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1.
Adaptation and acclimation of growth and photosynthesis of five Antarctic red algae to low temperatures 总被引:2,自引:0,他引:2
Temperature requirements for growth, photosynthesis and dark respiration were determined for five Antarctic red algal species.
After acclimation, the stenothermal species Gigartina skottsbergii and Ballia callitricha grew at 0 or up to 5 °C, respectively; the eurythermal species Kallymenia antarctica, Gymnogongrus antarcticus and Phyllophora ahnfeltioides grew up to 10 °C. The temperature optima of photosynthesis were between 10 and 15 °C in the stenothermal species and between
15 and 25 °C in the eurythermal species, irrespective of the growth temperature. This shows that the temperature optima for
photosynthesis are located well below the optima from species of other biogeographical regions, even from the Arctic. Respiratory
rates rose with increasing temperatures. In contrast to photosynthesis, no temperature optimum was evident between 0 and 25 °C.
Partial acclimation of photosynthetic capacity to growth temperature was found in two species. B. callitricha and Gymnogongrus antarcticus acclimate to 0 °C, and 5 and 0 °C, respectively. But acclimation did in no case lead to an overall shift in the temperature
optimum of photosynthesis. B. callitricha and Gymnogongrus antarcticus showed acclimation of respiration to 5 °C, and P. ahnfeltioides to 5 and 10 °C, resulting in a temperature independence of respiration when measured at growth temperature. With respect
to the acclimation potential of the species, no distinction can be made between the stenothermal versus the eurythermal group.
(Net)photosynthetic capacity:respiration (P:R) ratios showed in all species highest values at 0 °C and decreased continuously to values lower than 1.0 at 25 °C. In turn,
the low P:R ratios at higher temperatures are assumed to determine the upper temperature growth limit of the studied species. Estimated
daily carbon balance reached values between 4.1 and 30.7 mg C g−1 FW day−1 at 0 °C, 16:8 h light/dark cycle, 12–40 μmol m−2 s−1.
Received: 4 November 1999 / Accepted: 7 March 2000 相似文献
2.
Acclimation of brown algal photosynthesis to ultraviolet radiation in Arctic coastal waters (Spitsbergen, Norway) 总被引:9,自引:2,他引:7
Kai Bischof Dieter Hanelt Helmut Tüg Ulf Karsten Patty E. M. Brouwer Christian Wiencke 《Polar Biology》1998,20(6):388-395
In field studies conducted at the Kongsfjord (Spitsbergen) changes of the irradiance in the atmosphere and the sublittoral
zone were monitored from the beginning of June until the end of August 1997, to register the minimum and maximum fluxes of
ultraviolet and photosynthetically active radiation and to characterise the underwater light climate. Measurements of photosynthesis
in three abundant brown algal species (Alaria esculenta, Laminaria saccharina, Saccorhiza dermatodea) were conducted to test whether their photosynthetic performance reflects changing light climate in accordance with depth.
Plants sampled at various depths were exposed to controlled fluence rates of photosynthetically active radiation (400–700 nm),
UV-A (320–400 nm) and UV-B (280–320 nm). Changes in photosynthetic performance during the treatments were monitored by measuring
variable chlorophyll fluorescence of photosystem II. In each species, the degree of inhibition of photosynthesis was related
to the original collection depth, i.e. shallow-water isolates were more resistant than plants from deeper waters. The results
show that macroalgae acclimate effectively to increasing irradiance levels for both photosynthetically active and ultraviolet
radiation. However, the kinetics of acclimation are different within the different species. It is shown that one important
strategy to cope with higher irradiance levels in shallow waters is the capability for a faster recovery from high light stress
compared to isolates from deeper waters.
Received: 13 March 1998 / Accepted: 16 May 1998 相似文献
3.
