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1.
P. Becker Azman Asmat Julaihi Mohamad Misli Moksin Melvin T. Tyree 《Trees - Structure and Function》1997,11(7):432-435
In contrast with previous reports, we observed high transpiration rates in mangrove trees. Maximum sap velocities and mean
daytime sap flow rates were estimated from heat pulse velocity in entire, field grown trees of Avicennia cf. alba Blume and Rhizophora apiculata Blume. Results were within the range of values measured by identical techniques for trees in lowland dipterocarp and tropical
heath forests with a similar climate in Brunei Darussalam (north Borneo). High stomatal conductance (400 mmol m –
2 s –
1) was also measured for well insolated leaves of A. cf. alba, with midday water potentials reaching about – 3 MPa in both species.
Received: 11 September 1996 / Accepted: 27 January 1997 相似文献
2.
The rates of transpiration from a mature Eucalyptus globulus Labill. stand in Portugal were evaluated during a drying period of the spring-summer 1994. Transpiration was measured by
the Granier sap flow method and estimated by the Penman-Monteith model. During the experimental period daily transpiration
varied between 3.64 and 0.50 mm day−1. For high-transpiration days, a good agreement was observed between Penman-Monteith estimates and sap flow measurements,
both on a daily and on an hourly basis. However, for low-transpiration days, the Penman-Monteith model overestimated transpiration
in comparison with the sap flow method. The diurnal variation of sap flow was then smoother and lagged behind the estimates
of the Penman-Monteith model. E. globulus showed an efficient control of transpiration losses during dry periods through a progressive stomatal closure. As soil moisture
deficit increased, the daily maximum stomatal conductance decreased from 0.46 to 0.14 cm s−1. The results also show that, on a seasonal basis, stomatal conductance and daily transpiration were mainly related to predawn
leaf water potential and, thus, to soil moisture content.
Received: 26 January 1996 / Accepted: 20 October 1996 相似文献
3.
Short-chained oxygenated VOC (oxVOCs) emissions from Pinus halepensis saplings were monitored in response to changes in water availability. Online measurements were made with a proton transfer
reaction—mass spectrometer under controlled conditions, together with CO2 and H2O exchange measurements. Masses corresponding to methanol and acetone were the most emitted oxVOCs. All the oxVOC exchanges,
except that of acetone (M59), were significantly related to stomatal conductance and transpiration. Acetaldehyde (M45) emission
showed, moreover, a strong dependence on the concentration of acetaldehyde in the ambient: stomatal opening (stomatal conductance
above 75 mmol m−2 s−1) only allowed increased emissions when external concentration were below 6 ppb. Acetone (M59) presented an important peak
of emission following light and stomatal opening in the morning when plants were water stressed. Thus, the alterations in
oxVOC emissions in P. halepensis caused by the water deficit seem to be mainly driven by water stress effect on stomatal closure and oxVOC air concentrations. 相似文献
4.
Stomatal conductances (gs) of plants of Vicia faba, Raphanussativus, Phaseolus vulgaris, Heilanthus annuus, and Nicotianatabacum were measured in chambers containing either clean airor air containing between 18 and 1000 parts 109 SO2 atwater vapour pressure deficits (vpd) ranging from 1·0to 1·8 kPa. When vpd was low (<1·3 kPa at 22 °C) and stomatawere open, exposure to SO2 induced rapid and irreversible increasesin gs in V. faba. This response persisted throughout the exposure(3 d). The increase in gs, 2030% compared with cleanair, was independent of SO2 concentration up to 350 parts 109Stomatal conductances of polluted plants at night were greaterthan controls. When stomata were closed before exposure to SO2,there was no effect on gs. When vpd was varied, gs of unpolluted plants of P. vulgarisshowed no response, but that of R. sativus increased slightlywith increasing vpd. In both species exposure to SO2 causedan increase in gs at all vpd values. gs of unpolluted plantsof V. faba, H. annuus, and N. tabacum decreased with increasingvpd. At low vpd values exposure to SO2 in these species causedan increase in gs, but, above a certain value of vpd, dependingon species, gs decreased with exposure to SO2. It is postulated that SO2, once in the substomatal cavity, entersthe stomatal complex via adjacent epidermal cells and at lowconcentrations leads to a reduction in turgor in these cellsand consequently to stomatal opening. In vpd-sensitive species,increased transpiration from guard cells or epidermal cellsadjacent to the stomata induced by SO2 may lead to stomatalclosure at large vpd levels. Stomatal sensitivity to vpd insuch cases may be enhanced because adjacent epidermal cell turgoris lowered by SO2. At high SO2 concentrations direct disruptionof guard cell structure may lead to a loss of turgor and stomatalclosure. 相似文献
5.
