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1.
2.
Relation of water transport to leaf gas exchange properties in three mangrove species 总被引:16,自引:0,他引:16
M. A. Sobrado 《Trees - Structure and Function》2000,14(5):258-262
Mangrove species more tolerant to salinity may function with less efficient water transport, which may be related to more
conservative water use. To test the hypothesis, we investigate the gas exchange and hydraulic properties of three mangrove
species: Rhizophora mangle L., Laguncularia racemosa Gaert and Avicennia germinans (L.)L. Experiments were performed with adult plants growing naturally in the field under a salinity of 35‰. Gas exchange
parameters showed that A. germinans had significantly higher photosynthetic rates, and lower stomatal conductance and transpiration rates, compared to the other
two mangroves. In concert with this, instantaneous water use efficiency was significantly high in A. germinans, intermediate in L. racemosa and lowest in R. mangle. The hydraulic parameters of the three mangrove species were in the lowest end of the range reported for tropical trees.
However, the three mangrove species exhibited measurable differences in hydraulic parameters related to the control of water
requirements for maintenance of carbon gain. L. racemosa and A. germinans showed less efficient water transport at shoot level but were the more efficient species in water use at the leaf level in
comparison to R. mangle.
Received: 7 April 1999 / Accepted: 25 July 1999 相似文献
3.
4.
Response of photosynthesis of different plant functional types to environmental changes along Northeast China Transect 总被引:9,自引:0,他引:9
Net photosynthesis (Pn), transpiration (E), stomatal conductance (gs), internal CO2 concentration (Ci), and water use efficiency (WUE) were examined on 215 species from eight plant functional types (PFTs) along a precipitation
gradient in northeast China (the Northeast China Transect, or NECT). Among the eight PFTs, meadow steppe grasses had the highest
rates of net photosynthesis and forest grasses the lowest and the following order of Pn was noted: meadow steppe grasses >typical steppe grasses >steppe shrubs >desert grasses >forest trees >forest shrubs >desert
shrubs >forest grasses (P<0.05). Transpiration tended to be the highest in the steppe grasses and lowest in forest shrubs. Transpiration also decreased
rapidly with the appearance of C3 desert species at the desert end. The forest tree PFT had lower Pn, E, gs than the steppe PFTs, whereas WUE values were somewhat greater in the forest tree PFT than the desert shrubs and grasses.
Low Ci values along the steppe section (from 400 to 1100 km, east to west) indicated the presence of C4 species. Of all the PFTs, only shrubs and herbs were noted at all points along the transect. No clear relationship between
Pn, E, gs, WUE of herb and shrub PFTs and annual precipitation was noted – low values were found at both the high and low precipitation
ends of the transect. Highest values were noted when precipitation was intermediate.
Received: 28 October 1998 / Accepted: 10 May 1999 相似文献
5.
Two of the ways in which plants cope with water deficits are stomatal closure and “osmotic adjustment”. We sought to assess
the contributions of these processes to maintenance of leaf hydration in field-grown, 7-year-old Eucalyptus marginata. Plants were exposed to their normal summer drought (controls) or supplied with additional water (irrigated). Irrigation
increased photosynthesis by 30% in E. marginata. These increases in photosynthesis were related to an 80% increase in g
s. However, there was no difference in substomatal CO2 concentrations between treatments, or in chloroplast CO2 concentrations, as indicated by carbon isotope composition of leaf soluble sugars. This suggests that impaired mesophyll
metabolism may partially explain slower rates of photosynthesis in plants exposed to their normal summer drought. There was
no difference in concentrations of solutes or osmotic potential between non-irrigated and irrigated individuals, perhaps because
relative water content was the same in non-irrigated and irrigated plants due to stomatal sensitivity to water deficits. Irrespective
of the absence of osmotic adjustment, analysis of leaf solutes gave a clear indication of the major groups of compounds responsible
for maintaining cell osmotic potential. Soluble sugars were three times as abundant as amino acids. Proline, a putatively
osmotically active amino acid, contributed less than 1% of total solutes. These patterns of solutes in E.
marginata are consistent with a growing body of literature arguing a greater role for carbohydrates and cyclitols and lesser role for
amino acids in maintaining osmotic potential. Our data suggest the primary mechanism by which E.
marginata coped with drought was partial stomatal closure; however, we cannot discount the possibility of osmotic adjustment under
more severe water deficits. 相似文献
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7.
