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1.
P. Castro-Díez J. P. Puyravaud J. H. C. Cornelissen P. Villar-Salvador 《Oecologia》1998,116(1-2):57-66
Stem traits were analysed in laboratory-grown seedlings of 80 European woody and semiwoody species of known potential relative
growth rate (RGR) and of similar ontogenetic phase. The objectives were, firstly, to assess the relation between stem structure
and plant growth potential and, secondly, to explore how stem structure varies among species differing in life form and leaf
habit. Hydraulic conductance was represented by the mean diameter of the widest xylem conduits (Dmax), and structural strength by the percentage of xylem tissue occupied by cell wall material (CWx) or stem tissue density
(SD). Across all species RGR showed a weak positive correlation with Dmax and weak negative ones with CWx and SD, with slow-growers showing great dispersion of stem trait values. In the RGR-Dmax relationship this dispersion disappeared when trees were removed from the analysis. None of the relationships were significant
among tree species alone. It was suggested that fast-growers require a xylem with wide conduits (high Dmax) to achieve high hydraulic conductivity, and “cheaply” constructed stems (low CWx and SD) to maximise allocation to leaves.
However, the possession of such traits does not guarantee fast growth, as other factors may constrain RGR elsewhere in the
plant. Deciduous seedlings showed higher Dmax and lower CWx than evergreens. Higher Dmax could reflect an innate higher tolerance of conductivity loss by freeze-induced embolism in deciduous plants, which are
not burdened by the maintenance of foliage in winter. In contrast, life forms were differentiated most clearly by SD. For
instance, shrub seedlings had less dense stem tissues than tree seedlings, possibly because they need less investment in long-term
strength and stature.
Received: 3 January 1998 / Accepted: 9 April 1998 相似文献
2.
Question: Do thick‐twigged/large‐leaf species have an advantage in leaf display over their counterparts, and what are the effects of leaf habit and leaf form on the leaf‐stem relationship in plant twigs of temperature broadleaf woody species? Location: Gongga Mountain, southwest China. Methods: (1) We investigated stem cross‐sectional area and stem mass, leaf area and leaf/lamina mass of plant twigs (terminal branches of current‐year shoots) of 89 species belonging to 55 genera in 31 families. (2) Data were analyzed to determine leaf‐stem scaling relationships using both the Model type II regression method and the phylogenetically independent comparative (PIC) method. Results: (1) Significant, positive allometric relationships were found between twig cross‐sectional area and total leaf area supported by the twig, and between the cross‐sectional area and individual leaf area, suggesting that species with large leaves and thick twigs could support a disproportionately greater leaf area for a given twig cross‐sectional area. (2) However, the scaling relationships between twig stem mass and total leaf area and between stem mass and total lamina mass were approximately isometric, which indicates that the efficiency of deploying leaf area and lamina mass was independent of leaf size and twig size. The results of PIC were consistent with these correlations. (3) The evergreen species were usually smaller in total leaf area for a given twig stem investment in terms of both cross‐sectional area and stem mass, compared to deciduous species. Leaf mass per area (LMA) was negatively associated with the stem efficiency in deploying leaf area. (4) Compound leaf species could usually support a larger leaf area for a given twig stem mass and were usually larger in both leaf size and twig size than simple leaf species. Conclusions: Generally, thick‐twigged/large‐leaf species do not have an advantage over their counterparts in deploying photosynthetic compartments for a given twig stem investment. Leaf habit and leaf form types can modify leaf‐stem scaling relationships, possibly because of contrasting leaf properties. The leaf size‐twig size spectrum is related to the LMA‐leaf life span dimension of plant life history strategies. 相似文献
3.
Foliar nutrients in relation to growth, allocation and leaf traits in seedlings of a wide range of woody plant species and types 总被引:9,自引:0,他引:9
J. H. C. Cornelissen M. J. A. Werger P. Castro-Díez J. W. A. van Rheenen A. P. Rowland 《Oecologia》1997,111(4):460-469
This study aimed to identify functional correlates of seedling leaf nutrient content among woody species and to characterise
functional species groups with respect to leaf nutrient attributes. Seedlings of 81 woody species from the temperate zone
of western Europe were grown in a standard laboratory environment with standard, near-optimal nutrient availability. Weight-based
leaf N content (Nwght) was positively correlated with mean relative growth rate (RGR), but the correlation with mean RGR was tighter when leaf
N was expressed on a whole-plant weight basis: leaf nitrogen weight ratio (LNWR). Area-based leaf N content (Narea) was not associated with mean RGR, but was closely correlated with the quotient of saturated leaf weight and leaf area. Weight-based
leaf K content (Kwght) was a close correlate of the saturated/dry weight ratio of the foliage. Within the lower range, Kwght corresponded with growth-related nutrient attributes, but higher values appeared to indicate succulence or remobilisable
stored water. Functional groups of species and genera could be distinguished with respect to seedling leaf nutrient attributes.