The functional roles of the contrasting morphologies of sun and shade shoots of the evergreen shrub Heteromeles arbutifolia were investigated in chaparral and understory habitats by applying a three-dimensional plant architecture simulation model,
YPLANT. The simulations were shown to accurately predict the measured frequency distribution of photosynthetic photon flux
density (PFD) on both the leaves and a horizontal surface in the open, and gave reasonably good agreement for the more complex
light environment in the shade. The sun shoot architecture was orthotropic and characterized by steeply inclined (mean = 71o) leaves in a spiral phyllotaxy with short internodes. This architecture resulted in relatively low light absorption efficiencies
(E
A) for both diffuse and direct PFD, especially during the summer when solar elevation angles were high. Shade shoots were more
plagiotropic with longer internodes and a pseudo-distichous phyllotaxis caused by bending of the petioles that positioned
the leaves in a nearly horizontal plane (mean = 5o). This shade-shoot architecture resulted in higher E
A values for both direct and diffuse PFD as compared to those of the sun shoots. Differences in E
A between sun and shade shoots and between summer and winter were related to differences in projection efficiencies as determined
by leaf and solar angles, and by differences in self shading resulting from leaf overlap. The leaves exhibited photosynthetic
acclimation to the sun and the shade, with the sun leaves having higher photosynthetic capacities per unit area, higher leaf
mass per unit area and lower respiration rates per unit area than shade leaves. Despite having 7 times greater available PFD,
sun shoots absorbed only 3 times more and had daily carbon gains only double of those of shade shoots. Simulations showed
that sun and shade plants performed similarly in the open light environment, but that shade shoots substantially outperformed
sun shoots in the shade light environment. The shoot architecture observed in sun plants appears to achieve an efficient compromise
between maximizing carbon gain while minimizing the time that the leaf surfaces are exposed to PFDs in excess of those required
for light saturation of photosynthesis and therefore potentially photoinhibitory.
Received: 8 June 1997 / Accepted: 2 November 1997 相似文献
4.
In three tropical rain forest light environments in Sabah, Malaysia, we compared photosynthesis in seedlings of ten climax
tree species with putatively differing shade tolerances. The objectives of the study were (a) to characterise the range of
photosynthetic responses in ten species of the Dipterocarpaceae and (b) to elucidate those photosynthetic characteristics
that might provide a basis for niche partitioning. Seedlings were acclimated (c. 7 months) in three light environments; understorey, partial shade and a gap (140 m2). The light environments represented a gradation in median diurnal (0630–1830 hours) photon flux density (PFD) ranging from
understorey (4.7 μmol m−2 s−1), through partial shade (21.2 μmol m−2 s−1) to gap (113.7 μmol m−2 s−1). Integrated diurnal PFD were in the sequence gap > partial shade > understorey (15.2, 4.7, 1.3 mol m−2 day−1, respectively). In gap-acclimated plants, species differed in the photosynthetic light-response variables apparent quantum
yield, dark respiration rate, light compensation point, net saturated leaf assimilation rate (A
sat), and in stomatal conductance (g
s sat) when assimilation rate (A) was saturated. A light-demanding pioneer species (Macaranga hypoleuca) and a shade-demanding understorey species (Begonia sp.) had, respectively, higher and lower A
sat and g
s sat than the dipterocarp species. In high-light conditions A
sat and g
s sat were strongly positively correlated in dipterocarp species. Differing photosynthetic characteristics of gap-acclimated plants
suggest that, in these dipterocarp species, different rates of carbon fixation may be an important factor contributing towards
niche partitioning. Mean integrated diurnal A (A
diurnal) in the gap, partial shade and understory were, respectively, 122.9, 52.7, 20.5 mmol m−2 day−1. Differences occurred in A
diurnal of dipterocarp species between light environments. When Macaranga was included, differences in A
diurnal were evident in the gap and partial shade, and in both cases were attributed to the pioneer. For the variable A
diurnal, there was of a shift in the rank position of Macaranga among light environments, but a shift did not occur among the dipterocarp species. Results from this study are consistent
with the idea that rates of carbon fixation per unit leaf area may contribute towards niche differentiation between the climax
and single pioneer species, but not within the group of climax species. Other physiological and/or carbon allocation factors
may be involved in any niche partitioning; dipterocarp species often have inherently different growth rates and susceptibility
to herbivory. As an alternative to niche partitioning, dipterocarp species may co-exist in natural light environments as a
result of habitat disequilibrium or purely stochastic processes.