Species differ regarding their drought tolerance and individuals of a given species can modify their morphology and physiology in response to drought. However, since evolutionary and ecological selective pressures differ, individual and interspecific responses to drought might not match. We determined summer survival and a number of ecophysiological variables in two factorial experiments with seedlings of eleven tree species present in Mediterranean ecosystems, grown under slowly imposed water stress and control conditions. Plants experiencing drought exhibited reduced growth, low specific leaf area, chlorophyll content, and photosynthetic rate when compared to the controls, and species-specific drought tolerance was associated with an analogous set of trait values. However, while species with high leaf area ratio and shoot-root ratio exhibited greater drought tolerance, drought induced the reversed response within species. Contrary to expectations, water use efficiency was lower in drought-tolerant species and decreased in water-stressed individuals compared to the control plants. There was a distinctive phylogenetic signal in the functional grouping of species, with oaks, pines, and other genera being clearly different from each other in their drought tolerance and in their functional responses to drought. However, all relationships between ecophysiological variables and drought tolerance were significant after accounting for phylogenetic effects, with the exception of the relationship between drought tolerance and photochemical efficiency. Our results show that drought tolerance is not achieved by a single combination of trait values, and that even though evolutionary processes and individual responses tend to render similar results in terms of functional traits associated with drought, they do not necessarily match. 相似文献
8.
In situ gas-exchange data, for branchlets of white spruce [Picea glauca (Moench) Voss.] in a mature mixed-wood boreal forest in central Canada (53°44′N 105°14′W), were subjected to a multiple regression
analysis. Vapor pressure deficit (VPD) and branchlet temperature (tleaf) were both significant predictors (P<0.0001) of stomatal conductance to water vapor (gsw) and net photosynthesis (An), together explaining 67 and 64% of the variation in gsw and An, respectively. Since VPD and tleaf were autocorrelated in these field data, but also to further explore the nature of independent effects of temperature and
humidity on water and CO2 exchange in white spruce, steady-state gas-exchange was performed on well-watered greenhouse-grown seedlings of white spruce.
Results from laboratory experiments supported the following conclusions: (1) Transpiration (E) increases with VPD to an inflection
point that increases linearly with tleaf. This tleaf effect on E could not be explained by trends in VPD, RH, An or PFD. Rather, our data support a model in which E and gsw are influenced by the balance between ’supply’ and ’loss’ of water to and from leaf tissue, respectively. The supply of water
appears to be in accordance with Darcy’s law, where supply of water is proportional to the driving gradient in pressure/ tension,
specific permeability (k), and inverse of water viscosity (n
–1). Approximately half of the increase in E could be explained by the linear increase in n
–1 with increasing tleaf. We propose that increases in k explain the remainder of the increase in E with tleaf. (2) VPD and tleaf appear to have independent effects on gsw. In contrast, RH effects on gsw or E were subtle and could be explained by a combination of effects of tleaf and VPD. (3) An was affected primarily by tleaf, being reduced at low (10°C) and high (40°C) temperatures, and only indirectly by humidity parameters via stomatal conductance,
viz. intercellular CO2 concentrations. Our results have implications for the prediction of water fluxes from plants and canopies in areas where
plant temperatures vary diurnally or seasonally.
Received: 24 September 1998 / Accepted: 20 July 1999 相似文献
9.
G. Sills J. Nienhuis 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(1-2):275-282
Recurrent selection for specific combining ability (RS-SCA) and S1 family performance (RS-S1) were compared in replicated
selection programs initiated from a common C0 base population of Arabidopsis. Three cycles of selection for aerial biomass were completed in each of two replicate programs of each selection method.
