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1.
Water relations, mineral composition, growth and root morphology were studied in pepper plants (Capsicum annuum L. cv California Wonder). Two NaCl concentrations (30 and 60 mM) and two nutrient solutions in which the concentrations of
macronutrients were increased were used to assess the ionic and osmotic effects of NaCl in these plants. The hydraulic conductivity
(Lo), stomatal conductance (gs), percentage of open stomata and pressure potential (Ψp) decreased with all treatments, in a similar way for 30 mM NaCl and for its iso-osmotic solution of macronutrients, however,
the decrease was higher for 60 mM NaCl than for its iso-osmotic solution. Ion analyses also revealed that nutrient concentrations
were altered greatly at 60 mM NaCl. Also, changes in morphology, such as increases in cortex cell size and in intercellular
spaces, were detected. Therefore, at low salinity, the effect of NaCl was mainly osmotic, however, under higher salinity also
the toxicity of Na+ and Cl− participate. 相似文献
2.
To understand the mechanisms of salt tolerance in a halophyte, sea aster (Aster tripolium L.), we studied the changes of water relation and the factors of photosynthetic limitation under water stress and 300 mM
NaCl stress. The contents of Na+ and Cl- were highest in NaCl-stressed leaves. Leaf osmotic potentials (Ψ
s) were decreased by both stress treatments, whereas leaf turgor pressure (Ψ
t) was maintained under NaCl stress. Decrease inΨ
s without any loss ofΨ
t accounted for osmotic adjustment using Na+ and Cl- accumulated under NaCl stress. Stress treatments affected photosynthesis, and stomatal limitation was higher under water
stress than under NaCl stress. Additionally, maximum CO2 fixation rate and O2 evolution rate decreased only under water stress, indicating irreversible damage to photosynthetic systems, mainly by dehydration.
Water stress severely affected the water relation and photosynthetic capacity. On the other hand, turgid leaves under NaCl
stress have dehydration tolerance due to maintenance of Ψ
t and photosynthetic activity. These results show that sea aster might not suffer from tissue dehydration in highly salinized
environments. We conclude that the adaptation of sea aster to salinity may be accomplished by osmotic adjustment using accumulated
Na+ and Cl-, and that this plant has typical halophyte characteristics, but not drought tolerance.
Electronic Publication 相似文献
3.
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
4.
Water relations and xylem transport of nutrients in pepper plants grown under two different salts stress regimes 总被引:4,自引:0,他引:4
Josefa M. Navarro Consuelo Garrido Vicente Martínez Micaela Carvajal 《Plant Growth Regulation》2003,41(3):237-245
Two iso-osmotic concentrations of NaCl and Na2SO4 were used for discriminating between the effects of specific ion toxicities of salt stress on pepper plants (Capsicum annuum L.) grown in hydroponic conditions, in a controlled-environment greenhouse. The two salts were applied to plants at different electrical conductivities, and leaf water relations, osmotic adjustment and root hydraulic conductance were measured. Leaf water potential (w), leaf osmotic potential (o) and leaf turgor potential (p) decreased significantly when EC increased, but the decrease was less for NaCl- than for Na2SO4-treated plants. The reduction in stomatal conductance was higher for NaCl-treated plants. There were no differences in the effect of both treatments on the osmotic adjustment, and a reduction in root hydraulic conductance and the flux of solutes into the xylem was observed, except for the saline ions (Na+, Cl– and SO4
2–). Therefore, pepper growth decreased with increasing salinity because the plants were unable to adjust osmotically or because of the toxic effects of Cl–, SO4
2– and/or Na+. However, turgor of NaCl-treated plants was maintained at low EC (3 and 4 dS m–1) probably due to the maintenance of water transport into the plant (decrease of stomatal conductance), which, together with the lower concentration of Na+ in the plant tissues compared with the Na2SO4 treatment, could be the cause of the smaller decrease in growth. 相似文献
5.
