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1.
Foliar carbon isotope composition (δ 13C), total dry biomass, and long-term water use efficiency (WUEL) of 12 Populus deltoids clones were studied under water stress in a greenhouse. Total dry biomass of clones decreased greatly, while δ 13C increased. Single-element variance analysis in the same water treatment indicated that WUEL difference among clones was significant. Clones J2, J6, J7, J8, and J9 were excellent with high WUEL. Extremely significant δ 13C differences among water treatments and clones were revealed by two-element variance analysis. Water proved to be the primary factor affecting δ 13C under water stress. It showed that there was a good positive correlation between δ 13C and WUEL in the same water treatment, and that a high WUEL always coincided with a high δ 13C. δ 13C might be a reliable indirect index to estimate WUEL among P. deltoids clones. Translated from Scientia Silvae Sinicae, 2005, 41(1) (in Chinese)  相似文献   

2.
Variations in biomass productivity, plant water-use efficiency (WUEp), and carbon isotope composition (δ13C) were investigated among 10 Malus rootstocks. In the semi-controlled environmental of a greenhouse, plants were watered to either 75% or 50% of field capacity. For each treatment, significant differences were found in dry matter accumulation and allocation, δ13C, and WUEp. Relative growth rate (RGR) was correlated with WUEp but not with allocation pattern. Variations in whole-plant transpiration were a result of fluctuations in the rate of transpiration per unit leaf area rather than from differences in leaf area or root weight per plant. Values for transpiration per unit leaf area or root weight were lower when the proportion of either leaf area or root weight per unit plant weight was larger. Rootstock differences in δ13C were related to changes in stomatal conductance rather than in net photosynthesis. Finally, δ13C was significantly correlated with WUEp and rootstock rankings based on both of those parameters were maintained regardless of watering treatment.  相似文献   

3.
  • ? The effects of drought, enhanced UV-B radiation and their combination on plant growth and physiological traits were investigated in a greenhouse experiment in two populations of Populus cathayana Rehder originating from high and low altitude in south-west China.
  • ? In both populations, drought significantly decreased biomass accumulation and gas exchange parameters, including net CO2 assimilation rate (A), stomatal conductance (g s ), transpiration rate (E) and photosynthetic nitrogen use efficiency (PNUE). However, instantaneous water use efficiency (WUE i ), transpiration efficiency (WUE T ), carbon isotope composition (δ13C) and nitrogen (N) content, as well as the accumulation of soluble protein, UV-absorbing compounds and abscisic acid (ABA) significantly increased in response to drought. On the other hand, cuttings from both populations, when kept under enhanced UV-B radiation, showed very similar changes, as under drought, in all above-mentioned parameters.
  • ? Compared with the low altitude population, the high altitude population was more tolerant to drought and enhanced UV-B, as indicated by the higher level of biomass accumulation, gas exchange, water-use efficiency, ABA concentration and UV-absorbing compounds.
  • ? After one growing season of exposure to different UV-B levels and watering regimes, the decrease in biomass accumulation and gas exchange, induced by drought, was more pronounced under the combination of UV-B and drought. Significant interactions between drought and UV-B were observed in WUE i , WUET, δ13C, soluble protein, UV-absorbing compounds, ABA and in the leaf and stem N, as well as in the leaf and stem C:N ratio.
  • ? Our results showed that UV-B acts as an important signal allowing P. cathayana seedlings to respond to drought and that the combination of drought and UV-B may cause synergistically detrimental effects on plant growth.
    •   相似文献   

    4.
    水分胁迫对四倍体刺槐苗生长和光合作用的影响   总被引：1，自引：0，他引：1       下载免费PDF全文
    刺槐是我国三北地区的主要防护造林树种,尤其是西北干旱、半干旱地区有广泛的种植;但由于当地气候条件的制约,刺槐难于获得生长所需的足够水分[1],生长受到严重抑制,在黄土高原出现了大面积的"小老树"和低劣残次林[2-4],其生态、经济效益都很低.  相似文献   