Received: 2 April 1997 / Accepted: 13 July 1997 相似文献
5.
Microstegium vimineum (Trin.) A. Camus, a shade-tolerant C4 grass, has spread throughout the eastern United States since its introduction in 1919. This species invades disturbed understory
habitats along streambanks and surrounding mesic forests, and has become a major pest in areas such as Great Smoky Mountains
National Park. The focus of this study was to characterize the photosynthetic induction responses of M. vimineum, specifically its ability to utilize low light and sunflecks, two factors that may be critical to invasive abilities and
survival in the understory. In addition, we were curious about the ability of a grass with the C4 photosynthetic pathway to respond to sunflecks. Plants were grown under 25% and 50% ambient sunlight, and photosynthetic
responses to both steady-state and variable light were determined. Plants grown in both 25% and 50% ambient sun became 90%
light saturated between 750–850 μmol m−2 s−1; however, plants grown in 50% ambient sun had significantly higher maximum steady-state photosynthetic rates (16.09 ± 1.37 μmol m−2 s−1 vs. 12.71 ± 1.18 μmol m−2 s−1). Both groups of plants induced to 50% of the steady-state rate in 3–5 min, while it took 10–13 min to reach 90% of maximum
rates, under both flashing and steady-state light. For both groups of plants, stomatal conductance during induction reached
maximum rates in 6–7 min, after which rates decreased slightly. Upon return to low light, rates of induction loss and stomatal
closure were very rapid in both groups of plants, but were more rapid in those grown in high light. Rapid induction and the
ability to induce under flashing light may enable this species to invade and dominate mesic understory habitats, while rapid
induction loss due to stomatal closure may prevent excess water loss when low light constrains photosynthesis. The C4 pathway itself does not appear to present an insurmountable barrier to the ability of this grass species to respond to sunflecks
in an understory environment.
Received: 21 February 1997 / Accepted: 10 October 1997 相似文献
6.
Akio Takenaka 《Ecological Research》1986,1(2):129-140
Ecophysiological comparisons were made of the growth and photosynthetic characteristics between seedlings of deciduousQuercus serrata and evergreenQuercus myrsinaefolia. Q. myrsinaefolia seedlings naturally occurring in secondary coppice forests showed exponential-like growth in height with age, while sympatricQ. serrata seedlings were considerably smaller in height, their growth being limited by shortage of light. The photosynthetic characteristics
measured under laboratory conditions showed no bases for the differences in growth between the two species on the forest floor:
Light compensation points of the seedlings raised under 5% daylight were almost identical for the two species, being about
6.0 μE·m−2·s−1. Growth analysis of seedlings planted in a coppice forest showed that bothQ. serrata andQ. myrsinaefolia could hardly grow during the summer under the shrub layer, when relative photon flux density (RPFD) was 0.9±0.5%. In the
winter, when RPFD under the leafless canopy increased to 29.3±2.7%, the dry matter production of the evergreen seedlings ofQ. myrsinaefolia was much improved. Current-year seedlings of the species showed NAR of 0.102±0.021 g·dm−2·mo−1 during the winter. Temperature dependency of photosynthesis and increment of leaf temperature by direct solar beam also indicated
active photosynthesis ofQ. myrsinaefolia on the forest floor during the winter. 相似文献
7.
In this study, sun leaf carbon isotope composition (δ13C) of two co-occurring woody Mediterranean species (Quercus pubescens Willd., a deciduous oak, and Q. ilex L., an evergreen one) was investigated on four sites with different water availability. The total range of δ13C values was 4.4 and 3.1‰ for Q. pubescens and Q. ilex respectively. The intra-site variability was about 3‰. Total mean per species was equal. There were significant differences
among sites, but at each site means of δ13C were not significantly different between species. A simple physiological model predicts no difference in intrinsic water-use
efficiency (WUEi) between evergreen and deciduous oaks. The relationship between site means of δ13C and water parameters suggests that there is a leaf functional adjustment with respect to available water resource. No correlation
was found between δ13C and the contents of any mass-based biochemical constituent. Nevertheless there was a significant correlation between δ13C and leaf mass per area of Q. ilex. For both species, there is also a positive correlation between leaf δ13C and individual crown area, i.e. a structural characteristic at tree level. Causal relations between δ13C and plant-environment interactions are discussed.