Deciduous woody climbers and scramblers had consistently higher leaf Nwght, LNWR and (apparently) leaf Kwght than other deciduous species or genera, and shrubs had higher values than trees. These differences seemed due partly to variation
in specific leaf area. Evergreens had consistently higher leaf Narea than deciduous plants, but there were no significant differences in weight-based leaf nutrient attributes between these two
groups, possibly because of `luxury nutrient consumption' by the slow-growing evergreens. Another functional group was that
of the nitrogen-fixing species, which had consistently high innate leaf Nwght compared to non-N-fixers. The ecological significance of the leaf nutrient attributes in this study is discussed by comparing
the seedling data with those from field-collected material, and by brief reference to the natural habitats of the species.
Received: 22 September 1996 / Accepted: 1 March 1997 相似文献
4.
Leaf digestibility and litter decomposability are related in a wide range of subarctic plant species and types 总被引:7,自引:2,他引:5
J. H. C. CORNELISSEN† H. M. QUESTED‡§ D. GWYNN-JONES¶ R. S. P. VAN LOGTESTIJN M. A. H. DE BEUS A. KONDRATCHUK† T. V. CALLAGHAN‡ R. AERTS 《Functional ecology》2004,18(6):779-786
5.
Leaf gas exchange in a clonal eucalypt plantation as related to soil moisture, leaf water potential and microclimate variables 总被引:7,自引:0,他引:7
M. S. Mielke M. A. Oliva N.F. de Barros R. M. Penchel C. A. Martinez S. da Fonseca A.C. de Almeida 《Trees - Structure and Function》2000,14(5):263-270
In order to determine how environmental and physiological factors affect leaf gas exchange in a 9-year-old clonal eucalypt
plantation (Eucalyptus grandis Hill ex. Maiden hybrids) in the State of Espirito Santo, Brazil, the diurnal patterns of predawn leaf water potential (Ψpd), and leaf gas exchange were monitored from November 1995 to August 1996. Soil water content (Θ) and microclimatic variables
were also recorded. Most of the rainfall during the experimental period occurred from October to December 1995 and from March
to April 1996, causing a significant variation in Θ and Ψpd. A high positive correlation (r
2=0.92) was observed between Ψpd and Θ measured at 0.3 m depth from the soil surface. During conditions of high soil water availability, the maximum values
of stomatal conductance for water vapor (g
s) and net photosynthetic rate (A) were over 0.4 mol m–2 s–2 and l5 μmol m–2 s–1, respectively. The results showed that Ψpd and leaf gas exchange of the examined trees were susceptible to changes in the water content of the upper soil layers, where
the major concentration of active roots occur. Multiple linear regression analysis indicated that photosynthetic active radiation
(Q), vapor pressure deficit (VPD), atmospheric CO2 molar fraction (C
a), and Ψpd were the most important factors controlling g
s whereas Q and VPD were the main microclimatic variables controlling A.
Received: 5 November 1998 / Accepted: 10 November 1999 相似文献
6.
Grace P. John Christine Scoffoni Thomas N. Buckley Rafael Villar Hendrik Poorter Lawren Sack 《Ecology letters》2017,20(4):412-425
Leaf dry mass per unit leaf area (LMA) is a central trait in ecology, but its anatomical and compositional basis has been unclear. An explicit mathematical and physical framework for quantifying the cell and tissue determinants of LMA will enable tests of their influence on species, communities and ecosystems. We present an approach to explaining LMA from the numbers, dimensions and mass densities of leaf cells and tissues, which provided unprecedented explanatory power for 11 broadleaved woody angiosperm species diverse in LMA (33–262 g m?2; R2 = 0.94; P < 0.001). Across these diverse species, and in a larger comparison of evergreen vs. deciduous angiosperms, high LMA resulted principally from larger cell sizes, greater major vein allocation, greater numbers of mesophyll cell layers and higher cell mass densities. This explicit approach enables relating leaf anatomy and composition to a wide range of processes in physiological, evolutionary, community and macroecology. 相似文献
7.