    5.
    Seasonal changes in carbon isotope discrimination (Δ) and gas exchange traits were assessed in four Populus×euramericana clones differing in growth potential. Measurements were made during the second year after establishment in the field under two watering regimes, which were defined by the time-span between flood irrigations, hence resulting in different dry-down cycles: high irrigation (conservative schedule currently applied in the Ebro Valley, Spain) and low irrigation (equivalent to about a one-fourth reduction in water inputs). Net CO2 assimilation rate (A), stomatal conductance (gs), intrinsic water-use efficiency (A/gs) and other related photosynthetic traits (leaf nitrogen concentration, leaf greenness and leaf mass per area) were measured prior to watering, and Δ was analysed in water-soluble leaf extracts (Δs) and bulk leaves (Δl). Stem growth was monitored over 3 years starting at the year of establishment (1998). Data were subjected to a repeated measures ANOVA over time for a randomised block split-plot design across watering regimes. Significant differences between watering regimes were detected using a long-term estimate of photosynthetic performance such as Δl, in agreement with changes in soil water status and evapotranspirative demand. However, the lack of significant genotype×watering regime interactions for gas exchange traits and Δs suggested that water shortage imposed by low irrigation was not sufficient to reveal physiological adaptations to drought. In this regard, the reduction in water inputs brought about by low irrigation did not reduce tree growth for any of the clones, suggesting that the current irrigation scheme employed in the region is superfluous to the water consumption needs of poplars. Genotypic variation was detected in gas exchange traits, Δs, Δl and stem growth under both watering treatments. Significant correlations with stem volume for Δs (r = −0.60, p<0.05) and A (r = + 0.61, p<0.05) suggested that growth was improved by higher water-use efficiency (the ratio of carbon fixed to water lost, as inferred by Δs) due to variation in A rather than in gs. This observation corroborated the expectation derived from current theories that a lower Δ is related to higher stem volume, as a result of changes in net CO2 assimilation rates.  相似文献   

    6.
    Establishment of native timber trees on deforested land may contribute to the livelihood of farmers, to improved ecosystem services and to increased greenhouse gas uptake. Here, we present a new silvopastoral planting design to assess species performance and interspecific competition or facilitation effects among native timber and multipurpose trees in Central America. Two timber species, Tabebuia rosea and Cedrela odorata, were established in three low-density planting regimes allowing combined tree and future livestock production: (1) solitary planting, (2) companion planting with Guazuma ulmifolia, and (3) companion planting with the nitrogen-fixing Gliricidia sepium. We quantified survival, growth and reforestation potential of the two timber species subjected to the different planting regimes for the first 2 years after establishment. Nitrogen concentration as well as stable nitrogen and carbon isotope composition (δ15N, δ13C) of leaves of the timber saplings were determined. T. rosea showed higher survival and better growth than C. odorata under varying environmental conditions (soil, concomitant vegetation). Performance of the timber saplings was unaffected by either companion species. Planting regimes had no effect on foliar nitrogen concentration and δ15N of the two timber species, although δ15N values indicated nitrogen fixation activity in G. sepium trees. Planting regimes affected foliar δ13C values in T. rosea. δ13C values were significantly higher in solitarily growing individuals, suggesting lower exposition to water stress conditions in saplings surrounded by companion species. As we found positively correlated growth traits among timber and multipurpose trees, a combined planting may benefit farmers by providing additional goods and services.  相似文献   

