共查询到20条相似文献,搜索用时 135 毫秒
1.
Hemant Lata Suman Chandra Ikhlas Khan Mahmoud A. ElSohly 《In vitro cellular & developmental biology. Plant》2009,45(1):12-19
Induction of high-frequency shoot regeneration using nodal segments containing axillary buds from a 1-yr-old mother plants
of Cannabis sativa was achieved on Murashige and Skoog (MS) medium containing 0.05–5.0 μM thidiazuron. The quality and quantity of regenerants
were better with thidiazuron (0.5 μM thidiazuron) than with benzyladenine or kinetin. Adding 7.0 μM of gibberellic acid into
a medium containing 0.5 μM thidiazuron slightly increased shoot growth. Elongated shoots when transferred to half-strength
MS medium supplemented with 500 mg l−1 activated charcoal and 2.5 μM indole-3-butyric acid resulted in 95% rooting. The rooted plants were successfully acclimatized
in soil. Following acclimatization, growth performance of 4-mo-old in vitro propagated plants was compared with ex vitro vegetatively grown plants of the same age. The photosynthesis and transpiration characteristics were studied under different
light levels (0, 500, 1,000, 1,500, or 2,000 μmol m−2 s−1). An increase in photosynthesis was observed with increase in the light intensity up to 1,500 μmol m−2 s−1 and then decreased subsequently at higher light levels in both types of plants. However, the increase was more pronounced
at lower light intensities below 500 μmol m−2 s−1. Stomatal conductance and transpiration increased with light intensity up to highest level (2000 μmol m−2 s−1) tested. Intercellular CO2 concentration (C
i) and the ratio of intercellular CO2 concentration to ambient CO2 (C
i/C
a) decreased with the increase in light intensity in both in vitro as well as ex vitro raised plants. The results show that in vitro propagated and hardened plants were functionally comparable to ex vitro plants of same age in terms of gas and water vapor exchange characteristics, within the limits of this study. 相似文献
2.
Low light availability under a forest canopy often limits plant growth; however, sudden increase in light intensity may induce
photoinhibition of photosynthesis. The aim of this study was to evaluate the ecophysiological changes that occur in potted
plants of Minquartia guianensis and Swietenia macrophylla during the acclimation process to full sunlight. We used six full-sun independent acclimation periods (30, 60, 90, 120, 150,
and 180 days) and a control kept in the shade. Shading was obtained by placing plants under the canopy of a small forest.
The Fv/Fm ratio, net photosynthetic rate (P
N), the maximum carboxylation velocity of Rubisco (V
cmax), maximum electron transport rate (J
max), specific leaf area (SLA), and growth were assessed at the end of each of the six acclimation periods. Plant exposure to
full sunlight caused a sudden decrease in the Fv/Fm ratio (photoinhibition) particularly in Minquartia. Photooxidation (necrotic patches) of the leaf tissue was observed in upper leaves of Minquartia. The higher P
N values were observed in Swietenia under full sun, about 12 μmol(CO2) m−2 s−1. V
cmax25 values were higher after 90 days of acclimation, about 14 μmol(CO2) m−2 s−1 for Minquartia, and 35 μmol(CO2) m−2 s−1 for Swietenia. At the end of a 180-d acclimation period J
max25 was 35 μmol(electron) m−2 s−1 for Minquartia and 60 μmol(electron) m−2 s−1 for Swietenia. SLA was higher in Swietenia than in Minquartia. In Minquartia, monthly rate of leaf production per plant (MRLP) was positive (0.22 leaf month−1) after four months in the open. Whereas, in Swietenia MRLP was positive (0.56 leaf month−1) after an acclimation period of two months. After six months in the open, height growth rates were 3.5 and 28 mm month−1 for Minquartia and Swietenia, respectively. The greater acclimation capacity of Swietenia was associated to an enhanced photosynthetic plasticity under full sun. In Minquartia, transition to full-sun conditions and lack of physiological adjustment resulted in severe photoinhibition and loss of leaves. 相似文献
3.
