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1.
Water status and gas exchange of beech (Fagus sylvatica L.) and sessile oak [Quercus petraea (Mattuschka) Liebl.] were studied in a mixed stand in the Montejo de la Sierra forest (central Iberian Peninsula), one of
the southernmost locations of both species in Europe. Gas exchange and water potential were measured in leaves at different
canopy levels over several days in two growing seasons. The daily variation pattern was established with the measurements
of three selected dates per year, representative of the soil moisture content situations in early, mid- and late summer. A
similar daily time course of leaf water potential was found for the two species. Nevertheless, beech showed a most noticeable
decrease of water potential at midmorning and maintained lower leaf water potential than oak in the early afternoon. In 1994
the sessile oak saplings showed higher values of predawn water potential (Ψpd) than beech at the end of summer, when soil moisture content was lowest (20 cm depth). Beech showed a significantly lower
net assimilation rate (A) than sessile oak for leaves under the same PPFD. Maximum net photosynthesis values (A
max) for beech and sessile oak on sunny leaves were 10.1±0.4 μmol m–2 s–1 and 17.8±1.7 μmol m–2 s–1 respectively, and those for water vapour stomatal conductance (g
wv) were 265±31 mmol m–2 s–1 and 438±74 mmol m–2 s–1. Differences in A and g
wv between the two species were maintained throughout the day on all measurement dates. No clear relationship was found between
water status of saplings and stomata performance; there was only a negative correlation between Ψpd and g
wvmid in beech. Nevertheless, a significant response to the air vapour pressure gradient between leaf and air was translated into
stomata closure on an hourly basis, more intensively in beech.
Received: 4 March 1999 / Accepted: 21 December 1999 相似文献
2.
Water relations dynamics during simulated sunflecks at high (36°C) and medium (27°C) temperatures and high and low vapour
pressure deficits beween leaf and air (VPD) were studied on shade-grown Piper auritum H.B. & K. plants, a pioneer tree, common in gaps and clearings of tropical rain forests. The leaves of P. auritum wilt rapidly when exposed to high light. Exposure to high VPD and high light caused substantial and rapid dehydration of
leaves. Dehydration could be prevented under high humidity irrespective of temperature. Water stored in leaf cells served
as initial source for transpiration upon high light exposure. This effect increased with increasing VPD and temperature. The
pronounced decrease in leaf water content over time in high light caused a rapid decrease in leaf water potential (Ψl) and a concomitant increase in water potential gradient (ΔΨ/Δx) between trunk and leaf, yet the high leaf elasticity (small bulk elastic modulus, ε) allowed turgor maintenance under most
conditions. Under high VPD and high temperature, stomata remained open and ΔΨ/Δx frequently exceeded 0.95 MPa · m−1, the cavitation-inducing threshold (ΔΨ/Δx
cav) causing high rates of acoustic emissions from stems and leaf petioles and leading to concomitant losses in hydraulic conductance
per leaf area (k
l). At medium temperature (high VPD), stomatal closure contained xylem embolism by keeping ΔΨ/Δx at or below this threshold. We argue that wilting substantially contributes to creating a sufficient driving force for water
uptake from the soil, and reducing the VPD (through a decrease in radiation load and thus leaf temperature) to avoid excessive
dehydration.
Received: 3 March 1996 / Accepted: 10 November 1996 相似文献
3.
Miconia albicans, a common evergreen cerrado species, was studied under field conditions. Leaf gas exchange and pre-dawn leaf water potential
(Ψpd) were determined during wet and dry seasons. The potential photosynthetic capacity (P
Npmax) and the apparent carboxylation efficiency (ε) dropped in the dry season to 28.0 and 0.7 %, respectively, of the maximum
values in the wet season. The relative mesophyll (Lm) and stomatal (Ls) limitations of photosynthesis increased, respectively, from 24 and 44 % in the wet season to 79 and 57 % at the peak of
the dry season when mean Ψpd reached −5.2 MPa. After first rains, the P
Npmax, ε, and Lm recovered reaching the wet season values, but Ls was maintained high (63 %). The shallow root system growing on stonemason limited by lateral concrete wall to a depth of
0.33 m explained why extreme Ψpd was brought about. Thus M. albicans is able to overcome quickly the strains imposed by severe water stress. 相似文献
4.
