance was examined in cotton ( Gossypium hirsutum L.) across a range of environmental conditions. The purpose of this research was to separate and define the degree of stomatal and nonstomatal limitations in the photosynthetic process of field-grown cotton. Photosynthetic rates were related to leaf conductance of upper canopy leaves in a curvilinear manner. Increases in leaf conductance of CO2 in excess of 0.3 to 0.4 mole per square meter per second did not result in significant increases in gross or net photosynthetic rates. No tight coupling between environmental influences on photosynthetic rates and those affecting conductance levels was evident, since photosynthesis per unit leaf conductance did not remain constant. Slowly developing water stress caused greater reductions in photosynthesis than in leaf conductance, indicating nonstomatal limitations of photosynthesis. Increases in external CO2 concentration to levels above ambient did not produce proportional increases in photosynthesis even though substomatal or intercellular CO2 concentration increased. The lack of a linear increase in photosynthetic rate in response to increases in leaf conductance and in response to increases in external CO2 concentration demonstrated that nonstomatal factors are major photosynthetic rate determinants of cotton under field conditions. 相似文献
14.
A model of leaf photosynthesis of C 3, plants has been developed to describe their nitrogen economy. In this model, photosynthetic proteins are categorized into five groups depending on their functions. The effects of investment of nitrogen in each of these groups on the maximal rate of photosynthesis and/or the initial slope of the light-response curve are described as simple equations. Using this model, the optimal pattern of nitrogen partitioning which maximizes the daily rate of CO 2 exchange is estimated for various light environments and leaf nitrogen contents. When the leaf nitrogen content is fixed, the amount of nitrogen allocated to Calvin cycle enzymes and electron carriers increases with increasing irradiance, while that allocated to chlorophyll-protein complexes increases with decreasing irradiance. For chlorophyll-proteins of photosystem II, the amount of light-harvesting complex II relative to that of the core complex increases with decreasing irradiance. At any irradiance, partitioning into ribulose bisphosphate carboxylase increases with increasing leaf nitrogen content Taking the total leaf nitrogen content and the daily CO 2 exchange rate as ‘cost’ and ‘benefit’, respectively, the optimal amount and partitioning of nitrogen are examined for various conditions of light environment and nitrogen availability. The leaf nitrogen content that maximizes the rate of daily carbon fixation increases with increasing growth irradiance. It is also predicted that, at low nitrogen availabilities, low leaf nitrogen contents are advantageous in terms, of nitrogen use efficiency. These trends predicted by the present model are largely consistent with those reported for actual plants. The differences in the total amount of leaf nitrogen and in the organization of photosynthetic components that have been reported for plants from different environments would therefore be of adaptive significance, because such differences can contribute to realization of efficient photosynthesis. These results are fürther discussed in an ecological context. 相似文献
15.
Photosynthetic and transpiration (E) rates, stomatal conductance, and leaf nitrogen content were surveyed for Myrica gale
var. tomentosa, a N 2-fixing wetland shrub, Betula platyphylla var. japonica, and Rhododendron japonicum in Ozegahara moor, an oligotrophic moor
in Central Japan. Net photosynthetic rate saturated with irradiance (P max) of M. gale was 15.2-16.5 μmol(CO 2) m -2 s -1, higher than those of the other species throughout the growing season. P max was positively correlated with leaf N content among the three species. The large leaf N content in M. gale was due to N 2-fixation in root nodules. In a comparison of M. gale in two habitats, P max, leaf N content, and root nodule development were larger in the wetter habitat. M. gale showed high E and no midday depression
of P max even under high irradiance and large vapour pressure deficit between leaves and ambient air on a midsummer day. These traits
of photosynthesis and water relations were associated with the dominance of this shrub in wetter sites such as stream sides
and hollows.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
16.