Leaf nitrogen content per area (Narea) is a good indicator of assimilative capacity of leaves of deciduous broad-leaved trees. This study examined the degrees of increase in Narea in response to canopy openings as leaf mass per area (LMA) and leaf nitrogen content per mass (Nmass) in saplings of eight deciduous broad-leaved tree species in Hokkaido, northern Japan. Five of the species were well-branched species with a large number of small leaves (lateral-growth type), and the other three species were less-branched species with a small number of large leaves (vertical-growth type). The degrees of increase in Narea were compared between the two crown types. In closed-canopy conditions, leaves of the vertical-growth species tended to have a lower LMA and higher Nmass than those of the lateral-growth species, which resulted in similar Narea for both. LMA increased in canopy openings in the eight species, and the degrees of increase were not largely different between the lateral- and vertical-growth species. On the contrary, Nmass was unchanged in canopy openings in the eight species. As a result, Narea of each species increased in canopy openings in proportion to the increase in LMA, and the degrees of increase in Narea were similar in the lateral- and vertical-growth species. Therefore, this study showed that the degrees of increase in Narea were not correlated with the crown architecture (i.e., the lateral- and vertical-growth types). 相似文献
8.
Specific leaf area and leaf nitrogen concentration in annual and perennial grass species growing in Mediterranean old-fields 总被引:1,自引:0,他引:1
We evaluated the hypothesis that photosynthetic traits differ between leaves produced at the beginning (May) and the end
(November–December) of the rainy season in the canopy of a seasonally dry forest in Panama. Leaves produced at the end of
the wet season were predicted to have higher photosynthetic capacities and higher water-use efficiencies than leaves produced
during the early rainy season. Such seasonal phenotypic differentiation may be adaptive, since leaves produced immediately
preceding the dry season are likely to experience greater light availability during their lifetime due to reduced cloud cover
during the dry season. We used a construction crane for access to the upper canopy and sampled 1- to 2-month-old leaves marked
in monthly censuses for six common tree species with various ecological habits and leaf phenologies. Photosynthetic capacity
was quantified as light- and CO2-saturated oxygen evolution rates with a leaf-disk oxygen electrode in the laboratory (O2max) and as light-saturated CO2 assimilation rates of intact leaves under ambient CO2 (Amax). In four species, pre-dry season leaves had significantly higher leaf mass per unit area. In these four species, O2max and Amax per unit area and maximum stomatal conductances were significantly greater in pre-dry season leaves than in early wet season
leaves. In two species, Amax for a given stomatal conductance was greater in pre-dry season leaves than in early wet season leaves, suggesting a higher
photosynthetic water-use efficiency in the former. Photosynthetic capacity per unit mass was not significantly different between
seasons of leaf production in any species. In both early wet season and pre-dry season leaves, mean photosynthetic capacity
per unit mass was positively correlated with nitrogen content per unit mass both within and among species. Seasonal phenotypic
differentiation observed in canopy tree species is achieved through changes in leaf mass per unit area and increased maximum
stomatal conductance rather than by changes in nitrogen allocation patterns.
Received: 7 March 1996 / Accepted: 1 August 1996 相似文献
9.
An increase in leaf mass per area (MLA) of plants grown at elevated [CO2] is often accompanied by accumulation of non-structural carbohydrates, and has been considered to be a response resulting from source-sink imbalance. We hypothesized that the increase in MLA benefits plants by increasing the net assimilation rate through maintaining a high leaf nitrogen content per area (NLA). To test this hypothesis, Polygonum cuspidatum was grown at ambient (370 micro mol mol-1) and elevated (700 micro mol mol-1) [CO2] with three levels of N supply. Elevated [CO2] significantly increased MLA with smaller effects on NLA and leaf mass ratio (fLM). The effect of change in MLA on plant growth was investigated by the sensitivity analysis: MLA values observed at ambient and elevated [CO2] were substituted into a steady-state growth model to calculate the relative growth rate (R). At ambient [CO2], substitution of a high MLA (observed at elevated [CO2]) did not increase R, compared with R for a low MLA (observed at ambient [CO2]), whereas at elevated [CO2] the high MLA always increased R compared with R at the low MLA. These results suggest that the increase in MLA contributes to growth enhancement under elevated [CO2]. The optimal combination of fLM and MLA to maximize R was determined for different [CO2] and N availabilities. The optimal fLM was nearly constant, while the optimal MLA increased at elevated [CO2], and decreased at higher N availabilities. The changes in fLM of actual plants may compensate for the limited plasticity of MLA. 相似文献
10.