Precipitation pulse use by an invasive woody legume: the role of soil texture and pulse size 总被引:9,自引:0,他引:9
Plant metabolic activity in arid and semi-arid environments is largely tied to episodic precipitation events or “pulses”.
The ability of plants to take up and utilize rain pulses during the growing season in these water-limited ecosystems is determined
in part by pulse timing, intensity and amount, and by hydrological properties of the soil that translate precipitation into
plant-available soil moisture. We assessed the sensitivity of an invasive woody plant, velvet mesquite (Prosopis velutina Woot.), to large (35 mm) and small (10 mm) isotopically labeled irrigation pulses on two contrasting soil textures (sandy-loam
vs. loamy-clay) in semi-desert grassland in southeastern Arizona, USA. Predawn leaf water potential (Ψpd), the isotopic abundance of deuterium in stem water (δD), the abundance of 13C in soluble leaf sugar (δ13C), and percent volumetric soil water content (θv) were measured prior to irrigation and repeatedly for 2 weeks following irrigation. Plant water potential and the percent
of pulse water present in the stem xylem indicated that although mesquite trees on both coarse- and fine-textured soils quickly
responded to the large irrigation pulse, the magnitude and duration of this response substantially differed between soil textures.
After reaching a maximum 4 days after the irrigation, the fraction of pulse water in stem xylem decreased more rapidly on
the loamy-clay soil than the sandy-loam soil. Similarly, on both soil textures mesquite significantly responded to the 10-mm
pulse. However, the magnitude of this response was substantially greater for mesquite on the sandy-loam soil compared to loamy-clay
soil. The relationship between Ψpd and δ13C of leaf-soluble carbohydrates over the pulse period did not differ between plants at the two sites, indicating that differences
in photosynthetic response of mesquite trees to the moisture pulses was a function of soil water availability within the rooting
zone rather than differences in plant biochemical or physiological constraints. Patterns of resource acquisition by mesquite
during the dynamic wetting–drying cycle following rainfall pulses is controlled by a complex interaction between pulse size
and soil hydraulic properties. A better understanding of how this interaction affects plant water availability and photosynthetic
response is needed to predict how grassland structure and function will respond to climate change. 相似文献
5.
The responses of gas exchange and chlorophyll fluorescence of field-growing Ulmus pumila seedlings to changes in simulated precipitation were studied in Hunshandak Sandland, China. Leaf water potential (Ψwp), net photosynthetic rate (P
N), stomatal conductance (g
s), and transpiration rate (E) were significantly increased with enhancement of precipitation from 0 to 20 mm (p<0.01), indicating stomatal limitation of U. pumila seedlings that could be avoided when soil water was abundant. However, P
N changed slightly when precipitation exceeded 20 mm (p>0.05), indicating more precipitation than 20 mm had no significant effects on photosynthesis. Maximum photochemical efficiency
of photosystem 2, PS 2 (Fv/Fm) increased from 0.53 to 0.78 when rainfall increased from 0 to 10 mm, and Fv/Fm maintained a steady state level when rainfall was more than 10 mm. Water use efficiency (WUE) decreased significantly (from
78–95 to 23–27 μmol mol−1) with enhancement of rainfalls. P
N showed significant linear correlations with both g
s and Ψwp (p<0.0001), which implied that leaf water status influenced gas exchange of U. pumila seedlings. The 20-mm precipitation (soil water content at about 15 %, v/v) might be enough for the growth of elm seedlings.
When soil water content (SWC) reached 10 %, down regulation of PS2 photochemical efficiency could be avoided, but stomatal
limitation to photosynthesis remained. When SWC exceeded 15 %, stomatal limitation to photosynthesis could be avoided, indicating
elm seedlings might tolerate moderate drought. 相似文献
6.
Independent short-term effects of photosynthetic photon flux density (PPFD) of 50–400 μmol m−2 s−1, external CO2 concentration (C
a) of 85–850 cm3 m−3, and vapor pressure deficit (VPD) of 0.9–2.2 kPa on net photosynthetic rate (P
N), stomatal conductance (g
s), leaf internal CO2 concentration (C
i), and transpiration rates (E) were investigated in three cacao genotypes. In all these genotypes, increasing PPFD from 50 to 400 μmol m−2 s−1 increased P
N by about 50 %, but further increases in PPFD up to 1 500 μmol m−2 s−1 had no effect on P
N. Increasing C
a significantly increased P
N and C
i while g
s and E decreased more strongly than in most trees that have been studied. In all genotypes, increasing VPD reduced P
N, but the slight decrease in g
s and the slight increase in C
i with increasing VPD were non-significant. Increasing VPD significantly increased E and this may have caused the reduction in P
N. The unusually small response of g
s to VPD could limit the ability of cacao to grow where VPD is high. There were no significant differences in gas exchange
characteristics (g
s, C
i, E) among the three cacao genotypes under any measurement conditions. 相似文献
7.
