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1.
With the changing climate, plants will be facing increasingly harsh environmental conditions marked by elevated salinity in the soils and elevated concentrations of CO 2 in the atmosphere. These two factors have opposite effects on water status in plants. Therefore, our objective was to determine the interaction between these two factors and to determine whether elevated [CO 2] might alleviate the adverse effects of salt stress on water status in two barley cultivars, Alpha and Iranis, by studying their relative water content and their water potential and its components, transpiration rate, hydraulic conductance, and water use efficiency. Both cultivars maintained their water status under salt stress, increasing water use efficiency and conserving a high relative water content by (1) reducing water potential via passive dehydration and active osmotic adjustment and (2) decreasing transpiration through stomatal closure and reducing hydraulic conductance. Iranis showed a greater capacity to achieve osmotic adjustment than Alpha. Under the combined conditions of salt-stress and elevated [CO 2], both cultivars (1) achieved osmotic adjustment to a greater extent than at ambient [CO 2], likely due to elevated rates of photosynthesis, and (2) decreased passive dehydration by stomatal closure, thereby maintaining a greater turgor potential, relative water content, and water use efficiency. Therefore, we found an interaction between salt stress and elevated [CO 2] with regard to water status in plants and found that elevated [CO 2] is associated with improved water status of salt-stressed barley plants. 相似文献
2.
With the changing climate, plants will be facing increasingly harsh environmental conditions marked by elevated salinity in the soils and elevated concentrations of CO 2 in the atmosphere. These two factors have opposite effects on water status in plants. Therefore, our objective was to determine the interaction between these two factors and to determine whether elevated [CO 2] might alleviate the adverse effects of salt stress on water status in two barley cultivars, Alpha and Iranis, by studying their relative water content and their water potential and its components, transpiration rate, hydraulic conductance, and water use efficiency. Both cultivars maintained their water status under salt stress, increasing water use efficiency and conserving a high relative water content by (1) reducing water potential via passive dehydration and active osmotic adjustment and (2) decreasing transpiration through stomatal closure and reducing hydraulic conductance. Iranis showed a greater capacity to achieve osmotic adjustment than Alpha. Under the combined conditions of salt-stress and elevated [CO 2], both cultivars (1) achieved osmotic adjustment to a greater extent than at ambient [CO 2], likely due to elevated rates of photosynthesis, and (2) decreased passive dehydration by stomatal closure, thereby maintaining a greater turgor potential, relative water content, and water use efficiency. Therefore, we found an interaction between salt stress and elevated [CO 2] with regard to water status in plants and found that elevated [CO 2] is associated with improved water status of salt-stressed barley plants. 相似文献
3.
We investigated the photosynthetic capacity and plant growth of tobacco plants overexpressing ice plant ( Mesembryanthemum crystallinum L.) aquaporin McMIPB under (1) a well-watered growth condition, (2) a well-watered and temporal higher vapor pressure deficit (VPD) condition, and (3) a soil water deficit growth condition to investigate the effect of McMIPB on photosynthetic responses under moderate soil and atmospheric humidity and water deficit conditions. Transgenic plants showed a significantly higher photosynthesis rate (by 48 %), higher mesophyll conductance (by 52 %), and enhanced growth under the well-watered growth condition than those of control plants. Decreases in the photosynthesis rate and stomatal conductance from ambient to higher VPD were slightly higher in transgenic plants than those in control plants. When plants were grown under the soil water deficit condition, decreases in the photosynthesis rate and stomatal conductance were less significant in transgenic plants than those in control plants. McMIPB is likely to work as a CO 2 transporter, as well as control the regulation of stomata to water deficits. 相似文献
4.