Bartolomeo Dichio Giovanna Margiotta Cristos Xiloyannis Sabino A. Bufo Adriano Sofo Tommaso R. I. Cataldi 《Trees - Structure and Function》2009,23(2):247-256
Two-year-old olive trees (Olea europaea L., cv. Coratina) were subjected to a 15-day period of water deficit, followed by 12 days of rewatering. Water deficit caused
decreases in predawn leaf water potential (Ψw), relative water content and osmotic potential at full turgor (Ψ
π100) of leaves and roots, which were normally restored upon the subsequent rewatering. Extracts of leaves and roots of well-watered
olive plants revealed that the most predominant sugars are mannitol and glucose, which account for more than 80% of non-structural
carbohydrates and polyols. A marked increase in mannitol content occurred in tissues of water-stressed plants. During water
deficit, the levels of glucose, sucrose and stachyose decreased in thin roots (with a diameter <1 mm), whereas medium roots
(diameter of 1–5 mm) exhibited no differences. Inorganic cations largely contribute to Ψ
π100 and remained stable during the period of water deficit, except for the level of Ca2+, which increased of 25% in water-stressed plants. The amount of malate increased in both leaves and roots during the dry
period, whereas citrate and oxalate decreased. Thin roots seem to be more sensitive to water deficit and its consequent effects,
while medium roots present more reactivity and a higher osmotic adjustment. The results support the hypothesis that the observed
decreases in Ψw and active osmotic adjustment in leaves and roots of water-stressed olive plants may be physiological responses to tolerate
water deficit. 相似文献
6.
《Environmental and Experimental Botany》2011,70(3):279-285
This study aimed to assess the accumulation of organic and inorganic solutes and their relative contribution to osmotic adjustment in roots and leaves of Jatropha curcas subjected to different water deficit intensity. Plants were grown in vermiculite 50% (control), 40%, 30%, 20% and 10% expressed in gravimetric water content. The water potential, osmotic potential and turgor potential of leaves decreased progressively in parallel to CO2 photosynthetic assimilation, transpiration and stomatal conductance, as the water deficit increased. However, the relative water content, succulence and water content in the leaves did not show differences between the control and stressed plants, indicating osmotic adjustment associated with an efficient mechanisms to prevent water loss by transpiration through stomatal closure. The K+ ions had greater quantitative participation in the osmotic adjustment in both leaves and roots followed by Na+ and Cl−, while the NO3− ion only showed minor involvement. Of the organic solutes studied, the total soluble sugars showed the highest relative contribution to the osmotic adjustment in both organs and its concentration positively increased with more severe water deficit. The free amino acids and glycinebetaine also effectively contributed to the osmotic potential reduction of both the root and leaves. The role of proline was quantitatively insignificant in terms of osmotic adjustment, in both the control and stressed roots and leaves. Our data reveal that roots and leaves of J. curcas young plants display osmotic adjustment in response to drought stress linked with mechanisms to prevent water loss by transpiration by means of the participation of inorganic and organic solutes and stomatal closure. Of all the solutes studied, soluble sugars uniquely display a prominent drought-induced synthesis and/or accumulation in both roots and leaves. 相似文献
7.
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
8.
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
9.
Maize plants of CPB2 and CPB8 hybrids were kept under water deficit for 22 d. In the CPB8 hybrid, leaf rolling initiated at
the 9th d of water deficit period, while in CPB2 hybrid it was at the 15th d. Both hybrids showed leaf rolling initiation at the same leaf water potential, ΨW of -0.480±0.095 MPa. At leaf rolling initiation, the leaf osmotic potential, ΨS was -0.730±0.085 MPa in CPB8 and 0.630±0.110 MPa in CPB2. The leaf temperature and stomatal conductance were higher in CPB8
than in CPB2. Values of leaf ΨW, ribulose-1,5-bisphosphate carboxylase activity, chlorophyll content, and specific leaf area were similar in both hybrids.
Phosphoenolpyruvate carboxylase activity and protein content were lower in the CPB2 hybrid than in CPB8. In both hybrids leaf
rolling initiation was associated with: (1) higher leaf temperature, with leaf rolling effect related to leaf temperature reduction, and (2) lower leaf ΨS, related to osmotic adjustment as an additional component of drought-tolerance strategy.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
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
11.
