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1.
Photosynthetic Response of Carrots to Varying Irradiances 总被引:7,自引:3,他引:4
Response to irradiance of leaf net photosynthetic rates (P
N) of four carrot cultivars: Cascade, Caro Choice (CC), Oranza, and Red Core Chantenay (RCC) were examined in a controlled
environment. Gas exchange measurements were conducted at photosynthetic active radiation (PAR) from 100 to 1 000 μmol m−2 s−1 at 20 °C and 350 μmol (CO2) mol−1(air). The values of P
N were fitted to a rectangular hyperbolic nonlinear regression model. P
N for all cultivars increased similarly with increasing PAR but Cascade and Oranza generally had higher P
N than CC. None of the cultivars reached saturation at 1 000 μmol m−2 s−1. The predicted P
N at saturation (P
Nmax) for Cascade, CC, Oranza, and RCC were 19.78, 16.40, 19.79, and 18.11 μmol (CO2) m−2 s−1, respectively. The compensation irradiance (I
c) occurred at 54 μmol m−2 s−1 for Cascade, 36 μmol m−2 s−1 for CC, 45 μmol m−2 s−1 for Oranza, and 25 μmol m−2 s−1 for RCC. The quantum yield among the cultivars ranged between 0.057–0.033 mol(CO2) mol−1(PAR) and did not differ. Dark respiration varied from 2.66 μmol m−2 s−1 for Cascade to 0.85 μmol m−2 s−1 for RCC. As P
N increased with PAR, intercellular CO2 decreased in a non-linear manner. Increasing PAR increased stomatal conductance and transpiration rate to a peak between
600 and 800 μmol m−2 s−1 followed by a steep decline resulting in sharp increases in water use efficiency.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
P. L. Sáez L. A. Bravo K. L. Sáez M. Sánchez-Olate M. I. Latsague D. G. Ríos 《Biologia Plantarum》2012,56(1):15-24
The anatomic and functional leaf characteristics related to photosynthetic performance of Castanea sativa growing in vitro and in nursery were compared. The irradiance saturated photosynthesis in in vitro grown plantlets was significantly lower compared to nursery plants (65 vs. 722 μmol m−2 s−1). The maximum photosynthetic rate (PNmax) was 4.0 and 10.0 μmol(CO2) m−2 s−1 in in vitro microshoots and nursery plant leaves, respectively. Carboxylation efficiency (CE) and electron transport rate (ETR) were three-folds higher in nursery plants than in microshoots. The nonphotochemical quenching
(NPQ) was saturated at 80 μmol m−2 s−1 in microshoots suggesting limited photoprotection by thermal dissipation. The microshoots had wide open, spherical stomata
and higher stomatal density than nursery plants and they had almost no epicuticular wax. Consequently, the microshoots had
high stomatal conductance and high transpiration rate. These anatomic and functional leaf characteristics are likely major
causes of the low survival rates of plantlets after ex vitro transfer. 相似文献
3.
Charles R. Warren 《Trees - Structure and Function》2006,20(2):157-164
Rates of photosynthesis vary with foliage age and typically decline from full-leaf expansion until senescence occurs. This age-related decline in photosynthesis is especially important in species that retain foliage for several years, yet it is not known whether the internal conductance to CO2 movement (g
i) plays any role. More generally, g
i has been measured in only a few conifers and has never been measured in leaves or needles older than 1 year. The effect of ageing on g
i was investigated in Pinus pinaster, a species that retains needle for 4 or more years. Measurements were made in autumn when trees were not water limited and after leaf expansion was complete. Rates of net photosynthesis decreased with needle age, from 8 μmol m−2 s−1 in fully expanded current-year needles to 4.4 μmol m−2 s−1 in 3-year-old needles. The relative limitation due to internal conductance (0.24–0.35 out of 1) was in all cases larger than that due to stomatal conductance (0.13–0.19 out of 1). Internal conductance and stomatal conductance approximately scaled with rates of photosynthesis. Hence, there was no difference among year-classes in the relative limitations posed by internal and stomatal conductance or evidence that they cause the age-related decline in photosynthesis. There was little evidence that the age-related decline in photosynthesis was due to decreases in contents of N or Rubisco. The decrease in rates of photosynthesis from current-year to older needles was instead related to a twofold decrease in rates of photosynthesis per unit nitrogen and V
cmax/Rubisco (i.e., in vivo specific activity). 相似文献
4.