We evaluated the combined effects of elevated CO 2 and water availability on photosynthesis in barley. Soil and plant water content decreased with water stress, but less under
elevated CO 2 concentration (EC) compared with ambient CO 2 concentration (AC). During water stress, stomatal conductance, carboxylation rate, RuBP regeneration, and the rate of triose
phosphate utilisation (TPU) were decreased but less when plants grew under EC. Drought treatments caused only a slight effect
on maximum photochemical efficiency (variable to maximum fluorescence ratio, F v/F m), whereas the actual quantum yield (Φ PS2), maximum electron transport rate (J max) and photochemical quenching (qP) were decreased and the non photochemical quenching (NPQ) was enhanced. Under water deficit,
the allocation of electrons to CO 2 assimilation was diminished by 49 % at AC and by 26 % at EC while the allocation to O 2 reduction was increased by 15 % at AC and by 12 % at EC. 相似文献
5.
The response of adaxial and abaxial stomatal conductance in Rumex obtusifolius to growth at elevated atmospheric concentrations of CO 2 (250 μmol mol ?1 above ambient) was investigated over two growing seasons. The conductance of both the adaxial and abaxial leaf surfaces was found to be reduced by elevated concentrations of CO 2. Elevated CO 2 caused a much greater reduction in conductance for the adaxial surface than for the abaxial surface. The absence of effects upon stomatal density indicated that the reductions were probably the result of changes in stomatal aperture. Partitioning of gas exchange between the leaf surfaces revealed that increased concentrations of CO 2 caused increased rates of photosynthesis only via the abaxial surface. Additionally, leaf thickness was found to increase during growth at elevated concentrations of CO 2. The tendency for these amphistomatous leaves to develop a distribution of conductance approaching that of hypostomatous leaves clearly reduced their maximum photosynthetic potential. This conclusion was supported by measurements of stomatal limitation, which showed greater values for the adaxial surfaces, and greater values at elevated CO 2. This reduction in photosynthesis may in part be caused by higher diffusive limitations imposed because of increased leaf thickness. In an uncoupled canopy, asymmetrical stomatal responses of the kind identified here may appreciably reduce transpiration. Species which show symmetrical responses are less likely to show reduced transpirational rates, and a redistribution of water loss between species may occur. The implications of asymmetrical stomatal responses for photosynthesis and canopy transpiration are discussed. 相似文献
6.
Physiological processes that modulate photosynthetic acclimation to rising atmospheric CO 2 concentration are subjects of intense discussion recently. Apparently, the down-regulation of photosynthesis under elevated CO 2 is not understood clearly. In the present study, the response of soybean ( Glycine max L.) to CO 2 enrichment was examined in terms of nitrogen partitioning and water relation. The plants grown under potted conditions without combined N application were exposed to either ambient air (38 Pa CO 2) or CO 2 enrichment (100 Pa CO 2) for short (6 days) and long (27 days). Plant biomass, apparent photosynthetic rate, transpiration rate and 15N uptake and partitioning were measured consecutively after elevated CO 2 treatment. Long-term exposure reduced photosynthetic rate, stomatal conductance and transpiration rate. In contrast, short-term exposure increased biomass production of soybean due to increase in dry weight of leaves. Leaf N concentration tended to decrease with CO 2 enrichment, however such difference was not true for stem and roots.A close correlation was observed between transpiration rate and 15N partitioned into leaves, suggesting that transpiration plays an important role on nitrogen partitioning to leaves. In conclusion existence of a feed back mechanism for photosynthetic acclimation has been proposed. Down-regulation of photosynthetic activity under CO 2 enrichment is caused by decreasing leaf N concentration, and reduced rate of transpiration owing to decreased stomatal conductance is partially responsible for poor N translocation. 相似文献
7.
