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1.
Regenerants from tobacco(Nicotiana tabacum L. cv. White Burley) leaf segments cultivatedin vitro in vessels with solid agar medium under usual conditions (plantlets) grew under very low irradiance (I = 40 μxmol m?2 s?1), very high relative humidity (more than 90%) and decreased CO2 concentration (ca) during light period. In comparison with seedlings of a similar number of leaves and similar total leaf area grown in sand and nutrient solution, the plantlets had lower dry mass of shoots and roots per plant and thinner leaves almost without trichomes and epicuticular waxes. Due to a low transpiration rate under high relative humidity the water potential of plantlet leaves was higher than that of seedling leaves and the difference in water potential between leaves and medium was lowei. The rate of water loss from leaves detached from plantlets was considerably faster than that from seedlings under the same conditions (I = 110 μrnol m?2; s?1, temperature 30 °C, relative humidity 50 %). Net photosynthetie rates (Pn) of leaves of plantlets and seedlings measured under saturating I, natural ca and the leaf temperature 20 °C were similar, nevertheless the shape of curves relating Pn to c» indicated some differences in photosynthetie parameters(e.g. saturation of Pn under lower ca> higher CO2 compensation concentration in plantlets than in seedlings). Similarly compensation and saturating I were lower in plantlets than in seedlings. The shape of transpiration curves as well as the expressive linear phases of PN(ca) and PN(I) curves of plantlet leaves indicated ineffective stomatal control of gas exchance. These results were confirmed by microscopic observations of stomatal movementsin situ 相似文献
2.
We investigated seasonal patterns of photosynthetic responses to CO2 concentrations in Spartina alterniflora Loisel, an aerenchymous halophyte grass, from a salt marsh of the Bay of Fundy (NB, Canada), and from plants grown from rhizome in controlled-environment chambers. From late May to August, CO2 compensation concentrations () of field-grown leaves varied between 2.5–10.7 cm3(CO2) m–3, with a mean of 5.4 cm3(CO2) m–3. From September onwards field leaves showed CO2 compensation concentrations from 6.6–21.1 cm3(CO2) m–3, with a mean of 13.1 cm3 m–3 well into the C3–C4 intermediate range. The seasonal variability in did not result from changing respiration, but rather from a sigmoidal response of net photosynthetic rate (P
N) to applied CO2 concentration, found in all tested leaves but which became more pronounced late in the season. One explanation for the sigmoidal response of P
N to external CO2 concentration could be internal delivery of CO2 from roots and rhizomes to bundle sheath cells via the aerenchyma, but the sigmoidal responses in S. alterniflora persisted out to the tips of leaves, while the aerenchyma extend only to mid-leaf. The sigmoidicity persisted when CO2 response curves were measured from low to high CO2, or from high to low CO2, and even when prolonged acclimation times were used at each CO2 concentration. 相似文献
3.
Regulation of electron transport rate through Photosystem I (PS I) was investigated in intact sunflower leaves. The rate constant of electron donation via the cytochrome b
6
f complex (kq, s–1) was obtained from the postillumination P700+ reduction rate, measured as the exponential decay of the light-dark difference (D830) of the 830 nm transmission signal. D830 corresponding to maximum oxidisable P700 (D830m) was obtained by applying white light flashes of different intensity and extrapolating the plot of the quantum yield Y vs. D830 to the axis of abscissae (Y->0). Maximum quantum yield of PS I at completely reduced P700 (Ym) was obtained by extrapolating the same plot to the axis of ordinates (D830->0). Regulation of kq, D830m and Ym under rate-limiting CO2 and O2 concentrations applied after air (21% O2, 310 ppm CO2) was investigated. The amplitude of the downregulation of kq (photosynthetic control) was maximal when electron transport rate (ETR) was limited to about 3 nmol cm–2 s–1 and decreased when ETR was higher or lower. Downregulation did not occur in the absence of CO2 and O2. These gases acted only as substrates of ribulosebisphosphate carboxylase-oxygenase, no high-affinity reaction of O2 leading to enhanced photosynthetic control (e.g. Mehler reaction) was detected. After the transition, D830m at first decreased and then increased again, showing that the reduction of the PS I acceptor side disappeared as a result of the downregulation of kq. The variation of Ym had two reasons, PS I acceptor side reduction and variable excitation capture efficiency by P700. It is concluded that electron transport through PS I is coregulated by the rate of plastoquinol oxidation at Cyt b
6
f, excitation capture efficiency by P700, and by acceptor side reduction.Abbreviations Cyt b
6
f
cytochrome b
6
f complex
- D830
difference of the 830 nm signal from the dark level
- ETR
electron transport rate
- PAD
photon absorption density nmol cm–2 s–1
- PFD
incident photon flux density, nmol cm–2 s–1
- PS I
Photosystem I
- PS II
Photosystem II
- PQH2
plastoquinol
- P700
Photosystem I donor pigment
- Y
quantum yield of PS I electron transport, rel. un. 相似文献
4.
