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1.
Variation of physiological and antioxidative responses in tea cultivars subjected to elevated water stress followed by rehydration recovery 总被引:1,自引:0,他引:1
Hrishikesh Upadhyaya Sanjib Kumar Panda Biman Kumar Dutta 《Acta Physiologiae Plantarum》2008,30(4):457-468
Water stress is a major limitation for plant survival and growth. Several physiological and antioxidative mechanisms are involved
in the adaptation to water stress by plants. In this experiment, tea cultivars (TV-1, TV-20, TV-29 and TV-30) were subjected
to drought stress by withholding water for 20 days followed by rehydration. An experiment was thus performed to test and compare
the effect of dehydration and rehydration in growing seedlings of tea cultivars. The effect of drought stress and post stress
rehydration was measured by studying the reactive oxygen species (ROS) metabolism in tea. Water stress decreased nonenzymic
antioxidants like ascorbate and glutathione contents with differential responses of enzymic antioxidants in selected clones
of Camellia sinensis indicating an oxidative stress situation. This was also apparent from increased lipid peroxidation, O2
− and H2O2 content in water stress imposed plants. But the oxidative damage was not permanent as the plants recovered after rehydration.
Comparatively less decrease in antioxidants, higher activities of POX, GR, CAT with higher phenolic contents suggested better
drought tolerance of TV-1, which was also visible from the recovery study, where it showed lower ROS level and higher recovery
of antioxidant property in response to rehydration, thus proving its better recovery potential. On the other hand, highest
H2O2 and lipid peroxidation with decrease in phenolic content during stress in TV-29 suggested its sensitivity to drought. The
antioxidant efficiency and biochemical tolerance in response to drought stress thus observed in the tested clones of Camellia sinensis can be arranged in the order as TV-30 > TV-1 > TV-29 > TV-20. 相似文献
2.
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
3.
In sunflower (Helianthus annuus L.) grown under controlled conditions and subjected to drought by withholding watering, net photosynthetic rate (P
N) and stomatal conductance (g
s) of attached leaves decreased as leaf water potential (Ψw) declined from −0.3 to −2.9 MPa. Although g
s decreased over the whole range of Ψw, nearly constant values in the intercellular CO2 concentrations (C
i) were observed as Ψw decreased to −1.8 MPa, but C
i increased as Ψw decreased further. Relative quantum yield, photochemical quenching, and the apparent quantum yield of photosynthesis decreased
with water deficit, whereas non-photochemical quenching (qNP) increased progressively. A highly significant negative relationship between qNP and ATP content was observed. Water deficit did not alter the pyridine nucleotide concentration but decreased ATP content
suggesting metabolic impairment. At a photon flux density of 550 μmol m−2 s−1, the allocation of electrons from photosystem (PS) 2 to O2 reduction was increased by 51 %, while the allocation to CO2 assimilation was diminished by 32 %, as Ψw declined from −0.3 to −2.9 MPa. A significant linear relationship between mean P
N and the rate of total linear electron transport was observed in well watered plants, the correlation becoming curvilinear
when water deficit increased. The maximum quantum yield of PS2 was not affected by water deficit, whereas qP declined only at very severe stress and the excess photon energy was dissipated by increasing qNP indicating that a greater proportion of the energy was thermally dissipated. This accounted for the apparent down-regulation
of PS2 and supported the protective role of qNP against photoinhibition in sunflower. 相似文献
4.