The osmotic concentration (osmotic potential) of onion leaf sap did not adjust to chloride salinity, and consequently water potential, turgor, stomatal aperture and transpiration were reduced. Although osmotic concentration of bean and cotton leaf sap did adjust to a saline root medium and turgor was no less in the salinized plants than in the controls, stomata of the salinized plants remained only partly open and transpiration was reduced. Net photosynthesis of onion plants was reduced by salinity (this effect being much enhanced in a hot dry atmosphere) but it could be rapidly raised to the level of the controls by inducing elevated leaf turgor. Stomatal closure was initially responsible for most of the ~30 % reduction in photosynthesis of salinized beans. This was due to interference with CO 2 diffusion and could be overcome by raising the CO 2 concentration in the air. At a later stage of growth, salinity affected the light reaction of bean photosynthesis, and elevation of the air CO 2 had little effect. Closure of stomata of salinized cotton plants had only a relatively small effect on net photosynthesis. Light intensity and CO 2 concentration experiments showed that salinity was reducing the photosynthesis of cotton leaves mainly by affecting the light reaction of photosynthesis. It is concluded that chloride salinity does affect the water balance and rate of photosynthesis of plants and that the nature and degree of the effects will depend upon climatic conditions and may be very different between plant species and in the same species at different periods of growth. 相似文献
8.
The increase in water use efficiency (the ratio of photosynthetic to transpiration rates) is likely to be the commonest positive
effect of long-term elevation in CO 2 concentration (CE). This may not necessarily lead to decrease in long-term water use owing to increased leaf area. However,
some plant species seem to cope better with drought stress under CE, because increased production of photosynthates might
enhance osmotic adjustment and decreased stomatal conductance and transpiration rate under CE enable plants to maintain a
higher leaf water potential during drought. In addition, at the same stomatal conductance, internal CO 2 concentration might be higher under CE which results in higher photosynthetic rate. Therefore plants under CE of the future
atmosphere will probably survive eventual higher drought stress and some species may even be able to extend their biotope
into less favourable sites.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
We have investigated the role of polyunsaturated fatty acids in photosynthesis using a triple mutant of Arabidopsis thaliana that lacks trienoic fatty acids ( fad 3-2 fad 7-2 fad 8). Though this mutant is male sterile, vegetative growth and development under normal conditions are largely unaffected (McConn
and Browse, 1996 Plant Cell 8: 403–416). At 0.2–1.0 kPa vapor pressure deficit (low VPD), maximum photosynthetic rates of
wild-type and mutant plants were similar while stomatal conductance rates were up to 2 times higher in mutant plants. However,
light-saturated rates of carbon assimilation and stomatal conductance in the mutant were lower than in wild-type plants when
measured at ambient (35 Pa) CO 2 and 2.0–2.8 kPa vapor pressure deficit (high VPD). The limitation to photosynthesis in the mutant plants at high VPD was
overcome by saturating partial pressures of CO 2 suggesting a stomatal limitation. Chlorophyll fluorescence measurements indicate that differences observed in maximum assimilation
rates were not due to limitations within the photochemical reactions of photosynthesis. Stomatal response to VPD and intrinsic
water use efficiency was drastically different in mutant versus wild-type plants. The results of this investigation indicate
that for Arabidopsis, polyunsaturated fatty acids may be an important determinant of responses of photosynthesis and stomatal conductance to environmental
stresses such as high VPD.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
Stomata help plants regulate CO 2 absorption and water vapor release in response to various environmental changes, and plants decrease their stomatal apertures and enhance their water status under elevated CO 2. Although the bottom‐up effect of elevated CO 2 on insect performance has been extensively studied, few reports have considered how insect fitness is altered by elevated CO 2‐induced changes in host plant water status. We tested the hypothesis that aphids induce stomatal closure and increase host water potential, which facilitates their passive feeding, and that this induction can be enhanced by elevated CO 2. Our results showed that aphid infestation triggered the abscisic acid (ABA) signaling pathway to decrease the stomatal apertures of Medicago truncatula, which consequently decreased leaf transpiration and helped maintain leaf water potential. These effects increased xylem‐feeding time and decreased hemolymph osmolarity, which thereby enhanced phloem‐feeding time and increased aphid abundance. Furthermore, elevated CO 2 up‐regulated an ABA‐independent enzyme, carbonic anhydrase, which led to further decrease in stomatal aperture for aphid‐infested plants. Thus, the effects of elevated CO 2 and aphid infestation on stomatal closure synergistically improved the water status of the host plant. The results indicate that aphid infestation enhances aphid feeding under ambient CO 2 and that this enhancement is increased under elevated CO 2. 相似文献
11.