Responses of Quercus ilex L. seedlings from three different localities in Italy to experimentally imposed drought stress were analysed. Predawn (Ψpd) and midday (Ψm) leaf water potential of stressed seedlings decreased on an average until −4.0 and −4.2 MPa, respectively, in the severe
water stress. At the end of the severe water stress the relative water content (RWC) was 72.5 – 83.6 % and the photosynthetic
rates (PN) near zero. The critical threshold value of Ψpd for complete stomatal closure was from −4.0 to −4.5 MPa. The leaf damage after the severe water stress was significantly
greater in seedlings originated from the acorns of climax area (45 % total leaf injured area and 40 % fallen leaves) than
in the other seedlings (on an average 20.5 % total leaf injured area and 21 % fallen leaves).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
D. O Otieno C. Kurz-Besson J. Liu M. W. T. Schmidt R. Vale-Lobo do T. S. David R. Siegwolf J. S. Pereira J. D. Tenhunen 《Plant and Soil》2006,283(1-2):119-135
Studies were conducted to examine changes in soil (Ψs) and plant water status during summer in a 16-year old Quercus suber plantation in southern Portugal. Continuous measurements were conducted between May 2003 and August 2004, while discontinuous
measurements were conducted on a monthly basis between May and September 2003 and repeated between March and September 2004.
Intensive measurements were conducted on five trees with mean height and DBH of 5.3 m and 11.6 cm, respectively, growing at
close proximity to each other. Weather conditions and soil water potential (Ψs) at the rhizosphere of each of the trees measured
at 0.3 and 1 m soil depth were continuously monitored. Predawn (Ψpd) and midday (Ψmd) leaf water potentials were determined
every month. Soil and plant samples were also collected in June and September from different locations within the study site
for δ18O isotope composition analysis. Pressure–volume (p–v) curves were constructed from plant shoots at different times during the vegetative period to determine osmotic potential
at full saturation (Π100), water potential at turgor loss point (Ψtlp), relative water content at turgor loss point (R*tlp) and bulk modulus of elasticity (ε). Significant P < 0.05 decline in Ψs occurred between May and September, the lowest value recorded being –2.0 MPa. Decline in soil moisture
affected tree water status, but decline in leaf water potential varied significantly (P < 0.05) among the trees. At the end of summer drought, lowest Ψpd measured was –1.7 MPa while the highest measured during
this time was –0.8 MPa. Differences among trees were attributed to differences in rooting depth, as shown by regression analysis
of 18O isotopes. Radial stem growth ceased when Ψs within the upper 0.3 m depth approached –1.5 MPa. The upper soil layers contributed
approximately 33% of the total tree water requirement, between spring and mid summer when drought was experienced by trees.
Deep soil layers however, supplied most of the water required during drought and no growth was recorded during this time.
Stressed trees increased solute concentration of their tissues by a Magnitude of 0.7 MPa while bulk tissue elastic modulus
increased by about 17 MPa. The study emphasizes the significance of roots as determinants of tree productivity and survival
in the Mediterranean ecosystems. 相似文献
9.
Jes��s Rodr��guez-Calcerrada Nikos Nanos Ismael Aranda 《Trees - Structure and Function》2011,25(5):873-884
The size of seeds and the microsite of seed dispersal may affect the early establishment of seedlings through different physiological
processes. Here, we examined the effects of seed size and light availability on seedling growth and survival, and whether
such effects were mediated by water use efficiency. Acorns of Quercus petraea and the more drought-tolerant Quercus pyrenaica were sowed within and around a tree canopy gap in a sub-Mediterranean forest stand. We monitored seedling emergence and measured
predawn leaf water potential (Ψpd), leaf nitrogen per unit area (Na), leaf mass per area, leaf carbon isotope composition (δ13C) and plant growth at the end of the first summer. Survival was measured on the next year. Path analysis revealed a consistent
pattern in both species of higher δ13C as Ψpd decreased and higher δ13C as seedlings emerged later in the season, indicating an increase in 13C as the growing season is shorter and drier. There was a direct positive effect of seed size on δ13C in Q. petraea that was absent in Q. pyrenaica. Leaf δ13C had no effect on growth but the probability of surviving until the second year was higher for those seedlings of Q. pyrenaica that had lower δ13C on the first year. In conclusion, leaf δ13C is affected by seed size, seedling emergence time and the availability of light and water, however, leaf δ13C is irrelevant for first year growth, which is directly dependent on the amount of seed reserves. 相似文献
10.