Effect of drought stress on chlorophyll a fluorescence and electrical admittance of shoots in Norway spruce seedlings 总被引:1,自引:0,他引:1
Effects of mild and severe soil drought on the water status of needles, chlorophyll a fluorescence, shoot electrical admittance, and concentrations of photosynthetic pigments in needles of seedlings of Picea abies (L.) Karst. were examined under controlled greenhouse conditions. Drought stress reduced shoot admittance linearly with a decrease in shoot water potential (w) and increase in water deficit (WD) and led to a decrease in concentrations of chlorophyll a, b and carotenoids. Severe water stress (shoot w=–2.4 MPa) had a negative effect on chlorophyll a fluorescence parameters including PSII activity (Fv/Fm), and the vitality index (Rfd). Variations in these parameters suggest an inhibition of the photosynthetic electron transport in spruce needles. Water stress led to a decrease in the mobility of electrolytes in tissues, which was reflected by decreased shoot electrical admittance. After re-watering for 21 days the WD in needles decreased and the shoot water potential increased. In the re-watered plants, the chloroplast function was restored and chlorophyll a fluorescence returned to a similar level as in the control plants. This improved hydraulic adjustment in the seedlings triggered a positive effect on ion flow in the tissues and increased shoot electrical admittance. We conclude that the shoot electrical admittance and photosynthetic electron transport in leaves are closely linked to changes in water status and their decrease is among the initial responses of seedlings to water stress. 相似文献
5.
J. Huzulák 《Biologia Plantarum》1979,21(1):9-14
Diurnal and seasonal changes of the xylem pressure potential (Ψxylem) were investigated in five species during three years. Intraspecific comparison was made on the basis of the mathematically
expressed relationship Ψxylem of the individual species to Ψxylem inCrataegus oxyacantha, which exhibited the highest drought resistance. With increasing water stress the value for Ψxylem of the individual species decreases linearly in comparison with that ofC. oxyacantha, namely to −1.02 MPa inLigustrum vulgare, to −1.33 MPa inCornus mas, and to −2.09 MPa inEuonymus verrucosa. At a higher water deficit the value for Ψxylem of these species decreases more rapidly than inC. oxyacantha. On the basis of these findings, the relative drought resistance of the species may by evaluated, and from the value of Ψxylem forC. oxyacantha Ψxylem of the individual species may be derived. By measuring the difference between Ψxylem of free- and polyethylene-covered individuals the existence of water redistribution within the shrub individual was confirmed. 相似文献
6.
Water status of Pinus taeda L. callus supported on Murashige and Skoog (MS) liquid medium was characterized over an 8 week period using thermocouple
psychrometry. Medium with 30 gl−1 sucrose was used to produce a high water potential (Ψw) of −0.4 MPa (H), and the same medium was used to create a moderate Ψw of −0.7 MPa (M) by the addition of 10% polyethylene glycol (PEG, w/v, MW=8000). Calli were produced from cotyledon explants
on H medium for 2 weeks and then transferred to either M or H medium. Callus absorption of PEG accounted for 40% of the callus
dry weight and less than 7% of the callus fresh weight. Callus dry weight (without the PEG fraction) on M medium was 40% of
that observed on H medium. Fresh weight on M medium was only 15% of that observed on H medium. The Ψw of both H and M media remained constant throughout the culture period. On H medium, callus Ψw and osmotic potential (Ψs) both increased 0.05 MPa/week with the callus Ψw approaching that of the external medium. On M medium, callus Ψw and Ψs both decreased more than 0.1 MPa/week with the callus Ψw decreasing greatly below that of the external medium. The latter was attributed to a rapidly produced osmotic shock induced
upon callus transfer and/or PEG which caused less callus hydration and resulted in reduced growth. Callus turgor potential
(Ψp) was estimated to be +0.02 to +0.09 MPa and turgor was maintained as callus Ψw increased or decreased. After 8 weeks, cell volumes from callus on M medium were 50 to 60% less than on H medium, suggesting
that reduced cell volumes were related to turgor maintenance. 相似文献
7.
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
8.