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
4.
Pilar Pérez Aitor Alonso Gloria Zita Rosa Morcuende Rafael Martínez-Carrasco 《Plant Growth Regulation》2011,65(3):439-447
Increases in growth temperature have been observed to affect photosynthesis differently under long-term exposure to ambient-
and twice ambient-air CO2 concentrations. This study investigates the causes of this interaction in wheat (Triticum aestivum L.) grown in the field over two consecutive years under temperature gradient chambers in ambient (370 μmol mol−1) or elevated (700 μmol mol−1) atmospheric CO2 concentrations and at ambient or ambient +4°C temperatures, with either a low or a high nitrogen supply. The photosynthesis-internal
CO2 response curves and the activity, activation state, kcat and amount of Ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) were measured, as well as the soluble protein concentration
in flag leaves at ear emergence and 8–15 days after anthesis. A high nitrogen supply increased Vcmax, the Rubisco amount and activity and soluble protein contents, but did not significantly change the Rubisco kcat. Both elevated CO2 and above ambient temperatures had negative effects on Vcmax and Rubisco activity, but at elevated CO2, an increase in temperature did not decrease Vcmax or Rubisco activity in relation to ambient temperature. The amounts of Rubisco and soluble protein decreased with elevated
CO2 and temperature. The negative impact of elevated CO2 on Rubisco properties was somewhat counteracted at elevated temperatures by an increase in kcat. This effect can diminish the detrimental effects on photosynthesis of combined increases of CO2 and temperature. 相似文献
5.
Simultaneous measurements of chlorophyll (Chl) fluorescence and CO2 assimilation (A) in Vicia faba leaves were taken during the first weeks of growth to evaluate the protective effect of 24-epibrassinolide (EBR) against
damage caused by the application of the herbicide terbutryn (Terb) at pre-emergence. V. faba seeds were incubated for 24 h in EBR solutions (2 × 10−6 or 2 × 10−5 mM) and immediately sown. Terb was applied at recommended doses (1.47 or 1.96 kg ha−1) at pre-emergence. The highest dose of Terb strongly decreased CO2 assimilation, the maximum quantum yield of PSII photochemistry in the dark-adapted state (F
V/F
M), the nonphotochemical quenching (NPQ), and the effective quantum yield (ΔF/F′M) during the first 3–4 weeks after plant emergence. Moreover, Terb increased the basal quantum yield of nonphotochemical processes
(F
0/F
M), the degree of reaction center closure (1 − q
p), and the fraction of light absorbed in PSII antennae that was dissipated via thermal energy dissipation in the antennae
(1 − F′V/F′M). The herbicide also significantly reduced plant growth at the end of the experiment as well as plant length, dry weight,
and number of leaves. The application of EBR to V. faba seeds before sowing strongly diminished the effect of Terb on fluorescence parameters and CO2 assimilation, which recovered 13 days after plant emergence and showed values similar to those of control plants. The protective
effect of EBR on CO2 assimilation was detected at a photosynthetic photon flux density (PFD) of 650 μmol m−2 s−1 and the effect on ΔF/F′M and photosynthetic electron transport (J) was detected under actinic lightings up to 1750 μmol m−2 s−1. The highest dose of EBR also counteracted the decrease in plant growth caused by Terb, and plants registered the same growth
values as controls. 相似文献
6.
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
7.