Maize and grain sorghum seeds were sown in pots and grown for 39 days in sunlit controlled-environment chambers at 360 (ambient) and 720 (double-ambient, elevated) μmol mol −1 carbon dioxide concentrations [CO 2]. Canopy net photosynthesis (PS) and evapotranspiration (TR) was measured throughout and summarized daily from 08:00 to 17:00 h Eastern Standard Time. Irrigation was withheld from matched pairs of treatments starting on 26 days after sowing (DAS). By 35 DAS, cumulative PS of drought-stress maize, compared to well-watered plants, was 41% lower under ambient [CO 2] but only 13% lower under elevated [CO 2]. In contrast, by 35 DAS, cumulative PS of drought-stress grain sorghum, compared to well-watered plants, was only 9% lower under ambient [CO 2] and 7% lower under elevated [CO 2]. During the 27-35 DAS drought period, water use efficiency (WUE, mol CO 2 Kmol −1 H 2O), was 3.99, 3.88, 5.50, and 8.65 for maize and 3.75, 4.43, 5.26, and 9.94 for grain sorghum, for ambient-[CO 2] well-watered, ambient-[CO 2] stressed, elevated-[CO 2] well-watered and elevated-[CO 2] stressed plants, respectively. Young plants of maize and sorghum used water more efficiently at elevated [CO 2] than at ambient [CO 2], especially under drought. Reductions in biomass by drought for young maize and grain sorghum plants were 42 and 36% at ambient [CO 2], compared to 18 and 14% at elevated [CO 2], respectively. Results of our water stress experiment demonstrated that maintenance of relatively high canopy photosynthetic rates in the face of decreased transpiration rates enhanced WUE in plants grown at elevated [CO 2]. This confirms experimental evidence and conceptual models that suggest that an increase of intercellular [CO 2] (or a sustained intercellular [CO 2]) in the face of decreased stomatal conductance results in relative increases of growth of C 4 plants. In short, drought stress in C 4 crop plants can be ameliorated at elevated [CO 2] as a result of lower stomatal conductance and sustaining intercellular [CO 2]. Furthermore, less water might be required for C 4 crops in future higher CO 2 atmospheres, assuming weather and climate similar to present conditions. 相似文献
12.
Open-top chambers were used to study the effects of CO 2 enrichment on leaf-level photosynthetic rates of the C 4 grass Andropogon gerardii in the native tallgrass prairie ecosystem near Manhattan, Kansas. Measurements were made during a year with abundant rainfall
(1993) and a year with below-normal rainfall (1994). Treatments included: No chamber, ambient CO 2 (A); chamber with ambient CO 2 (CA); and chamber with twice-ambient CO 2 (CE). Measurements of photosynthesis were made at 2-hour intervals, or at midday, on cloudless days throughout the growing
season using an open-flow gas-exchange system. No significant differences in midday rates of photosynthesis or in daily carbon
accumulation as a result of CO 2 enrichment were found in the year with abundant precipitation. In the dry year, midday rates of photosynthesis were significantly
higher in the CE treatment than in the CA or A treatments throughout the season. Estimates of daily carbon accumulation also
indicated that CO 2 enrichment allowed plants to maximize carbon acquisition on a diurnal basis. The increased carbon accumulation was accounted
for by greater rates of photosynthesis in the CE plots during midday. During the wet year, CO 2 enrichment decreased stomatal conductance, which allowed plants to decrease transpiration while still photosynthesizing at
rates similar to plants in ambient conditions. During the dry year, CO 2 enrichment allowed plants to maintain photosynthetic rates even though stomatal conductance and transpiration had been reduced
in all treatments due to stress. Estimates of instantaneous water-use efficiency were reduced under CO 2 enrichment for both years.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
13.