Effects of phosphorus deficiency on the photosynthesis and respiration of leaves of sugar beet 总被引:9,自引:6,他引:3
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Phosphorus deficiency was induced in sugar beet plants (Beta vulgaris L. var. F5855441), cultured hydroponically under standardized environmental conditions, by removal of phosphorus from the nutrient supply at the ten leaf stage 28 days after germination. CO2 and water vapor exchange rates of individual attached leaves were determined at intervals after P cutoff. Leaves grown with an adequate nutrient supply attained net rates of photosynthetic CO2 fixation of 125 ng CO2 cm−2 sec−1 at saturating irradiance, 25 C, and an ambient CO2 concentration of about 250 μl l−1. After P cutoff, leaf phosphorus concentrations decreased as did net rates of photosynthetic CO2 uptake, photorespiratory evolution of CO2 into CO2-free air, and dark respiration, so that 30 days after cutoff these rates were about one-third of the control rates. The decrease in photosynthetic rates during the first 15 days after cutoff was associated with increased mesophyll resistance (rm) which increased from 2.4 to 4.9 sec cm−1, while from 15 to 30 days there was an increase in leaf (mainly stomatal) diffusion resistance (rl′) from 0.3 to 0.9 sec cm−1, as well as further increases in rm to 8.5 sec cm−1. Leaf diffusion resistance (rl′) was increased greatly by low P at low but not at high irradiance, rl′ for plants at low P reaching values as high as 9 sec cm−1. 相似文献
5.
Salt dust in rump lake areas in arid regions has long been considered an extreme stressor for both native plants and crops. In recent years, research on the harmful effects of salt dust on native plants has been published by many scholars, but the effect on crops has been little studied. In this work, in order to determine the impact of salt dust storms on cotton, we simulated salt dust exposure of cotton leaves in Ebinur Basin in Northwest China, and measured the particle sizes and salt ions in the dust, and the photosynthesis, the structure and the cell physiological properties of the cotton leaves. (1) Analysis found that the salt ions and particle sizes in the salt dust used in the experiments were consistent with the natural salt dust and modeled the salt dust deposition on cotton leaves in this region. (2) The main salt cations on the surface and inside the cotton leaves were Na+, Ca2+, Cl- and SO42-, while the amounts of CO3- and HCO3- were low. From the analysis, we can order the quantity of the salt cations and anions ions present on the surface and inside the cotton leaves as Na+>Ca2+>Mg2+>K+ and Cl->SO42->HCO3->CO3-, respectively. Furthermore, the five salt dust treatment groups in terms of the total salt ions on both the surface and inside the cotton leaves were A(500g.m-2)>B(400g.m-2)>C(300g.m-2)>D(200g.m-2)>E(100g.m-2)>F(0g.m-2). (3)The salt dust that landed on the surface of the cotton leaves can significantly influence the photosynthetic traits of Pn, PE, Ci, Ti, Gs, Tr, WUE, Ls, φ, Amax, k and Rady of the cotton leaves. (4)Salt dust can significantly damage the physiological functions of the cotton leaves, resulting in a decrease in leaf chlorophyll and carotenoid content, and increasing cytoplasmic membrane permeability and malondialdehyde (MDA) content by increasing the soluble sugar and proline to adjust for the loss of the cell cytosol. This increases the activity of antioxidant enzymes to eliminate harmful materials, such as the intracellular reactive oxygen and MDA, thus reducing the damage caused by the salt dust and maintaining normal physiological functioning. Overall, this work found that the salt dust deposition was a problem for the crop and the salt dust could significantly influence the physiological and biochemical processes of the cotton leaves. This will eventually damage the leaves and reduce the cotton production, leading to agricultural economic loss. Therefore, attention should be paid to salt dust storms in the Ebinur Basin and efficient measures should be undertaken to protect the environment. 相似文献
6.