Summary Stem photosynthetic responses to environmental parameters were investigated with Psorothamnus spinosus in the Sonoran Desert of California. Light saturation of stem photosynthesis was equal to maximum midday summer irradance (1600–2000 mol·m-2·s-1). The optimum temperature for stem photosynthesis was 39°C, and lower stem temperatures (27–35°C) caused significant decreases (up to 50%) in stem photosynthesis. Positive stem photosynthesis was maintained up to 51°C. Stem photosynthesis was relatively insensitive to increasing vpd up to 5 kPa; However, stem conductance decreased by 25% at a vpd of 5 kPa. At vpd greater than 5 kPa stem photosynthesis decreased relatively more than that of stem conductance causing a decrease in water use efficiency and an increase an intercellular carbon dioxide concentration. Maximum stem photosynthetic rates were low (6.2–10.6 mol·m-2·s-1) on a stem surface area, but, stem photosynthetic rates of young shoots were substantially higher (19.5–33.3 mol· m-2·s-1) on a projected area basis.Dedicated to the memory of Dr. W.H. Muller 相似文献
6.
Carla V. Giordano Aranzazú Guevara Hernán E. Boccalandro Carmen Sartor Pablo E. Villagra 《Plant Ecology》2011,212(7):1123-1134
Prosopis flexuosa trees dominate woodlands in the Central Monte Desert (Mendoza, Argentina), with <200 mm rainfall, exploiting the water table
recharged by Andean rivers, and also growing in dunes with no access to the water table. Prosopis woodlands were extensively logged during development of the agricultural oasis, and surface and groundwater irrigation could
lower the depth of the water table in the future. We evaluated tree populations with decreasing access to the water table:
valley adult trees, valley saplings, and dune adult trees, in order to assess their ecophysiological response to water table
accessibility. High and seasonally stable pre-dawn leaf water potentials (−2.2 ± 0.2 to −1.2 ± 0.07 MPa) indicated that valley
adults utilize larger and more stable water reservoirs than valley saplings and dune adults (−3.8 ± 0.3 to −1.3 ± 0.07 MPa),
with higher midday leaf conductance to water vapor (valley adults ~250; dune adults <60 mmol m−2 s−1), potentially higher CO2 uptake, and increased radial growth rate (valley adults 4.1 ± 0.07; dune adults 2.9 ± 0.02 mm year−1). Trees with poor access to the water table exhibited drought tolerance responses such as midday stomata closure, leaflet
closure, and osmotic adjustment. Stomata density decreased in response to drought when leaf expansion was restricted. The
combination of phreatophytism and drought tolerance would enlarge P. flexuosa habitats and buffer populations against changes in rainfall dynamics and water table depth. 相似文献
7.
