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B.m.p. Singhakumara - One of the best experts on this subject based on the ideXlab platform.
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Change in Leaf Structure in relation to crown position and size class for tree species within a Sri Lankan tropical rain forest
Botany, 2008Co-Authors: P.a.k.a.k. Panditharathna, B.m.p. Singhakumara, Heather P. Griscom, Mark S. AshtonAbstract:The purpose of our study was to examine change in Leaf Structure (anatomy and morphology) through different phases of tree size and crown position within a Sri Lankan rain forest. We selected four late-successional canopy species that represented dominant genera (Shorea, Mesua) within an Asian tropical rain forest. All are considered shade-tolerant and capable of growing to maturity beneath closed-canopy late-successional forests. Species within each genus were either restricted to seepages and bottom slopes (valley species) or to upper slopes and ridges (ridge species). The size classes represented (i) seedlings, (ii) saplings, (iii) poles growing beneath closed-canopy conditions, and (iv) trees of the rain forest canopy. Between size classes, leaves were thicker and with higher stomatal densities for canopy trees than for seedling, sapling, and pole size classes. Plasticities for measures of Leaf Structure were greater for ridge species than valley species; except for cuticle thickness, which showed the...
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Leaf Structure of Syzygium spp. (Myrtaceae) in relation to site affinity within a tropical rain forest
Botanical Journal of the Linnean Society, 2003Co-Authors: Harshi K. Gamage, Mark S. Ashton, B.m.p. SinghakumaraAbstract:This study examined four species of Syzygium (S. firmum, S. makul, S. operculatum, S. rubicundum) Myrtaceae, a tree genus that dominates the canopy of rain forests of south-west Sri Lanka. Syzygium spp. occupy differing habitats with relation to succession and forest topography. We examined differences in Leaf morphology and physiology in response to amount of shade, an important environmental variable affecting Syzygium distribution within the forest. To study change in Leaf Structure and physiology, environmental shelters were constructed simulating forest shade that differed in quality, quantity and duration. Seedlings were exposed to: (i) 0% shade (full sun, FS), red : far red (R : FR) ratio 1.27; (ii) 65% shade (large opening, LO) with direct sunlight similar to the centre of a large canopy opening, R : FR ratio 1.27; (iii) 82% shade (small opening, SO) with direct sunlight similar to the centre of a small canopy opening, R : FR ratio 1.27; (iv) 58% uniform light shade (LS) with a quality similar to the outside edge of a large canopy opening, R : FR ratio 1.05; (v) 85% uniform medium shade (MS) with a quality similar to the inside forest edge of a large canopy opening, R : FR ratio 0.97; (vi) 99% uniform deep shade (DS) similar to that of the forest understorey, R : FR ratio 0.23. The shelters were constructed in a large open area at the field station of the Sinharaja World Heritage site, Sri Lanka. Seedlings of each species were grown for two years in their respective shade treatments before physiological, morphological and anatomical measurements were made on leaves. Variation in Leaf Structure and physiology between the species was associated with differences in shade-tolerance and water-use. All species increased in photosynthesis rates and dimensions in Leaf Structure (Leaf blade and cuticle thickness, stomatal density, thickness of upper and lower epidermis, and thickness of palisade mesophyll) with decrease in shade. In contrast, stomatal conductivity was highest in the DS (99% shade) treatment. Leaves of Syzygium firmum were thickest and largest in area. S. firmum also had highest photosynthesis in the SO (82% shade) treatment. S. firmum was the most shade-tolerant of all species: it grows well in low shade and its Leaf Structure suggests it to be the most conservative in water-use of the Syzygium spp. In the forest S. firmum can persist in the forest shade as established seedlings, but grows best within canopy openings of late-seral rain forest. Leaves of S. operculatum were thinnest but had highest stomatal densities of the four species. S. operculatum is considered shade-intolerant, with a Leaf Structure suggesting it to be prone to desiccation, and by implication susceptible to drought. S. operculatum is found along streams within early seral rain forest habitat, often originating on stream banks after land clearance for cultivation. In the FS (0% shade) treatment, S. rubicundun had highest photosynthesis rates and greatest number of leaves but smallest Leaf area of the Syzygium species. S. rubicundum is more shade-intolerant but more efficient in water-use than S. operculatum. S. rubicundum is a mid-seral canopy tree of the midslope stands that are thought to have originated after catastrophic windthrows or swidden cultivation. The Leaf physiology and Structure of S. makul suggests it to be both moderately shade-tolerant and conservative in water-use. It is the most widely distributed Syzygium species across the topography of late-seral rain forest. We suggest forest disturbance and hydrology are important environmental factors that influence distribution of Syzygium species across the topography. Results from this study contribute to a body of knowledge suggesting that canopy tree species of rain forests in south-west Sri Lanka have discrete affinities to topography and differences in successional status, and that adaptations in Leaf Structure and physiology are indicative of such phenomena. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 141, 365–377.