Received: 25 October 1996 / Accepted: 19 January 1997 相似文献
8.
Kun-dong Bai De-bao Liao De-bing Jiang Kun-fang Cao 《Trees - Structure and Function》2008,22(4):449-462
Photosynthetic induction times and photoinhibition in relation to simulated sunflecks (sudden increase of irradiance from
20 to 1,500 μmol m−2 s−1) were examined in leaves of co-occurring Fagus lucida (a deciduous tree) and Castanopsis lamontii (an evergreen tree) saplings grown either in a beech forest understory or in an adjacent open site during a late rainy season.
Two hypotheses were tested: (1) understory leaves would display faster photosynthetic induction times and greater photoinhibition
than open-grown leaves; and (2) evergreen species would have slower photosynthetic induction times and lighter photoinhibition
than deciduous species. Times to reach 90% of maximal CO2 assimilation rate (t
90%A
) and stomatal conductance
did not differ between species, but showed faster by 3–5 min in open-grown leaves than understory leaves due to higher initial
stomatal conductance (g
s
initial) and induction state 1 min into simulated sunflecks (IS1min) in the former. Our analysis across the published data on photosynthetic induction of 48 broad-leaved woody species again
revealed the negative correlations between t
90%A
and either g
s initial or IS1min, and the similarity of t
90%A
and between evergreen and deciduous species. Measurements of maximum PSII photochemical efficiency (F
v/F
m) indicated that photoinhibition occurred in saplings in any of the growth habitats during sunfleck-induced photosynthetic
induction. Despite no interspecific differences in the degree of photoinhibition, understory leaves of both species suffered
heavier photoinhibition than open-grown leaves, as indicated by a stronger decrease of F
v/F
m in the former. Dynamic changes in the quantum yields of PSII photochemistry and ΔpH- and xanthophyll-regulated thermal dissipation
and adjustments in the partitioning of electron flow between assimilative and non-assimilative processes were functional to
resist photoinhibition. However, such photoinhibition, together with stomatal and biochemical limitations, would decrease
carbon gain during simulated sunflecks, particularly in understory leaves. 相似文献
9.
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
10.
Deciduous and evergreen species are segregated on northeast and southwest slopes of the southern Appalachian Mountains. The segregated distributions of three ericaceous shrubs (Rhododendron maximum valley positions; Rhododendron periclymenoides on northeast slopes; Kalmia latifolia on southwest slopes) were compared to the respective irradiance environments. Growth patterns of field plants, and photosynthetic acclimation of each species to three irradiance treatments in a phytotron were studied. Rhododendron maximum, an evergreen species, was found to be most sensitive to high radiation. In phytotron experiments, quantum yield, light saturated photosynthetic capacity, photosynthesis per chlorophyll, and water use efficiency decreased at high ambient irradiance for R. maximum. These characteristics limit the growth of R. maximum on high irradiance southwestern slopes. Both K. latifolia and R. periclymenoides were able to improve their photosynthetic performance at high ambient irradiance. Rhododendron periclymenoides, a deciduous species, was found to continue increasing leaf conductance at high irradiance without an increase in photosynthesis indicating a possible limitation by water in high light environments such as southwest slopes. Kalmia latifolia, an evergreen species, had reduced photosynthetic capacity and reduced water use efficiency when grown in low irradiance conditions which coincides with the higher K. latifolia abundance on high light, southwestern slopes. 相似文献
11.