The Influence of Spatial Patterns of Soil Moisture on the Grass and Shrub Responses to a Summer Rainstorm in a Chihuahuan Desert Ecotone 总被引:4,自引:0,他引:4
The cycling of surface water, energy, nutrients, and carbon is different between semiarid grassland and shrubland ecosystems.
Although differences are evident when grasslands are compared to shrublands, the processes that contribute to this transition
are more challenging to document. We evaluate how surface redistribution of precipitation and plant responses to the resulting
infiltration patterns could contribute to the changes that occur during the transition from grassland to shrubland. We measured
soil water potential under grasses (Bouteloua eriopoda), shrubs (Larrea tridentata) and bare soil and changes in plant water relations and gas exchange following a 15 mm summer storm in the grassland–shrubland
ecotone at the Sevilleta National Wildlife Refuge in central New Mexico USA. Following the storm, soil water potential (Ψs) increased to 30 cm depth beneath both grass and shrub canopies, with the greatest change observed in the top 15 cm of the
soil. The increase in Ψs was greater beneath grass canopies than beneath shrub canopies. Ψs under bare soil increased only to 5 cm depth. The substantial redistribution of rainfall and different rooting depths of
the vegetation resulted in high Ψs throughout most of the rooting volume of the grasses whereas soil moisture was unchanged throughout a large portion of the
shrub rooting volume. Consistent with this pattern, predawn water potential (ΨPD) of grasses increased more than 5 MPa to greater than −1 MPa whereas ΨPD of shrubs increased to −2.5 MPa, a change of less than 2 MPa. Transpiration increased roughly linearly with ΨPD in both grasses and shrubs. In grasses, assimilation was strongly correlated with ΨPD whereas there was no relationship in shrubs where assimilation showed no significant response to the pulse of soil moisture
following the storm. These data show that preferential redistribution of water to grass canopies enhances transpiration and
assimilation by grasses following large summer storms. This process may inhibit shrubland expansion at the ecotone during
periods without extreme drought. 相似文献
11.
Marcelo S. Mielke M. A. Oliva Nairam F. de Barros Ricardo M. Penchel Carlos A. Martinez Auro C. de Almeida 《Trees - Structure and Function》1999,13(3):152-160
Predawn leaf water potential, stomatal conductance and microclimatic variables were measured on 13 sampling days from November
1995 through August 1996 to determine how environmental and physiological factors affect water use at the canopy scale in
a plantation of mature clonal Eucalyptus grandis Hill ex-Maiden hybrids in the State of Espirito Santo, Brazil. The simple ”big leaf” Penman-Monteith model was used to estimate
canopy transpiration. During the study period the predawn leaf water potential varied from –0.4 to –1.3 MPa, with the minimum
values observed in the winter months (June and August 1996), while the average estimated values for canopy conductance and
canopy transpiration fell from 17.3 to 5.8 mm s–1 and from 0.54 to 0.18 mm h–1, respectively. On the basis of all measurements, the average value of the decoupling coefficient was 0.25. During continuous
soil water shortage a proportional reduction was observed in predawn leaf water potential and in daily maximum values of stomatal
conductance, canopy transpiration and decoupling coefficient. The results showed that water vapour exchange in this canopy
is strongly dominated by the regional vapour pressure deficit and that canopy transpiration is controlled mainly by stomatal
conductance. On a seasonal basis, stomatal conductance and canopy transpiration were mainly related to predawn leaf water
potential and, thus, to soil moisture and rainfall. Good results were obtained with a multiplicative empirical model that
uses values of photosynthetically active radiation, vapour pressure deficit and predawn leaf water potential to estimate stomatal
conductance.