B. R. Lee L. S. Li W. J. Jung Y. L. Jin J. C. Avice A. Ourry T. H. Kim 《Biologia Plantarum》2009,53(3):505-510
The objective of this study was to determine the development of the antioxidant enzymes induced by drought stress in white
clover (Trifolium repens L.) leaves. Water stress was imposed during 28 d by decreasing the daily irrigation. Leaf water potential (Φw) gradually decreased from −0.46 to −2.33 MPa. For the first 7 d, dry mass (DM), H2O2 and lipid peroxidation were not significantly affected by water deficit. From 14 d of treatment, water stress decreased dry
mass and increased content of reactive oxygen species (O2
·− and H2O2) and oxidative stress (malondialdehyde content). The ascorbate peroxidase (APOD) was activated most rapidly, already during
the first week of water stress, but then its activity slowly decreased. Activation of superoxide dismutase (SOD) and catalase
(CAT) by water deficit continued during the 14 d (Φw ≥ −1.65 MPa) and then their activities remain on the similar level. The activity of guaiacol-peroxidase (GPOD) increased
mostly under progressive water stress and was correlated with increase in lipid peroxidation and growth restriction. 相似文献
9.
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
10.
Karen L. Koster Ronald A. Balsamo Catherine Espinoza Melvin J. Oliver 《Plant Growth Regulation》2010,62(3):293-302
The moss Physcomitrella patens is becoming the model of choice for functional genomic studies at the cellular level. Studies report that Physcomitrella survives moderate osmotic and salt stress, and that desiccation tolerance can be induced by exogenous ABA. Our goal was to
quantify the extent of dehydration tolerance in wild type moss and to examine the nature of cellular damage caused by desiccation.
We exposed Physcomitrella to humidities that generate water potentials from −4 (97% RH) to −273 MPa (13% RH) and monitored water loss until equilibrium.
Water contents were measured on a dry matter basis to determine the extent of dehydration because fresh weights (FW) were
found to be variable and, therefore, unreliable. We measured electrolyte leakage from rehydrating moss, assessed overall regrowth,
and imaged cells to evaluate their response to drying and rehydration. Physcomitrella did not routinely survive water potentials <−13 MPa. Upon rehydration, moss dried to water contents >0.4 g g dm−1 maintained levels of leakage similar to those of hydrated controls. Moss dried to lower water contents leaked extensively,
suggesting that plasma membranes were damaged. Moss protonemal cells were shrunken and their walls twisted, even at −13 MPa.
Moss cells rehydrated after drying to −273 MPa failed to re-expand completely, again indicating membrane damage. ABA treatment
elicited tolerance of desiccation to at least −273 MPa and limited membrane damage. Results of this work will form the basis
for ongoing studies on the functional genomics of desiccation tolerance at the cellular level. 相似文献
11.
Hanna Bandurska 《Acta Physiologiae Plantarum》1998,20(4):375-381
The aim of this work was to examine the ability of ABA and proline to counteract the deleterious effect of water deficit stress
on cell membrane injuries.
Six-day-old seedlings of two barley genotypes (cv. Aramir, line R567) were treated with ABA (2·10−4 M) or proline (0.1 M) for 24 h, and then subjected to osmotic stress for 24h, by immersing their roots in polyethylene glycol
(PEG 6000) solution of osmotic potential of −1.0 MPa and −1.5 MPa or by submerging the leaf pieces in PEG solution of osmotic
potential of −1.6 MPa.
Pretreatment of plants with ABA and proline caused an increase of free proline level in the leaves. Plants treated with ABA
exhibited a lower membrane injury index under water stress conditions than those untreated even when no effect of this hormone
on RWC in the leaves of stressed plants was observed. Pretreatment of plants with proline prevented to some extent membrane
damage in leaves of the stressed seedlings, but only in the case when stress was imposed to roots. Improvement in water status
of leaves was also observed in seedlings pretreatment with proline. The protective effect of both ABA and proline was more
pronounced in line R567 that exhibited higher membrane injury under water deficit stress conditions. 相似文献
12.