Rising atmospheric carbon dioxide concentration ([CO 2]) significantly influences plant growth, development, and biomass. Increased photosynthesis rate, together with lower stomatal conductance, has been identified as the key factors that stimulate plant growth at elevated [CO 2] (e[CO 2]). However, variations in photosynthesis and stomatal conductance alone cannot fully explain the dynamic changes in plant growth. Stimulation of photosynthesis at e[CO 2] is always associated with post‐photosynthetic secondary metabolic processes that include carbon and nitrogen metabolism, cell cycle functions, and hormonal regulation. Most studies have focused on photosynthesis and stomatal conductance in response to e[CO 2], despite the emerging evidence of e[CO 2]'s role in moderating secondary metabolism in plants. In this review, we briefly discuss the effects of e[CO 2] on photosynthesis and stomatal conductance and then focus on the changes in other cellular mechanisms and growth processes at e[CO 2] in relation to plant growth and development. Finally, knowledge gaps in understanding plant growth responses to e[CO 2] have been identified with the aim of improving crop productivity under a CO 2 rich atmosphere. 相似文献
14.
Plants can modify xylem anatomy and hydraulic properties to adjust to water status. Elevated [CO 2] can increase plant water potential via reduced stomatal conductance and water loss. This raises the question of whether elevated [CO 2], which thus improves plant water status, will reduce the impacts of soil water deficit on xylem anatomy and hydraulic properties of plants. To analyse the impacts of water and [CO 2] on maize stem xylem anatomy and hydraulic properties, we exposed potted maize plants to varying [CO 2] levels (400, 700, 900, and 1,200 ppm) and water levels (full irrigation and deficit irrigation). Results showed that at current [CO 2], vessel diameter, vessel roundness, stem cross-section area, specific hydraulic conductivity, and vulnerability to embolism decreased under deficit irrigation; yet, these impacts of deficit irrigation were reduced at elevated [CO 2]. Across all treatments, midday stem water potential was tightly correlated with xylem traits and displayed similar responses. A distinct trade-off between efficiency and safety in stem xylem water transportation in response to water deficit was observed at current [CO 2] but not observed at elevated [CO 2]. The results of this study enhance our knowledge of plant hydraulic acclimation under future climate environments and provide insights into trade-offs in xylem structure and function. 相似文献
15.
The future environment may be altered by high concentrations of salt in the soil and elevated [CO 2] in the atmosphere. These have opposite effects on photosynthesis. Generally, salt stress inhibits photosynthesis by stomatal
and non-stomatal mechanisms; in contrast, elevated [CO 2] stimulates photosynthesis by increasing CO 2 availability in the Rubisco carboxylating site and by reducing photorespiration. However, few studies have focused on the
interactive effects of these factors on photosynthesis. To elucidate this knowledge gap, we grew the barley plant, Hordeum vulgare (cv. Iranis), with and without salt stress at either ambient or elevated atmospheric [CO 2] (350 or 700 μmol mol −1 CO 2, respectively). We measured growth, several photosynthetic and fluorescence parameters, and carbohydrate content. Under saline
conditions, the photosynthetic rate decreased, mostly because of stomatal limitations. Increasing salinity progressively increased
metabolic (photochemical and biochemical) limitation; this included an increase in non-photochemical quenching and a reduction
in the PSII quantum yield. When salinity was combined with elevated CO 2, the rate of CO 2 diffusion to the carboxylating site increased, despite lower stomatal and internal conductance. The greater CO 2 availability increased the electron sink capacity, which alleviated the salt-induced metabolic limitations on the photosynthetic
rate. Consequently, elevated CO 2 partially mitigated the saline effects on photosynthesis by maintaining favorable biochemistry and photochemistry in barley
leaves. 相似文献
16.