Carlos Eduardo Aragón Maritza Escalona Roberto Rodriguez Maria Jesús Cañal Iris Capote Danilo Pina Justo González-Olmedo 《In vitro cellular & developmental biology. Plant》2010,46(1):89-94
In vitro physiology and carbon metabolism can be affected by the sink–source relationship. The effect of different sucrose concentrations
(10, 30, and 50 g L−1), light intensities (80 and 150 μmol m−2 s−1), and CO2 levels (375 and 1,200 μmol mol−1) were tested during plantain micropropagation in temporary immersion bioreactors. Activities of pyruvate kinase, phosphoenol
pyruvate carboxylase, and the photosynthesis rate were recorded. From the morphological and practical point of view, the best
results were obtained when plants were cultured with 30 g L−1 sucrose, 80 μmol m−2 s−1 light intensity, and 1,200 μmol mol−1 CO2 concentration. This treatment improved leaf and root development, reduced respiration during in vitro culture, and increased starch level at the end of the hardening phase. In addition to that, the number of competent plants
was increased from 80.0% to 91.0% at the end of the in vitro phase and the survival percentage from 95.71% to 99.80% during ex vitro hardening. 相似文献
8.
Rajneesh K. Agnihotri Janhvi Mishra Shyamal Kumar Nandi 《Acta Physiologiae Plantarum》2009,31(5):961-967
An efficient in vitro regeneration protocol and field performance of a multipurpose bamboo species Dendrocalamus hamiltonii Nees et Arn. Ex Munro has been demonstrated using single node cuttings taken from the lateral branches of a 20-year-old bush.
Axillary buds on the nodal explant sprouted within 10 days of culture on Murashige and Skoog (MS) medium without any plant
growth substance. High-frequency proliferation was induced on the propagules (small clusters with 3–5 multiple shoots and
rhizomatous portions). Subsequent removal of the shoots (about 1.5 cm) from the rhizomatous portion of propagules (shoot cut)
influenced the plantlet formation capacity. A multiplication of about 20-folds was achieved on MS medium supplemented with
8 μM BAP and 1 μM NAA. Rooting efficiency was also markedly enhanced (>90%) when the propagules, following shoot cut, were
placed on to MS medium supplemented with 100 μM IBA for 10 days and then transferred to IBA-free medium. This is the first
report from this species where 20-fold increment in multiplication was observed at the end of second subculture followed by
>90% rooting. The hardened plants, established in the field, exhibited normal growth; their physiological performance has
been monitored at 6-month intervals. The rate of photosynthesis increased from 3.55 μmol CO2 m−2 s−1 (hardened, ready for field transfer) to 5.44 μmol m−2 s−1 (6 months of field transfer); following a year of plantation net photosynthesis recorded was 14.0 μmol CO2 m−2 s−1 while after 1.5 years it was 12.76 μmol CO2 m−2 s−1. These values were compared with those observed for the mother bush. Genetic fidelity of these regenerants was established
by RAPD analysis advocating clonal propagation of this species through nodal segment culture and its commercial cultivation. 相似文献
9.
In an experimental site for reforestation of degraded area, three-year-old plants of Bertholletia excelsa Humb. & Bonpl. were subjected to different fertilization treatments: T0 = unfertilized control, T1 = green fertilization
(branches and leaves) and T2 = chemical fertilization. Higher net photosynthetic rates (P
N) were observed in T1 [13.2±1.0 μmol(CO2) m−2 s−1] compared to T2 [8.0±1.8 μmol(CO2) m−2 s−1] and T0 [4.8±1.3 μmol(CO2) m−2 s−1]. Stomatal conductance (g
s), transpiration rate (E) and water use efficiency (WUE) of individuals of T1 and T2 did not differ significantly, however, they were by 88, 55 and
63%, respectively, higher in T1 than in the control. The mean values of variable fluorescence (Fv), performance index (P.I.) and total chlorophyll [Chl (a+b)] were higher in T1. Our results indicate that green fertilization improves photosynthetic structure and function in plants
of B. excelsa in young phase. 相似文献
10.