Kolluru Viswanatha Chaitanya Girish Kumar Rasineni Attipalli Ramachandra Reddy 《Acta Physiologiae Plantarum》2009,31(3):437-443
Five popularly grown mulberry cultivars (K-2, MR-2, TR-10, BC2-59 and S-13) were subjected to drought stress by withholding
irrigation, to obtain leaf water potentials (Ψw) ranging from −0.75, −1.50 and −2.25 MPa. Accumulation of proline, glycine betaine and abscisic acid (ABA) were quantified
in control and water stressed mulberry leaves. The activities of enzymes involved in proline accumulation including glutamate
dehydrogenase (EC1.4.1.2-4), pyrroline-5-carboxylate synthetase (EC 1.2.1.41), pyrroline-5-carboxylate reductase (EC1.5.1.2),
ornithine transaminase (EC 2.6.1.13) were significantly enhanced in the leaves of all the cultivars with decreasing leaf water
potentials, while the activities of proline dehydrogenase (EC 1.5.1.2) were reduced with progressive increase in water stress.
Accumulation of proline, glycine betaine and abscisic acid was relatively higher in S-13 and BC2-59 compared to K-2, MR-2
and TR-10 under water deficit conditions. Our results demonstrate that S-13 and BC2-59 have superior osmoprotectant mechanisms
under water-limited growth regimes. 相似文献
13.
Sandra J. Bucci Fabian G. Scholz Guillermo Goldstein Frederick C. Meinzer Maria E. Arce 《Oecologia》2009,160(4):631-641
Adaptations of species to capture limiting resources is central for understanding structure and function of ecosystems. We
studied the water economy of nine woody species differing in rooting depth in a Patagonian shrub steppe from southern Argentina
to understand how soil water availability and rooting depth determine their hydraulic architecture. Soil water content and
potentials, leaf water potentials (ΨLeaf), hydraulic conductivity, wood density (ρw), rooting depth, and specific leaf area (SLA) were measured during two summers. Water potentials in the upper soil layers
during a summer drought ranged from −2.3 to −3.6 MPa, increasing to −0.05 MPa below 150 cm. Predawn ΨLeaf was used as a surrogate of weighted mean soil water potential because no statistical differences in ΨLeaf were observed between exposed and covered leaves. Species-specific differences in predawn ΨLeaf were consistent with rooting depths. Predawn ΨLeaf ranged from −4.0 MPa for shallow rooted shrubs to −1.0 MPa for deep-rooted shrubs, suggesting that the roots of the latter
have access to abundant moisture, whereas shallow-rooted shrubs are adapted to use water deposited mainly by small rainfall
events. Wood density was a good predictor of hydraulic conductivity and SLA. Overall, we found that shallow rooted species
had efficient water transport in terms of high specific and leaf specific hydraulic conductivity, low ρw, high SLA and a low minimum ΨLeaf that exhibited strong seasonal changes, whereas deeply rooted shrubs maintained similar minimum ΨLeaf throughout the year, had stems with high ρw and low hydraulic conductivity and leaves with low SLA. These two hydraulic syndromes were the extremes of a continuum with
several species occupying different portions of a gradient in hydraulic characteristics. It appears that the marginal cost
of having an extensive root system (e.g., high ρw and root hydraulic resistance) contributes to low growth rates of the deeply rooted species. 相似文献
14.
U. Celikkol Akcay O. Ercan M. Kavas L. Yildiz C. Yilmaz H. A. Oktem M. Yucel 《Plant Growth Regulation》2010,61(1):21-28
Two cultivars of peanut (Arachis
hypogaea L.) which were designated as resistant (Florispan) and sensitive (Gazipasa) according to their growth retardation under drought
stress conditions were compared for their oxidative damage and antioxidant responses. Sixteen days-old peanut seedlings were
subjected to PEG-6000 solutions of two different osmotic potentials; −0.4 and −0.8 MPa, and various growth parameters, photosystem
II activity, changes in malondialdehyde (MDA), hydrogen peroxide (H2O2) and proline levels, activities of ascorbate peroxidase (APX), catalase (CAT), peroxidase (POX) and gluthatione reductase
(GR) enzymes were determined. Both cultivars exhibited water deficit at −0.8 MPa osmotic potential of PEG-6000 and H2O2 levels significantly increased during exposure to −0.4 MPa osmotic potential. However, H2O2 levels were under control in both cultivars at exposure to −0.8 MPa osmotic potential. Significant proline accumulation was
observed in the tissues of cv. Florispan at −0.8 MPa osmotic potential, whereas proline accumulation did not appear to be
an essential part of the protection mechanism against drought in cv. Gazipasa. No significant variation in chlorophyll fluorescence
values were detected in neither of the cultivars. Enzyme activity measurements revealed that Gazipasa copes well with lesser
magnitudes of drought stress by increasing the activity of mainly APX, and during harsh stress conditions, only APX maintains
its activity in the tissues. In cultivar Florispan, GR activity appears to take role in lesser magnitudes of drought stress,
whereas CAT and APX activities appear to be very crucial antioxidative defenses during intense stress conditions. The results
indicate that, the level of proline and activities of the enzymes CAT and APX are important mechanisms for the maintenance
of drought tolerance in peanut plants. 相似文献
15.
