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71.
72.
Interactive effects of ozone and soil volume on Plantago major 总被引:4,自引:2,他引:2
73.
The grass flora of Namibia (374 species in 110 genera) shows surprisingly little variation in 13C values along a rainfall gradient (50–600 mm) and in different habitat conditions. However, there are significant differences in the 13C values between the metabolic types of the C4 photosynthetic pathway. NADP-ME-type C4 species exhibit the highest 13C values (–11.7 ) and occur mainly in regions with high rainfall. NAD-ME-type C4 species have significantly lower 13C values (–13.4 ) and dominate in the most arid part of the precipitation regime. PCK-type C4 species play an intermediate role (–12.5 ) and reach a maximum abundance in areas of intermediate precipitation. This pattern is also evident in genera containing species of different metabolic types. Within the same genus NAD species reach more negative 13C values than PCK species and 13C values decreased with rainfall. Also in Aristida, with NADP-ME-type photosynthesis, 13C values decreased from –11 in the inland region (600 mm precipitation) to –15 near the coast (150 mm precipitation), which is a change in discrimination which is otherwise associated by a change in metabolism. The exceptional C3 species Eragrostis walteri and Panicum heterostachyum are coastal species experiencing 50 mm precipitation only. Many of the rare species and monotypic genera grow in moist habitats rather than in the desert, and they are not different in their carbon isotope ratios from the more common flora. The role of species diversity with respect to habitat occupation and carbon metabolism is discussed. 相似文献
74.
Hydraulic control of stomatal conductance in Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] and alder [Alnus rubra (Bong)] seedlings 总被引:1,自引:0,他引:1
Experiments were conducted on 1-year-old Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] and 2- to 3-month-old alder [Alnus rubra (Bong)] seedlings growing in drying soils to determine the relative influence of root and leaf water status on stomatal conductance (gc). The water status of shoots was manipulated independently of that of the roots using a pressure chamber that enclosed the root system. Pressurizing the chamber increases the turgor of cells in the shoot but not in the roots. Seedling shoots were enclosed in a whole-plant cuvette and transpiration and net photosynthesis rates measured continuously. In both species, stomatal closure in response to soil drying was progressively reversed with increasing pressurization. Responses occurred within minutes of pressurization and measurements almost immediately returned to pre-pressurization levels when the pressure was released. Even in wet soils there was a significant increase in gc with pressurization. In Douglas fir, the stomatal response to pressurization was the same for seedlings grown in dry soils for up to 120 d as for those subjected to drought stress over 40 to 60 d. The stomatal conductance of both Douglas fir and alder seedlings was less sensitive to root chamber pressure at higher vapour pressure deficits (D), and stomatal closure in response to increasing D from 1.04 to 2.06 kPa was only partially reversed by pressurization. Our results are in contrast to those of other studies on herbaceous species, even though we followed the same experimental approach. They suggest that it is not always appropriate to invoke a ‘feedforward’ model of short-term stomatal response to soil drying, whereby chemical messengers from the roots bring about stomatal closure. 相似文献
75.
The relationship between the relative growth rate and nitrogen economy of alpine and lowland Poa species 总被引:4,自引:2,他引:2
This study investigates the nitrogen economy of six altitudinally contrasting Poa species which differ in their relative growth rate (R). Two alpine (Poa fawcettiae and P. costiniana), one sub-alpine (P. alpina)and three temperate lowland species (P. pratensis, P. campressa and P. trivialis) were grown hydroponically under identical conditions in a growth room. The low R exhibited by the alpine species was associated with lower plant organic nitrogen concentration (np) and lower nitrogen productivity (Πp, amount of biomass accumulation per mol organic nitrogen and time). The differences in Πp between the alpine and lowland species did not appear to be due to differences in the carbon concentration or the proportion of total plant organic nitrogen allocated to the leaves, stems or roots. Variations in ΠP were also not due to variations in photosynthetic nitrogen use efficiency (ΨN, the rate of photosynthesis per unit organic leaf nitrogen) or shoot or root respiration rates per unit organic nitrogen (ΛSH and ΛR, respectively) per se. Rather, the lower Λp in the alpine species was probably due to a combination of small variations in several of the parameters (e.g. slightly lower ΨN, slightly higher ΛSH and ΛR, and slightly higher proportions of total plant organic nitrogen allocated to the roots). The alpine species exhibited lower organic acid and mineral concentrations. However, no differences in whole-plant construction costs (grams of glucose needed to synthesize one gram of biomass) were observed between She alpine and lowland Poa species. The lack of sub-stantial differences in ΨN between the alpine and lowland species contrasts with the large differences in ΨN between slow- and fast-growing lowland species that have been reported in the literature. The reasons for the unusually high ΨN values exhibited by the alpine Poa species are discussed. 相似文献
76.