Response to selection was measured on the basis of per se, S1 progeny, and testcross performance with a common tester. All
selection programs improved testcross performance. Testcross gain per cycle in RS-S1 (7.15% cycle-1) and RS-SCA (5.31% cycle-1) were not significantly different. Performance of S1 progeny and populations per se significantly improved over cycles of
selection using RS-S1 but were unchanged by RS-SCA. Codominant molecular marker-allele frequencies were recorded for each
population at 22 polymorphic loci. Trends in marker-allele frequencies were tested by linear regression. Significant trends
in marker-allele frequencies pooled over replicate programs were detected at 8 and 7 loci in the RS-S1 and RS-SCA programs,
respectively. Marker alleles at 2 loci significantly changed frequency in response to both RS-S1 and RS-SCA programs. Marker
alleles at 6 loci significantly changed frequency only in response to RS-SCA. Marker alleles at 6 other loci showed significant
linear trends pooled over replicates only in RS-S1. No markers revealed increases in the frequency of different marker alleles
within loci using the two selection methods. Possible genetic causes of marker frequency changes are discussed, as well as
breeding implications. 相似文献
10.
Intraspecific variation of drought adaptation in brittlebush: leaf pubescence and timing of leaf loss vary with rainfall 总被引:4,自引:0,他引:4
Reflective leaf pubescence of the desert shrub Encelia farinosa (brittlebrush) reduces leaf temperature and plant water loss, and is considered adaptive in xeric environments. Yet, little
is known about intraspecific variation in this trait. Among three populations in the northern range of E. farinosa, which span a very broad precipitation gradient, both leaf absorptance variation and differences in the timing of drought-induced
leaf loss were broadly associated with climatic variability. Where mean annual rainfall was greatest, drought-induced leaf
loss was earliest, but these plants also had higher population-level mean leaf absorptance values. Higher absorptance increases
the relative dependence on latent heat transfer (transpirational cooling), but it also provides greater instantaneous carbon
assimilation. Plants at the driest site reached lower leaf absorptance values and maintained leaves longer into the drought
period. Lower leaf absorptance reduces water consumption, and extended leaf longevity may buffer against the unpredictability
of growing conditions experienced in the driest site. These observations are consistent with a trade-off scenario in which
plants from wetter regions might trade off water conservation for higher instantaneous carbon gain, whereas plants from drier
regions reduce water consumption and extend leaf longevity to maintain photosynthetic activity in the face of unpredictable
growing conditions.
Received: 2 April 1997 / Accepted: 11 August 1997 相似文献
11.
Spatial variations in xylem sap flux density in evergreen oak trees with radial-porous wood: comparisons with anatomical observations 总被引:1,自引:0,他引:1
Makiko Tateishi Tomo’omi Kumagai Yasuhiro Utsumi Toshihiro Umebayashi Yasuki Shiiba Kazunobu Inoue Kiyohiro Kaji Keiichiro Cho Kyoichi Otsuki 《Trees - Structure and Function》2008,22(1):23-30
To estimate whole-tree water use when employing sap flow measurements, integration of the sap flux density (F
d) over the sapwood area is needed. Accordingly, it is necessary to obtain information on the characteristics of stem water
transportation such as spatial variations in F
d and the active xylem area in the stem cross-section. Although evergreen oak trees with radial-porous wood represent a major
component of secondary forests in western Japan, detailed information on their stem water transportation characteristics remains
unclear. In the present study, we used the heat dissipation method (Granier method) to conduct measurements of azimuthal and
radial variations in the F
d of Quercus glauca Thunb. ex Murray, a representative evergreen broad-leaved tree in western Japan. Further, by analyzing the anatomy of the
xylem structure, we examined why F
d varies spatially in the stem cross-section. By using a dye solution injected into a radial hole bored into the tree trunk,
we confirmed that the entire stem is hydroactive. We also compared the spatial variations in F
d and water conductivity per xylem area (K
s) which were estimated by using the observed vessel diameters and their density over the stem cross-section and Hagen–Poiseuille’s
law. Azimuthal and radial variations in F
d reached about 60 and 50% of the maximum values, respectively, and could be explained by spatial variation in K
s. As a result, we obtained statistical parameters describing the spatial variation in F
d in Q. glauca and determined that whole-tree water use estimated from measurements in one direction had at most ±20% potential errors for
studied trees. 相似文献
12.