The morphological, anatomical and physiological variations of leaf traits were analysed during Quercus ilex L. leaf expansion. The leaf water content (LWC), leaf area relative growth rate (RGRl) and leaf dry mass relative growth rate (RGRm) were the highest (76±2 %, 0.413 cm2 cm−2 d−1, 0.709 mg mg−1 d−1, respectively) at the beginning of the leaf expansion process (7 days after bud break). Leaf expansion lasted 84±2 days when
air temperature ranged from 13.3±0.8 to 27.6±0.9 °C. The net photosynthetic rate (P
N), stomatal conductance (g
s), and chlorophyll content per fresh mass (Chl) increased during leaf expansion, having the highest values [12.62±1.64 μmol
(CO2) m−2 s−1, 0.090 mol (H2O) m−2 s−1, and 1.03±0.08 mg g−1, respectively] 56 days after bud break. Chl was directly correlated with leaf dry mass (DM) and P
N. The thickness of palisade parenchyma contributed to the total leaf thickness (263.1±1.5 μm) by 47 %, spongy layer thickness
38 %, adaxial epidermis and cuticle thickness 9 %, and abaxial epidermis and cuticle thickness 6 %. Variation in leaf size
during leaf expansion might be attributed to a combination of cells density and length, and it is confirmed by the significant
(p<0.001) correlations among these traits. Q. ilex leaves reached 90 % of their definitive structure before the most severe drought period (beginning of June — end of August).
The high leaf mass area (LMA, 15.1±0.6 mg cm−2) at full leaf expansion was indicative of compact leaves (2028±100 cells mm−2). Air temperature increasing might shorten the favourable period for leaf expansion, thus changing the final amount of biomass
per unit leaf area of Q. ilex. 相似文献
7.
The relationship between leaf resistance to water vapour diffusion and each of the factors leaf water potential, light intensity and leaf temperature was determined for leaves on seedling apple trees (Malus sylvestris Mill. cv. Granny Smith) in the laboratory. Leaf cuticular resistance was also determined and transpiration was measured on attached leaves for a range of conditions. Leaf resistance was shown to be independent of water potential until potential fell below — 19 bars after which leaf resistance increased rapidly. Exposure of leaves to CO2-free air extended the range for which resistance was independent of water potential to — 30 bars. The light requirement for minimum leaf resistance was 10 to 20 W m?2 and at light intensities exceeding these, leaf resistance was unaffected by light intensity. Optimum leaf temperature for minimum diffusion resistance was 23 ± 2°C. The rate of change measured in leaf resistance in leaves given a sudden change in leaf temperature increased as the magnitude of the temperature change increased. For a sudden change of 1°C in leaf temperature, diffusion resistance changed at a rate of 0.01 s cm?1 min?1 whilst for a 9°C leaf temperature change, diffusion resistance changed at a rate of 0.1 s cm?1 min?1. Cuticular resistance of these leaves was 125 s cm?1 which is very high compared with resistances for open stomata of 1.5 to 4 s cm?1 and 30 to 35 s cm?1 for stomata closed in the dark. Transpiration was measured in attached apple leaves enclosed in a leaf chamber and exposed to a range of conditions of leaf temperature and ambient water vapour density. Peak transpiration of approximately 5 × 10?6 g cm?2 s?1 occurred at a vapour density gradient from the leaf to the air of 12 to 14 g m?3 after which transpiration declined due presumably to increased stomatal resistance. Leaves in CO2-free air attained a peak transpiration of 11 × 10?6 g cm?2 s?1 due to lower values of leaf resistance in CO2 free air. Transpiration then declined in these leaves due to development of an internal leaf resistance (of up to 2 s cm?1). The internal resistance was masked in leaves at normal CO2 concentrations by the increase in stomatal resistance. 相似文献
8.