Received: 10 June 1998 / Accepted: 20 July 1998 相似文献
12.
We analysed plant growth, ion accumulation, leaf water relations, and gas exchange of Avicennia germinans (L.) L. subjected to a long-term, controlled salinity gradient from 0 to 55 ‰. Growth and leaf area were affected by salinity
higher than 10 ‰. As salinity increased, the predawn leaf water potential (Ψw) and leaf osmotic potential (Ψs) decreased. Leaf Ψw was at least −0.32 MPa lower than the Ψw of solution. Na+ and K+ ions explained about 78 % of decrease in Ψs. K+ tissue water concentration decreased by more than 60 % in all salinity treatments as compared with those grown at 0 ‰. Inversely,
Na+ concentration in tissue water increased with nutrient solution salinity. The maximum net photosynthetic rate (P
N) and stomatal conductance (g
s) decreased by 68 and 82 %, respectively, as salinity increased from 0 to 55 ‰; the intercellular CO2 concentration (C
i) followed the same trend. The P
N as a function of C
i showed that both the initial linear slope and upper plateau of the P
N
vs. C
i curve were markedly affected by high salinity (40 and 55 ‰). 相似文献
13.
A. L. García L. Marcelis F. Garcia-Sanchez N. Nicolas V. Martínez 《Biologia Plantarum》2007,51(4):707-712
The responses of water relations, stomatal conductance (gs) and growth parameters of tomato (Lycopersicon esculentum Mill. cv. Royesta) plants to nitrogen fertilisation and drought were studied. The plants were subjected to a long-term, moderate
and progressive water stress by adding 80 % of the water evapotranspirated by the plant the preceding day. Well-watered plants
received 100 % of the water evapotranspirated. Two weeks before starting the drought period, the plants were fertilised with
Hoagland’s solution with 14, 60 and 110 mM NO3
− (N14, N60 and N110, respectively). Plants of the N110 treatment had the highest leaf area. However, gs was higher for N60 plants and lower for N110 plants. At the end of the drought period, N60 plants showed the lowest values
of water potential (Ψw) and osmotic potential (Ψs), and the highest values of pressure potential (Ψp). N60 plants showed the highest Ψs at maximum Ψp and the highest bulk modulus of elasticity. 相似文献
14.
Francesco Ripullone Maria Rosa Guerrieri Angelo Nole’ Federico Magnani Marco Borghetti 《Trees - Structure and Function》2007,21(3):371-378
In this study, tree hydraulic conductance (K
tree) was experimentally manipulated to study effects on short-term regulation of stomatal conductance (g
s), net photosynthesis (A) and bulk leaf water potential (Ψleaf) in well watered 5–6 years old and 1.2 m tall maritime pine seedlings (Pinus pinaster Ait.). K
tree was decreased by notching the stem and increased by progressively excising the root system and stem. Gas exchange was measured
in a chamber at constant irradiance, vapour pressure deficit, leaf temperature and ambient CO2 concentration. As expected, we found a strong and positive relationship between g
s and K
tree (r = 0.92, P = 0.0001) and between A and K
tree (r = 0.9, P = 0.0001). In contrast, however, we found that the response of Ψleaf to K
tree depended on the direction of change in K
tree: increases in K
tree caused Ψleaf to decrease from around −1.0 to −0.6 MPa, but reductions in K
tree were accompanied by homeostasis in Ψleaf (at −1 MPa). Both of these observations could be explained by an adaptative feedback loop between g
s and Ψleaf, with Ψleaf prevented from declining below the cavitation threshold by stomatal closure. Our results are consistent with the hypothesis
that the observed stomatal responses were mediated by leaf water status, but they also suggest that the stomatal sensitivity
to water status increased dramatically as Ψleaf approached −1 MPa. 相似文献
15.