The impact of water stress was analysed in the xero-halophyte Mediterranean shrub Atriplex halimus using two Tunisian populations originating from a sub-humid coastal site (Monastir) or from a semi-arid area (Kairouan).
Seedlings were exposed for 10 days to nutrient solution containing either 0 or 15% polyethylene glycol. Water potential (Ψw), osmotic potential (Ψs), osmotic potential at full turgor [Ψs(100)], relative water content (RWC), shoot dry weight (DW) and changes in solute concentrations were quantified every 2 days
throughout the stress period and inorganic solutes contents were determined at the end of the treatment. The water deficit
induced a decrease in Ψw, Ψs and RWC in both populations, recorded changes being higher in plants of Monastir than those of Kairouan while the shoot dry
weight was reduced in a similar extent in stressed plants from both populations. Water deficit induced an increase in proline,
glycinebetaine and sugar concentrations. Proline accumulated as early as after the 24-h stress treatment while, glycinebetaine
required more than 6 days of stress to accumulate. At the end of the stress period, the plants of Kairouan population accumulated
higher amounts of proline than those of Monastir, while an opposite trend was reported for glycinebetaine. Both populations
specifically accumulated Na+ in response to drought stress, suggesting that this element could play a physiological role in the stress response of this
xero-halophyte species. Presented results suggest that the non-recyclable osmotic solute glycinebetaine does not necessarily
preferentially accumulates in population facing permanent water stress and that other strategy than osmotic adjustment might
be involved in drought tolerance of A. halimus. 相似文献
12.
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
13.
AbstractThe role of abscisic acid (ABA) was analyzed in roots and leaves of the halophyte Prosopis strombulifera in response to low osmotic potential (Ψo: ?1.0, ?1.9, and ?2.6?MPa) induced by sodium chloride (NaCl), sodium sulfate (Na2SO4), and the iso-osmotic combination of both compounds (NaCl?+?Na2SO4). P. strombulifera plants were sprayed with ABA, as well as with inhibitors of ABA biosynthesis (sodium tungstate and fluridone). Different parameters were measured, including total plant height, leaf number, root length, root and shoot biomass, water content, transpiration rate, and total soluble carbohydrates, specific carbohydrates and ABA concentrations. Results showed that sodium salts affected growth parameters in varying ways, depending on the type of salts used as well as the osmotic potentials. ABA-sprayed plants displayed the lowest transpiration values. These plants had a higher content of total soluble carbohydrates in roots, greater root biomass and length and increased root/shoot rate. This study shows that ABA triggers different biochemical and physiological responses after the perception of a stressful condition, and that the interaction between different concentrations and types of salts, and the addition of ABA or its inhibitors generates responses that affect development and growth in the halophyte P. strombulifera. 相似文献
14.
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
15.
An experiment was conducted to determine soil and plant resistance to water flow in faba bean under field conditions during
the growing season. During each sampling period transpiration flux and leaf water potential measured hourly were used with
daily measurements of root and soil water potential to calculate total resistance using Ohm's law analogy. Plant growth, root
density and soil water content distributions with depth were measured. Leaf area and root length per plant reached their maximum
value during flowering and pod setting (0.31 m2 and 2200 m, respectively), then decreasing until the end of the growing period. Root distribution decreased with depth ranging,
on average, between 34.2% (in the 0–0.25 m soil layer) and 18.1% (in the 0.75–1.0 m soil layer). Mean root diameter was 0.6
mm but most of the roots were less than 0.7 mm in diameter. Changes in plant and soil water potentials reflected plant growth
characteristics and climatic patterns. The overall relationship between the difference in water potential between soil and
leaf and transpiration was linear, with the slope equal to average plant resistance (0.0165 MPa/(cm3 m-1 h-1 10-3). Different regression parameters were obtained for the various measurement days. The water potential difference was inversely
related to transpiration at high leaf stomatal resistance and at high values of VPD. Total resistance decreased with transpiration
flux in a linear relationship (r=−0.68). Different slope values were obtained for the different measurement days. Estimated
soil resistance was much lower than the observed total resistance to water flow. The change from vegetative growth to pod
filling was accompanied by an increase in plant resistance. The experimental results support previous findings that resistance
to water flow through plants is not constant but is influenced by plant age, growth stage and environmental conditions. A
more complex model than Ohm's law analogy may be necessary for describing the dynamic flow system under field conditions.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
16.