We investigated the functional and structural responses of Scots pine to climate and estimated the importance of the genotype
on the traits studied. We analysed 13C isotope discrimination (Δ13C) of various provenances in a common garden experiment and gas exchange characteristics for provenances growing in their
natural environment. No clear climatic trend was found in the foliar Δ13C values of common garden trees. Similar results were obtained from estimation of λ (a largely VPD, temperature and light
independent measure of intrinsic water use efficiency) from the gas exchange data. The ratio of needle mass to unit stem area
and branch area to stem area increased towards south in both experiments and hence, seemed to be genetic. Trees from drier
and warmer conditions seemed not to have either lower needle mass or higher intrinsic water use efficiency compared to northern
latitudes.
Received: 6 November 1998 / Accepted: 1 July 1999 相似文献
13.
Seed output is determined by two processes: resource acquisition and the allocation of resources to seeds. In order to clarify
how the reaction norm of seed output is controlled by the phenotypic expression of its two components, we examined the genetic
components of plasticity of seed dry mass, plant size, and reproductive allocation under different conditions of soil nutrient
availability and conspecific competition among eight families of Abutilon theophrasti. Without competition, the reaction norm of seed mass of the families crossed between the lowest and other nutrient levels,
although neither of its components, plant size and reproductive allocation, showed such a response. The crossing reaction
norm (i.e., reversal of relative fitnesses of different genotypes along the environmental gradient) of seed mass resulted
from (1) a trade-off between plant size and reproductive allocation, and (2) changes in the relative magnitude of genetic
variances in plant size and reproductive allocation with soil nutrient availability. While allocation was more important in
determining seed mass under limiting nutrient conditions, plant size became more important under high-nutrient conditions.
There were no significant genetic variances in seed mass, plant size, and reproductive allocation in the competition treatment,
except at the highest nutrient level. The results show that plant competition mitigated the effects of genetic differences
in plant performance among the families. We discuss the results in relation to maintenance of genetic variation within a population.
Received: 16 August 1996 / Accepted 26 April 1997 相似文献
14.
A. Lerchl 《International journal of biometeorology》1998,42(2):84-88
Based on records from the Federal Bureau for Statistics of Germany, the seasonality of mortality was investigated for the
period 1946–1995. Lowest mortality rates were found during summer (August or September) while highest values were found in
winter (January through March). Non-linear regression of all monthly mortality data with the average monthly temperatures
in Germany revealed a significant negative relationship (r=–0.739; n=600; P<0.0001). The fact that the differences between the long-range monthly temperatures and the individual monthly temperatures
also showed a distinct relationship to the mortality rates speaks against a mere coincidence of both parameters. The amplitude
of this seasonal rhythm declined steadily within the observation period. It is concluded that low temperatures cause an increase
in mortality rates and that this effect has become less important during recent decades due to the increased use of central
heating and because of improvements in the public health system.
Received: 27 April 1998 / Revised: 10 July 1998 / Accepted: 9 September 1998 相似文献
15.
G. Renger G. Christen M. Karge H.-J. Eckert K.-D. Irrgang 《Journal of biological inorganic chemistry》1998,3(4):360-366
The temperature dependence of donor side reactions was analysed within the framework of the Marcus theory of nonadiabatic electron transfer. The following results were obtained for PS II membrane fragments from spinach: (1) the reorganisation energy of P680+? reduction by YZ is of the order of 0.5?eV in samples with a functionally fully competent water oxidising complex (WOC); (2) destruction of the WOC by Tris-washing gives rise to a drastic increase of λ to values of the order of 1.6?eV; (3) the reorganisation energies of the oxidation steps in the WOC are dependent, on the redox states S i with values of about 0.6?eV for the reactions YZ OX S 0→YZ S 1 and YZ OX S 1→YZ S 2, 1.6?eV for the reaction YZ OX S 2→YZ S 3 and 1.1?eV (above a characteristic temperature uc of about 6??°C) for the reaction YZ OX S 3→→YZ S 0+O2. Using an empirical rate constant-distance relationship, the van der Waals distance between YZ and P680 was found to be about 10?Å, independent of the presence or absence of the WOC, whereas the distance between YZ and the manganese cluster in the WOC was ≥15?Å. Based on the calculated activation energies the environment of YZ is inferred to be almost "dry" and hydrophobic when the WOC is intact but becomes enriched with water molecules after WOC destruction. Furthermore, it is concluded that the transition S 2→S 3 is an electron transfer reaction gated by a conformational change, i.e. it comprises significant structural changes of functional relevance. Measurements of kinetic H/D isotope exchange effects support the idea that none of these reactions is gated by the break of a covalent O-H bond. The implications of these findings for the mechanism of water oxidation are discussed. 相似文献
16.