Predawn disequilibrium between plant and soil water potentials in two cold-desert shrubs 总被引:15,自引:0,他引:15
L. A. Donovan D. J. Grisé J. B. West R. A. Pappert N. N. Alder J. H. Richards 《Oecologia》1999,120(2):209-217
Classical water relations theory predicts that predawn plant water potential should be in equilibrium with soil water potential
(soil Ψw) around roots, and many interpretations of plant water status in natural populations are based on this expectation. We examined
this expectation for two salt-tolerant, cold-desert shrub species in glasshouse experiments where frequent watering assured
homogeneity in soil Ψw and soil-root hydraulic continuity and where NaCl controlled soil Ψw. Plant water potentials were measured with a pressure chamber (xylem Ψp) and thermocouple psychrometers (leaf Ψw). Soil Ψw was measured with in situ thermocouple psychrometers. Predawn leaf Ψw and xylem Ψp were significantly more negative than soil Ψw, for many treatments, indicating large predawn soil-plant Ψw disequilibria: up to 1.2 MPa for Chrysothamnus nauseosus (0 and 100 mm NaCl) and 1.8 MPa for Sarcobatus vermiculatus (0, 100, 300, and 600 mm NaCl). Significant nighttime canopy water loss was one mechanism contributing to predawn disequilibrium, assessed by comparison
of xylem Ψp for bagged (to minimize transpiration) and unbagged canopies, and by gas exchange measurements. However, nighttime transpiration
accounted for only part of the predawn disequilibrium. Other mechanisms that could act with nighttime transpiration to generate
large predawn disequilibria are described and include a model of how leaf apoplastic solutes could contribute to the phenomenon.
This study is among the first to conclusively document such large departures from the expectation of predawn soil-plant equilibrium
for C3 shrubs, and provides a general framework for considering relative contributions of nighttime transpiration and other plant-related
mechanisms to predawn disequilibrium.
Received: 12 November 1998 / Accepted: 5 May 1999 相似文献
16.
Net photosynthetic rate (P
N), transpiration rate (E), stomatal conductance (g
s), leaf water potential (ψleaf), leaf nitrogen content, and photosynthetic nitrogen use efficiency (PNUE) were compared between a typical C4 plant, Agriophyllum squarrosum and a C3 plant, Leymus chinensis, in Hunshandak Sandland, China. The plant species showed different diurnal gas exchange patterns on June 12–14 when photosynthetic
photon flux density (PPFD), air temperature (T
air), and water potential were moderate. P
N, E, and g
s of A. squarrosum showed distinct single peak while those of L. chinensis were depressed at noon and had two peaks in their diurnal courses. Gas exchange traits of both species showed midday depression
under higher photosynthetic photon flux density (PPFD) and T
air when Ψleaf was significantly low down on August 6–8. However, those of A. squarrosum were depressed less seriously. Moreover, A. squarrosum had higher P
N, Ψleaf, water use efficiency (WUE), and PNUE than L. chinensis. Thus A. squarrosum was much more tolerant to heat and high irradiance and could utilise the resources on sand area more efficiently than L. chinensis. Hence species like A. squarrosum may be introduced and protected to reconstruct the degraded sand dunes because of their higher tolerance to stress and higher
resource use efficiency.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
Chun-Wang Xiao Osbert J. Sun Guang-Sheng Zhou Jing-Zhu Zhao Gang Wu 《Trees - Structure and Function》2005,19(6):712-721
We studied the responses of leaf water potential (Ψw), morphology, biomass accumulation and allocation, and canopy productivity index (CPI) to the combined effects of elevated
CO2 and drought stress in Caragana intermedia seedlings. Seedlings were grown at two CO2 concentrations (350 and 700 μmol mol−1) interacted with three water regimes (60–70%, 45–55%, and 30–40% of field capacity of soil). Elevated CO2 significantly increased Ψw, decreased specific leaf area (SLA) and leaf area ratio (LAR) of drought-stressed seedlings, and increased tree height, basal
diameter, shoot biomass, root biomass as well as total biomass under the all the three water regimes. Growth responses to
elevated CO2 were greater in well-watered seedlings than in drought-stressed seedlings. CPI was significantly increased by elevated CO2, and the increase in CPI became stronger as the level of drought stress increased. There were significant interactions between
elevated CO2 and drought stress on leaf water potential, basal diameter, leaf area, and biomass accumulation. Our results suggest that
elevated CO2 may enhance drought avoidance and improved water relations, thus weakening the effect of drought stress on growth of C. intermedia seedings. 相似文献
18.
Plants of peanut (Arachis hypogaea L.) were subjected to 7-d and 14-d waterlogging and sprayed with 10 and 100 mg 1-1 of gibberellic acid (GA3). Waterlogging decreased the leaf area (A), net photosynthetic rate (Pn), chlorophyll content (Chi) and temporarily the leaf water potential (Ψw) and increased stomatal diffusive resistance (rs) of both leaf surfaces. Application of GA3 increased A and Pn and significantly decreased the rs of both leaf surfaces but did not affect Ψw or Chl. Thus GA3 partially alleviated the effects of waterlogging on A, rs and Pn. 相似文献
19.