M. Schutter J. Crocker A. Paijmans M. Janse R. Osinga A. J. Verreth R. H. Wijffels 《Coral reefs (Online)》2010,29(3):737-748
To study the effect of water flow on coral growth, four series of ten coral nubbins of Galaxea fascicularis were exposed to four different flow regimes (0, 10, 20, and 25 cm s−1, bidirectional flow) for 42 weeks. Buoyant weight, surface area, and polyp number were measured at regular intervals. Net
photosynthesis and dark respiration were measured at the corresponding flow speeds, and daily amount of photosynthetic carbon
left for coral growth was calculated. Finally, skeletal density and CN content, chlorophyll concentration and dry weight of
coral tissue were determined for each coral. Specific growth rate (in day−1) decreased with time in each flow treatment. Absence of flow resulted in significantly lower growth rates. Average specific
growth rate calculated over the entire experiment was not significantly different between 10 and 20 cm s−1, while it was significantly higher at 25 cm s−1. From 10 to 25 cm s−1, average net photosynthetic rate decreased and average dark respiration rate did not change significantly. Scope for growth
based on phototrophic carbon decreased with increasing flow. Growth was not positively correlated with either photosynthesis
or respiration, or scope for growth. It is suggested that higher flow rates reduce the chance of disturbance of coral growth
by competing algae or cyanobacteria, allowing corals to grow more readily with the maximum specific growth rate possible under
the given environmental conditions. Notably, other effects of increased flow, such as increased respiratory rates and increased
(in)organic nutrient uptake, might have been equally responsible for the increased growth of the corals in 25 cm s−1. 相似文献
8.
Oxygen tensions and osmotic potentials are important physiological factors of plant growth and development. To optimize these
variables for cotton (Gossypium hirsutum L.) embryo culture, we quantified dissolved O2 (dO2) tensions, osmotic potentials, and pH at several locations in cotton ovules during embryony. Clark O2 microelectrodes were micromanipulated into intact ovules at an angle lateral to the developing embryo, and dO2 tensions were determined in integuments, nucelli and embryos. Ovular osmotic potentials and pH were determined from extracted
ovule sap using vapor pressure osmometers and pH microelectrodes. Dissolved O2 tensions near or in embryos decreased from 104 mmol m−3 at 5 days post-anthesis (DPA) to 83 mmol m−3 at 18 DPA. Osmotic potentials of ovule sap decreased from −0.70 megapascals (MPa) at 2 DPA to −1.12 MPa at 8 DPA but then
increased to −0.84 MPa by 17 DPA. Ovule sap pH at 5–17 DPA varied inconsistently and ranged from 5.4 to 6.5. Based on these
results, a factorial experiment with two osmotic and three O2 treatments was designed. Immature embryos of cotton cultivar HS-26 were randomly assigned to the treatment combinations and
cultured for 33 days. Oxygen treatments did not affect embryo growth, and there were no differences among treatments with
regard to percentage of embryos that progressed to a more advanced stage of embryo development. However, cotyledons of embryos
grown without osmotic adjustment were abnormally large, and embryos exposed to these treatments were abnormally brown. Browning
was less severe for embryos exposed to low O2 tensions. Growth and pigmentation were most normal for embryos simultaneously exposed to O2 tensions and osmotic potentials that best simulated the observed in ovulo conditions. 相似文献
9.
Two 60-day experiments were conducted to study the influence of photon flux density (PFD) and temperature on the attachment
and development of Gloiopeltis tenax and Gloiopeltis furcata tetraspores. In the first experiment, tetraspores of the two Gloiopeltis species were incubated at five temperature ranges (8°C, 12°C, 16°C, 20°C, 24°C) under a constant PFD of 80 μmol photons m−2 s−1 with a photoperiod of 12:12. In a second experiment, tetraspores were incubated under five PFD gradients (30, 55, 80, 105,
130 μmol photons m−2 s−1) at a constant temperature of 16°C with a photoperiod of 12:12. Maximum density of attached tetraspores was observed at 16°C
for both species. Maximum per cent of spore germinating into disc was recorded at 12–16°C for G. tenax and 8–12°C for G. furcata. Maximum per cent of discs producing erect axes for G. tenax and G. furcata were recorded at 24°C and 20°C, respectively. Light had no significant effect on tetraspore attachment and developing into
disc, but it affected the growth, sprouting and survival of its discs. Under 30–55 μmol photons m−2 s−1, the discs of the two species of Gloiopeltis did not form thallus until the end of the experiment. Optimum PFD range for G. tenax discs was 80–105 μmol photons m−2 s−1, whilst it was 80–130 μmol photons m−2 s−1 for G. furcata. Results presented in this study are expected to assist the progress of artificial seeding of Gloiopeltis. 相似文献
10.