Chill-induced inhibition of photosynthesis was alleviated by 24-epibrassinolide pretreatment in cucumber during chilling and subsequent recovery 总被引:4,自引:0,他引:4
To investigate whether brassinosteroids (BRs) could be used to alleviate chill-induced inhibition of photosynthesis in cucumber
(Cucumis sativus L) during chilling and subsequent recovery, the effects of exogenously applied 24-epibrassinolide (EBR) on gas exchange,
chlorophyll fluorescence parameters, and antioxidant enzyme activity were studied. Cucumber plants were exposed to chilling
under low light (12/8°C and 100 μmol m−2 s−1 PPFD) for 3 days and then recovered under normal temperature and high irradiance (28/18°C and 600 μmol m−2 s−1 PPFD) for 6 days. Chilling significantly decreased the net photosynthetic rate (P
N) and stomatal conductance (g
s), and increased rate of O2
·− formation and H2O2 and malondialdehyde (MDA) content in cucumber leaves, but did not influence the optimal quantum yield of PSII (Fv/Fm). Chilling also decreased the effective quantum yield of PSII photochemistry (ΦPSII) and photochemical quenching (qP), but induced an increase in nonphotochemical quenching (NPQ), and the activities of superoxide dismutase (SOD) and ascorbate
peroxidase (APX). High irradiance (600 μmol m−2 s−1) further aggravated the decrease in P
N, g
s, ΦPSII and qP, and enhanced the increase in reactive oxygen species (ROS) generation and accumulation in the first day of recovery after
chilling. However, high irradiance induced a sharp decrease in Fv/Fm and NPQ, as well as the activities of SOD and APX on the first day of recovery. EBR pretreatment significantly alleviated
chill-induced inhibition of photosynthesis during chilling stress and subsequent recovery period, which was mainly due to
significant increases in g
s, ΦPSII, qP and NPQ. EBR pretreatment also reduced ROS generation and accumulation, and increased the activities of SOD and APX during
chilling and subsequent recovery. Those results suggest that EBR pretreatment alleviates the chill reduction in photosynthesis
and accelerated the recovery rate mainly by increasing of the stomatal conductance, the efficiency of utilization and dissipation
of leaf absorbed light, and the activity of the ROS scavenging system during chilling and subsequent recovery period. 相似文献
5.
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 CO2 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 CO2 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
- Ci
CO2 concentration in the leaf
- Ca
CO2 concentration in ambient air
- LWP
leaf water potential
- OP
osmotic potential
- PAR
photosynthetically active radiation 相似文献
6.
Light-emitting diodes as a light source for photosynthesis research 总被引:10,自引:0,他引:10
Light-emitting diodes (LED) can provide large fluxes of red photons and so could be used to make lightweight, efficient lighting systems for photosynthetic research. We compared photosynthesis, stomatal conductance and isoprene emission (a sensitive indicator of ATP status) from leaves of kudzu (Pueraria lobata (Willd) Ohwi.) enclosed in a leaf chamber illuminated by LEDs versus by a xenon arc lamp. Stomatal conductance was measured to determine if red LED light could sufficiently open stomata. The LEDs produced an even field of red light (peak emission 656±5 nm) over the range of 0–1500 mol m-2 s-1. Under ambient CO2 the photosynthetic response to red light deviated slightly from the response measured in white light and stomatal conductance followed a similar pattern. Isoprene emission also increased with light similar to photosynthesis in white light and red light. The response of photosynthesis to CO2 was similar under the LED and xenon arc lamps at equal photosynthetic irradiance of 1000 mol m-2 s-1. There was no statistical difference between the white light and red light measurements in high CO2. Some leaves exhibited feedback inhibition of photosynthesis which was equally evident under irradiation of either lamp type. Photosynthesis research including electron transport, carbon metabolism and trace gas emission studies should benefit greatly from the increased reliability, repeatability and portability of a photosynthesis lamp based on light-emitting diodes. 相似文献
7.