Effects of nitrogen nutrition and root medium water potential on growth, nitrogen uptake and osmotic adjustment of rice 总被引:2,自引:0,他引:2
The effects of nitrogen (N) nutrition on growth, N uptake and leaf osmotic potential of rice plants (Oryza sativa L. ev. IR 36) during simulated water stress were determined. Twenty-one-day-old seedlings in high (28.6 × 10 ?4M) and low (7.14 × 10 4M) N levels were exposed to decreased nutrient solution water potentials by addition of polyethylene glycol 6000. The roots were separated from the solution by a semi-permeable membrane. Nutrient solution water potential was ?0.6 × 105 Pa and was lowered stepwise to ?1 × 105, ?2 × 105, ?4 × 105 and ?6 × 105 Pa at 2-day intervals. Plant height, leaf area and shoot dry weight of high and low nitrogen plants were reduced by lower osmotic potentials of the root medium. Osmotic stress caused greater shoot growth reduction in high N than in low N plants. Stressed and unstressed plants in 7.14 × 104M N had more root dry matter than the corresponding plants in 28.6 × 104M N. Dawn leaf water potential of stressed plants was 1 × 105 to 5.5 × 105 Pa lower than nutrient solution water potential. Nitrogen-deficient water-stressed plants, however, maintained higher dawn leaf water potential than high nitrogen water-stressed plants. It is suggested that this was due to higher root-to-shoot ratios of N deficient plants. The osmotic potentials of leaves at full turgor for control plants were about 1.3 × 105 Pa higher in 7.14 × 10?4M than in 28.6 × 10?4M N and osmotic adjustment of 2.6 × 105 and 4.3 × 105 Pa was obtained in low and high N plants, respectively. The nitrogen status of plants, therefore, affected the ability of the rice plant to adjust osmotically during water stress. Plant water stress decreased transpiration and total N content in shoots of both N treatments. Reduced shoot growth as a result of water stress caused the decrease in amount of water transpired. Transpiration and N uptake were significantly correlated. Our results show that nitrogen content is reduced in water-stressed plants by the integrated effects of plant water stress per se on accumulation of dry matter and transpiring leaf area as well as the often cited changes in soil physical properties of a drying root medium. 相似文献
17.
M. B. Kirkham 《Plant and Soil》1988,105(1):19-24
Genotypes of sorghum [Sorghum bicolor (L.) Moench] vary in drought resistance. Yet it is not known if their hydraulic resistances vary. The objective of this study
was to determine if the hydraulic resistance of a drought-resistant sorghum was the same as that of a drought-sensitive sorghum.
Leaf water and osmotic potentials were measured daily, during a 14-d period, in leaves of a drought-resistant (‘KS9’) and
a drought-sensitive (‘IA25’) sorghum, which had the roots in pots with a commercial potting soil that was either well watered
or allowed to dry. Soil water potential, adaxial stomatal resistance, and transpiration rate were determined daily. Hydraulic
resistance of the plants was calculated from the slope of the line relating soil water potential minus leaf water potential
versus transpiration rate. When the soil was not watered, the drought-sensitive sorghum had a water potential that averaged
−0.50 MPa lower and an osmotic potential that averaged −0.57 MPa lower, but a similar adaxial stomatal resistance (1.19 s
mm−1), compared with the drought-resistant sorghum. Seven days after the beginning of the experiment, the water potential of the
soil with the drought-sensitive sorghum was −0.25 MPa lower than that of the soil with the drought-resistant sorghum. With
the water-limited conditions, the drought-sensitive sorghum depleted the soil-water reserve more quickly and died 2 d before
the drought-resistant sorghum. Under well watered conditions, the two sorghums had similar water potentials (−1.64 MPa), osmotic
potentials (−2.83 MPa), and adaxial stomatal resistances (0.78 s mm−1). The calculated hydraulic resistance of the two sorghums did not differ and averaged 3.4 × 107 MPa s m−1. The results suggested that the variation in susceptibility to drought between the two genotypes was due to differences in
rate of soil-water extraction.