The review is done to summarise the history of the discoveries of the many anatomical, agronomical, and physiological aspects
of C 4 photosynthesis (where the first chemical products of CO 2 fixation in illuminated leaves are four-carbon dicarboxylic acids) and to document correctly the scientists at the University
of Arizona and the University of California, Davis, who made these early discoveries. The findings were milestones in plant science that occurred shortly after the biochemical pathway of C 3 photosynthesis in green algae (where the first chemical product is a three-carbon compound) was elucidated at the University
of California, Berkeley, and earned a Nobel Prize in chemistry. These remarkable achievements were the result of ground-breaking
pioneering research efforts carried out by many agronomists, plant physiologists and biochemists in several laboratories,
particularly in the USA. Numerous reviews and books written in the past four decades on the history of C 4 photosynthesis have focused on the biochemical aspects and give an unbalanced history of the multidisciplinary/multinstitutional
nature of the achievements made by agronomists, who published much of their work in Crop Science. Most notable among the characteristics of the C 4 species that differentiated them from the C 3 ones are: (I) high optimum temperature and high irradiance saturation for maximum leaf photosynthetic rates; (II) apparent
lack of CO 2 release in a rapid stream of CO 2-free air in illuminated leaves in varying temperatures and high irradiances; (III) a very low CO 2 compensation point; (IV) lower mesophyll resistances to CO 2 diffusion coupled with higher stomatal resistances, and, hence, higher instantaneous leaf water use efficiency; (V) the existence
of the so-called “Kranz leaf anatomy” and the higher internal exposed mesophyll surface area per cell volume; and (VI) the
ability to recycle respiratory CO 2 by illuminated leaves. 相似文献
17.
Lower respiratory costs were hypothesized as providing an additional benefit in C 4 plants compared to C 3 plants due to less investment in proteins in C 4 leaves. Therefore, photosynthesis and dark respiration of mature leaves were compared between a number of C 4 and C 3 species. Although photosynthetic rates were generally greater in C 4 when compared to C 3 species, no differences were found in dark respiration rates of individual leaves at either the beginning or after 16 h of the dark period. The effects of nitrogen on photosynthesis and respiration of individual leaves and whole plants were also investigated in two species that occupy similar habitats, Amaranthus retroflexus (C 4) and Chenopodium album (C 3). For mature leaves of both species, there was no relationship between leaf nitrogen and leaf respiration, with leaves of both species exhibiting a similar rate of decline after 16 h of darkness. In contrast, leaf photosynthesis increased with increasing leaf nitrogen in both species, with the C 4 species displaying a greater photosynthetic response to leaf nitrogen. For whole plants of both species grown at different nitrogen levels, there was a clear linear relationship between net CO 2 uptake and CO 2 efflux in the dark. The dependence of nightly CO 2 efflux on CO 2 uptake was similar for both species, although the response of CO 2 uptake to leaf nitrogen was much steeper in the C 4 species, Amaranthus retroflexus. Rates of growth and maintenance respiration by whole plants of both species were similar, with both species displaying higher rates at higher leaf nitrogen. There were no significant differences in leaf or whole plant maintenance respiration between species at any temperature between 18 and 42°C. The data suggest no obvious differences in respiratory costs in C 4 and C 3 plants. 相似文献
18.