P. Castro-Díez P. Villar-Salvador C. Pérez-Rontomé Melchor Maestro-Martínez Gabriel Montserrat-Martí 《Trees - Structure and Function》1997,11(3):127-134
Leaf features were examined in three Quercus species (Q. coccifera, Q. ilex and Q. faginea) along a steep rainfall gradient in NE Spain. The analyzed leaf traits were area, thickness, density, specific mass, leaf
concentration of nitrogen, phosphorous, lignin, cellulose and hemicellulose, both on a dry weight basis (Nw, Pw, Lw, Cw, Hw) and on an area basis (Na, Pa, La, Ca, Ha). These traits were regressed against annual precipitation and correlated with each other, revealing different response patterns
in the three species. Q. faginea, a deciduous tree, did not show any significant correlation with rainfall. In Q. coccifera, an evergreen shrub, Nw, Na, Lw, La and Ca increased with higher annual rainfall, while Hw decreased. In Q. ilex, an evergreen tree, leaf area, Pw and Lw increased with precipitation, whereas specific leaf mass, thickness and Ha showed the reverse response. Correlations between the leaf features revealed that specific mass variation in Q. faginea and Q. coccifera could be explained by changes in leaf density, while in Q. ilex specific leaf mass was correlated with thickness. Specific leaf mass in the three species appeared positively correlated
with all the chemical components on a leaf area basis except with lignin in Q. ilex and with P in Q. ilex and Q. faginea. In these two tree species Pw showed a negative correlation with specific leaf mass. It is suggested that each species has a different mechanism to cope
with water shortage which is to a great extent related to its structure as a whole, and to its habit.
Received: 18 December 1995 / Accepted: 8 March 1996 相似文献
11.
Leaf lifespan as a determinant of leaf structure and function among 23 amazonian tree species 总被引:26,自引:0,他引:26
Summary The relationships between resource availability, plant succession, and species' life history traits are often considered key to understanding variation among species and communities. Leaf lifespan is one trait important in this regard. We observed that leaf lifespan varies 30-fold among 23 species from natural and disturbed communities within a 1-km radius in the northern Amazon basin, near San Carlos de Rio Negro, Venezuela. Moreover, leaf lifespan was highly correlated with a number of important leaf structural and functional characterisues. Stomatal conductance to water vapor (g) and both mass and area-based net photosynthesis decreased with increasing leaf lifespan (r2=0.74, 0.91 and 0.75, respectively). Specific leaf area (SLA) also decreased with increasing leaf lifespan (r2=0.78), while leaf toughness increased (r2=0.62). Correlations between leaf lifespan and leaf nitrogen and phosphorus concentrations were moderate on a weight basis and not significant on an area basis. On an absolute basis, changes in SLA, net photosynthesis and leaf chemistry were large as leaf lifespan varied from 1.5 to 12 months, but such changes were small as leaf lifespan increased from 1 to 5 years. Mass-based net photosynthesis (A/mass) was highly correlated with SLA (r2=0.90) and mass-based leaf nitrogen (N/mass) (r2=0.85), but area-based net photosynthesis (A/area) was not well correlated with any index of leaf structure or chemistry including N/area. Overall, these results indicate that species allocate resources towards a high photosynthetic assimilation rate for a brief time, or provide resistant physical structure that results in a lower rate of carbon assimilation over a longer time, but not both. 相似文献
12.
13.