M. Angélica Casanova-Katny Gustavo E. Zúñiga Luis J. Corcuera Leon Bravo Miren Alberdi 《Polar Biology》2010,33(4):477-483
Primary photochemistry of photosystem II (F
v/F
m) of the Antarctic hair grass Deschampsia antarctica growing in the field (Robert Island, Maritime Antarctic) and in the laboratory was studied. Laboratory plants were grown
at a photosynthetic photon flux density (PPFD) of 180 μmol m−2 s−1 and an optimal temperature (13 ± 1.5°C) for net photosynthesis. Subsequently, two groups of plants were exposed to low temperature
(4 ± 1.5°C day/night) under two levels of PPFD (180 and 800 μmol m−2 s−1) and a control group was kept at 13 ± 1.5°C and PPFD of 800 μmol m−2 s−1. Chlorophyll fluorescence was measured during several days in field plants and weekly in the laboratory plants. Statistically
significant differences were found in F
v/F
m (=0.75–0.83), F
0 and F
m values of field plants over the measurement period between days with contrasting irradiances and temperature levels, suggesting
that plants in the field show high photosynthetic efficiency. Laboratory plants under controlled conditions and exposed to
low temperature under two light conditions showed significantly lower F
v/F
m and F
m. Moreover, they presented significantly less chlorophyll and carotenoid content than field plants. The differences in the
performance of the photosynthetic apparatus between field- and laboratory-grown plants indicate that measurements performed
in ex situ plants should be interpreted with caution. 相似文献
11.
The response of barley (Hordeum vulgare L. cv. Akcent) to various photosynthetic photon flux densities (PPFDs) and elevated [CO2] [700 μmol (CO2) mol−1; EC] was studied by gas exchange, chlorophyll (Chl) a fluorescence, and pigment analysis. In comparison with barley grown under ambient [CO2] [350 μmol (CO2) mol−1; AC] the EC acclimation resulted in a decrease in photosynthetic capacity, reduced stomatal conductance, and decreased total
Chl content. The extent of acclimation depression of photosynthesis, the most pronounced for the plants grown at 730 μmol
m−2 s−1 (PPFD730), may be related to the degree of sink-limitation. The increased non-radiative dissipation of absorbed photon energy for
all EC plants corresponded to the higher de-epoxidation state of xanthophylls only for PPFD730 barley. Further, a pronounced decrease in photosystem 2 (PS2) photochemical efficiency (given as FV/FM) for EC plants grown at 730 and 1 200 μmol m−2 s−1 in comparison with AC barley was related to the reduced epoxidation of antheraxanthin and zeaxanthin back to violaxanthin
in darkness. Thus the EC conditions sensitise the photosynthetic apparatus of high-irradiance acclimated barley plants (particularly
PPFD730) to the photoinactivation of PS2.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
12.
Light acclimatisation capabilities of Elodea nuttallii at nearly ambient DIC conditions were investigated by determining growth characteristics, main photosynthetic parameters
and pigmentation of plants incubated at 5 different irradiances (10–146 μmol photons m−2 s−1). Positive net growth was observed under all light treatments tested. Maximum ratio root versus shoot (r:s) of 1.86 was achieved
at medium irradiances (72–94 μmol photons m−2 s−1), whereas at low (10 μmol photons m−2 s−1) and high irradiances (146 μmol photons m−2 s−1) r:s was significantly lower (0.39 and 1.05, respectively). With respect to main photosynthetic parameters, an increase of
light compensation points (E
c), attended by decreasing ratios of light saturation points of photosynthesis (E
k)/irradiance were observed. E
c values were comparable to other low-light adapted macrophytes, which indicate that E. nuttallii can be regarded as a low-light adapted plant, under photorespiratory conditions. This was also confirmed by maximum E
k values of just 73 μmol photons m−2 s−1. Further support was achieved from pigmentation and non-photochemical quenching (NPQ) data, both indicating rather limited
acclimatisation ability at light treatments above 90 μmol photons m−2 s−1. These results are discussed with respect to the competitive abilities of E. nuttallii under nearly ambient (photorespiratory) DIC conditions, especially in dense stands and turbid phytoplankton-dominated waters. 相似文献
13.