While global climate change in polar regions is expected to cause significant warming, the annual cycle of light and dark
will remain unchanged. Cultures of three species of Antarctic sea ice diatoms, Fragilariopsis cylindrus (Grunow) Krieger, Thalassiosira antarctica Comber and Entomoneis kjellmanii (P.T. Cleve) Poulin and Cardinal, were incubated in the dark and exposed to differing temperatures. Maximum dark survival times varied between 30 and 60 days.
Photosynthetic parameters, photosynthetic efficiency (α), maximum quantum yield (Fv/Fm), maximum relative electron transport
rate (rETRmax) and non-photochemical quenching (NPQ), showed that dark exposure had a significant impact on photoacclimation.
In contrast, elevated temperatures had a relatively minor impact on photosynthetic functioning during the dark exposure period
but had a considerable impact on dark survival with minimal dark survival times reduced to only 7 days when exposed to 10°C.
Recovery of maximum quantum yield of fluorescence (Fv/Fm) was not significantly impacted by temperature, species or dark exposure
length. Recovery rates of Fv/Fm ranged from −5.06E−7 ± 2.71E−7 s−1 to 1.36E−5 ± 1.53E−5 s−1 for monthly experiments and from −9.63E−7 ± 7.71E−7 s−1 to 2.65E−5 ± 2.97E−5 s−1 for weekly experiments. NPQ recovery was greater and more consistent than Fv/Fm recovery, ranging between 5.74E−7 ± 8.11E−7 s−1 to 7.50E−3 ± 7.1E−4 s−1. The concentration of chl-a and monosaccharides remained relatively constant in both experiments. These results suggest that there will probably be little
effect on Antarctic microalgae with increasing water temperatures during the Antarctic winter. 相似文献
11.
Barton D. Clinton Chris A. Maier Chelcy R. Ford Robert J. Mitchell 《Trees - Structure and Function》2011,25(6):997-1007
In 20-year-old longleaf pine, we examined short-term effects of reduced live leaf area (A
L) via canopy scorching on sap flow (Q; kg H2O h−1), transpiration per unit leaf area (E
L; mm day−1), stem CO2 efflux (R
stem; μmol m−2 s−1) and soil CO2 efflux (R
soil; μmol m−2 s−1) over a 2-week period during early summer. R
stem and Q were measured at two positions (1.3-m or BH, and base of live crown—BLC), and R
soil was measured using 15 open-system chambers on each plot. E
L before and after treatment was estimated using Q measured at BLC with estimates of A
L before and after scorching. We expected Q to decrease in scorched trees compared with controls resulting from reduced A
L. We expected R
stem at BLC and BH and R
soil to decrease following scorching due to reduced leaf area, which would decrease carbon supply to the stem and roots. Scorching
reduced A
L by 77%. Prior to scorching, Q at BH was similar between scorch and control trees. Following scorching, Q was not different between control and scorch trees; however, E
L increased immediately following scorching by 3.5-fold compared to control trees. Changes in E
L in scorched trees corresponded well with changes in VPD (D), whereas control trees appeared more decoupled over the 5-day period following treatment. By the end of the study, R
stem decreased to 15–25% in scorched trees at both stem positions compared to control trees. Last, we found that scorching resulted
in a delayed and temporary increase in R
soil rather than a decrease. No change in Q and increased E
L following scorching indicates a substantial adjustment in stomatal conductance in scorched trees. Divergence in R
stem between scorch and control trees suggests a gradual decline in stem carbohydrates following scorching. The absence of a strong
R
soil response is likely due to non-limiting supplies of root starch during early summer. 相似文献
12.