A branch bag technique for simultaneous CO2 enrichment and assimilation measurements on beech (Fagus sylvatica L.) 总被引:7,自引:4,他引:3
A cheap CO2 enrichment system was designed to perform continuous gas exchange measurements of branches of mature European beech trees (Fagus sylvatica L.). Branches were grown at ambient (350 cm3 m-3) and elevated CO2 (700cm3 m-3) during the whole 1992 leafy period. Leaks resulting from airtightness defaults in the system appeared to be low enough to measure accurately net CO2 assimilation and transpiration rates during the day. However, the CO2 exchange rates during the night (respiration) were too low to allow accurate measurements. Elevated CO2 had a great effect on the net assimilation rate of branches via its influence on both the C3 photosynthetic pathway and the shade-tolerance of beech trees (85% increase). The A/Ca curves showed no acclimation effect to high CO2, both control and enriched branches increasing their net assimilation in the same way. The decrease of net assimilation rates in mature leaves was similar for both control and enriched branches. The pattern of daily transpiration rates remained the same for both control and enriched branches, hence we can assume that there was no visible CO2 effect on stomata. 相似文献
9.
Growth and photosynthesis of two eucalypt species during high temperature stress under ambient and elevated [CO2 ] 总被引:1,自引:0,他引:1
Two species of eucalypt (Eucalyptus macrorhyncha and E. rossii) were grown under conditions of high temperatures (45 °C, maximum) and high light (1500 μmol m?2 s?1, maximum) at either ambient (350 μL L?1) or elevated (700 μL L?1) CO2 concentrations for 8 weeks. The growth enhancement, in terms of total dry weight, was 41% and 103% for E. macrorhyncha and E. rossii, respectively, when grown in elevated [CO2]. A reduction in specific leaf area and increased concentrations of non-structural carbohydrates were observed for leaves grown in elevated [CO2]. Plants grown in elevated [CO2] had an overall increase in photosynthetic CO2 assimilation rate of 27%; however, when measured at the same CO2 concentration a down-regulation of photosynthesis was evident especially for E. macrorhyncha. During the midday period when temperatures and irradiances were maximal, photosynthetic efficiency as measured by chlorophyll fluorescence (Fv/Fm) was lower in E. macrorhyncha than in E. rossii. Furthermore, Fv/Fm was lower in leaves of E. macrorhyncha grown under elevated than under ambient [CO2]. These reductions in Fv/Fm were accompanied by increases in both photochemical (qP) and nonphotochemical quenching (qN and NPQ), and by increases in the concentrations of xanthophyll cycle pigments with an increased proportion of the total xanthophyll cycle pool comprising of antheraxanthin and zeaxanthin. Thus, increased atmospheric [CO2] may enhance photoinhibition when environmental stresses such as high temperatures limit the capacity of a plant to respond with growth to elevated [CO2]. 相似文献
10.
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 CO2 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. CO2 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 CO2 cm-2 sec-1 for high irradiance grown leaves. A very unusual finding was that leaf conductances to H2O 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 CO2 partial pressure and also responded more steeply to increasing CO2 partial pressure than did low irradiance grown leaves. Leaves from both treatments showed reduced photosynthetic capability after being subjected to low CO2 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
11.