    7.
    Spiraea pubescens, a common shrub in the warm-temperate deciduous forest zone which is distributed in the Dongling Mountain area of Beijing, was exposed to ambient and enhanced ultraviolet-B (UV-B, 280–320 nm) radiation by artificially supplying a daily dose of 9.4 kJ/m2 for three growing seasons, a level that simulated a 17% depletion in stratospheric ozone. The objective of this study was to explore the effects of long-term UV-B enhancement on stomatal conductance, leaf tissue δ 13C, leaf water content, and leaf area. Particular attention was paid to the effects of UV-B radiation on water use efficiency (WUE) and leaf total nitrogen content. Enhanced UV-B radiation significantly reduced leaf area (50.1%) but increased leaf total nitrogen content (102%). These changes were associated with a decrease in stomatal conductance (16.1%) and intercellular CO2 concentration/ air CO2 concentration (C i /C a) (4.0%), and an increase in leaf tissue δ 13C (20.5‰), leaf water content (3.1%), specific leaf weight (SLW) (5.2%) and WUE (4.1%). The effects of UV-B on the plant were greatly affected by the water content of the deep soil (30–40 cm). During the dry season, differences in the stomatal conductance, δ 13C, and WUE between the control and UV-B treated shrubs were very small; whereas, differences became much greater when soil water stress disappeared. Furthermore, the effects of UV-B became much less significant as the treatment period progressed over the three growing seasons. Correlation analysis showed that enhanced UV-B radiation decreased the strength of the correlation between soil water content and leaf water content, δ 13C, C i/C a, stomatal conductance, with the exception of WUE that had a significant correlation coefficient with soil water content. These results suggest that WUE would become more sensitive to soil water variation due to UV-B radiation. Based on this experiment, it was found that enhanced UV-B radiation had much more significant effects on morphological traits and growth of S. pubescens than hydro-physiological characteristics. __________ Translated from Journal of Plant Ecology, 2006, 30(1): 47–56 [译自: 植物生态学报]  相似文献   

    8.
    In order to offer a scientific basis for cultivation and management of forests, effects of light radiation intensity on photosynthetic characteristics and water use efficiency of Platycladus orientalis and Pinus tabulaeformis were studied under different soil moisture contents. By adopting artificial control methods to soil moisture, and under simulated photosynthetic radiation (SPR), the net photosynthetic rate (P N), transpiration rate (T r), water use efficiency (WUE) and intercellular CO2 concentration (C i) of Platycladus orientalis and Pinus tabulaeformis in the semi-arid region of the Loess Plateau, were studied. Results are as follows: within the photon range of 0–2,200 μmol/(m2·s), P N, T r and WUE were enhanced with an increase in SPR in both species. P N and WUE of Platycladus orientalis and Pinus tabulaeformis, however, declined with continued increase in SPR. P N, T r, WUE and light saturation point (LSP) of Platycladus orientalis were higher than those of Pinus tabulaeformis, while light compensation point (LCP) of Platycladus orientalis was lower than that of Pinus tabulaeformis at the same soil moisture content. The efficiency of light energy utilization of Platycladus orientalis was higher than that of Pinus tabulaeformis; P N, T r and C i of Platycladus orientalis and Pinus tabulaeformis were enhanced by increasing soil moisture content, whereas WUE declined. At soil moistures of 7.90%, 13.00% and 19.99%, LSP of Platycladus orientalis was 1,275, 1,450 and 1,675 μmol/(m2·s) respectively, and LCP was 42, 25 and 13 μmol/(m2·s) respectively, with corresponding maximal net CO2 photosynthetic rates (P max) of 3.04, 4.06 and 5.53 μmol/(m2·s). At soil moistures of 7.83%, 13.04% and 20.15%, the LSP of Pinus tabulaeformis was 1,100, 1,325 and 1,500 μmol/(m2·s) respectively, and LCP was 60, 30 and 23 μmol/(m2·s), with P max of 1.08, 3.35 and 4.36 μmol/(m2·s) respectively. __________ Translated from Science of Soil and Water Conservation, 2006, 4(3): 108–113 [译自: 中国水土保持科学]  相似文献   