William K. Smith - One of the best experts on this subject based on the ideXlab platform.
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seasonal and diurnal Leaf orientation bifacial sunlight incidence and Leaf Structure in the sand dune herb hydrocotyle bonariensis
Environmental and Experimental Botany, 2012Co-Authors: Heather M Joesting, Michael O Sprague, William K. SmithAbstract:A conceptual model has been proposed whereby Leaf orientation and resulting sunlight exposure dictate functional Leaf Structure. Specifically, the model states that this relationship is driven by the absolute amount and ratio of incident sunlight on adaxial and abaxial Leaf surfaces. To test this model, the relationships between corresponding values of Leaf orientation and incident sunlight on both Leaf surfaces were measured for the sand dune herb Hydrocotyle bonariensis over a growth season, along with examination of Leaf Structure. For mature leaves, Leaf angle from horizontal and azimuth angle significantly increased over the growing season, indicating diurnal midday avoidance and seasonal maximization of incident sunlight. Consequently, seasonal changes in Leaf orientation resulted in an overall decrease in midday sunlight incidence on the adaxial surface and a slight shift in the daily occurrence of peak abaxial incidence. Adaxial surfaces received three to four times more sunlight than abaxial surfaces, and Leaf cross-sections revealed relatively thick (564 μm) leaves with multiple adaxial palisade layers and stomata on both Leaf surfaces, as predicted by the conceptual model and measured ratio of incident sunlight on adaxial and abaxial Leaf surfaces. These data provide further evidence of the relationship between Leaf orientation and resulting absolute levels of sunlight incidence on both Leaf surfaces, as well as their ratio, and corresponding differences in internal and external Leaf Structure.
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associations between Leaf Structure orientation and sunlight exposure in five western australian communities
American Journal of Botany, 1998Co-Authors: William K. Smith, David T Bell, Kelly A ShepherdAbstract:Five plant communities in Western Australia, as well as selected desert and Rocky Mountain species of the western USA, were surveyed to evaluate associations among Leaf Structure, orientational properties, and the sunlight exposure and precipitation characteristic of each community. Selected Leaf structural features have been associated previously with photosynthetic function and included shape, thickness, the ratio of thickness to width, stomatal distribution, Leaf surface coloration, and the number and distribution of palisade cell layers. Decreases in annual precipitation ( ,4 to over 15 cm/yr) and increases in total daily sunlight (4.2 to 29.2 mol photons/m 2) corresponded strongly to an increase in the percentage of species in a given community with more inclined (more inclined than 6 458 from horizontal) or thicker Leaf mesophyll (.0.4 mm) leaves. Also, the percentage of species with a Leaf thickness to width ratio .0.1, which were amphistomatous, or which had palisade cell layers beneath both Leaf surfaces, increased from .20% in the highest rainfall and lowest sunlight community to .80% in the community with least rainfall but greatest sunlight exposure. Over 70% of the species in the most mesic, shaded community had lighter abaxial than adaxial Leaf surfaces (Leaf bicoloration). All of the above structural features were positively associated with a more inclined Leaf orientation ( r 2 5 0.79), except for Leaf bicoloration, which was negatively associated (r 2 5 0.75). The ratio of adaxial to abaxial light was more strongly associated with Leaf bicoloration (r 2 5 0.83) and the presence of multiple adaxial and isobilateral palisade cell layers( r2 5 0.80) than with total incident sunlight on just the adaxial Leaf surface ( r2 5 0.69 and 0.73, respectively). These results provide field evidence that Leaf orientation and Structure may have evolved in concert to produce a photosynthetic symmetry in Leaf Structure in response to the amount of sunlight and other limiting factors of the community. This structural symmetry may serve fundamentally to regulate the distribution of both light and CO 2 levels inside the Leaf and, thus, increase photosynthetic CO2 uptake per unit Leaf biomass.