Andreas Bertsch 《Planta》1969,87(1-2):102-109
Summary The lower epidermis from leaves of Primula palinuri can be stripped off. Light-saturation curves of the CO2-exchange were measured at 20°C and 300 ppm CO2. Whereas the normal leaf reaches light-saturation at 0.3 cal cm-2 min-1, even 0.6 cal cm-2 min-1 is not sufficient to saturate the stripped leaf. Transpiration, apparent CO2-uptake and leaf-temperature were measured simultaneously. The data were used to calculate the diffusion resistances for CO2 with the usual methods, that is, from the diffusion resistances for water-vapour transport. The comparison of the CO2-exchange of stripped and normal leaves makes it possible to determine the resistances—in particular those of the stomata—directly from the CO2-exchange. Both methods agree well. When CO2 exchanges only through the lower surface of the leaf the epidermis is—even with opened stomata—a considerable diffusion resistance. It lowers the CO2-concentration in the intercellular system to 160 ppm and limits the CO2-uptake. 相似文献
12.
The kinetics of the postillumination reduction of P700+ which reflects the rate constant for plastoquinol (PQH2) oxidation was recorded in sunflower leaves at different photon absorption densities (PAD), CO2 and O2 concentrations. The P700 oxidation state was calculated from the leaf transmittance at 830 nm logged at 50 s intervals. The P700+ dark reduction kinetics were fitted with two exponents with time constants of 6.5 and about 45 ms at atmospheric CO2 and O2 concentrations. The time constant of the fast component, which is the major contributor to the linear electron transport rate (ETR), did not change over the range of PADs of 14.5 to 134 nmol cm-2 s-1 in 21% O2, but it increased up to 40 ms under severe limitation of ETR at low O2 and CO2. The acceptor side of Photosystem I (PS I) became reduced in correlation with the downregulation of the PQH2 oxidation rate constant. It is concluded that thylakoid pH-related downregulation of the PQH2 oxidation rate constant (photosynthetic control) is not present under normal atmospheric conditions but appears under severe limitation of the availability of electron acceptors. The measured range of photosynthetic control fits with the maximum variation of ETR under natural stress in C3 plants. Increasing the carboxylase/oxygenase specificity would lead to higher reduction of the PS I acceptor side under stress.Abbreviations Cyt b
6
f
cytochrome b
6
f complex
- Cw
cell-wall CO2 concentration, M
- ETR
electron transport rate
- Fd
ferredoxin
- FNR
ferredoxin-NADP reductase
- FRL
far-red light
- PC
plastocyanin
- PAD
photon absorption density nmol cm-2 s-1
- PFD
photon flux density nmol cm-2 s-1
- PS I
Photosystem I complex
- PQ
plastoquinon
- PQH2
plastoquinol
- PS II
Photosystem II complex
- P700
Photosystem I donor pigment, reduced
- S830
830 nm signal (D830, difference of S830 from the dark level)
- WL
white light
- Yl
maximum quantum yield of PS I electron transport, rel. un 相似文献
13.
Rates of net photosynthesis and dark respiration were determined under submersed and emerged conditions for Hesperophycus harveyanus S. & G. and Pelvetia fastigiata f. gracilis (Decne.) S. & G. Both species exhibited submersed photosynthesis-light relationships and dark respiration rates similar to those established for other closely related intertidal, fucoids. Maximal net photosynthesis of H. harveyanus (0.21 mmol O2 g dry wt.-1· h-1; 0.18 mmol CO2 g dry wt.-1· h-1) was similar to that of P. fastigiata f. gracilis (0.17 mmol. O2 g dry wt.-1· h-1; 0.14 mmol CO2 g dry wt. -1· h-1). Light saturation occurred between 150 and 250 μE · m-2· s-1 for H. harveyanus and between 75 and 150 μE · m-2· s-1 for P. fastigiata f. gracilis; photon flux densities required for compensation were 6.4 and 9.2 μE · m-2· s-1, respectively. Photoinhibition was not observed for either species. The light-saturated, submersed net photosynthetic performances of both species varied significantly with temperature. Greatest photosynthetic rates were obtained at 23° C for H. harveyanus and at 18° C for P. fastigiata f. gracilis. Under emersed conditions, the maximal net photosynthetic rate and the photon flux densities required for saturation were greater for H. harveyanus (0.08 mmol CO2 g dry wt.-1· h-1; 260 to 700 μE · m-2· s-1) than for P. fastigiata f. gracilis (0.02 mmol CO2g dry wt.-1· h-1; 72 to 125 μE · m-2· s-1). However, for both species, emersed photosynthetic rates were much lower (14–44%) than those obtained under submersed conditions. Desiccation negatively influenced emersed photosynthesis, of both species, but H. harveyanus thalli contained more water when fully hydrated and lost water more slowly during dehydration, thus suggesting greater photosynthetic potential during field conditions of emersion. 相似文献
14.