We investigated how photosynthesis by understory seedlings of the lowland tropical tree species Alseis blackiana responded to 10 years of soil nutrient fertilization with N, P and K. We ask whether nutrients are limiting to light and
CO2 acquisition in a low light understory environment. We measured foliar nutrient concentrations of N, P and K, isotopic composition
of carbon (δ13C) and nitrogen (δ15N), and light response curves of photosynthesis and chlorophyll fluorescence. Canopy openness was measured above each study
seedling and included in statistical analyses to account for variation in light availability. Foliar N concentration increased
by 20% with N addition. Foliar P concentration increased by 78% with P addition and decreased by 14% with N addition. Foliar
K increased by 8% with K addition. Foliar δ13C showed no significant responses, and foliar δ15N decreased strongly with N addition, matching the low δ15N values of applied fertilizer. Canopy openness ranged from 0.01 to 6.71% with a mean of 1.76 ± 0.14 (±1SE). Maximum photosynthetic
CO2 assimilation rate increased by 9% with N addition. Stomatal conductance increased with P addition and with P and K in combination.
Chlorophyll fluorescence measurements revealed that quantum yield of photosystem II increased with K addition, maximum electron
transport rate trended 9% greater with N addition (p = 0.07), and saturating photosynthetically active radiation increased with N addition. The results demonstrate that nutrient
addition can enhance photosynthetic processes, even under low light availability. 相似文献
12.
Analysis of differences in photosynthetic nitrogen use efficiency of alpine and lowland Poa species 总被引:1,自引:0,他引:1
This study investigates factors determining variation in photosynthetic nitrogen use efficiency (φN) in seven slow- and fast-growing Poa species from altitudinally contrasting sites. The species and their environmental origin were (in order of increasing relative
growth rate): two alpine (Poa fawcettiae and P. costiniana), one sub-alpine (P. alpina) and three temperate lowland perennials (P. pratensis, P. compressa and P. trivialis), as well as one temperate lowland annual (P. annua). Plants were grown hydroponically under identical conditions with free access to nutrients in a growth room. Photosynthesis
per unit leaf area measured at growth irradiance (500 μmol m−2 s−1) was slightly higher in the slow-growing alpine species. At saturating light intensities, photosynthesis was considerably
higher in the alpine species than in the lowland species. Carboxylation capacity and Rubisco content per unit leaf area were
also greater in the alpine species. Despite variation between the species, the in vivo specific activity of Rubisco showed
little relationship to relative growth rate or photosynthetic rate. Both at light saturation and at the growth irradiance,
φN was lowest in the slow-growing alpine species P. fawcettiae, P. costiniana and P. alpina, and highest in the fast-growing P. compressa and P. annua. The proportion of leaf nitrogen that was allocated to photosynthetic capacity and the in vivo catalytic constant of Rubisco
accounted for most of the variation in φN at light saturation. Minor variations in intercellular CO2 partial pressure also contributed to some extent to the variations in φN at light saturation. The low φN values at growth irradiance exhibited by the alpine species were additionally due to a lower percentage utilisation of their
high photosynthetic capacity compared to the lowland species.
Received: 28 May 1998 / Accepted: 28 March 1999 相似文献
13.
Seasonal differences in xanthophyll cycle characteristics and antioxidants in Mahonia repens growing in different light environments 总被引:1,自引:0,他引:1
Barry A. Logan Stephen C. Grace William W. Adams III Barbara Demmig-Adams 《Oecologia》1998,116(1-2):9-17
We investigated differences between summer and winter in photosynthesis, xanthophyll cycle-dependent energy dissipation,
and antioxidant systems in populations of Mahonia repens (Lindley) Don growing in the eastern foothills of the Colorado Rocky Mountains in deep shade, full exposure, and under a
single-layered canopy of Pinus ponderosa (partially shaded). In summer, increasing growth irradiance (from deep shade to partial shade to full exposure) was associated
with increased xanthophyll cycle-dependent energy dissipation in PSII and an increased capacity to detoxify reactive reduced
oxygen species, as measured by increases in the activities of ascorbate peroxidase, superoxide scavenging, glutathione reductase,
and monodehydroascorbate reductase, as well as increases in leaf ascorbate and glutathione content. Leaves of exposed and
partially shaded plants exhibited decreased capacities for photosynthetic O2 evolution in winter compared to summer, while in the deeply shaded plants this parameter did not differ seasonally. Seasonal
differences in the levels of antioxidants generally exhibited an inverse response to photosynthesis, being higher in winter
compared to summer in the exposed and partially shaded populations, but remaining unchanged in the deeply shaded population.