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 CO2 (35 μM) and inability to utilize other inorganic carbon species, their photosynthetic rate at air-equilibrated water was
CO2-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
8.
Leaf photosynthesis, plant growth and nitrogen allocation in rice under different irradiances 总被引:6,自引:0,他引:6
The photosynthetic rates and various components of photosynthesis including ribulose-1,5-bisphosphate carboxylase (Rubisco;
EC 4.1.1.39), chlorophyll (Chl), cytochrome (Cyt) f, and coupling factor 1 (CF1) contents, and sucrose-phosphate synthase (SPS; EC 2.4.1.14) activity were examined in young, fully expanded leaves of rice
(Oryza sativa L.) grown hydroponically under two irradiances, namely, 1000 and 350 μmol quanta · m−2 · s−1, at three N concentrations. The light-saturated rate of photosynthesis measured at 1800 μmol · m−2 · s−1 was almost the same for a given leaf N content irrespective of growth irradiance. Similarly, Rubisco content and SPS activity
were not different for the same leaf N content between irradiance treatments. In contrast, Chl content was significantly greater
in the plants grown at 350 μmol · m−2 · s−1, whereas Cyt f and CF1 contents tended to be slightly smaller. However, these changes were not substantial, as shown by the fact that the light-limited
rate of photosynthesis measured at 350 μmol · m−2 · s−1 was the same or only a little higher in the plants grown at 350 μmol · m−2 · s−1 and that CO2-saturated photosynthesis did not differ between irradiance treatments. These results indicate that growth-irradiance-dependent
changes in N partitioning in a leaf were far from optimal with respect to N-use efficiency of photosynthesis. In spite of
the difference in growth irradiance, the relative growth rate of the whole plant did not differ between the treatments because
there was an increase in the leaf area ratio in the low-irradiance-grown plants. This increase was associated with the preferential
N-investment in leaf blades and the extremely low accumulation of starch and sucrose in leaf blades and sheaths, allowing
a more efficient use of the fixed carbon. Thus, morphogenic responses at the whole-plant level may be more important for plants
as an adaptation strategy to light environments than a response of N partitioning at the level of a single leaf.
Received: 23 February 1997 / Accepted: 8 May 1997 相似文献
9.
Genotypic variation in photosynthesis in cacao is correlated with stomatal conductance and leaf nitrogen 总被引:1,自引:0,他引:1
Variation in photosynthetic parameters was observed between eight contrasting cacao (Theobroma cacao) genotypes. Net photosynthetic rate (PN) ranged from 3.4 to 5.7 μmol(CO2) m−2 s−1 for the genotypes IMC 47 and SCA 6, respectively. Furthermore, genotypic differences were detected in quantum efficiency
ranging from 0.020 to 0.043 μmol(CO2) μmol−1(photon) for UF 676 and AMAZ 15/15, respectively. Differences in PN were correlated with both stomatal conductance (gs) and leaf nitrogen per unit area. Some variation in water use efficiency was observed between genotypes, both intrinsic (PN/gs) and instantaneous (PN/transpiration rate). Both measures of water use efficiency were a negative function of specific leaf area. Evidence was found
for a trade-off mechanism between cacao genotypes in photosynthesis and leaf structure. High photosynthetic rate, expressed
on a mass basis was associated with smaller leaves. Furthermore, thinner leaves were compensated for by a higher nitrogen
content per unit mass. 相似文献
10.
We studied seasonal fluctuations in the rates of photosynthesis, transpiration, PAR, and stomatal conductance for 16 species
of true mangroves from the Sundarbans region of West Bengal. Soil salinity and pH were also measured. Leaf temperatures were
almost always higher than the ambient temperature. We observed considerable seasonal (summer vs winter) as well as interspecific
variations in photosynthesis, with the highest rates occurring inHeritiera fomes (13.21 pmol m-2s-1) andAvicennia marina (11.8 mol m-2s-1), and the lowest inNypa fruticans (1.56 mol m-2s-1) andCeriops decandra (2.32 pmol m-2s-1), in many species, an abrupt rise in leaf temperature retarded the photosyn-thetic process. In winter, the rate of transpiration
and stomatal conductance reached their maxima inA. marina (4.83 mmol ra-2s-1 and 124.23 m mol m-2s-1, respectively) and their mimima inExcoecaria agallocha (1.85 mmol m-2s-1 and 49.19 mmol m-2s-1, respectively). In contrast, the maximum summer readings were recorded in E.agallocha (6.07 mmol m-2s-1 and 192.74 mmol m-2s-1 respectively). 相似文献
11.