S. Sai Kachout A. Ben Mansoura K. Jaffel Hamza J. C. Leclerc M. N. Rejeb Z. Ouerghi 《Acta Physiologiae Plantarum》2011,33(2):335-342
The impact of salinity and water stress was analyzed in the xero-halophyte Atriplex hortensis using two varieties: green orach (A. hortensis var. purpurea) and red orach (A. hortensis var. rubra). A. hortensis L. is a C3 species well adapted to salt and drought conditions. To collect information on the physiological impact of different salt
and water deficit levels on their water stress resistance, plants were exposed for 3 months to solution containing four levels
of NaCl or to water stress regimes including four levels of field capacity. Osmotic potential at zero turgor Ψs0, osmotic potential at full turgor (Ψs100), relative water content (RWC), ion concentration (Na+, K+, Ca2+, Mg2+, and Cl−), and malondialdehyde (MDA) were determined at the end of the treatment. The salinity and water stress induced a decrease
in Ψs100, Ψs0, and RWC in both varieties, recorded changes being higher in plants of red variety than those of green variety. Both varieties
specifically accumulated Na+ in response to drought and salt stress, suggesting that this element could play a physiological role in the stress response
of this xero-halophyte species. In contrast, the presence of NaCl and water stress induced a decrease in K+, Ca2+, and Mg2+ concentration in both varieties. Salinity clearly induced an increase in Cl– concentration in all tissues, but water stress had no impact on this parameter. MDA concentration increased in response to
water stress and exogenous NaCl. Based on these findings the more drought-tolerant red orach may be grown in water-limiting
soils. 相似文献
20.
Seasonal variation in photosynthesis in six woody species with different leaf phenology in a valley savanna in southwestern China 总被引:3,自引:0,他引:3
During 2003–2005, we examined the effect of seasonal drought on water status, gas exchange, δ13C, chlorophyll fluorescence and spectral reflectance in six woody species in a valley savanna near the Yuanjiang River (the
upper Red River) in southwestern China. Three different phenological types of these woody species were compared, i.e., an
evergreen species, Cyclobalanopsis helferiana, two winter-deciduous (WD) species, Buchanania latifolia and Symplocos racemosa, and three drought-deciduous (DD) species, Terminthia paniculata, Wendlandia tinctoria and Woodfordia fruticosa. We aimed to test the following three hypotheses: (1) the evergreen and WD species employ a drought avoidance strategy, whereas
DD species employ a drought tolerance strategy; (2) the evergreen and WD species have a more economical water use strategy
than the DD species and (3) the evergreen and WD species have a stronger photoprotection capacity through thermal dissipation
than the DD species. At the end of a prolonged drought, the predawn leaf water potential (Ψpd) in C. helferiana and S. racemosa dropped to ca. −0.8 MPa, whereas the Ψpd in B. latifolia remained close to zero and DD species were leafless. In the rainy seasons, maximal photosynthetic rates of the evergreen
(18.4 μmol m−2 s−1) and W. fruticosa (18.0 μmol m−2 s−1) were higher than those of the other four species (12.2−13.8 μmol m−2 s−1). The evergreen and WD species responded to drought by closing stomata and thus maintained a constant relative water content
(RWC), which is a typical drought avoidance strategy; however, it is at the expense of carbon gain. DD species maintained
a high photosynthetic capacity with a decrease in both stomatal conductance and RWC until the driest period, and then shifted
from the drought tolerance strategy to the avoidance mechanism by shoot dieback. There was no significant difference in the
means of δ13C across the phenological groups. The evergreen and WD species had stronger heat dissipation than the DD species in dry seasons.
All species increased leaf spectral reflectance, probably because of degradation of chlorophyll as indicated by the leaf reflectance
index, which should reduce light harvesting. All species showed a strong increase in the ratio of red to green spectral reflectance
of leaves during dry seasons, indicating the accumulation of anthocyanin, which may contribute to screening sunlight and scavenging
reactive oxygen species. Different responses to drought of savanna woody species with different leaf phenologies may facilitate
the partitioning of resource use and hence their co-existence. 相似文献