In addition, total pool size and conversion state of the xanthophyll cycle were higher in winter than in summer in all populations.
These trends suggest that both xanthophyll cycle-dependent energy dissipation in PSII and the capacity to detoxify reactive
reduced oxygen species responded to the level of excess light absorption.
Received: 23 October 1997 / Accepted: 23 March 1998 相似文献
14.
The success of P. juliflora, an evergreen woody species has been largely attributed to temperature acclimation and stomatal control of photosynthesis
under wide range of environmental conditions prevalent in India. We studied the contribution of the enzyme ribulose-1,5 bisphosphate
carboxylase/oxygenase (Rubisco) in diurnal and seasonal photosynthesis changes in P. juliflora. The changes observed in photosynthesis under natural conditions could be effected by the growth temperatures, which ranged
from 10–30 °C in winter to 30–47 °C in summer. However, the Total Rubisco activity displayed a constant diurnal pattern and
showed a maximum at 1200 in all seasons namely spring, summer, monsoon and winter irrespective of the changes in temperature.
The Total Rubisco activity from two cohorts of leaves produced in spring and monsoon appeared to be down-regulated differentially
at low PPFD during the evening. The in vivo and in vitro measurements of carboxylation efficiency of Rubisco showed wide variation during the day and were correlated with the photosynthesis
rate. The light activation of Rubisco showed the acclimation to moderately high temperatures in different seasons except in
summer. The exceptionally high temperatures (>45 °C) in summer, though not affecting Total activity, severely inhibited the
light activation of Rubisco and also modulated the recovery process for the activation of Rubisco. Our studies suggest that
the modulation of Rubisco driven by Rubisco activase and not Rubisco per se was crucial for the diurnal regulation of photosynthesis.
NBRI Publication No.: 528 相似文献
15.
广东南岭天然常绿阔叶林林下光环境对林下幼树功能性状的影响 总被引:3,自引:0,他引:3
光环境与幼树功能性状的关系对天然林的更新与演替具有重要的生态学意义。以广东南岭区域天然常绿阔叶林下不同林龄(幼龄林,中龄林,老龄林)的森林群落为研究对象,通过监测冠层结构、林下光照数据和林下幼树功能性状等指标,研究林龄梯度下其冠层结构与林下光环境之间的关系,以及林下幼树功能性状对光环境的响应。结果表明:(1)中龄林叶面积指数显著高于幼龄林和老龄林(P0.05),随着林龄的增长,林冠开度和透光率逐渐下降,林龄梯度下透光率、R/FR(红光/远红光比值)、Bw/Rw(宽带蓝光/宽带红光比值)差异极显著(P0.001);(2)天然常绿阔叶林中透光率与光质之间极显著相关(P0.001),R/FR随着透光率的增加而增加,Bw/Rw随着透光率的增加而减少。(3)林下幼树功能性状在光环境之间差异显著(P0.05),老龄林林下幼树叶片氮含量显著高于幼龄林,而叶片重叠率显著低于幼龄林;(4)在本试验地中,R/FR和Bw/Rw的变化对林下幼树的高径比和光合作用并无显著影响,光强对同种植物不同光环境下最大净光合速率的影响较大。总体而言,林龄梯度冠层结构和光环境的差异能在一定程度上解释幼树功能性状的差异,这将有助于我们理解光环境对林下幼树更新的影响机制,同时为天然植被恢复和森林经营提供指导。 相似文献
16.