The eco-physiological responses of three nitrogen-fixing cyanobacteria (N-fixing cyanobacteria), Aphanizomenon gracile, Anabaena minderi, and Ana. torques-reginae, to light were assessed under nutrient saturation. The N-fixing cyanobacteria were isolated into monocultures from a natural
bloom in a shallow colored lake and their growth irradiance parameters and pigment composition were assessed. The different
ecological traits related to light use (μmax, α, I
k) suggest that these N-fixing cyanobacteria are well adapted to low light conditions at sufficient nutrients, yet interspecific
differences were observed. Aphanizomenon gracile and Anabaena minderi had high relative growth rates at low irradiances (ca. 70% of those in high light), low half saturation constant for light-limited
growth (I
k < 9.09 μmol photon m−2 s−1) and high efficiency (α < 0.11 day−1 μmol photon−1 m2 s). Conversely, Ana. torques-reginae showed poorer light competitiveness: low relative growth rates at low irradiances (ca. 40% of those in high light), low α
(0.009 day−1 μmol photon−1 m2 s) and higher I
k (35.5 μmol photon m−2 s−1). Final densities in Aphanizomenon gracile and Anabaena minderi reached bloom densities at irradiances above 30 μmol photon m−2 s−1 with different hierarchy depending on irradiance, whereas Ana. torques-reginae never achieved bloom densities. All species had very low densities at irradiances ≤17 μmol photon m−2 s−1, thus no N-fixing blooms would be expected at these irradiances. Also, under prolonged darkness and at lowest irradiance
(0 and 3 μmol photon m−2 s−1) akinetes were degraded, suggesting that in ecosystems with permanently dark sediments, the prevalence of N-fixing cyanobacteria
should not be favored. All species displayed peaks of phycocyanin, but no phycoeritrin, probably due to the prevailing red
light in the ecosystem from which they were isolated. 相似文献
13.
Environmental factors that influence stomatal conductance (g
s) interact through a complex network of signal transduction and have therefore highly interdependent effect.
In the present study we examined how plant water status affects stomatal sensitivity to the change of CO2 concentration ([CO2]). We investigated the short-term dynamic of stomatal response to a sudden [CO2] increase (from 400 to 700 μmol(CO2) mol−1) in maize supplied with different amounts of water (resulting ψw = −0.35, −0.52 and −0.75 MPa). Gas exchange measurements were performed in short logging intervals and the response was monitored
under two different levels of water vapour pressure deficit (VPD) of 1 and 2 kPa in order to observe the impact of air humidity.
Generalized logistic curves were fitted to standardized stomatal response data, which enabled us to objectively estimate the
level (relative decrease of g
s) and the dynamics of the response. 相似文献
14.
A controlled growth chamber experiment was conducted to investigate the short-term water use and photosynthetic responses
of 30-d-old carrot seedlings to the combined effects of CO2 concentration (50–1 050 μmol mol−1) and moisture deficits (−5, −30, −55, and −70 kPa). The photosynthetic response data was fitted to a non-rectangular hyperbola
model. The estimated parameters were compared for effects of moisture deficit and elevated CO2 concentration (EC). The carboxylation efficiency (α) increased in response to mild moisture stress (−30 kPa) under EC when
compared to the unstressed control. However, moderate (−55 kPa) and extreme (−70 kPa) moisture deficits reduced α under EC.
Maximum net photosynthetic rate (P
Nmax) did not differ between mild water deficit and unstressed controls under EC. Moderate and extreme moisture deficits reduced
P
Nmax by nearly 85 % compared to controls. Dark respiration rate (R
D) showed no consistent response to moisture deficit. The CO2 compensation concentration (Γ) was 324 μmol mol−1 for −75 kPa and ranged 63–93 μmol mol−1 for other moisture regimes. Interaction between moisture deficit and EC was noticed for P
N, ratio of intercellular and ambient CO2 concentration (C
i/C
a), stomatal conductance (g
s
), and transpiration rate (E). P
N was maximum and C
i/C
a was minimum at −30 kPa moisture deficit and at C
a of 350 μmol mol−1. The g
s and E showed an inverse relationship at all moisture deficit regimes and EC. Water use efficiency (WUE) increased with moisture
deficit up to −55 kPa and declined thereafter. EC showed a positive influence towards sustaining P
N and increasing WUE only under mild moisture stress, and no beneficial effects of EC were noticed at moderate or extreme moisture
deficits. 相似文献
15.