The leakage of various inorganic carbon species from air-grown cells of Synechococcus UTEX 625 was investigated after a light to dark transition or during a light period using a mass spectrometer under a wide variety of experimental conditions. Total inorganic carbon efflux and CO2 efflux during the initial period of darkness were measured with or without carbonic anhydrase in the reaction medium respectively. The HCO3? efflux after a light to dark transition was estimated by difference. Carbon dioxide efflux in the light was measured by inhibiting CO2 transport with either Na2S or COS3 or quenching the 13C inorganic carbon transport by the addition of 12C inorganic carbon in excess. In cells in which CO2 fixation was inhibited, when only the HCO3? transport system was fully operative, CO2 effluxed continuously during the light period at a rate equal to about 25% of that in darkness. When only the CO2 transport system was operative, HCO3? effluxed during the light period. The difference between the light and dark efflux rates was consistent with a 0.6 unit decrease in the intracellular pH upon darkening the cells. The permeabilities of the cell for CO2 (2.94 ± 0.14 ± 10?8ms?1; mean ± SE, n=137) and HCO3? (1.4–1.7 ± 10?9 ms?1) were calculated. 相似文献
77.
Nikolai G. Bukhov Christian Wiese Spidola Neimanis Ulrich Heber 《Photosynthesis research》1996,50(2):181-191
The light-induced induction of components of non-photochemical quenching of chlorophyll fluorescence which are distinguished by different rates of dark relaxation (qNf, rapidly relaxing and qNs, slowly relaxing or not relaxing at all in the presence brief saturating light pulses which interrupt darkness at low frequencies) was studied in leaves of spinach.After dark adaptation of the leaves, a fast relaxing component developed in low light only after a lag phase. Quenching increased towards a maximum with increasing photon flux density. This fast component of quenching was identified as energy-dependent quenching qE. It required formation of an appreciable transthylakoid pH and was insignificant when darkened spinach leaves received 1 s pulses of light every 30 s even though zeaxanthin was formed from violaxanthin under these conditions.Another quenching component termed qNs developed in low light without a lag phase. It was not dependent on a transthylakoid pH gradient, decayed exponentially with a long half time of relaxation and was about 20% of total quenching irrespective of light intensity. When darkened leaves were flashed at frequencies higher than 0.004 Hz with 1 s light pulses, this quenching also appeared. Its extent was very considerable, and it did not require formation of zeaxanthin. Relaxation was accelerated by far-red light, and this acceleration was abolished by NaF.We suggest that qNs is the result of a so-called state transition, in which LHC II moves after its phosphorylation from fluorescent PS II to nonfluorescent PS I. This state transition was capable of decreasing in darkened leaves the potential maximum quantum efficiency of electron flow through Photosystem II by about 20%.Abbreviations PFD
photon flux density
- PS
photosystem 相似文献
78.
Bernard L. Strehler 《Photosynthesis research》1996,48(1-2):11-18
The circumstances that led to the discovery that plants luminesce after they are illuminated are described, as are other discoveries that would not have been possible were it not for the fortuitous association I had with my dear and most admirable friend, W.A. Arnold, to whom this special issue is dedicated. 相似文献
79.