Terrestrial plant photosynthesis may be limited both by stomatal behavior and leaf biochemical capacity. While inferences
have been made about the importance of stomatal and biochemical limitations to photosynthesis in a variety of species in a
range of environments, genetic variation in these limitations has never been documented in wild plant populations. Genetic
variation provides the raw material for adaptive evolution in rates of carbon assimilation. We examined genetic variation
in gas exchange physiology and in stomatal and biochemical traits in 16 genetic lines of the annual plant, Polygonum arenastrum. The photosynthesis against leaf internal CO2 (A−ci) response curve was measured on three greenhouse-grown individuals per line. We measured the photosynthetic rate (A) and
stomatal conductance (g), and calculated the internal CO2 concentration (ci) at ambient CO2 levels. In addition, the following stomatal and biochemical characteristics were obtained from the A−ci curve on each individual: the degree of stomatal limitation to photosynthesis (Ls), the maximum ribulose 1,5-biphosphate carboxylase-oxygenase (Rubisco) activity (Vcmax) and electron transport capacity (Jmax). All physiological traits were genetically variable, with broad sense heritabilities ranging from 0.66 for Ls to 0.94 for Jmax. Strong positive genetic correlations were found between Vcmax and Jmax, and between g and biochemical capacity. Path analyses revealed strong causal influences of stomatal conductance and leaf
biochemistry on A and ci. Path analysis also indicated that Ls confounds both stomatal and biochemical effects, and is an appropriate measure of stomatal influences on photosynthesis, only
when biochemical variation is accounted for. In total, our results indicate that differences among lines in photosynthesis
and ci result from simultaneous changes in biochemical and stomatal characteristics and are consistent with theoretical predictions
that there should be co-limitation of photosynthesis by ribulose-1,5-biphosphate (RuBP) utilization and regeneration, and
by stomatal conductance and leaf biochemistry. Gas exchange characteristics of genetic lines in the present study were generally
consistent with measurements of the same lines in a previous field study. Our new results indicate that the mechanisms underlying
variation in gas exchange include variation in both stomatal conductance and biochemical capacity. In addition, A, g, and
ci in the present study tended also to be positively correlated with carbon isotope discrimination (Δ), and negatively correlated
with time to flowering, life span, and leaf size based on earlier work. The pattern of correlation between physiology and
life span among genetic lines of P. arenastrum parallels interspecific patterns of character correlations. We suggest that the range of trait constellations among lines
in P. arenastrum represents a continuum between stress avoidance (rapid development, high gas exchange metabolism) and stress tolerance (slow
development, low gas exchange metabolism), and that genetic variation in these character combinations may be maintained by
environmental variation in stress levels in the species’ ruderal habitat.
Received: 28 March 1996 / Accepted: 13 August 1996 相似文献
14.
R. Prins J. Z. Groenewald G. F. Marais J. W. Snape R. M. D. Koebner 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(4):618-624
Amplified fragment length polymorphism (AFLP) markers were used to enrich the map of the wheat chromosomal region containing
the Thinopyrum-derived Lr19 leaf rust resistance gene. The region closest to Lr19 was targeted through the use of deletion and recombinant lines of the translocated segment. One of the AFLP bands thus identified
was converted into a sequence-tagged-site (STS) marker. This assay generated a 130-bp PCR fragment in all Lr19-carrying lines tested, except for one deletion mutant, while non-carrier template failed to amplify any product. This sequence
represents the first marker to map on the distal side of Lr19 on chromosome 7el1. The conversion process of AFLP fragments to STS markers was technically difficult, mainly because of the presence of contaminating
fragments. Various approaches were taken to reduce the frequency of false positives and to identify the correct clone. We
were able to formulate a general verification strategy prior to clone sequencing. Various other factors causing problems with
converting AFLP bands to an STS assays are also discussed.
Received: 15 September 2000 / Accepted: 5 January 2001 相似文献
15.