Increasing photosynthetic photon flux density (PPFD) received during development from 5.5 to 31.2 mol m-2 d-1 resulted in greater leaf and mesophyll cell surface areas in cotton (Gossypium hirsutum L.). The relationships between the amounts of these surface areas and potential CO2 assimilation by these leaves were evaluated. Leaf area (epidermal surface area of one side of a leaf), mesophyll cell surface area, and net rate of CO2 uptake (Pn) were measured from the time leaves first unfolded until P., was substantially reduced. At the higher PPFD, leaf and mesophyll surface areas increased more rapidly during expansion, and Pn per unit leaf area was greater than at the lower PPFD. Although leaves at the higher PPFD reached the maximum P., per unit mesophyll cell surface area 4 to 5 days earlier than leaves at the lower PPFD, the maxima for these P., were similar. Leaves grown at the higher PPFD had the potential to assimilate 2.2, 3.5, or 5.8 times the amount of CO2 as leaves from the lower PPFD when P., was expressed per unit mesophyll surface, per unit leaf surface, or per whole leaf, respectively. Greater and earlier development of both P., and mesophyll cell surface area at higher PPFD apparently had a compounding effect on the potential for carbon assimilation by a leaf. 相似文献
15.
The impact of elevated carbon dioxide (CO2, 600/700 μmol mol-1) and temperature (+ 4°C) on phyllosphere fungi colonising flag leaves of mini crops of winter wheat cv. Mercia between anthesis and harvest was determined in a computer-controlled environment facility in 1993 and 1994. In both years the total fungal populations (cm2 leaf) were found to have increased due to exposure to either elevated CO2 and elevated CO2+ temperature treatments. This was mainly due to significant increases in populations of Cladosporium spp. (C. cladosporioides and C. herbarum) on the flag leaves during ripening. Other phyllosphere component species such as white and pink yeasts were not markedly affected by treatments. The range of fungal species found in such controlled environment chambers was narrower than that commonly found on flag leaves of field grown crops. Common and important colonisers of leaves and ripening ears such as Aureobasidium pullulans, Epicoccum nigrum and Fusarium spp. were seldom isolated. 相似文献
16.
Predicted increases in atmospheric carbon dioxide (CO2) concentrations are expected to increase primary productivity in many terrestrial ecosystems, which could lead to plants becoming N limited. Studies suggest that legumes may partially overcome this by increasing biological nitrogen fixation. However, these studies have not yet considered how these changes may be affected by the altered dynamics of insect herbivores feeding on the plant. This study investigated how elevated CO2 (700 μl l?1) affected the clover root weevil (Sitona lepidus), a significant pest of white clover (Trifolium repens). Adults feed on leaves aboveground where they lay eggs; soil-dwelling larvae initially feed on root nodules that house N2-fixing bacteria. Foliar C:N ratios rose by 9% at elevated CO2, but the biggest responses were observed belowground, with increases in root mass (85% greater) and nodule abundance (220% more abundant). Root C:N ratios increased significantly from 10.95 to 11.60 under elevated CO2, which increased even further to 13.13 when nodules were attacked by larval S. lepidus. Adult S. lepidus consumed significantly more leaf tissue at elevated CO2 (0.47 cm2 day?1) compared with ambient CO2 (0.35 cm2 day?1), suggesting compensatory feeding, but laid 23% fewer eggs at elevated CO2. Even though fewer eggs were laid at elevated CO2, 38% more larvae were recovered suggesting that larval survival was much better under elevated CO2. Increased larval abundance and performance at elevated CO2 were positively correlated with the number of nodules available. In conclusion, reduced foliar quality at elevated CO2 was generally disadvantageous for adult S. lepidus living aboveground, but extremely beneficial for S. lepidus larvae living belowground, due to the enhanced nodulation. Climate change may, therefore, enhance biological nitrogen fixation by T. repens, but potential benefits (e.g. provision of N without chemical fertilizers) may be undermined by larger populations of S. lepidus larvae belowground. 相似文献
17.