James C. Kathilankal Thomas J. Mozdzer José D. Fuentes Karen J. McGlathery Paolo D’Odorico Jay C. Zieman 《Hydrobiologia》2011,669(1):167-181
Physiological measurements were used to investigate the dependence of photosynthesis on light, temperature, and intercellular
carbon dioxide (CO2) levels in the C4 marsh grass Spartina alterniflora. Functional relationships between these environmental variables and S. alterniflora physiological responses were then used to improve C4-leaf photosynthesis models. Field studies were conducted in monocultures of S. alterniflora in Virginia, USA. On average, S. alterniflora exhibited lower light saturation values (~1000 μmol m−2 s−1) than observed in other C4 plants. Maximum carbon assimilation rates and stomatal conductance to water vapor diffusion were 36 μmol (CO2) m−2 s−1 and 200 mmol (H2O) m−2 s−1, respectively. Analysis of assimilation-intercellular CO2 and light response relationships were used to determine Arrhenius-type temperature functions for maximum rate of carboxylation
(V
cmax), phosphoenolpyruvate carboxylase activity (V
pmax), and maximum electron transport rate (J
max). Maximum V
cmax values of 105 μmol m−2 s−1 were observed at the leaf temperature of 311 K. Optimum V
pmax values (80.6 μmol m−2 s−1) were observed at the foliage temperature of 308 K. The observed V
pmax values were lower than those in other C4 plants, whereas V
cmax values were higher, and more representative of C3 plants. Optimum J
max values reached 138 μmol (electrons) m−2 s−1 at the foliage temperature of 305 K. In addition, the estimated CO2 compensation points were in the range of C3 or C3–C4 intermediate plants, not those typical of C4 plants. The present results indicate the possibility of a C3–C4 intermediate or C4-like photosynthetic mechanism rather than the expected C4-biochemical pathway in S. alterniflora under field conditions. In a scenario of atmospheric warming and increased atmospheric CO2 concentrations, S. alterniflora will likely respond positively to both changes. Such responses will result in increased S. alterniflora productivity, which is uncharacteristic of C4 plants. 相似文献
16.
The influence of water activity and water content was investigated with farnesyl laurate synthesis catalyzed by Lipozyme RM
IM. Lipozyme RM IM activity depended strongly on initial water activity value. The best results were achieved for a reaction
medium with an initial water activity of 0.11 since it gives the best conversion value of 96.80%. The rate constants obtained
in the kinetics study using Ping-Pong-Bi-Bi and Ordered-Bi-Bi mechanisms with dead-end complex inhibition of lauric acid were
compared. The corresponding parameters were found to obey the Ordered-Bi-Bi mechanism with dead-end complex inhibition of
lauric acid. Kinetic parameters were calculated based on this model as follows: V
max = 5.80 mmol l−1 min−1 g enzyme−1, K
m,A = 0.70 mmol l−1 g enzyme−1, K
m,B = 115.48 mmol l−1 g enzyme−1, K
i = 11.25 mmol l−1 g enzyme−1. The optimum conditions for the esterification of farnesol with lauric acid in a continuous packed bed reactor were found
as the following: 18.18 cm packed bed height and 0.9 ml/min substrate flow rate. The optimum molar conversion of lauric acid
to farnesyl laurate was 98.07±0.82%. The effect of mass transfer in the packed bed reactor has also been studied using two
models for cases of reaction limited and mass transfer limited. A very good agreement between the mass transfer limited model
and the experimental data obtained indicating that the esterification in a packed bed reactor was mass transfer limited. 相似文献
17.