The purpose of this study was to clarify effects of anthocyanins on photosynthesis and photoinhibition in green and red leaves
of Oxalis triangularis. Gas analysis indicated that green plants had the highest apparent quantum yield for CO2 assimilation [0.051 vs. 0.031 μmol(CO2) μmol−1(photon)] and the highest maximum photosynthesis [10.07 vs. 7.24 μmol(CO2) m−2 s−1], while fluorescence measurements indicated that red plants had the highest PSII quantum yield [0.200 vs. 0.143 μmol(e−) μmol−1(photon)] and ETRmax [66.27 vs. 44.34 μmol(e−) m−2 s−1]. Red plants had high contents of anthocyanins [20.11 mg g−1(DM)], while green plants had low and undetectable levels of anthocyanin. Red plants also had statistically significantly
(0.05>p>0.01) lower contents of xanthophyll cycle components [0.63 vs. 0.76 mg g−1(DM)] and higher activities of the reactive oxygen scavenging enzyme ascorbate peroxidase [41.2 vs. 10.0 nkat g−1(DM)]. Anthocyanins act as a sunscreen, protecting the chloroplasts from high light intensities. This shading effect causes
a lower photosynthetic CO2 assimilation in red plants compared to green plants, but a higher quantum efficiency of photosystem II (PSII). Anthocyanins
contribute to photoprotection, compensating for lower xanthophyll content in red plants, and red plants are less photoinhibited
than green plants, as illustrated by the Fv/Fm ratio. 相似文献
14.
M. Gouasmi P. Mordelet V. Demarez J. -P. Gastellu-Etchegorry V. Le Dantec G. Dedieu J. -C. Menaut J. -C. Calvet T. Lamaze 《Photosynthetica》2009,47(3):331-339
The objectives of the study were to characterize photosynthesis of temperate fallow C3herbaceous species and examine the performance of a simple photosynthesis model (based on the Farquhar’s equations) to simulate
carbon fluxes at the leaf and canopy levels. The maximum rate of carboxylation at 25°C (V
m0) was estimated for sunlit leaves using in situ gas exchange data under saturating irradiance. Throughout the seasons, leaf measurements indicate that values of V
m0 were similar for the four major species of the fallow. The rate declined from March (100 μmol m−2 s−1) to July (50 μmol m−2 s−1) and remained almost constant until November. The maximum quantum yield estimated for Potentilla reptans L. (dominant species) was 0.082 mol(CO2) mol−1(photon absorbed), similar to values already published for C3 species. Leaf area index (LAI) increased from winter (less than 0.2 m2 m−2) to spring (up to 4 m2 m−2). Rates of canopy photosynthesis (measured with a canopy chamber) strongly depended on LAI and temperature, in addition to
irradiance. They reached a maximum of 25 μmol m−2 s−1 and were intermediate between those published for C4 grassland or cultivated species, and on woody species. At leaf level, simulations gave realistic predictions. At canopy level,
the model had the ability to reproduce the effects of environmental and seasonal conditions. However, simulations underestimated
the photosynthetic activity of the fallow canopy. 相似文献
15.
This work aimed to evaluate if gas exchange and PSII photochemical activity in maize are affected by different irradiance
levels during short-term exposure to elevated CO2. For this purpose gas exchange and chlorophyll a fluorescence were measured on maize plants grown at ambient CO2 concentration (control CO2) and exposed for 4 h to short-term treatments at 800 μmol(CO2) mol−1 (high CO2) at a photosynthetic photon flux density (PPFD) of either 1,000 μmol m−2 s−1 (control light) or 1,900 μmol m−2 s−1 (high light). At control light, high-CO2 leaves showed a significant decrease of net photosynthetic rate (P
N) and a rise in the ratio of intercellular to ambient CO2 concentration (C
i/C
a) and water-use efficiency (WUE) compared to control CO2 leaves. No difference between CO2 concentrations for PSII effective photochemistry (ΦPSII), photochemical quenching (qp) and nonphotochemical quenching (NPQ) was detected. Under high light, high-CO2 leaves did not differ in P
N, C
i/C
a, ΦPSII and NPQ, but showed an increase of WUE. These results suggest that at control light photosynthetic apparatus is negatively
affected by high CO2 concentration in terms of carbon gain by limitations in photosynthetic dark reaction rather than in photochemistry. At high
light, the elevated CO2 concentration did not promote an increase of photosynthesis and photochemistry but only an improvement of water balance due
to increased WUE. 相似文献
16.