Locating genomic regions associated with components of drought resistance in rice: comparative mapping within and across species 总被引:32,自引:2,他引:30
J. Zhang H. G. Zheng A. Aarti G. Pantuwan T. T. Nguyen J. N. Tripathy A. K. Sarial S. Robin R. C. Babu Bay D. Nguyen S. Sarkarung A. Blum H. T. Nguyen 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(1):19-29
17.
Oliver Brendel Didier Le Thiec Caroline Scotti-Saintagne Catherine Bodénès Antoine Kremer Jean-Marc Guehl 《Tree Genetics & Genomes》2008,4(2):263-278
Genetic variation for intrinsic water use efficiency (W
i) and related traits was estimated in a full-sib family of Quercus robur L. over 3 years. The genetic linkage map available for this F1 family was used to locate quantitative trait loci (QTL) for
W
i, as estimated by leaf carbon stable isotope composition (δ
13C) or the ratio of net CO2 assimilation rate (A) to stomatal conductance to water vapour (g
w) and related leaf traits. Gas exchange measurements were used to standardize estimates of A and g
w and to model the sensitivity of g
w to leaf-to-air vapour pressure deficit (sgVPD). δ
13C varied by more than 3‰ among the siblings, which is equivalent to 40% variation of W
i. Most of the studied traits exhibited high clonal mean repeatabilities (>50%; proportion of clonal mean variability in global
variance). Repeatabilities for δ
13C, leaf mass per area (LMA) and leaf nitrogen content were higher than 70%. For δ
13C, ten QTLs were detected, one of which was detected repeatedly for all 3 years and consistently explained more than 20% of
measured variance. Four genomic regions were found in which co-localizing traits linked variation in W
i to variations in leaf chlorophyll and nitrogen content, LMA and sgVPD. A positive correlation using clonal means between δ
13C and A/g
w, as well as a co-localisation of QTL detected for both traits, can be seen as validation of the theoretical model linking
the genetic architecture of these two traits. 相似文献
18.
Behaviour of interleukin-2 serum levels in advanced non-small-cell lung cancer patients: relationship with response to therapy and survival 总被引:8,自引:0,他引:8
Orditura M Romano C De Vita F Galizia G Lieto E Infusino S De Cataldis G Catalano G 《Cancer immunology, immunotherapy : CII》2000,49(10):530-536
Interleukin(IL)-2 is a T helper (Th) 1 type cytokine that has been shown to play an important role in antitumour immune responses.
In this study, the prognostic significance of serum IL-2 levels was investigated in 60 advanced non-small-cell lung cancer
(NSCLC) patients. IL-2 serum levels were determined before chemotherapy, at the end of chemotherapy and during follow-up,
using a commercially available enzyme-linked immunoadsorbent assay kit. The results were analysed according to the response
to therapy and were used to generate a model predicting overall survival and time to treatment failure. All 60 patients were
shown to have higher IL-2 serum levels than controls (P < 0.0001). Stage IV patients had significantly lower IL-2 levels than stage III patients (P < 0.0001), although they were still significantly higher than controls (P < 0.0001). It is interesting that, when patients were divided into responders and non-responders according to the response
to therapy, the former were shown to have significantly higher pre-chemotherapy levels than the latter (P < 0.0001). Moreover, a further significant increase in IL-2 serum levels (P=0.004) and a significant decrease (P < 0.0001) were shown in responders and non-responders, respectively at the end of the therapy. Using univariate and multivariate
analyses, both overall survival and time to treatment failure were shown to be affected by the mean pathological levels of
IL-2. Furthermore, the prognostic significance of the serum level of IL-2 was confirmed by the stepwise regression analysis.