    9.
    Using the PMS pressure chamber and isotope mass spectrometer (MAT-252), the leaf juice of Acacia mangium was obtained, and the carbon isotope discrimination (D) representing the most recently fixed carbon in the juice was determined. At the same time, the water-use efficiency of A. mangium was estimated. The results indicated that the carbon isotope ratio in the air of forest canopy (δ a), 10 m high a bove ground averaged − 7.57 ± 1.41 ‰ in cloudy days, and − 8.54±0.67‰ in sunny days, respectively. The diurnal change of the carbon isotope ratio in the photosynthetic products of the leaf juice (δ p) was of saddle type in cloudy days, but dropped down from morning to later afternoon in sunny days. A strong negative correlation between δ p and leaf-to-air vapor pressure deficit (D) was observed in sunny days, but a slight change in δ p was found in cloudy days. The δ p also decreased with decreasing leaf water potential (Ψ), reflecting that water stress could cause the decrease of δ p. The carbon isotope discrimination of the leaf juice was positively correlated with the ratio between intercellular (P i) and atmospheric (P a) partial pressure of CO2. For A. mangium, the isotope effect on diffusion of atmospheric CO2 via stomata was denoted by a = 4.6‰, and that in net C3 diffusion with respect to P i was indicated by b = 28.2‰. The results were in reasonable accord with the theoretically diffusive and biochemical fractionation of carbon isotope. It was defined that carbon isotope discrimination of photosynthetic products in A. mangium leaf juice was in proportion to that from photosynthetic products in dry material. The water-use efficiency estimated by the carbon isotope discrimination in leaf juice, fit well with that measured by gas exchange system (R 2 = 0.86, p < 0.0001). The application of leaf juice in measuring the stable carbon isotope discrimination would reduce the effects of fluctuating environmental factors during the synthesis of dry matter, and improve the ecophysiological studies on carbon and water balance when scaling from the plant to canopy in the fields. __________ Translated from Chinese Journal of Ecology, 2008, 27(4): 497–503 [译自: 生态学杂志]  相似文献   

    10.
    Due to the expected increases of number and intensity of summer droughts in Central Europe the identification of drought tolerant ecotypes becomes more important in future forestry. A common garden experiment with seedlings of Fagus sylvatica provenances from the center (Germany) and eastern margin (Poland) of the species’ distribution range was conducted. Responses of morphological, physiological, chemical and growth parameters to three drought treatments were analyzed. Relative growth rates of the marginal provenance were lower as compared to the central provenance. The marginal seedlings showed a tendency to higher total biomasses because of higher seed masses. In both provenances drought decreased biomass production and root/shoot ratio which was lower in the central provenance. A lower specific root area of the marginal provenance indicated a better adaptation to low xylem water potentials. Under moderate drought, lower leaf δ13C signatures may indicate lower stomatal limitation (or a reduced rate of CO2 assimilation) in the marginal provenance. We conclude that marginal beech provenances may exhibit a better drought adaptation.  相似文献   

    11.

    Improving drought tolerance of container seedlings of Japanese larch is of high importance to afforestation. We hypothesized that adequate nitrogen (N) and limited water supply would increase the tolerance of container seedlings to water-deficit stress, circumventing photoinhibition, by means of (i) enhanced photosynthetic capacity with higher leaf N and (ii) decreased water loss from leaves with lower biomass allocation into aboveground parts. Container seedlings of Japanese larch were grown under the treatment combinations of adequate (+?N: 300 mg N container?1) or limited (??N: 150 mg N container?1) N and adequate (+?W: daily irrigation) or limited (??W: twice-a-week irrigation) water. Then, seedlings were subjected to a progressive drought treatment. Higher leaf N was observed in container seedlings grown under?+?N and???W. During progressive drought, lower stomatal conductance and net photosynthetic rate were observed in leaves with higher leaf N at a given predawn leaf water potential. Furthermore, the maximum efficiency of PSII photochemistry (Fv/Fm) was lower in leaves with higher leaf N, suggesting that higher leaf N might impair intrinsic tolerance to drought at the leaf level contrary to expectations. Conversely,???N and???W seedlings with lower shoot biomass delayed soil drying as a whole-plant response via a reduction in leaf transpiration, leading to delayed photoinhibition as indicated by a decline in Fv/Fm. To circumvent stress at the initial stage of water deficit, lower leaf N via limited N regime and smaller shoot biomass driven by limited N and water regimes would be important.