Peter B Reich - One of the best experts on this subject based on the ideXlab platform.
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Responses of Leaf Structure and photosynthetic properties to intra-canopy light gradients: a common garden test with four broadLeaf deciduous angiosperm and seven evergreen conifer tree species
Oecologia, 2012Co-Authors: Tomasz P Wyka, Piotr Karolewski, Jacek Oleksyn, Andrzej M. Jagodziński, R. Żytkowiak, Peter B ReichAbstract:Spectra of Leaf traits in northern temperate forest canopies reflect major differences in Leaf longevity between evergreen conifers and deciduous broadLeaf angiosperms, as well as plastic modifications caused by within-crown shading. We investigated (1) whether long-lived conifer leaves exhibit similar intra-canopy plasticity as short-lived broadleaves, and (2) whether global interspecific relationships between photosynthesis, nitrogen, and Leaf Structure identified for sun leaves adequately describe leaves differentiated in response to light gradients. We studied structural and photosynthetic properties of intra-tree sun and shade foliage in adult trees of seven conifer and four broadLeaf angiosperm species in a common garden in Poland. Shade leaves exhibited lower Leaf mass-per-area (LMA) than sun leaves; however, the relative difference was smaller in conifers than in broadleaves. In broadleaves, LMA was correlated with lamina thickness and tissue density, while in conifers, it was correlated with thickness but not density. In broadleaves, but not in conifers, reduction of lamina thickness was correlated with a thinner palisade layer. The more conservative adjustment of conifer leaves could result from a combination of phylogenetic constraints, contrasting Leaf anatomies and shoot geometries, but also from functional requirements of long-lived foliage. Mass-based nitrogen concentration (N_mass) was similar between sun and shade leaves, and was lower in conifers than in deciduous broadleaved species. Given this, the smaller LMA in shade corresponded with a lower area-based N concentration (N_area). In evergreen conifers, LMA and N_area were less powerful predictors of area-based photosynthetic rate ( A _max(area)) in comparison with deciduous broadleaved angiosperms. Multiple regression for sun and shade leaves showed that, in each group, A _max(mass) was related to N_mass but not to LMA, whereas LMA became a significant codeterminant of A _max(mass) in analysis combining both groups. Thus, a fundamental mass-based relationship between photosynthesis, nitrogen, and Leaf Structure reported previously also exists in a dataset combining within-crown and across-functional type variation.