In conclusion, determination of pre-treatment IL-2 serum levels was shown to be of independent prognostic utility in patients
with advanced NSCLC; therefore, its possible use for prediction of outcome is proposed.
Received: 16 March 2000 / Accepted: 27 July 2000 相似文献
19.
Nitrogen response efficiency increased monotonically with decreasing soil resource availability: a case study from a semiarid grassland in northern China 总被引:10,自引:0,他引:10
The concept of nutrient use efficiency is central to understanding ecosystem functioning because it is the step in which plants can influence the return of nutrients to the soil pool and the quality of the litter. Theory suggests that nutrient efficiency increases unimodally with declining soil resources, but this has not been tested empirically for N and water in grassland ecosystems, where plant growth in these ecosystems is generally thought to be limited by soil N and moisture. In this paper, we tested the N uptake and the N use efficiency (NUE) of two Stipa species (S. grandis and S. krylovii) from 20 sites in the Inner Mongolia grassland by measuring the N content of net primary productivity (NPP). NUE is defined as the total net primary production per unit N absorbed. We further distinguished NUE from N response efficiency (NRE; production per unit N available). We found that NPP increased with soil N and water availability. Efficiency of whole-plant N use, uptake, and response increased monotonically with decreasing soil N and water, being higher on infertile (dry) habitats than on fertile (wet) habitats. We further considered NUE as the product of the N productivity (NP the rate of biomass increase per unit N in the plant) and the mean residence time (MRT; the ratio between the average N pool and the annual N uptake or loss). The NP and NUE of S. grandis growing usually in dry and N-poor habitats exceeded those of S. krylovii abundant in wet and N-rich habitats. NUE differed among sites, and was often affected by the evolutionary trade-off between NP and MRT, where plants and communities had adapted in a way to maximize either NP or MRT, but not both concurrently. Soil N availability and moisture influenced the community-level N uptake efficiency and ultimately the NRE, though the response to N was dependent on the plant community examined. These results show that soil N and water had exerted a great impact on the N efficiency in Stipa species. The intraspecific differences in N efficiency within both Stipa species along soil resource availability gradient may explain the differences in plant productivity on various soils, which will be conducive to our general understanding of the N cycling and vegetation dynamics in northern Chinese grasslands. 相似文献
20.
Pooja Bhatnagar-Mathur Vincent Vadez M. Jyostna Devi M. Lavanya G. Vani Kiran K. Sharma 《Molecular breeding : new strategies in plant improvement》2009,23(4):591-606
Abiotic stresses including water deficit severely limits crop yields in the semi-arid tropics. In chickpea, annual losses
of over 3.7 million tones have been estimated to be due to water deficit conditions alone. Therefore, major efforts are needed
to improve its tolerance to water deficit, and genetic engineering approaches provide an increasing hope for this possibility.
We have used transgenic technology for the introduction of an osmoregulatory gene P5CSF129A encoding the mutagenized Δ1-pyrroline-5-carboxylate synthetase (P5CS) for the overproduction of proline. A total of 49 transgenic events of chickpea were produced with the 35S:P5CSF129A gene
through Agrobacterium tumefaciens-mediated gene transfer through the use of axillary meristem explants. Eleven transgenic events that accumulated high proline
(2–6 folds) were further evaluated in greenhouse experiments based on their transpiration efficiency (TE), photosynthetic
activity, stomatal conductance, and root length under water stress. Almost all the transgenic events showed a decline in transpiration
at lower values of the fraction of transpirable soil water (dryer soil), and extracted more water than their untransformed
parents. The accumulation of proline in the selected events was more pronounced that increased significantly in the leaves
when exposed to water stress. However, the overexpression of P5CSF129A gene resulted only in a modest increase in TE, thereby indicating that the enhanced proline had little bearing on the components
of yield architecture that are significant in overcoming the negative effects of drought stress in chickpea. 相似文献