The influence of far-red (FR; 700–800 nm) radiation on steady-state stomatal conductance and net photosynthesis in P. vulgaris has been studied. Whereas FR radiation alone was relatively ineffective, addition of FR to a background of white light (WL; predominantly 400–700 nm) resulted in increased stomatal conductance. Stomata exhibited a marked diurnal sensitivity to FR. The action maximum for enhancing stomatal conductance was near 714 nm. A combination of FR and infra-red (IR; >800 nm) enhanced net photosynthesis when added to a background of WL. When IR alone was added to WL, there was a net decrease in photosynthesis, indicating that it is the FR waveband which is responsible for the observed photosynthetic effects. Naturally occurring levels of FR radiation (235 mol·m-2·s-1) in vegetation-canopy shade enhanced net photosynthetic CO2 gain by 28% when added to a background of 55 mol·m-2·s-1 WL.Abbreviations BL
blue
- FR
far-red
- IR
infra-red
- PAR
photosynthetically active radiation
- R
red
- WL
white light 相似文献
12.
Photosynthetic and transpiration (E) rates, stomatal conductance, and leaf nitrogen content were surveyed for Myrica gale
var. tomentosa, a N2-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 (Pmax) of M. gale was 15.2-16.5 μmol(CO2) m-2 s-1, higher than those of the other species throughout the growing season. Pmax was positively correlated with leaf N content among the three species. The large leaf N content in M. gale was due to N2-fixation in root nodules. In a comparison of M. gale in two habitats, Pmax, leaf N content, and root nodule development were larger in the wetter habitat. M. gale showed high E and no midday depression
of Pmax 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
13.
Interaction effects of phosphorus and zinc on photosynthesis, growth and yield of dwarf bean grown in two environments 总被引:2,自引:0,他引:2
Giorgio Gianquinto Azmi Abu-Rayyan Livia Di Tola Diletta Piccotino Beatrice Pezzarossa 《Plant and Soil》2000,220(1-2):219-228
Two experiments were conducted in a factorial combination of three Zn levels (0, 10 and 40 mg Zn kg-1 soil) and two P levels (0 and 200 mg P kg-1 soil). Experiment 1 was carried out during winter in a heated glasshouse, and experiment 2 during summer under a rain shelter.
Plants of dwarf bean (Phaseolus vulgaris L., cv. Borlotto nano) were grown in pots filled with sandy soil. In both experiments, leaf Zn concentration was reduced
by the addition of P to plants grown at low Zn supply. However, leaf Zn concentration lower than the critical level was observed
only during experiment 2, and the main effects of low Zn were reductions of internode length, light use efficiency and maximum
photosynthetic rate. In plants with leaf Zn concentration lower than the critical level, saturating irradiance levels fell
from ∼1000 μmol m-2 s-1 PPFD to ∼300–400 μmol m-2 s-1 PPFD. Reduction of net photosynthesis was observed from the beginning of flowering and led to decreased seed production.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
de la Viña Gloria Barceló-Muñoz Araceli Pliego-Alfaro Fernando 《Plant Cell, Tissue and Organ Culture》2001,65(3):229-237
Avocado shoots were multiplied in vitro in two culture media of different consistency, double phase and solid medium, at three different irradiance levels: 35, 60
and 85 μmol m−2 s−1. Effects of culture and environmental conditions in multiplication rate, rooting capacity, hyperhydricity and leaf surface
morphology of microcuttings were evaluated. Double phase medium induced hyperhydricity, producing leaf microcuttings with
deformed stomata and low crystalline epicuticular waxes; microcuttings also showed reduced rooting capacity. By contrast,
solid medium promoted leaf area development on microcuttings and decreased hyperhydricity. Stomatal index was not affected
by these treatments but stomatal density was, interacting with the amount of irradiance applied. Increasing irradiance decreased
concentration of chlorophyll a and carotenoids in the leaf but did not affect leaf hyperhydricity.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
15.