Photosynthetic rates and related anatomical characteristics of leaves developed at three levels of irradiance (1200, 300 and 80 umol · m –2 · s –1) were determined in the C 4-like species Flaveria brownii A.M. Powell, the C 3–C 4-intermediate species F. linearis Lag., and the F 1 hybrid between them ( F. brownii × F. linearis). In the C 3–C 4 and F 1 plants, increases in photosynthetic capacity per unit leaf area were strongly correlated with changes in mesophyll area per unit leaf area. The C 4-like plant F. brownii, however, showed a much lower correlation between photosynthetic capacity and mesophyll area per unit leaf area. Plants of F. brownii developed at high irradiance showed photosynthetic rates per unit of mesophyll cell area 50% higher than those plants developed at medium irradiance. These results along with an increase in water-use efficiency are consistent with an increase of C 4 photosynthesis in high-irradiance-grown F. brownii plants, whereas in the other two genotypes such plasticity seems to be absent. Photosynthetic discrimination against 13C in the three genotypes was less at high than at low irradiance, with the greatest change occurring in F. brownii. Discrimination against 13C expressed as
13C was linearly correlated ( r
2 = 0.81; P<0.001) with the ratio of bundle-sheath volume to mesophyll cell area when all samples from the three genotypes were combined. This tissue ratio increased for F. brownii and the F 1 hybrid as growth irradiance increased, indicating a greater tendency towards Kranz anatomy. The results indicated that F. brownii had plasticity in its C 4-related anatomical and physiological characteristics as a function of growth irradiance, whereas plasticity was less evident in the F 1 hybrid and absent in F. linearis.Abbreviations A
leaf surface area
- A ma, A mn, A lm
total ma, mn or lm cell surface area
- bs
vascular bundle sheath
- lm
large spongy-mesophyll cells
- ma
mesophyll cells adjacent to bundle sheath
- mn
mesophyll cells not adjacent to bundle sheath
- P n
net photosynthesis
- (H, M, L) PPFD
(high, medium, low) photosynthetic photon flux density
- SLDW
specific leaf dry wight
- V bs
bs volume
- V (ma + mn + bs)
total photosynthetic tissue volume
- 13C
13C discrimination
We thank Mrs. Lisa Smith for technical assistance in light microscopy and Dr. Ned Friedman (Department of Botany, University of Georgia, Athens, GA, USA) for the use of digitizing equipment. Participation of Dr. J.L. Araus in this work was supported by a grant Beca de Especialización para Doctores y Tecnólogos en el Extranjero, from Ministerio de Educatión y Ciencia, Spain. 相似文献
19.
A biochemical model of C
3photosynthesis has been developed by G.D. Farquhar et al. (1980, Planta 149, 78–90) based on Michaelis-Menten kinetics of ribulose-1,5-bisphosphate (RuBP) carboxylase-oxygenase, with a potential RuBP limitation imposed via the Calvin cycle and rates of electron transport. The model presented here is slightly modified so that parameters may be estimated from whole-leaf gas-exchange measurements. Carbon-dioxide response curves of net photosynthesis obtained using soybean plants ( Glycine max (L.) Merr.) at four partial pressures of oxygen and five leaf temperatures are presented, and a method for estimating the kinetic parameters of RuBP carboxylase-oxygenase, as manifested in vivo, is discussed. The kinetic parameters so obtained compare well with kinetic parameters obtained in vitro, and the model fits to the measured data give r
2values ranging from 0.87 to 0.98. In addition, equations developed by J.D. Tenhunen et al. (1976, Oecologia 26, 89–100, 101–109) to describe the light and temperature responses of measured CO 2-saturated photosynthetic rates are applied to data collected on soybean. Combining these equations with those describing the kinetics of RuBP carboxylase-oxygenase allows one to model successfully the interactive effects of incident irradiance, leaf temperature, CO 2 and O 2 on whole-leaf photosynthesis. This analytical model may become a useful tool for plant ecologists interested in comparing photosynthetic responses of different C 3 plants or of a single species grown in contrasting environments.Abbreviations PCO
photorespiratory carbon oxidation
- PCR
photosynthetic carbon reduction
- PPFD
photosynthetic photon-flux density
- RuBP
ribulose bisphosphate 相似文献
20.
Net photosynthetic rates and mesophyll conductances were measured under standardized conditions for leaves of two C 3 and one C 4 annual species grown at temperatures of 20 to 32°C. Plants were grown with varying day and night temperatures, and also at constant temperatures equal to all the day and night temperatures used. Plants were grown with 8, 12, and 16 hours of light per day. This design allowed determination of whether photosynthetic characteristics were best correlated with day, night, mean, or time-weighted mean temperatures, The results showed that for Glycine max (L.) Merr. (C 3) night temperature was most important in determining photosynthetic characteristics, while in Helianthus annuus L. (C 3) and Amaranthus hypochondriacus L. (C 4) the time-weighted mean temperature was most important. The results for all species were consistent with the hypothesis that development of photosynthetic characteristics is related to a balance between the rate of leaf expansion and the rate of photosynthesis under the growth conditions. 相似文献
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