      相似文献   

    12.
    Grain deviations and high extractives content are common features of many tropical woods. This study aimed at clarifying their respective impact on vibrational properties, referring to African Padauk (Pterocarpus soyauxii Taub.), a species selected for its interlocked grain, high extractives content and uses in xylophones. Specimens were cut parallel to the trunk axis (L), and local variations in grain angle (GA), microfibril angle (MFA), specific Young’s modulus (E′ L /ρ, where ρ stands for the density) and damping coefficient (tanδL) were measured. GA dependence was analysed by a mechanical model which allowed to identify the specific Young’s modulus (E′3/ρ) and shear modulus (G′/ρ) along the grain (3) as well as their corresponding damping coefficients (tanδ3, tanδG). This analysis was done for native and then for extracted wood. Interlocked grain resulted in 0–25° GA and in variations of a factor 2 in E′L/ρ and tanδL. Along the grain, Padauk wood was characterized, when compared to typical hardwoods, by a somewhat lower E′3/ρ and elastic anisotropy (E′/G′), due to a wide microfibril angle plus a small weight effect of extracts, and a very low tanδ3 and moderate damping anisotropy (tanδG/tanδ3). Extraction affected mechanical parameters in the order: tanδ3 ≈ tanδG > G′/ρ > > E′3/ρ. That is, extractives’ effects were nearly isotropic on damping but clearly anisotropic on storage moduli.  相似文献   

    13.
    We studied the importance of effective rainfall for interannual variation in water use efficiency (WUE) and tree-ring growth of Chinese pine (Pinus tabulaeformis Carr.) and black locust (Robinia pseudoacacia L.) by examining correlations of seasonal precipitation with annual values of stable carbon isotope ratio (δ13C) and tree-ring width in early and late wood. The correlations with precipitation were examined for each month and for periods of all possible lengths from 2 to 22 months starting from January of the previous year to October of the current year. The period with the highest correlation was adopted as the most effective rainfall season for interannual variations in WUE and tree-ring width. In early wood, precipitation during the dry season (October to May) before the growing season was negatively correlated with δ13C in pine trees and positively correlated with ring width in pine and locust trees. In late wood, rainfall during the growing season in the current year was negatively correlated with δ13C in pine and locust trees, and positively correlated with ring width in locust trees. Our results demonstrated the differences in the water use strategies of pine and locust trees. The δ13C in pines indicated higher WUE and more conservative water use than in locust trees. Precipitation during the dry season affected the interannual variation in WUE and tree-ring growth in pine and locust trees, indicating that rainfall during the dry season is important for carbon gain and tree-ring growth during the following growing season.  相似文献   

    14.
    Water potential (ϕ w) and net photosynthetic rate (Pn) ofLarix olgensis andPinus. sylvestris var.mongolica decreased with the decrease of soil water content. ϕ w and Pn ofL. olgensis changed hardly during the first 9 days after stopping watering, then decreased sharply at the 10th day Pn ofP. sylvestris varmongolica decreased slightly during the first 8 days, then decreased sharply at the 9th day. Their respiration rate, chlorophyll content and their a/b ratio changed hardly. The following 3 conclusions were obtained and discussed exhaustively. (1) ϕ w can be used to direct watering as a sensitive index of judging whetherL. olgensis andP. sylvestris var.mongolica lacking water. (2) The decrease of Pn ofL. olgensis andP. sylvestris var.mongolica when drought had nothing to do with chlorophyll. (3)P. sylvestris var.mongolica had morphological drought resistance, while Lolgensis had physiological drought resistance, and their drought resistance was discussed comparatively first time.  相似文献   

    15.
    The conversion of silvopasture to different land use systems cause effective changes in soil carbon distribution, due to disturbances in soil aggregation promoted by soil management and changes in crop residues inputs and decomposability. We evaluate the C and N stocks, and organic C fractions in soils under continuous arable land (AR) and silvopasture with apple trees and grass (SP); and after 4 years of conversion from silvopasture to arable land (SP-AR) and grassland (SP-GL). Total N (TN) and organic C (TOC), as well as microbial biomass carbon (CMB), light fraction (CLF) and heavy fraction (CHF) were evaluated at two different depths (0–10 and 10–20 cm). After 4 years of conversion, SP-AR and SP-GL presented C and N stocks similar to the observed for SP when the 0–20 cm depth was considered. However, AR presented TOC and TN stocks around 21 and 10% lower than SP, respectively. SP-AR tended to present the lowest CMB stocks and was positively correlated with salt extractable organic C (r 2 = 0.60, P < 0.001). CLF values declined by 62% from 0–10 to the 10–20 cm at SP and SP-GL, however there was no variation with increasing depth for AR and SP-AR. CHF represented the highest C fraction in soil, corresponding to 82% of TOC. Except for AR, δ13C values of the light fraction increased with increasing depth. In general, heavy fraction tended to be more enriched in δ13C than light fraction. In a long-term, conventional tillage can significantly contribute to reduce TOC and TN stocks when compared to the silvopastoral system.  相似文献   