Mostafa Hojati Seyed Ali Mohammad Modarres-Sanavy Mojtaba Karimi Faezeh Ghanati 《Acta Physiologiae Plantarum》2011,33(1):105-112
An investigation was carried out to find out the extent of changes occurred in two safflower (Carthamus tinctorius L.) cultivars in response to water deficit stress. Two safflower cultivars namely IL.111 and Isfahan were used for the study.
Thirty days after sowing, plants were grown under soil moisture corresponding to 100, 85, 70 and 55% field capacity for next
30 days. Water deficit treatments significantly decreased the shoot length, shoot dry matter, root dry matter, relative growth
rate, leaf relative water content (LRWC) and leaf water potential (ΨW), whereas root length, root-to-shoot ratio, lipid peroxidation and antioxidant compounds such as ascorbic acid (AA), α-tocopherol
(α-Toc) and reduced glutathione (GSH) and superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), and peroxidase
(POX, EC 1.11.1.7) activities were increased. Water deficit stressed plants maintained higher levels of compounds and scavenging
enzymes. Significant differences were observed between cultivars and irrigation levels treatments. The cv. IL.111 could be
considered more tolerant to water stress than cv. Isfahan, registering greater biomass, LRWC and leaf water potential (ΨW), associated with high antioxidant activity. 相似文献
16.
Arne Sellin 《Plant and Soil》1996,184(2):273-280
Variation in base water potential (Ψb, a daily maximum level of plant water potential, which is presumed to correspond to the condition of equilibrium between
the soil and plant water potentials) was examined in shoots of Norway spruce trees growing in well-drained and waterlogged
soils. The influence of soil water content, air temperature, and vapour pressure deficit of the atmosphere on Ψb was studied using the pressure chamber technique. Maximum daily water potentials were not always observable before dawn;
some were registered up to two hours later. This tendency being characteristic of trees growing under stress (shade, waterlogging)
conditions, increased with declining soil water availability. In trees growing in well-drained soil, Ψb depended asymptotically on the available soil water storage (R2=0.73), while the values were slightly influenced by vapour pressure deficit of the atmosphere as well. In trees growing in
waterlogged soil, Ψb was independent of the soil water storage, but sensitive to the vapour pressure deficit. 相似文献
17.