Foliar carbon isotope discrimination in Larix species and sympatric evergreen conifers: a global comparison 总被引:2,自引:0,他引:2
Larches (Larix spp.), deciduous conifers, occur in the northern hemisphere in cold-temperate and boreal climates – an environment normally
thought to favor evergreen tree species. We compare foliar carbon isotope discrimination (Δ), instantaneous water use efficiency,
total foliar nitrogen concentration, and specific leaf area (for a subset of sites) between Larix spp. and co-occurring evergreen conifers at 20 sites throughout the natural range of larches. Except for Larix occidentalis in the xeric Intermountain West, USA, Δ is significantly (P < 0.05) greater for larches than co-occurring evergreen conifers at 77% of the sites, suggesting that larches use water less
efficiently. At elevations greater than 3000 m, the Δ of Larix spp. and co-occurring conifers converge, suggesting that water is not the limiting resource. Foliar nitrogen concentration
and specific leaf area are two ecophysiological characteristics that are positively correlated with high photosynthetic capacity.
Foliar nitrogen concentration is significantly greater for larches than evergreen conifers at 88% of the sites and specific
leaf area is approximately three times greater for larches than co-occurring conifers. Future studies should examine the potential
effect that global warming may have on the distribution of larch forests because the water use efficiency of larches is commonly
less than co-occurring evergreen conifers and the boreal and high-latitude environments are likely to experience the greatest
climate warming.
Received: 23 May 1997 / Accepted: 28 October 1997 相似文献
17.
In a temperate climate, evergreen species in the understory are exposed to large changes in photosynthetic photon flux density
(PPFD) and temperature over the year. We determined the photosynthetic traits of leaves of an evergreen understory shrub Aucuba japonica at three sites at monthly intervals: understorys of a deciduous forest; an evergreen forest; and a gap in a mixed forest.
This set up enabled us to separate the effects of seasonal change in PPFD and temperature on photosynthetic acclimation under
natural conditions. The effects of PPFD and temperature were analysed by simple and multiple regression analyses. The amounts
of light utilisation components (LU), represented by nitrogen and rubisco contents per area, were higher in winter, when temperature
was low and PPFD was high. The LU relative to the amount of light harvesting components (LH), represented by chlorophyll a/b and rubisco/chlorophyll ratios, and the inverse of chlorophyll/nitrogen ratio were also higher in winter. We quantified the
effects of PPFD and temperature on the LU and LH components. Across sites PPFD had stronger effects than air temperature,
while within a site temperature had stronger effects on photosynthetic acclimation. We concluded that the photosynthetic apparatus
is strongly affected by the prevailing PPFD at the time of leaf development. Within a given light regime, however, plants
acclimated by increasing LU relative to LH primarily in response to temperature and to a lesser extent to PPFD. 相似文献
18.
Growth, biomass allocation and photosynthesis of invasive and native Hawaiian rainforest species 总被引:29,自引:0,他引:29
Growth, biomass allocation, and photosynthetic characteristics of seedlings of five invasive non-indigenous and four native
species grown under different light regimes were studied to help explain the success of invasive species in Hawaiian rainforests.
Plants were grown under three greenhouse light levels representative of those found in the center and edge of gaps and in
the understory of Hawaiian rainforests, and under an additional treatment with unaltered shade. Relative growth rates (RGRs)
of invasive species grown in sun and partial shade were significantly higher than those for native species, averaging 0.25
and 0.17 g g−1 week−1, respectively, while native species averaged only 0.09 and 0.06 g g−1 week−1, respectively. The RGR of invasive species under the shade treatment was 40% higher than that of native species. Leaf area
ratios (LARs) of sun and partial-shade-grown invasive and native species were similar but the LAR of invasive species in the
shade was, on average, 20% higher than that of native species. There were no differences between invasive and native species
in biomass allocation to shoots and roots, or in leaf mass per area across light environments. Light-saturated photosynthetic
rates (Pmax) were higher for invasive species than for native species in all light treatments. Pmax of invasive species grown
in the sun treatment, for example, ranged from 5.5 to 11.9 μmol m−2 s−1 as compared with 3.0−4.5 μmol m−2 s−1 for native species grown under similar light conditions. The slope of the linear relationship between Pmax and dark respiration
was steeper for invasive than for native species, indicating that invasive species assimilate more CO2 at a lower respiratory cost than native species. These results suggest that the invasive species may have higher growth rates
than the native species as a consequence of higher photosynthetic capacities under sun and partial shade, lower dark respiration
under all light treatments, and higher LARs when growing under shade conditions. Overall, invasive species appear to be better
suited than native species to capturing and utilizing light resources, particularly in high-light environments such as those
characterized by relatively high levels of disturbance.