To understand the interactive effects of O3 and CO2 on rice leaves; gas exchange, chlorophyll (Chl) fluorescence, ascorbic acid and glutathione were examined under acute (5
h), combined exposures of O3 (0, 0.1, or 0.3 cm3 m−3, expressed as O0, O0.1, or O0.3, respectively), and CO2 (400 or 800 cm3 m−3, expressed as C400 or C800, respectively) in natural-light gas-exposure chambers. The net photosynthetic rate (P
N), maximum (Fv/Fm) and operating (Fq′/Fm′) quantum efficiencies of photosystem II (PSII) in young (8th) leaves decreased during O3 exposure. However, these were ameliorated by C800 and fully recovered within 3 d in clean air (O0 + C400) except for the O0.3 + C400 plants. The maximum PSII efficiency at 1,500 μmol m−2 s−1 PPFD (Fv′/Fm′) for the O0.3 + C400 plants decreased for all measurement times, likely because leaves with severely inhibited P
N also had a severely damaged PSII. The P
N of the flag (16th) leaves at heading decreased under O3 exposure, but the decline was smaller and the recovery was faster than that of the 8th leaves. The Fq′/Fm′ of the flag leaves in the O0.3 + C400 and O0.3 + C800 plants decreased just after gas exposure, but the Fv/Fm was not affected. These effects indicate that elevated CO2 interactively ameliorated the inhibition of photosynthesis induced by O3 exposure. However, changes in antioxidant levels did not explain the above interaction. 相似文献
18.
Vertical structure of plant stands and canopies may change under conditions of elevated CO2 due to differential responses of overstory and understory plants or plant parts. In the long term, seedling recruitment,
competition, and thus population or community structure may be affected. Aside from the possible differential direct effects
of elevated CO2 on photosynthesis and growth, both the quantity and quality of the light below the overstory canopy could be indirectly affected
by CO2-induced changes in overstory leaf area index (LAI) and/or changes in overstory leaf quality. In order to explore such possible
interactions, we compared canopy leaf area development, canopy light extinction and the quality of light beneath overstory
leaves of two-storied monospecific stands ofRicinus communis exposed to ambient (340 μl l−1) and elevated (610 μl l−1) CO2. Plants in each stand were grown in a common soil as closed “artificial ecosystems” with a ground area of 6.7 m2. LAI of overstory plants in all ecosystems more than doubled during the experiment but was not different between CO2 treatments at the end. As a consequence, extinction of photosynthetically active radiation (PAR) was also not altered. However,
under elevated CO2 the red to far-red ratio (R:FR) measured beneath overstory leaves was 10% lower than in ecosystems treated with ambient CO2. This reduction was associated with increased thickness of palisade layers of overstory leaves and appears to be a plausible
explanation for the specific enhancement of stem elongation of understory plants (without a corresponding biomass response)
under elevated CO2. CO2 enrichment led to increased biomass of overstory plants (mainly stem biomass) but had no effect on understory biomass. The
results of this study raise the possibility of an important indirect effect of elevated CO2 at the stand-level. We suggest that, under elevated CO2, reductions in the R:FR ratio beneath overstory canopies may affect understory plant development independently of the effects
of PAR extinction. 相似文献
19.