Identification and mode of action of quantitative trait loci affecting seedling height and leaf area in Eucalyptus nitens 总被引:6,自引:0,他引:6
M. Byrne J. C. Murrell J. V. Owen P. Kriedemann E. R. Williams G. F. Moran 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(5):674-681
Regions of the genome influencing height and leaf area in seedlings of a three-generation outbred pedigree of Eucalyptus nitens have been identified. Three QTLs affecting height and two QTLs affecting leaf area were located using single-factor analysis
of variance. The three QTLs affecting height each explained between 10.3 and 14.7% of the phenotypic variance, while the two
QTLs for leaf area each explained between 9.8 and 11.6% of the phenotypic variation. Analysis of fully informative marker
loci linked to the QTLs enabled the mode of action of the QTLs to be investigated. For three loci the QTL effect segregated
from only one parent, while for two loci the QTL showed multiple alleles and the effect segregated from both parents in the
pedigree. The two QTLs affecting leaf area were located in the same regions as two of the QTLs affecting height. Analysis
of these regions with fully informative markers showed that both QTLs were linked to the same markers, but one had a similar
size of effects and a similar mode of action for both height and leaf area, whilst the other showed a different mode of action
for the two traits. These regions may contain two closely linked genes or may involve a single gene with a pleiotrophic effect
on both height and leaf area. The QTL with the greatest effect showed multiple alleles and an intra-locus interaction that
reduced the size of the effect. Assessment for two of the QTLs in a second related family did not show an effect associated
with the marker loci; however, this was consistent with the mode of action of these QTLs and the pattern of inheritance in
the second family.
Received: 1 August 1996 / Accepted: 25 October 1996 相似文献
16.
Development of a molecular marker for the adult plant leaf rust resistance gene Lr35 in wheat 总被引:14,自引:0,他引:14
R. Seyfarth C. Feuillet G. Schachermayr M. Winzeler B. Keller 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,99(3-4):554-560
The objective of this work was to develop a marker for the adult plant leaf rust resistance gene Lr35. The Lr35 gene was originally introgressed into chromosome 2B from Triticum speltoides, a diploid relative of wheat. A segregating population of 96 F
2
plants derived from a cross between the resistant line ThatcherLr35 and the susceptible variety Frisal was analysed. Out of 80 RFLP probes previously mapped on wheat chromosome 2B, 51 detected
a polymorphism between the parents of the cross. Three of them were completely linked with the resistance gene Lr35. The co-segregating probe BCD260 was converted into a PCR-based sequence-tagged-site (STS) marker. A set of 48 different
breeding lines derived from several European breeding programs was tested with the STS marker. None of these lines has a donor
for Lr35 in its pedigree and all of them reacted negatively with the STS marker. As no leaf rust races virulent on Lr35 have been found in different areas of the world, the STS marker for the Lr35 resistance gene is of great value to support the introgression of this gene in combination with other leaf rust (Lr) genes into breeding material by marker-assisted selection.
Received: 14 December 1998 / Accepted: 30 January 1999 相似文献
17.
Xine Li Xin Zhao Yuki Tsujii Yueqi Ma Renyi Zhang Cheng Qian Zixi Wang Feilong Geng Shixuan Jin 《Ecology and evolution》2022,12(6)
Leaf anatomy varies with abiotic factors and is an important trait for understanding plant adaptive responses to environmental conditions. Leaf mass per area (LMA) is a key morphological trait and is related to leaf performance, such as light‐saturated photosynthetic rate per leaf mass, leaf mechanical strength, and leaf lifespan. LMA is the multiplicative product of leaf thickness (LT) and leaf density (LD), both of which vary with leaf anatomy. Nevertheless, how LMA, LT, and LD covary with leaf anatomy is largely unexplored along natural environmental gradients. Slope aspect is a topographic factor that underlies variations in solar irradiation, air temperature, humidity, and soil fertility. In the present study, we examined (1) how leaf anatomy varies with different slope aspects and (2) how leaf anatomy is related to LMA, LD, and LT. Leaf anatomy was measured for 30 herbaceous species across three slope aspects (south‐, west‐, and north‐facing slopes; hereafter, SFS, WFS, and NFS, respectively) in an eastern Tibetan subalpine meadow. For 18 of the 30 species, LMA data were available from previous studies. LD was calculated as LMA divided by LT. Among the slope aspects, the dominant species on the SFS exhibited the highest LTs with the thickest spongy mesophyll layers. The thicker spongy mesophyll layer was related to a lower LD via larger intercellular airspaces. In contrast, LD was the highest on NFS among the slope aspects. LMA was not significantly different among the slope aspects because higher LTs on SFS were effectively offset by lower LDs. These results suggest that the relationships between leaf anatomy and LMA were different among the slope aspects. Mechanisms underlying the variations in leaf anatomy may include different solar radiation, air temperatures, soil water, and nutrient availabilities among the slope aspects. 相似文献
18.