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responses of Leaf Structure and photosynthetic properties to intra canopy light gradients a common garden test with four broadLeaf deciduous angiosperm and seven evergreen conifer tree species
Oecologia, 2012Co-Authors: Tomasz P Wyka, R Zytkowiak, Piotr Karolewski, Jacek Oleksyn, Andrzej M. Jagodziński, Peter B ReichAbstract:Spectra of Leaf traits in northern temperate forest canopies reflect major differences in Leaf longevity between evergreen conifers and deciduous broadLeaf angiosperms, as well as plastic modifications caused by within-crown shading. We investigated (1) whether long-lived conifer leaves exhibit similar intra-canopy plasticity as short-lived broadleaves, and (2) whether global interspecific relationships between photosynthesis, nitrogen, and Leaf Structure identified for sun leaves adequately describe leaves differentiated in response to light gradients. We studied structural and photosynthetic properties of intra-tree sun and shade foliage in adult trees of seven conifer and four broadLeaf angiosperm species in a common garden in Poland. Shade leaves exhibited lower Leaf mass-per-area (LMA) than sun leaves; however, the relative difference was smaller in conifers than in broadleaves. In broadleaves, LMA was correlated with lamina thickness and tissue density, while in conifers, it was correlated with thickness but not density. In broadleaves, but not in conifers, reduction of lamina thickness was correlated with a thinner palisade layer. The more conservative adjustment of conifer leaves could result from a combination of phylogenetic constraints, contrasting Leaf anatomies and shoot geometries, but also from functional requirements of long-lived foliage. Mass-based nitrogen concentration (Nmass) was similar between sun and shade leaves, and was lower in conifers than in deciduous broadleaved species. Given this, the smaller LMA in shade corresponded with a lower area-based N concentration (Narea). In evergreen conifers, LMA and Narea were less powerful predictors of area-based photosynthetic rate (Amax(area)) in comparison with deciduous broadleaved angiosperms. Multiple regression for sun and shade leaves showed that, in each group, Amax(mass) was related to Nmass but not to LMA, whereas LMA became a significant codeterminant of Amax(mass) in analysis combining both groups. Thus, a fundamental mass-based relationship between photosynthesis, nitrogen, and Leaf Structure reported previously also exists in a dataset combining within-crown and across-functional type variation. Electronic supplementary material The online version of this article (doi:10.1007/s00442-012-2279-y) contains supplementary material, which is available to authorized users.
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Leaf Structure specific Leaf area modulates photosynthesis nitrogen relations evidence from within and across species and functional groups
Functional Ecology, 1998Co-Authors: Peter B Reich, David S Ellsworth, Michael B WaltersAbstract:1. Net photosynthetic capacity (Amax, defined as light-saturated net photosynthesis under near optimal ambient environmental conditions) of mature leaves often depends on the level of Leaf nitrogen (N), but an assortment of relationships between these variables has been observed in studies of diverse plant species. Variation in Leaf Structure has been identified as an important factor associated with differences between the area- and mass-based expressions of the Amax–N relationship. In this paper we test the hypothesis that Leaf Structure, quantified using a measure of Leaf area displayed per unit dry mass invested [specific Leaf area (SLA)], is more than just a conversion factor, but itself can influence Amax–N relationships. We test this using several kinds of comparisons, based on field data for 107 species from sites representing six biomes and on literature data for 162 species from an equally diverse set of biomes. 2. Species and genera with thicker and/or denser leaves (lower SLA) consistently have flatter slopes of the Amax–N (mass-based) relationship than those with higher SLA. These and all other contrasts usually applied as well using area-based expressions, although such relationships were less consistent and weaker overall. A steeper slope indicates greater incremental change in Amax per unit variation in N. 3. Functional groups (e.g. needle-Leafed evergreen trees, broad-Leafed trees or shrubs, forbs) show the same patterns: groups with lower SLA have lower Amax–N slopes. Functional groups differ in mean Leaf traits as well as in Amax–N relationships. Forbs have the highest SLA and mass-based N and Amax, followed by deciduous species (whether needle-Leafed or broad-Leafed, shrub or tree), with lowest values in evergreen species (again regardless of Leaf type or functional group). 4. Interspecific variation in mass-based Amax is highly significantly related to the combination of Leaf N and SLA (r2 = 0·86). At any value of Leaf N, Amax increases with increasing SLA and at any value of SLA, Amax increases with increasing Leaf N. Because this relationship, between Amax and the combination of N and SLA, is similar in two independent data sets, and as well, across broad taxonomic and geographic gradients, we hypothesize that it is universal in nature. Therefore, for broad interspecific contrasts among dicotyledons in any biome, we can reasonably well predict Amax based on the combination of SLA and Leaf N. These findings have important implications for convergent evolution of Leaf adaptation and great potential utility in models of global vegetation functioning.