We examined the elongation rate, water status and solute accumulation in the seminal roots of wheat seedlings (Triticum aestivum L.) that were growing in vermiculite with a water potential (Ψw) ranging from −0 03 to −1 10 MPa. The elongation rate of the primary seminal root was similar to that of the first pair of
seminal roots but that of the second pair of seminal roots was lower at all values of Ψw tested. The elongation rate was highest in vermiculite with a Ψw of −0.03 MPa but did not decrease significantly until the Ψw was reduced to −0.15 MPa. Further reductions in Ψw reduced the elongation rate markedly. The Ψw of mature tissues was always similar to that of vermiculite. The osmotic potential (Ψo) decreased to the same extent as the decrease in Ψw. Thus, the turgor pressure (Ψp) remained unchanged even in vermiculite with a low Ψw. In elongating tissues, Ψw and Ψo were far lower than they were in mature tissues and, thus, reductions in turgor were not significant. Even when the Ψw of vermiculite changed, there were no consistent changes in terms of a difference in Ψw between elongating plus mature tissues and vermiculite. There were also no consistent changes in levels of osmotica, calculated
using the van’t Hoff’s law, in the elongating tissues but the levels in mature tissues increased in vermiculite with a low
Ψw. Our results suggest that (1) reductions in root elongation in vermiculite with a low Ψw were caused by reductions in the extensibility and/or increases in the yield threshold of cell walls and by reductions in
the hydraulic conductivity of the tissues; and (2) a seminal root regulates its growth to keep turgor pressure unchanged. 相似文献
18.
Summary Short-term absorption experiments were conducted with intact barley (Hordeum vulgare L.) seedlings to observe the effects of the osmotic potential (Ψπ) and salt species on nitrate uptake andin vivo nitrate reduction. The experiments consisted of growing barley seedlings for 5 days in complete nutrient solutions salinized
to (Ψπ) levels of −0.6, −1.8, −3.0, −4.2, and −5.4 bars with NaCl, CaCl2 or Na2SO4. After the absorption period, the seedlings were separated into shoots and roots, weighed, then analyzed for NO3. The nutrient solutions were sampled for NO3 analysis each day immediately before renewing the solutions. The accumulative loss of NO3 from the solutions was considered to be uptake whereas NO3 reduction was the difference between uptake and seedling content. Lowering the (Ψπ) of the nutrient solutions resulted in decreased concentrations of NO3 in the plant, little or no effect (except at the lowest (Ψπ) level) on uptake, and increased nitrate reductase activity. Increased rates of NO3 reduction were in particular associated with the Cl concentration of the nutrient solution. 相似文献
19.
Summary
Bromus inermis Leyss. was grown in a 2×2×2 factorial design using different levels of mycorrhizal inoculation (inoculated and noninoculated),
soil water stress (Ψ1 or −0.8 MPa) and potassium (K) fertilization (0 or 150 ppm) as factors. Soil water stress and mycorrhizal inoculation significantly
reduced plant top dry weight during the 18 week study. Chlamydospore production by the mycorrhizal symbiontGlomus fasciculatum (Thaxter sensu. Gerd.) Gerd. and Trappe was significantly reduced by soil water stress of −0.8 MPa. Potassium (K) fertilization
did not significantly influence plant top growth or mycorrhizal colonization. However, foliar Ca and Mg were significantly
lower in plants fertilized with K. Foliar Ca and Mg concentrations of P, K, N, Mn, Zn and Cu were significantly greater in
drought stressed plants whereas Ca and Mg concentrations were significantly greater in well-watered plants. 相似文献
20.
The hypothesis was tested that invasive trees have hydraulic traits that contribute to their invasive nature. Five pairs of co-occurring invasive and native trees, in mesic habitats, were selected: (1) Tamarix ramosissima and Salix amygdaloides; (2) Robinia pseudoacacia and Alnus rhombifolia (3) Schinus terebinthifolius and Myrica cerifera; (4) Ligustrum sinense and Acer negundo; and (5) Sapium sebiferum and Diospyros virginiana, respectively. Resistance to cavitation (the water potential [Ψ
x
] at 75% loss of hydraulic conductivity [Ψ75]) was not consistently greater for invasive compared to native species (Ψ75=−1.91 and −1.67 MPa, respectively). Xylem specific conductivity (K
s), a measure of xylem efficiency, was not different between native and invasive species (K
s = 3.50 and 3.70 kg s−1 MPa−1 m−1, respectively). The lack of difference for resistance to cavitation among invasive and native species suggests that the sampled invaders are not more tolerant to water stress than co-occurring native species. Apparently the spread and invasive nature of the sampled species cannot be explained by hydraulic traits alone. 相似文献