Single leaf photosynthesis (Pn) and stomatal conductance (Cg) of drought stressed and nonstressed pearl millet [Pennisetum americanum (L.) Leeke] were measured across growth stages to determine if a pattern exists in Pn and Cg during the growing season and to evaluate the influence of air vapor pressure deficit (VPDa) on the seasonal variations of Pn and Cg. Leaf photosynthesis and Cg were measured independently on pearl millet plants grown at the driest (drought stressed) and wettest (nonstressed) ends of a line-source irrigation gradient system. Well defined and predictable variations in both Pn and Cg were found across two growing seasons. Leaf photosynthesis of the nonstressed plants declined from a maximumof 25.8 mol m–2 s–1 at the flag leaf emergence (48 days after planting, DAP) to a minimum of 14.5 mol m–2 s–1 at physiological maturity. Stomatal conductance of the nonstressed plants peaked at the flowering and early grain fill stages and declined as plants approached maturity. In contrast, Pn and Cg of the stressed plants declined from a maximum at flag leaf emergence to a minimum at flowering and increased as plants approached maturity. High VPDa during the flowering and grain fill stages induced stomatal closure and decreased Pn in the stressed plants. High mid-season VPDa did not induce stomatal closure and did not reduce leaf photosynthesis in nonstressed plants. The lack of sensitivity of Pn to VPDa in the nonstressed treatment suggests large air VPD such as that prevalent in southern Arizona does not limit the growth of irrigated pearl millet by limiting CO2 assimilation.Abbreviations Cg
stomatal conductance
- DAP
days after planting
- Pn
leaf photosynthesis
- VPDa
air vapor pressure deficit
- VPD1-a
leaf to air vapor pressure deficit
Contribution of the Arizona Agricultural Experimental Station. Research supported in part by INTSORMIL/USAID. 相似文献
16.
We determined the interactive effects of irradiance, elevated CO2 concentration (EC), and temperature in carrot (Daucus carota var. sativus). Plants of the cv. Red Core Chantenay (RCC) were grown in a controlled environmental plant growth room and exposed to 3
levels of photosynthetically active radiation (PAR) (400, 800, 1 200 μmol m−2 s−1), 3 leaf chamber temperatures (15, 20, 30 °C), and 2 external CO2 concentrations (C
a), AC and EC (350 and 750 μmol mol−1, respectively). Rates of net photosynthesis (P
N) and transpiration (E) and stomatal conductance (g
s
) were measured, along with water use efficiency (WUE) and ratio of internal and external CO2 concentrations (C
i/C
a). P
N revealed an interactive effect between PAR and C
a. As PAR increased so did P
N under both C
a regimes. The g
s
showed no interactive effects between the three parameters but had singular effects of temperature and PAR. E was strongly influenced by the combination of PAR and temperature. WUE was interactively affected by all three parameters.
Maximum WUE occurred at 15 °C and 1 200 μmol m−2 s− 1 PAR under EC. The C
i
/C
a
was influenced independently by temperature and C
a. Hence photosynthetic responses are interactively affected by changes in irradiance, external CO2 concentration, and temperature. EC significantly compensates the inhibitory effects of high temperature and irradiance on
P
N and WUE. 相似文献
17.
Responses of CO2 assimilation to changes in irradiance: laboratory and field data and a model for beans (Phaseolus vulgaris L.) 总被引:1,自引:0,他引:1
The responses of net CO2 assimilation to sudden changes in irradiancewere studied in Phaseolus vulgaris L. in the laboratory andthe field. For irradiance changes between 50 µmol m2s1 to 350 µmol m2 s1 in the laboratory,assimilation rate increased with half-times of 2.7 and 4.1 minin well-watered and water-stressed plants, respectively. Ina field experiment with a change in irradiance from 400 to 1200µmol m2 s1 the response was faster (half-time=c.1.2 min). In all cases when irradiance was returned to a lowvalue, assimilation declined rapidly with a half-time of approximately1 min, which approached the time resolution of the gas-exchangesystem. The corresponding changes in stomatal conductance in responseto both increasing and decreasing irradiance were much slowerthan the assimilation responses, indicating that biochemicalprocesses, rather than CO2 supply, primarily determined theactual rate of assimilation in these experiments. The conceptof stomatal limitation to photosynthesis is discussed in relationto these results. A simple model for assimilation in a fluctuating light environmentis proposed that depends on a steadystate light response curve,an induction lag on increasing irradiance, andan induction-state memory. The likely importance of taking accountof such induction lags in natural canopy microclimates is considered. Key words: Models, Phaseolus vulgaris, photosynthetic induction, CO2 assimilation, stomatal limitation, sunflecks, water stress 相似文献
18.