Soybean ( Glycine max L. Merrill cv `Bragg') plants were grown in pots at six elevated atmospheric CO 2 concentrations and two watering regimes in open top field chambers to characterize leaf xylem potential, stomatal resistance and conductance, transpiration, and carbohydrate contents of the leaves in response to CO 2 enrichment and water stress conditions. Groups of plants at each CO 2 concentration were subjected to water stress by withholding irrigation for 4 days during the pod-filling stage. Under well watered conditions, the stomatal conductance of the plants decreased with increasing CO2 concentration. Therefore, although leaf area per plant was greater in the high CO2 treatments, the rate of water loss per plant decreased with CO2 enrichment. After 4 days without irrigation, plants in lower CO2 treatments showed greater leaf tissue damage, lower leaf water potential, and higher stomatal resistance than high CO2 plants. Stomatal closure occurred at lower leaf water potentials for the low CO2 grown plants than the high CO2 grown plants. Significantly greater starch concentrations were found in leaves of high CO2 plants, and the reductions in leaf starch and increases in soluble sugars due to water stress were greater for low CO2 plants. The results showed that even though greater growth was observed at high atmospheric CO2 concentrations, lower rates of water use delayed and, thereby, prevented the onset of severe water stress under conditions of low moisture availability. 相似文献
17.
Gas exchange and abscisic acid content of Digitalis lanata EHRH. have been examined at different levels of plant water stress. Net photosynthesis, transpiration and conductance of attached leaves declined rapidly at first, then more slowly following the withholding of irrigation. The intercellular partial pressure of CO 2 decreased slightly. The concentration of 2-cis(S)ABA increased about eight-fold in the leaves of non-irrigated plants as compared with well-watered controls. A close linear correlation was found between the ABA content of the leaves and their conductance on a leaf area basis. In contrast, the plot of net assimilation versus ABA concentration was curvilinear, leading to an increased efficiency of water use during stress. After rewatering, photosynthesis reached control values earlier than transpiration, leaf conductance and ABA content. From these data it is concluded that transpiration through the stomata is directly controlled by the ABA content, whereas net photosynthesis is influenced additionally by other factors.Possible reasons for the responses of photosynthesis and water use efficiency to different stress and ABA levels are discussed.Abbreviations A
net CO 2 assimilation
- ABA
abscisic acid
- C i
intercellular CO 2 concentration
- g
stomatal conductance
- T
transpiration
- WUE
water use efficiency 相似文献
18.
BackgroundIn contrast to C 3 photosynthesis, the response of C 4 photosynthesis to water stress has been less-well studied in spite of the significant contribution of C 4 plants to the global carbon budget and food security. The key feature of C 4 photosynthesis is the operation of a CO 2-concentrating mechanism in the leaves, which serves to saturate photosynthesis and suppress photorespiration in normal air. This article reviews the current state of understanding about the response of C 4 photosynthesis to water stress, including the interaction with elevated CO 2 concentration. Major gaps in our knowledge in this area are identified and further required research is suggested. ScopeEvidence indicates that C 4 photosynthesis is highly sensitive to water stress. With declining leaf water status, CO 2 assimilation rate and stomatal conductance decrease rapidly and photosynthesis goes through three successive phases. The initial, mainly stomatal phase, may or may not be detected as a decline in assimilation rates depending on environmental conditions. This is because the CO 2-concentrating mechanism is capable of saturating C 4 photosynthesis under relatively low intercellular CO 2 concentrations. In addition, photorespired CO 2 is likely to be refixed before escaping the bundle sheath. This is followed by a mixed stomatal and non-stomatal phase and, finally, a mainly non-stomatal phase. The main non-stomatal factors include reduced activity of photosynthetic enzymes; inhibition of nitrate assimilation, induction of early senescence, and changes to the leaf anatomy and ultrastructure. Results from the literature about CO 2 enrichment indicate that when C 4 plants experience drought in their natural environment, elevated CO 2 concentration alleviates the effect of water stress on plant productivity indirectly via improved soil moisture and plant water status as a result of decreased stomatal conductance and reduced leaf transpiration. ConclusionsIt is suggested that there is a limited capacity for photorespiration or the Mehler reaction to act as significant alternative electron sinks under water stress in C 4 photosynthesis. This may explain why C 4 photosynthesis is equally or even more sensitive to water stress than its C 3 counterpart in spite of the greater capacity and water use efficiency of the C 4 photosynthetic pathway.Key words: C3 and C4 photosynthesis, stomatal and non-stomatal limitation, high CO2, water stress 相似文献
19.