Terence J. Evens Randall P. Niedz Gary J. Kirkpatrick 《Journal of applied phycology》2008,20(4):411-422
The microalga Haematococcus pluvialis Flotow has been the subject of a number of studies concerned with maximizing astaxanthin production for use in animal feeds
and for human consumption. Several of these studies have specifically attempted to ascertain the optimal temperature and irradiance
combination for growth of H. pluvialis, but there has been a great deal of disagreement between laboratories. “Ideal” levels of temperature and irradiance have
been reported to range from 14 to 28°C and 30 to 200 μmol photons m−2 s−1. The objective of the present study was to simultaneously explore temperature and irradiance effects for a single strain
of H. pluvialis (UTEX 2505) across an experimental region that encompassed the reported “optimal” combinations of these factors for multiple
strains. To this end, a two-dimensional experimental design based on response surface methodology (RSM) was created. Maximum
growth rates for UTEX 2505 were achieved at 27°C and 260 μmol photons m−2 s−1, while maximum quantum yield for stable charge separation at PSII (Fv/Fm) was achieved at 27°C and 80 μmol photons m−2 s−1. Maximum pigment concentrations correlated closely with maximum Fv/Fm. Numeric optimization of growth rate and Fv/Fm produced an optimal combination of 27°C and 250 μmol photons m−2 s−1. Polynomial models of the various response surfaces were validated with multiple points and were found to be very useful
for predicting several H. pluvialis UTEX 2505 responses across the entire two-dimensional experimental design space. 相似文献
18.
We compared variation in sun-canopy leaf anatomy, morphology and photosynthetic rates of coexisting woody species (trees and
lianas) in an 8-year-old secondary forest (SF) and mature forest (MF) in the wet season in Xishuangbanna, SW China. Variability
of leaf traits of 66 species within growth-form groups in each forest was quantified using coefficients of variation (CV).
For the mean values, the woody species in the SF had significantly higher leaf thickness and stomatal density, but lower nonmesophyll/mesophyll
ratios than those in the MF. The average leaf area and leaf mass area (LMA) in the studied woody species did not change greatly
during the successional process, but differed significantly between the growth forms, with trees having higher values than
lianas. The light-saturated photosynthetic rate per unit leaf area (A
a) of the woody species in the SF ranged from 11.2 to 34.5 μmol m−2 s−1, similarly to pioneer tree species from literature data in southeast Asia. The A
a and photosynthetic nitrogen-use efficiency (PNUE) were significantly higher than those in the MF; whereas A
a in the MF ranged between 9 to 21 μmol m−2 s−1, with similar values between lianas and trees. For all woody species in both SF and MF, there were no significant differences
in the average values of the CV of all measured variables for both lianas and trees. However, considerable variation in leaf
anatomy, morphology, and photosynthetic rates within both growth forms and forests existed, as well as substantial variation
in leaf size and stomatal density. We concluded that the tropical woody species formed a heterogeneous functional group in
terms of leaf morphology and physiology in both secondary and mature forests. 相似文献
19.
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
20.
Philip G. Oguntunde 《Plant and Soil》2005,278(1-2):371-383
Cassava (Manihot esculenta Crantz), a perennial woody shrub, is known to be highly productive under favourable conditions and produce reasonably well
under adverse conditions where other crops fail. Using constant heat sap flow sensors, sap flow density (F
d
) of cassava was monitored for 10 days in December 2002. Sap flow was highly correlated (R
2
=0.72, P<0.05) to incoming solar radiation (R
s) than to other climatic factors. Using cross-correlation analysis, no time shift was detected between F
d
and solar radiation, whereas vapour pressure deficit (VPD) lags F
d
by 110 min. Solar radiation and VPD together explained 83% of diurnal variation in sap flow. Whole-plant transpiration ranged
from 0.8 to 1.2 mm day−1 and daily canopy conductance (g
c), computed based on the inverted Penman–Monteith model, varied between 0.7 and 2.1 mm s−1 (mean = 1.4 ± 0.5 mm s−1). For the measurement period, characterized by high evaporative demand coupled with low available soil water, transpiration
accounted for 21% of the available energy and was only able to meet 24% of the atmospheric water demand. Average decoupling
factor (Ω) of 0.05±0.02 estimated suggested that a 10% change in g
c may lead to more than 9% change in transpiration which further supports the notion that stomata play significant role in
regulating cassava water use compared to other known mechanisms. Beyond light saturation (R
s
>300 W m−2) and at higher VPD (>1.0 kPa), wind effects on the canopy transpiration under water stress condition were low, while VPD
explains 94% of the observed variance in daily canopy conductance. 相似文献