Photosynthetic properties of carnivorous plants have not been well characterized and the extent to which photosynthesis contributes
to carbon gain in most carnivorous plants is also largely unknown. We investigated the photosynthetic light response in three
carnivorous plant species, Drosera rotundifolia L. (sundew; circumpolar and native to northern British Columbia, Canada), Sarracenia leucophylla Rafin. (‘pitcher-plant’; S.E. United States), and D. capensis L. (sundew; Cape Peninsula, South Africa), using portable gas-exchange systems to explore the capacity for photosynthetic
carbon gain in carnivorous plant species. Maximal photosynthetic rates (1.32–2.22 μmol m−2 s−1 on a leaf area basis) and saturating light intensities (100 to 200 μmol PAR m−2 s−1) were both low in all species and comparable to shade plants. Field or greenhouse-grown D. rotundifolia had the highest rates of photosynthesis among the three species examined. Dark respiration, ranging from −1.44 (S. leucophylla) to −3.32 (D. rotundifolia) μmol m−2 s−1 was high in comparison to photosynthesis in the species examined. Across greenhouse-grown plants, photosynthetic light compensation
points scaled with light-saturated photosynthetic rates. An analysis of gas-exchange and growth data for greenhouse-grown
D. capensis plants suggests that photosynthesis can account for all plant carbon gain in this species. 相似文献
19.
Single leaf photosynthetic characteristics of Alnus glutinosa, A. incana, A. rubra, Elaeagnus angustifolia, and E. umbellata seedlings conditioned to ambient sunlight in a glasshouse were assessed. Light saturation occurred between 930 and 1400 mol m-2s-1 PAR for all species. Maximum rates of net photosynthesis (Pn) measured at 25°C ranged from 12.8 to 17.3 mol CO2m-2s-1 and rates of dark respiration ranged from 0.74 to 0.95 mol CO2m-2s-1. These values of leaf photosynthetic variables are typical of early to midsuccessional species. The rate of Pn measured at optimal temperature (20°C) and 530mol m-2s-1 PAR was significantly (p<0.01) correlated with leaf nitrogen concentration (r=0.69) and negatively correlated with the mean area of a leaf (r=–0.64). We suggest that the high leaf nitrogen concentration and rate of Pn observed for Elaeagnus umbellata and to a lesser degree for E. angustifolia are genetic adaptations related to their crown architecture.Abbreviations Pn
net photosynthesis 相似文献
20.
Effects of Micropropagation Conditions of Rose Shootlets on Chlorophyll Fluorescence 总被引:1,自引:0,他引:1
Rosa hybrida plantlets were rooted on solid sucrosed medium (MS) under an irradiance (PPFD) of 45 μmol m-2 s-1 or on liquid hydroponic solution (MH) at 100 μmol m-2 s-1. Then all plantlets were acclimated without sucrose under 100 μmol m-2 s-1 PPFD. After 7 d in rooting stage, the ratio of variable over maximal chlorophyll fluorescence (Fv/Fm) was significantly higher for plants grown in MH than in MS and hence the higher irradiance at this stage of growth had no
photoinhibitory effect. The radiant energy was used by the photochemical process and also by photoprotective mechanisms of
photosystem 2, expressed by increases in the rates of electron flux, net photosynthesis, and non-photochemical quenching.
This effect on Fv/Fm was maintained during three weeks in acclimation phase. The resistance of plantlets increased as new leaves formed, and after
six weeks in acclimation, there was no difference between the two conditions. The study under higher irradiance (100, 150,
or 300 μmol m-2 s-1) indicated that photoinhibition might take place at 300 μmol m-2 s-1 whatever the growth conditions.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献