Highly productive papyrus (Cyperus papyrus L.) wetlands dominate many permanently flooded areas of tropical East Africa; however, the cycling of carbon and water within
these ecosystems is poorly understood. The objective of this study was to utilise Eddy Covariance (EC) techniques to measure
the fluxes of carbon dioxide and water vapour between papyrus vegetation and the atmosphere in a wetland located near Jinja,
Uganda on the Northern shore of Lake Victoria. Peak, midday rates of photosynthetic CO2 net assimilation were approximately 40 μmol CO2 m−2 s−1, while night time losses through respiration ranged between 10 and 20 μmol CO2 m−2 s−1. Numerical integration of the flux data suggests that papyrus wetlands have the potential to sequester approximately 0.48 kg C m−2 y−1. The average daily water vapour flux from the papyrus vegetation through canopy evapotranspiration was approximately 4.75 kg
H2O m−2 d−1, which is approximately 25% higher than water loss through evaporation from open water. 相似文献
17.
Summary
In vitro banana (Musa spp.) shoots were cultured under photomixotrophic (30 gl−1 sucrose and 0.2 h−1 number of air exchanges of culture vessels) and photoautotrophic (0 gl−1 sucrose and 3.9 h−1 number of air exchanges) conditions for 28 d in 370 cm3 Magenta boxes (GA7-type) containing 70 ml of half-strength Murashige and Skoog (MS) medium with 22.2 μM N6-benzyladenine (BA). The effects of varying CO2 concentration (475 or 1340 μmol mol−1) and light intensity (photosynthetic photon flux (PPF) of 100 or 200 μmol m−2 s−1) were investigated. Fresh and dry weights of banana shoots grown photomixotrophically were significantly greater on day 28
than those grown photoautotrophically. Photoautorophic shoots had a larger number of unfolded leaves and greater leaf area
than photomixotrophic plants by days 14 and 28, regardless of CO2 concentration. The shoot fresh and dry weights on day 14 in photoautotrophic conditions were significantly greater at PPF
of 200 μmol m−2 s−1 than at 100 μmol m−2 s−1. The increase in net photosynthetic rate of photoautotrophic banana shoots was significant compared with photomixotrophic
shoots. The multiplication ratio of in vitro banana shoots grown photoautotrophically in a 28-d culture period was the greatest at 100 μmol m−2 s−1 PPF and 475 μmol mol−1 CO2. 相似文献
18.