    16.
    The biomass and ratio of root-shoot ofPinus sylvestriformis seedlings at CO2 concentration of 700 μL·L−1 and 500 μL·L−1 were measured using open-top chambers (OTCs) in Changbai Mountain during Jun. to Oct. in 1999. The results showed that doubling CO2 concentration was benefit to seedling growth of the species (500 μL·L−1 was better than 700 μL·L−1) and the biomass production was increased in both above-ground and underground parts of seedlings. Carbon transformation to roots was evident as rising of CO2 concentration. This project is supported by Chinese Academy of Sciences Responsible editor: Chai Ruihai  相似文献   

    17.

    Faidherbia albida is one of the scattered trees commonly intercropped with most cereals in Ethiopia due to its positive impacts. The tree is pruned for various purposes including for fencing and fuelwood. In this study, the impact of pruning on water relations of F. albida and on understorey wheat productivity was investigated. The on-farm study was conducted in Ejerssa Joro, semi-arid Ethiopia. Six mature trees were selected; three were fully pruned and three were left unpruned. Sap flow and leaf water potential were measured on these trees. Crop gas exchange, aboveground biomass and grain yield were measured under and outside tree canopies. The highest and the lowest sap volumes, recorded from unpruned F. albida, during the dry period, were 153 L day?1 and 20 L day?1, respectively. The highest and the lowest sap volumes were 13.4 L day?1 and 0.04 L day?1 recorded during the wet period. Wheat CO2 assimilation was highest (7.8 µmolm?2 s?1) at 1 m distance and declined away from the tree trunk under unpruned trees. Aboveground biomass and grain yield under unpruned treatments were significantly (P?<?0.05) higher than outside of canopy of same tree and outside canopies of pruned trees. Pruning reduced aboveground biomass and grain yield by 30% and 27%, respectively; despite the higher water uptake by unpruned trees. We recommend that intensive pruning of F. albida be discouraged and propose further studies on optimal pruning for increased food production and provision of tree products to meet farmers’ needs.

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    18.
    Growth and physiological performance of multipurpose tree species can be severely constrained by low phosphorus (P) availability in highly weathered soils. Limitations to plant growth are accentuated by seasonal dry periods. The overall objective of this study was to examine P fertilization and irrigation effects on survival, growth, biomass partitioning, foliar nutrients, intrinsic water-use efficiency (WUE) indexed by δ13C, Rhizobium nodulation, and carbohydrate content as an indicator of resprouting potential, of mimosa (Albizia julibrissin Durz.), a N2-fixing tree species being tested for browse in agroforestry practices in south-central USA. In a field experiment carried out during two growing seasons near Booneville, Arkansas, USA, mimosa had a strong growth response to irrigation. The trial was arranged in a split plot design with three replications with irrigation as main plot treatment and P as sub-plot treatment. Mean total plant aboveground biomass at the end of the second growing season was 9.8 and 44.1 g plant−1 for the rainfed treatment without and with 300 mm of irrigation water, respectively. Placed P fertilization increased mean total aboveground biomass from 19 g plant−1 for the 0-P treatment to 69 g plant−1 for the treatment with 90 kg P ha−1 year−1. Similarly, irrigation consistently increased stem basal diameter, total height, survival, root, stem, foliar and total aboveground biomass, and number of nodules per plant. Phosphorus fertilization increased basal diameter, and root and stem biomass in both irrigation treatments, survival and nodulation in the rainfed treatment, and foliar and total aboveground biomass in the rainfed +300 mm irrigation treatment. There was a decrease of foliar δ13C suggesting that WUE decreased with P fertilization. In a pot experiment, seedlings were subjected to a factorial combination of two irrigation treatments and six P levels in a randomized complete block design. Irrigation increased basal diameter, root, stem, foliar and total biomass, leaf area and nodulation, whereas P fertilization (i.e., levels from 0 to 3.68 g P kg−1 soil) had similar effect in all the above variables except foliar biomass. Foliar P concentration to obtain 90% of the maximum total plant biomass (critical level) was estimated at 0.157%. Total nonstructural and water soluble carbohydrate, and starch concentrations increased non-linearly with irrigation and P addition suggesting impaired re-growth potential after defoliation of seedlings with reduced water supply and at low soil P availability. Results of this study indicated strong limitations for growth and regrowth potential of mimosa on a highly weathered soil with very low P availability and seasonal water content shortages. Placed (i.e., near the plant base) application of P appeared to be a good strategy to fertilize perennial woody plants.  相似文献   