Photosynthesis in C 3 plants is CO 2 limited and therefore any increase in Rubisco carboxylation substrate may increase net CO 2 fixation, unless plants experience acclimation or other limitations. These aspects are largely unexplored in grapevine. Photosynthesis analysis was used to assess the stomatal, mesophyll, photochemical and biochemical contributions to the decreasing photosynthesis observed in Tempranillo grapevines ( Vitis vinifera) from veraison to ripeness, modulated by CO 2, temperature and water availability. Photosynthesis and photosystem II photochemistry decreased from veraison to ripeness. The elevated CO 2 and temperature increased photosynthesis, but transiently, in both well irrigated (WI) and water‐stressed plants. Photosynthetic rates were maxima 1 week after the start of elevated CO 2 and temperature treatments, but differences with treatments of ambient conditions disappeared with time. There were not marked changes in leaf water status, leaf chlorophyll or leaf protein that could limit photosynthesis at ripeness. Leaf total soluble sugars remained at ripeness as high as 2 weeks after the start of treatments. On the other hand, and as expected, CO 2 diffusional limitations impaired photosynthesis in grapevine plants grown under water scarcity, stomatal and mesophyll conductances to CO 2 decreased and in turn low chloroplastic CO 2 concentrations limited photosynthetic CO 2 fixation. In summary, photochemistry and photosynthesis from veraison to ripeness in Tempranillo grapevine were dominated by a developmental‐related decreasing trend that was only transiently influenced by elevated CO 2 concentrations. 相似文献
20.
In the global change scenario, increased CO 2 may favour water use efficiency (WUE) by plants. By contrast, in arid and semiarid areas, salinity may reduce water uptake from soils. However, an elevated WUE does not ensure a reduced water uptake and upon salinity this fact may constitute an advantage for plant tolerance. In this work, we aimed to determine the combined effects of enhanced [CO 2] and salinity on the plant water status, in relation to the regulation of PIP aquaporins, in the root and leaf tissues of broccoli plants ( Brassica oleracea L. var Italica), under these two environmental factors. Thus, different salinity concentrations (0, 60 and 90 mM NaCl) were applied under ambient (380 ppm) and elevated (800 ppm) [CO 2]. Under non-salinised conditions, stomatal conductance ( Gs) and transpiration rate ( E) decreased with rising [CO 2] whereas water potential ( Ψω) was maintained stable, which caused a reduction in the root hydraulic conductance ( L0). In addition, PIP1 and PIP2 abundance in the roots was decreased compared to ambient [CO 2]. Under salinity, the greater stomatal closure observed at elevated [CO 2] – compared to that at ambient [CO 2] – caused a greater reduction in Gs and E and allowed plants to maintain their water balance. In addition, a lower decrease in L0 under salt stress was observed at elevated [CO 2], when comparing with the decrease at ambient [CO 2]. Modifications in PIP1 and PIP2 abundance or their functionality in the roots is discussed. In fact, an improved water status of the broccoli plants treated with 90 mM NaCl and elevated [CO 2], evidenced by a higher Ψω, was observed together with higher photosynthetic rate and water use efficiency. These factors conferred on the salinised broccoli plants greater leaf area and biomass at elevated [CO 2], in comparison with ambient [CO 2]. We can conclude that, under elevated [CO 2] and salt stress, the water flow is influenced by the tight control of the aquaporins in the roots and leaves of broccoli plants and that increased PIP1 and PIP2 abundance in these organs provides a mechanism of tolerance that maintains the plant water status. 相似文献
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