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Leaf lifespan as a determinant of Leaf Structure and function among 23 amazonian tree species
Oecologia, 1991Co-Authors: Peter B Reich, Christopher Uhl, M B Walters, David S EllsworthAbstract: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.
Kelly A Shepherd - One of the best experts on this subject based on the ideXlab platform.
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associations between Leaf Structure orientation and sunlight exposure in five western australian communities
American Journal of Botany, 1998Co-Authors: William K. Smith, David T Bell, Kelly A ShepherdAbstract:Five plant communities in Western Australia, as well as selected desert and Rocky Mountain species of the western USA, were surveyed to evaluate associations among Leaf Structure, orientational properties, and the sunlight exposure and precipitation characteristic of each community. Selected Leaf structural features have been associated previously with photosynthetic function and included shape, thickness, the ratio of thickness to width, stomatal distribution, Leaf surface coloration, and the number and distribution of palisade cell layers. Decreases in annual precipitation ( ,4 to over 15 cm/yr) and increases in total daily sunlight (4.2 to 29.2 mol photons/m 2) corresponded strongly to an increase in the percentage of species in a given community with more inclined (more inclined than 6 458 from horizontal) or thicker Leaf mesophyll (.0.4 mm) leaves. Also, the percentage of species with a Leaf thickness to width ratio .0.1, which were amphistomatous, or which had palisade cell layers beneath both Leaf surfaces, increased from .20% in the highest rainfall and lowest sunlight community to .80% in the community with least rainfall but greatest sunlight exposure. Over 70% of the species in the most mesic, shaded community had lighter abaxial than adaxial Leaf surfaces (Leaf bicoloration). All of the above structural features were positively associated with a more inclined Leaf orientation ( r 2 5 0.79), except for Leaf bicoloration, which was negatively associated (r 2 5 0.75). The ratio of adaxial to abaxial light was more strongly associated with Leaf bicoloration (r 2 5 0.83) and the presence of multiple adaxial and isobilateral palisade cell layers( r2 5 0.80) than with total incident sunlight on just the adaxial Leaf surface ( r2 5 0.69 and 0.73, respectively). These results provide field evidence that Leaf orientation and Structure may have evolved in concert to produce a photosynthetic symmetry in Leaf Structure in response to the amount of sunlight and other limiting factors of the community. This structural symmetry may serve fundamentally to regulate the distribution of both light and CO 2 levels inside the Leaf and, thus, increase photosynthetic CO2 uptake per unit Leaf biomass.
Mark S. Ashton - One of the best experts on this subject based on the ideXlab platform.
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Change in Leaf Structure in relation to crown position and size class for tree species within a Sri Lankan tropical rain forest
Botany, 2008Co-Authors: P.a.k.a.k. Panditharathna, B.m.p. Singhakumara, Heather P. Griscom, Mark S. AshtonAbstract:The purpose of our study was to examine change in Leaf Structure (anatomy and morphology) through different phases of tree size and crown position within a Sri Lankan rain forest. We selected four late-successional canopy species that represented dominant genera (Shorea, Mesua) within an Asian tropical rain forest. All are considered shade-tolerant and capable of growing to maturity beneath closed-canopy late-successional forests. Species within each genus were either restricted to seepages and bottom slopes (valley species) or to upper slopes and ridges (ridge species). The size classes represented (i) seedlings, (ii) saplings, (iii) poles growing beneath closed-canopy conditions, and (iv) trees of the rain forest canopy. Between size classes, leaves were thicker and with higher stomatal densities for canopy trees than for seedling, sapling, and pole size classes. Plasticities for measures of Leaf Structure were greater for ridge species than valley species; except for cuticle thickness, which showed the...