Contribution No. 86-249-J from the Kansas Agricultural Experiment Station. The paper is dedicated to the memory of Dr Dan
M Rodgers. 相似文献
18.
The responses of leaf water parameters to drought were examined using three sunflower (Helianthus annuus L.) genotypes. Osmotic potential at full water saturation (π100), apoplastic water fraction (AWF) and bulk elastic modulus (BEM) were determined by pressure-volume curve analysis on well
watered or on water-stressed plants (−1.0 MPa Ψ1 < −1.5 MPa) previously drought-pretreated or not. The drought-pretreated plants were subjected to a 7-day drought period
(predawn leaf water potential reached −0.9 MPa) followed by 8 days of rewatering. In well watered plants, all genotypes in
response to drought acclimation displayed a significantly decreased π100 associated with a decrease in the leaf water potential at the turgor-loss point (decrease in Ψtlp was between 0.15 and 0.21 MPa, depending on the genotype). In two genotypes, drought acclimation affected the partitioning
of water between the apoplastic and symplastic fractions without any effect on the total amount of water in the leaves. As
a third genotype displayed no modification of AWF and BEM after drought acclimation, the decreased π100 was only due to the net accumulation of solutes and was consistent with the adjustment of the photochemical efficiency observed
previously in this genotype in response to drought acclimation. In water-stressed plants, the osmotic adjustment (OA) can
increase further beyond that observed in response to the drought pretreatment. However, the maintenance of photosynthetic
rate and stomatal conductance at low leaf water potentials not only depends on the extent of osmotic adjustment, but also
on the interaction between OA and AWF or BEM. Adaptative responses of leaf water parameters to drought are thus quite contrasted
in sunflower genotypes.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
19.
Roser Tolrà Paula Pongrac Charlotte Poschenrieder Katarina Vogel-Mikuš Marjana Regvar Juan Barceló 《Plant and Soil》2006,282(1-2):333-341
We investigated the hypothesis that continuous water application allows favorable and steady water content and hydraulic conductivity
in the root zone, thus enabling higher water potential in the soil–root interface (ψroot). Elevated ψroot increases transpiration (T) and prevents yield loss due to stomatal closure or to low root osmotic potential that develops in response to low ψroot. We assume further, that the advantage of continuous water application is more pronounced for young plants, where water uptake
per root length and competition on resources in the root system is higher. We investigated this hypothesis by examining the
average water content of the root zone and T as a function of time for sunflowers grown under varied irrigation frequencies experimentally and in a modeled simulations,
and by solving for the necessary effective root length and ψroot for each case. High frequency water application was shown to positively affect root water uptake efficiency and yield, especially
when plants were young. Irrigation frequency affected growth through the water content in the bulk soil (θsoil) which in turn affects ψroot. A low θsoil and coupled low hydraulic conductivity decreased T and yield. Moreover, a decreased θsoil caused low ψroot, inefficient allocation of energy and carbohydrates and eventual yield loss. It was likely that these phenomena were more
pronounced with young plants due to higher water uptake per root length. 相似文献
20.
M.A.A. Gadallah 《Biologia Plantarum》1999,42(2):249-257
Plants of bean (Vicia faba L. cv. Calvor 103) were salt-stressed with NaCl and CaCl2 in concentrations inducing soil osmotic potentials (ψsoil) from 0 to -1.2 MPa and were sprayed with proline (8.7 μM) and glycinebetaine (8.5 μM) solutions. Bean plants respond to
increasing soil salinity by decreased leaf relative water content and osmotic potential. Salinity decreased the contents of
dry mass, chlorophyll, soluble and hydrolysable sugars, soluble proteins and enhanced content of total free amino acids, Na+, Ca2+ and Cl-. The ratio of K+/Na+ was decreased on salinization. The membranes of leaf discs from salt-stressed plants appeared to be less stable under heat
stress (51 °C) than that of unstressed plants. The reverse was true for discs placed under dehydration stress (40 % polyethylene
glycol 6000). Proline and glycinebetaine application reduced membrane injury, improved K+ uptake and growth. Also both solutes increased chlorophyll contents.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献