Manure slurries (n = 3) prepared from the feces and urine of lactating dairy cattle (1 part urine, 2.2 parts feces, and 6.8
parts distilled water) had an initial pH of 8.6 ± 0.1; dissolved carbonate concentrations of 48 ± 4 mm, and Escherichia coli counts of 5.9 ± 0.7 logs per ml slurry. The pH of untreated slurries declined to pH 7.0 ± 0.1 by the 10th day of incubation,
and the E. coli count increased approximately 10-fold (P < 0.05). When slurries were treated with Na2CO3, K2CO3, NaHCO3 or Na2CO3·NaHCO3 (0 to 16 g/kg slurry), the dissolved carbonates increased in a linear fashion, but only Na2CO3 and K2CO3 (8 g/kg or greater) or Na2CO3·NaHCO3 (16 g/kg) ensured an alkaline pH. Even relatively low concentrations of Na2CO3 or K2CO3 (8 or 12 g/kg) caused a decrease in E. coli viability (P < 0.05), and E. coli could not be detected if 16 g/kg was added (day 5 or 10 of incubation). Na2CO3·NaHCO3 also caused a decrease in E. coli viability, (P < 0.05), but some E. coli (approximately 104 cells per g) were detected on day 10 even if the concentration was 16 g/kg. NaHCO3 did not prevent the decrease in pH or cause a decrease in E. coli numbers (P > 0.05). Calculations based on the Henderson-Hasselbalch equation (pH and dissolved carbonates) indicated that little E. coli killing was noted until the dissolved carbonate anion concentrations (CO3
−2) were greater than 1 mm, but bicarbonate anion (HCO3
−) concentrations as high as 180 mm did not affect E. coli viability. These results are consistent with the idea that carbonate anion has antimicrobial properties and can kill E. coli in dairy cattle manure.
Received: 20 December 2000 / Accepted: 7 February 2001 相似文献
20.
Ch. Körner 《Oecologia》1982,53(1):98-104
Summary The temperature and light responses of CO2 uptake (Fn) in the sedge Carex curvula were investigated in situ by IRGA technic in the Austrian Central Alps at an altitude of 2,310 m. Fn in Carex leaves reaches a maximum of 15.6 mg CO2 dm-2 h-1 at a leaf temperature of 22.5°C and a quantum flux density larger than 1.0 mmol photons m-2 s-1 (400–700 nm). A model based on a polynomal regression analysis of the Fn responses and informations about the microclimate and the canopy structure was used to simulate F
n for individual days and for a whole season. It turned out that the major rate limiting factor is the availability of light in the canopy: The calculated photosynthetic yield for a hypothetical optimum season of clear days with fully illuminated leaves and optimum temperature as well as for a typical season with the actual light and temperature conditions in the canopy, shows that insufficient illumination of the leaves accounts for almost 40% reduction of the possible CO2 uptake while suboptimal temperatures cause only a loss of 8%. Half of the light deficit is caused by mutual shading of the leaves. The minor importance of temperature for the annual CO2 uptake results from the fact that temperature adaptation of F
n in this sedge allows optimal utilization of short periods with high light intensity and hence high photosynthetic yield. The weaker the quantum supply the more becomes temperature limiting. This indicates that the length of the growing season is probably less important for the success of this prominent alpine plant than the sum of hours with high radiation.List of Symbols
I
o
quantum flux density in a horizontal plane above the plant canopy (mol photons m-2 s-1, 400–700 nm)
-
I
z
as I
o, but at level z in the leaf canopy
-
I
1
quantum flux density received by a leaf at level z and with leaf inclination (for diffuse light I
z=I
1)
-
solar elevation angle (°)
-
leaf angle to the vertical (°)
-
extinction coefficient
- LAI
leaf area index
-
T
1
leaf temperature (°C)
-
F
n
rate of net photosynthesis (CO2 uptake; mg CO2 g dry weight-1 h-1, or mg CO2 dm-2 h-1, projected leaf area)
-
R
d
rate of dark respiration (mg CO2 g-1 h-1) 相似文献