Received: 30 December 1997 / Accepted: 1 September 1998 相似文献
19.
Photosynthetic responses to dynamic light under field conditions in six tropical rainforest shrubs occuring along a light gradient 总被引:3,自引:0,他引:3
We examined in the field the photosynthetic utilization of fluctuating light by six neotropical rainforest shrubs of the
family Rubiaceae. They were growing in three different light environments: forest understory, small gaps, and clearings. Gas
exchange techniques were used to analyse photosynthetic induction response, induction maintenance during low-light periods,
and lightfleck (simulated sunfleck) use efficiency (LUE). Total daily photon flux density (PFD) reaching the plants during
the wet season was 37 times higher in clearings than in the understory, with small gaps exhibiting intermediate values. Sunflecks
were more frequent, but shorter and of lower intensity in the understory than in clearings. However, sunflecks contributed
one-third of the daily PFD in the understory. Maximum rates of net photosynthesis, carboxylation capacity, electron transport,
and maximum stomatal conductance were lower in understory species than in species growing in small gaps or clearings, while
the reverse was true for the curvature factor of the light response of photosynthesis. No significant differences were found
in the apparent quantum yield. The rise of net photosynthesis during induction after transfer from low to high light varied
from a hyperbolic shape to a sigmoidal increase. Rates of photosynthetic induction exhibited a negative exponential relationship
with stomatal conductance in the shade prior to the increase in PFD. Leaves of understory species showed the most rapid induction
and remained induced longer once transferred to the shade than did leaves of medium- or high-light species. LUE decreased
rapidly with increasing lightfleck duration and was affected by the induction state of the leaf. Fully induced leaves exhibited
LUEs up to 300% for 1-s lightflecks, while LUE was below 100% for 1–80 s lightflecks in uninduced leaves. Both induced and
uninduced leaves of understory species exhibited higher LUE than those of species growing in small gaps or clearings. However,
most differences disappeared for lightflecks 10 s long or longer. Thus, understory species, which grew in a highly dynamic
light environment, had better capacities for utilization of rapidly fluctuating light than species from habitats with higher
light availability.
Received: 4 January 1997 / Accepted: 28 April 1997 相似文献
20.
We studied the effect of NaCl salinity on the development of cellular photosynthesis using a green, photomixotrophic, cell-suspension
culture of Alternanthera philoxeroides (Mart.) Griseb. For these cells, increasing the concentration of sucrose in the media produces a rapid drop in net photosynthetic
rate, which recovers as sucrose is depleted from the media. This predictable recovery provides a simple system to examine
cellular photosynthetic development. Cells, unadapted to high salinity, were transferred to nutrient media with 30 mM sucrose
(Control) or nutrient media with 30 mM sucrose and 100 mM NaCl (Salt). A dramatic increase in the dark respiration rate of
Control and Salt cells during the first 6 d of the experiment produced net oxygen consumption in the light. The high dark
respiration rates during this period were accompanied by a decline in total Chl and the amounts of two photosynthetic proteins,
the light harvesting Chl a/b binding protein of photosystem II (LHCP) and the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco
SSU). The dark respiration rate of Salt cells was greater than that of Control cells on days 4–8. After day 4, dark respiration
rates decreased and net photosynthesis increased to stable values in both treatments at day 11 after media sucrose concentration
reached a minimum. As dark respiration rates decreased and net photosynthetic rates increased, total Chl and the amounts of
LHCP and rubisco SSU increased in both Control and Salt cells. The slower development of photosynthetic capacity in salt cells
was correlated with a fresh weight that was 20% lower than that of control cells at the end of the experiment. 相似文献