Metrosideros polymorpha, a dominant tree species in Hawaiian ecosystems, occupies a wide range of habitats. Complementary field and common-garden
studies of M. polymorpha populations were conducted across an altitudinal gradient at two different substrate ages to ascertain if the large phenotypic
variation of this species is determined by genetic differences or by phenotypic modifications resulting from environmental
conditions. Several characteristics, including ecophysiological behavior and anatomical features, were largely induced by
the environment. However, other characteristics, particularly leaf morphology, appeared to be mainly determined by genetic
background. Common garden plants exhibited higher average rates of net assimilation (5.8 μmol CO2 m−2 s−1) and higher average stomatal conductance (0.18 mol H2O m−2 s−1) than their field counterparts (3.0 μmol CO2 m−2 s−1, and 0.13 mol H2O m−2 s−1 respectively). Foliar δ13C of most common-garden plants was similar among sites of origin with an average value of −26.9‰. In contrast, mean values
of foliar δ13C in field plants increased substantially from −29.5‰ at low elevation to −24.8‰ at high elevation. Leaf mass per unit area
increased significantly as a function of elevation in both field and common garden plants; however, the range of values was
much narrower in common garden plants (211–308 g m−2 for common garden versus 107–407 g m−2 for field plants). Nitrogen content measured on a leaf area basis in common garden plants ranged from 1.4 g m−2 to 2.4 g m−2 and from 0.8 g m−2 to 2.5 g m−2 in field plants. Photosynthetic nitrogen use efficiency (PNUE) decreased 50% with increasing elevation in field plants and
only 20% in plants from young substrates in the common garden. This was a result of higher rates of net CO2 assimilation in the common garden plants. Leaf tissue and cell layer thickness, and degree of leaf pubescence increased significantly
with elevation in field plants, whereas in common garden plants, variation with elevation of origin was much narrower, or
was entirely absent. Morphological characteristics such as leaf size, petiole length, and internode length decreased with
increasing elevation in the field and were retained when grown in the common garden, suggesting a potential genetic basis
for these traits. The combination of environmentally induced variability in physiological and anatomical characteristics and
genetically determined variation in morphological traits allows Hawaiian M. polymorpha to attain and dominate an extremely wide ecological distribution not observed in other tree species.
Received: 12 March 1997 / Accepted: 27 August 1997 相似文献
19.
Part of the Larsen A Ice Shelf (64°15′S to 74°15′S) collapsed during January 1995. A first oceanographic and biological data
set from the newly free waters was obtained during December 1996. Typical shelf waters with temperatures near and below the
freezing point were found. A nutrient-rich water mass (max: PO4
3− 1.80 μmol L−1 and NO3
− 27.64 μmol L−1) was found between 70 and 200 m depth. Chlorophyll-a (Chl-a) values (max 14.24 μg L−1) were high; surface oxygen saturation ranged between 86 and 148%. Diatoms of the genera Nitzschia and Navicula and the prymnesiophyte Phaeocystis sp. were the most abundant taxa found. Mean daily primary production (Pc) estimated from nutrient consumption was 14.80 ± 0.17 mgC m−3 day−1. Pc was significantly correlated with total diatom abundance and Chl-a. Calculated ΔpCO2 (difference of the CO2 partial pressure between surface seawater and the atmosphere) was –30.5 μatm, which could have contributed to a net CO2 flux from the atmosphere to the sea and suggests the area has been a CO2 sink during the studied period. High phytoplankton biomass and production values were found in this freshly open area, suggesting
its importance for biological CO2 pumping. 相似文献
20.
The concept of using higher plants to maintain a sustainable life support system for humans during long-duration space missions is dependent upon photosynthesis. The effects of extended exposure to microgravity on the development and functioning of photosynthesis at the leaf and stand levels were examined onboard the International Space Station (ISS). The PESTO (Photosynthesis Experiment Systems Testing and Operations) experiment was the first long-term replicated test to obtain direct measurements of canopy photosynthesis from space under well-controlled conditions. The PESTO experiment consisted of a series of 21–24 day growth cycles of Triticum aestivum L. cv. USU Apogee onboard ISS. Single leaf measurements showed no differences in photosynthetic activity at the moderate (up to 600 μmol m−2 s−1) light levels, but reductions in whole chain electron transport, PSII, and PSI activities were measured under saturating light (>2,000 μmol m−2 s−1) and CO2 (4000 μmol mol−1) conditions in the microgravity-grown plants. Canopy level photosynthetic rates of plants developing in microgravity at ∼280 μmol m−2 s−1 were not different from ground controls. The wheat canopy had apparently adapted to the microgravity environment since the CO2 compensation (121 vs. 118 μmol mol−1) and PPF compensation (85 vs. 81 μmol m−2 s−1) of the flight and ground treatments were similar. The reduction in whole chain electron transport (13%), PSII (13%), and PSI (16%) activities observed under saturating light conditions suggests that microgravity-induced responses at the canopy level may occur at higher PPF intensity. 相似文献