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Leaf Structure of Syzygium spp. (Myrtaceae) in relation to site affinity within a tropical rain forest
Botanical Journal of the Linnean Society, 2003Co-Authors: Harshi K. Gamage, Mark S. Ashton, B.m.p. SinghakumaraAbstract:This study examined four species of Syzygium (S. firmum, S. makul, S. operculatum, S. rubicundum) Myrtaceae, a tree genus that dominates the canopy of rain forests of south-west Sri Lanka. Syzygium spp. occupy differing habitats with relation to succession and forest topography. We examined differences in Leaf morphology and physiology in response to amount of shade, an important environmental variable affecting Syzygium distribution within the forest. To study change in Leaf Structure and physiology, environmental shelters were constructed simulating forest shade that differed in quality, quantity and duration. Seedlings were exposed to: (i) 0% shade (full sun, FS), red : far red (R : FR) ratio 1.27; (ii) 65% shade (large opening, LO) with direct sunlight similar to the centre of a large canopy opening, R : FR ratio 1.27; (iii) 82% shade (small opening, SO) with direct sunlight similar to the centre of a small canopy opening, R : FR ratio 1.27; (iv) 58% uniform light shade (LS) with a quality similar to the outside edge of a large canopy opening, R : FR ratio 1.05; (v) 85% uniform medium shade (MS) with a quality similar to the inside forest edge of a large canopy opening, R : FR ratio 0.97; (vi) 99% uniform deep shade (DS) similar to that of the forest understorey, R : FR ratio 0.23. The shelters were constructed in a large open area at the field station of the Sinharaja World Heritage site, Sri Lanka. Seedlings of each species were grown for two years in their respective shade treatments before physiological, morphological and anatomical measurements were made on leaves. Variation in Leaf Structure and physiology between the species was associated with differences in shade-tolerance and water-use. All species increased in photosynthesis rates and dimensions in Leaf Structure (Leaf blade and cuticle thickness, stomatal density, thickness of upper and lower epidermis, and thickness of palisade mesophyll) with decrease in shade. In contrast, stomatal conductivity was highest in the DS (99% shade) treatment. Leaves of Syzygium firmum were thickest and largest in area. S. firmum also had highest photosynthesis in the SO (82% shade) treatment. S. firmum was the most shade-tolerant of all species: it grows well in low shade and its Leaf Structure suggests it to be the most conservative in water-use of the Syzygium spp. In the forest S. firmum can persist in the forest shade as established seedlings, but grows best within canopy openings of late-seral rain forest. Leaves of S. operculatum were thinnest but had highest stomatal densities of the four species. S. operculatum is considered shade-intolerant, with a Leaf Structure suggesting it to be prone to desiccation, and by implication susceptible to drought. S. operculatum is found along streams within early seral rain forest habitat, often originating on stream banks after land clearance for cultivation. In the FS (0% shade) treatment, S. rubicundun had highest photosynthesis rates and greatest number of leaves but smallest Leaf area of the Syzygium species. S. rubicundum is more shade-intolerant but more efficient in water-use than S. operculatum. S. rubicundum is a mid-seral canopy tree of the midslope stands that are thought to have originated after catastrophic windthrows or swidden cultivation. The Leaf physiology and Structure of S. makul suggests it to be both moderately shade-tolerant and conservative in water-use. It is the most widely distributed Syzygium species across the topography of late-seral rain forest. We suggest forest disturbance and hydrology are important environmental factors that influence distribution of Syzygium species across the topography. Results from this study contribute to a body of knowledge suggesting that canopy tree species of rain forests in south-west Sri Lanka have discrete affinities to topography and differences in successional status, and that adaptations in Leaf Structure and physiology are indicative of such phenomena. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 141, 365–377.