    19.
    Water availability and salt excess are limiting factors in Mexican mixed pine-oak forest. In order to characterise the acclimatation of native species to these stresses, leaf water (Ψw) and osmotic potentials (Ψs) of Juniperus flaccida, Pinus pseudostrobus and Quercus canbyi were measured under natural drought and non-drought conditions under two different aspects in the Sierra Madre Oriental. Factorial ANOVA revealed significant differences in Ψw and Ψs between two aspects, species and sampling dates. In general, all species showed high predawn and low midday values that declined progressively with increasing drought and soil–water loss. Seasonal and diurnal fluctuation of Ψw and Ψs were higher for J. flaccida and Q. canbyi than for P. pseudostrobus. Leaf Ψw and Ψs were mainly correlated with soil water content, while Ψs of P. pseudostrobus were hardly correlated with environmental variables. Thus, species have different strategies to withstand drought. P. pseudostrobus was identified as a species with isohydric water status regulation, while J. flaccida and Q. canbyi presented water potential patterns typical for anisohydric species. The type of water status regulation may be a critical factor for plant survival and mortality in the context of climate change. Nevertheless, for precise conclusions about the advantages and disadvantages of each type, further long-term investigations are required.  相似文献   

    20.
    Absorbing water from soil by roots in vascular plants is an important physiological function and plays an essential role on their water balance. The root hydraulic conductance (L P) determined by radical water transport inside the root is a major influence on the shoot water status, plant growth, and development. However, a few studies have focused on the effect of different substances on L P of roots, and the role of radical water transport was poorly understood. Based on the pressure-flux approach, this study used the roots of Fraxinus mandshurica seedlings with different treatments, i.e., distilled water, NH4NO3 solution, and HgCl2 to determine the effect of various substances on L P of roots. The objectives are: 1) to evaluate the difference in L P occurred between distilled water and NH4NO3 solution with various concentrations; and 2) to examine the changes of L P under distilled water and NH4NO3 solution with various concentrations after HgCl2 treatment. The results showed that L P of roots were 18.85×10−8 m/(s·MPa) in distilled water, 31.25–34.15×10−8 m/(s·MPa) in four NH4NO3 solutions (2, 4, 8 and 16 mmol/L), 14.69×10−8 m/(s·MPa) in distilled water after HgCl2-treated, and 9.63–13.57×10−8 m/(s·MPa) in four NH4NO3 solutions after HgCl2-treated, respectively. Aquaporins play an important role in regulating water uptake and transport in roots. NH4 + and NO3 − could stimulate activity of aquaporins, and L P of roots in NH4NO3 solution was distinctly 77% higher than in distilled water. Nevertheless, Hg2+ can inhibit activity of aquaporins, and and L P of roots decreased 22% in distilled water and 68% in NH4NO3 solution after treatment by HgCl2 respectively. These evidences suggested that both Hg2+-sensitive aquaporins and ion channels existing in the protoplasm and vacuole membranes could regulate root water uptake, transport, and integral plant water balance. __________ Translated from Acta Phytoecologica Sinica, 2005, 29(5): 706–712 [译自: 植物生态学报, 2005, 29(5): 706–712]  相似文献   

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