Contribution of carbohydrate pools to the variations in leaf mass per area within a tomato plant 总被引:2,自引:1,他引:1
N. BERTIN M. TCHAMITCHIAN P. BALDET C. DEVAUX B. BRUNEL & C. GARY 《The New phytologist》1999,143(1):53-61
The contribution of the starch and soluble carbohydrate pools to the diurnal variations of leaf mass per unit area (LMA) has been investigated in tomato leaves. A glasshouse experiment was carried out with plants pruned to two or five fruits per truss. Leaflets were sampled at sunrise, noon and sunset at different positions within the leaf (basal or terminal), and on different sympods along the stem. Carbohydrate contents and LMA were significantly higher in the terminal than in the basal leaflets, except at sunrise. During the day, differences in starch accumulation between terminal and basal leaflets increased with leaf height on the plant. Among sympods, the soluble carbohydrate content of the terminal leaflets did not vary significantly, whereas at 13.00 h the LMA was minimum in the middle of the plant and maximum at the top, and the leaf starch content significantly increased half-way up the plant. The plant fruit load had only small and non-significant effects on the LMA and carbohydrate contents. The response of LMA and carbohydrate contents to changing source activity was observed under controlled climatic conditions. The starch pool of fully expanded leaves was rapidly filled and emptied under increasing and decreasing source activity. In young expanding leaves, this pool was hardly filled during daylight. On average the soluble carbohydrates did not contribute significantly to the diurnal variations in LMA, whereas fluctuations in starch explained c . 70% and 44% of these variations in the upper and lower leaves, respectively. The results are discussed with respect to the modelling of LMA at the level of individual tomato leaves or sympods. 相似文献
19.
D. White Chris Beadle Dale Worledge John Honeysett Maria Cherry 《Trees - Structure and Function》1998,12(7):406-414
Development of the relationship between leaf area (A
l
) and sapwood area (A
s
) was investigated in two important hardwoods, Eucalyptus globulus (Labill) and E. nitens (Deane and Maiden) Maiden, growing in an experimental plantation established in a low rainfall zone (approx. 515 mm year–1) of Tasmania. The experiment compared irrigated controls and a rainfed treatment which was subjected to cyclical summer droughts
from age 1 to 6 years old. Leaf area and sapwood area were determined by destructive sampling at ages 2, 3 and 6 years old.
There was no effect of stand age on A
l
:A
s
when sapwood area was measured at crown break. At age 3 years old A
l
:A
s
was significantly greater in the rainfed than the irrigated trees. It was concluded that this difference was due to earlier
canopy closure in the irrigated trees. When the plantation was 6 years old A
l
:A
s
was significantly greater in the irrigated than the rainfed treatment. An analysis based on an equation which links A
l
:A
s
with transpiration and volumetric flow rate (Whitehead et al. 1984) was used to infer a positive correlation between stem
hydraulic conductivity (k
h
) and water availability. Independent of water availability E. globulus maintained a higher A
l
:A
s
than E. nitens at all ages.
Received: 20 March 1997 / Accepted: 30 December 1997 相似文献
20.
Computer prediction of human thermoregulatory and temperature responses to a wide range of environmental conditions 总被引:1,自引:0,他引:1
A mathematical model for predicting human thermal and regulatory responses in cold, cool, neutral, warm, and hot environments
has been developed and validated. The multi-segmental passive system, which models the dynamic heat transport within the body
and the heat exchange between body parts and the environment, is discussed elsewhere. This paper is concerned with the development
of the active system, which simulates the regulatory responses of shivering, sweating, and peripheral vasomotion of unacclimatised
subjects. Following a comprehensive literature review, 26 independent experiments were selected that were designed to provoke
each of these responses in different circumstances. Regression analysis revealed that skin and head core temperature affect
regulatory responses in a non-linear fashion. A further signal, i.e. the rate of change of the mean skin temperature weighted
by the skin temperature error signal, was identified as governing the dynamics of thermoregulatory processes in the cold.
Verification and validation work was carried out using experimental data obtained from 90 exposures covering a range of steady
and transient ambient temperatures between 5°C and 50°C and exercise intensities between 46 W/m2 and 600 W/m2. Good general agreement with measured data was obtained for regulatory responses, internal temperatures, and the mean and
local skin temperatures of unacclimatised humans for the whole spectrum of climatic conditions and for different activity
levels.
Received: 20 November 2000 / Revised: 24 April 2001 / Accepted: 14 May 2001 相似文献