The objective of this study was to determine whether exposure of plants to ozone (O3) increased the foliar levels of glucose, glucose sources, e.g., sucrose and starch, and glucose-6-phosphate (G6P), because in leaf cells, glucose is the precursor of the antioxidant, L-ascorbate, and glucose-6-phosphate is a source of NADPH needed to support antioxidant capacity. A further objective was to establish whether the response of increased levels of glucose, sucrose, starch and G6P in leaves could be correlated with a greater degree of plant tolerance to O3. Four commercially available Spinacia oleracea varieties were screened for tolerance or susceptibility to detrimental effects of O3 employing one 6.5 hour acute exposure to 25O nL O3 L-1 air during the light. One day after the termination of ozonation (29 d post emergence), leaves of the plants were monitored both for damage and for gas exchange characteristics. Cultivar Winter Bloomsdale (cv Winter) leaves were least damaged on a quantitative grading scale. The leaves of cv Nordic, the most susceptible, were approximately 2.5 times more damaged. Photosynthesis (Pn) rates in the ozonated mature leaves of cv Winter were 48.9% less, and in cv Nordic, 66.2% less than in comparable leaves of their non-ozonated controls. Stomatal conductance of leaves of ozonated plants was found not to be a factor in the lower Pn rates in the ozonated plants. At some time points in the light, leaves of ozonated cv Winter plants had significantly higher levels of glucose, sucrose, starch, G6P, G1P, pyruvate and malate than did leaves of ozonated cv Nordic plants. It was concluded that leaves of cv Winter displayed a higher tolerance to ozone mediated stress than those of cv Nordic, in part because they had higher levels of glucose and G6P that could be mobilized during diminished photosynthesis to generate antioxidants (e.g., ascorbate) and reductants (e.g., NADPH). Elevated levels of both pyruvate and malate in the leaves of ozonated cv Winter suggested an increased availability of respiratory substrates to support higher respiratory capacity needed for repair, growth, and maintenance.Abbreviations ADPG-PPiase
ADPglucose pyrophosphorylase
- ASC
L-ascorbic acid
- APX
ascorbate peroxidase
- Ce
CO2 concentration in air in the measuring cuvette during photosynthesis measurements
- Ci
CO2 concentration in the leaf intercellular spaces during photosynthesis measurement
- Chl
chlorophyll
- DHA
dehydroascorbic acid
- DHA reductase
dehydroascorbate reductase
- DHAP
dihydroxyacetone phosphate
- GAP
glyceraldehyde-3-phosphate
- Gluc
glucose
- GR
glutathione reductase
- Gsw
stomatal conductance with units as mmol H2O m-2 s-1
- GSSG
oxidized glutathione
- GSH
reduced glutathione
- G1P
glucose-1-phosphate
- G6P
glucose-6-phosphate
- G6P dehydrogenase
glucose-6-phosphate dehydrogenase
- 6PG
6-phosphogluconate
- 6PG dehydrogenase
6-phosphogluconate dehydrogenase
- F6P
fructose-6-phosphate
- FBP
fructose-1,6-bisphosphate
- MAL
malate
- MDHA reductase
monodehydroascorbate reductase
- PE
post-emergence
- PEP
phosphoenolpyruvate
- PGA
3-phosphoglycerate
- Pi
orthophosphate
- PYR
pyruvate
- Pn
net CO2 photoas-similation in leaves
- PPFD
photosynthetic photon flux density with units of mol photons m-2 s-1
- PPRC
pentose phosphate reductive cycle
- RuBP
ribulose-1,5-bisphosphate
- rubisco
ribulose-1,5-bisphosphate carboxylase/oxygenase
- SLW
specific leaf weight
- TCA cycle
tricarboxylic acid cycle
- Triose-P
DHAP+GAP 相似文献
80.
Mepiquat chloride (N, N-dimethylpiperidinium chloride), well known as PIX, is a potential systemic plant growth regulator. The effects of PIX on plant height, stem elongation, leaf area, net photosynthetic rates, chlorophyll content, sucrose and starch levels, and RuBP carboxylase activity in cotton (Gossypium hirsutum L. cv. DES 119) plants were measured. PIX was sprayed (0, 7.65, 15.3, 30.6 or 61.2 g active ingredient ha–1) on the plants at first square (25 days after emergence) and measurements were made at frequent intervals. Plant height was clearly reduced by PIX. The total length of vegetative branches and fruiting branches was 40% and 50% less than the control. Total leaf area in PIX treated plants was 16% less than the control. Net photosynthetic rates were 25% less in PIX-treated leaves. PIX treated leaves had more chlorophyll content. The activity of RuBP carboxylase was decreased in PIX treated plants. Starch accumulation was noticed in PIX treated leaves while sucrose content was not changed. The data reported here suggest that reduced growth responses induced by PIX results in partial loss of photosynthetic capacity in cotton at least up to 20 days after application of the growth regulator. 相似文献