Thickness Of Palisade Mesophyll Research Articles

Limited Acclimation in Leaf Morphology and Anatomy to Experimental Drought in Temperate Forest Species.

Simple SummaryClimate change shown to have a significant impact on the forest ecosystem due to increased and more frequent occurrence of extreme drought. However, in order to successfully adjust to the xeric environments, plants can usually adopt a variety of adaptation strategies. Here, we investigated the morpho-anatomical traits and biomass allocation patterns as acclimation mechanisms in drought conditions. We found that the interrelation between leaf morphological and anatomical traits were equally affected by drought conditions across all species. This suggests that there is no convincing evidence to classify taxa based on drought resistance vs. drought tolerance. However, based on the biomass allocation pattern, we found that P. koraiensis and F. mandshurica had the higher RMF and total PB, but lower LFM, suggesting higher drought tolerance than those of the other species. Therefore, our dataset revealed some easily measurable traits, such as LMF, RMF, and PB, which demonstrated the seedling’s ability to cope with drought and which could be utilized to choose drought-tolerant species for reforestation in the temperate forest.Drought is a critical and increasingly common abiotic factor that has impacts on plant structures and functioning and is a challenge for the successful management of forest ecosystems. Here, we test the shifts in leaf morpho-anatomical or hydraulic traits and plant growth above ground caused by drought. A factorial experiment was conducted with two gymnosperms (Larix gmelinii and Pinus koraiensis) and two angiosperms (Fraxinus mandshurica and Tilia amurensis), tree species grown under three varying drought intensities in NE China. Considering all the species studied, the plant height (PH), root collar diameter (RCD), and plant biomass (PB) were significantly decreased by drought. The leaf thickness (LT) increased, while the leaf area (LA) decreased with drought intensity. In the gymnosperms, the mesophyll thickness (MT) increased, and the resin duct decreased, while in the angiosperms the palisade mesophyll thickness (PMT), the spongy mesophyll thickness (SMT), and the abaxial (ABE) and adaxial epidermis (ADE) thickness were increased by drought. The correlation analysis revealed that P. koraiensis and F. mandshurica had the higher RMF and total plant biomass, but the least LMF, suggesting drought tolerance. In contrast, the L. gmelinii had the least RMF and higher LMF, suggesting vulnerability to drought. Similarly, T. amurensis had the higher leaf size, which increased the evaporative demand and depleted the soil water quickly relative to the other species. The interrelation among the morpho-anatomical leaf traits was equally affected by drought across all the studied species, suggesting that there is no clear evidence to differentiate the taxa based on drought resistance vs. drought tolerance. Thus, we have identified some easily measurable traits (i.e., LMF, RMF, and PB) which evidenced the seedling’s ability to cope with drought and which therefore could be used as proxies in the selection of drought tolerant species for reforestation in the temperate forest.

Physio-biochemical, anatomical and functional responses of Helianthus annuus L. and Brassica juncea (Linn) to cypermethrin pesticide exposure

Pesticides are applied all over the world to protect plants from pests. However, their application also causes toxicity to plants, which negatively affects the growth and development of plants.This study compared the physiological, biochemical and anatomical modifications of two oil seed crops viz., Helianthus annuus L. and Brassica juncea under different levels of pesticides. The present research was aimed to assess responses at the biochemical, physiological and anatomical levels to Cypermethrin (CYP) pesticide to discriminate the effects of osmotic stress and micronutrients availability. The two different concentrations of CYP-pesticide (20 mg /kg and 40 mg /kg) were examined. The obtained results showed that as the concentration of cypermethrin increased in soil, the fresh and dry weight of growing plants gradually decreased. The application of 40 mg /kg −1 soil of cypermethrin reduced the fresh weight of root in both H. annuus and B. juncea (up to 33 % and 29.4 % %, respectively) decreased root length (up to 2.3 % and 11 %, respectively). While shoot length was increased in both plant species at both levels of CYP relative to control. Shoot fresh weight decreased at 20 mg /kg CYP-treatment in H. annuus whereas in B. juncea at same level of cypermethrin increased fresh weight of shoot was found relative to un-treated seedlings. Reactive oxygen species viz., H2O2 and MDA contents in roots increased by 40 mg/kg-1 CYP in B. juncea followed by H. annuus (upto 50.27 % and 19.79 %; 36.33 % and 35.21 %, respectively). Furthermore, pesticide increased the activities of antioxidant enzymes in H. annuus followed by B. juncea. SOD, POD and CAT enzyme activities significantly decreased in B. juncea under 40 mg/kg-1 CYP by 38.8 %, 44.78 % and 36.83 %, respectively. In 20 mg /kg cypermethrin treatment declined antioxidant enzyme activities were found in H. annuus shoot compared to B. juncea shoot. In case of B. juncea increased APX enzyme activity was observed at 20 mg /kg-1 cypermethrin treatment. While significantly decreased activities of an antioxidant enzymes were found to be at 40 mg /kg CYP-treatment. The main aimed of this study to determine the anatomical responses of H. annuus and B. juncea roots to the cypermethrin exposure. Cypermethrin stress (40 mg /kg-1) change the root diameter (smaller), damaged epidermis layer, irregular form of epidermal cells of both species. The area of vascular bundle is decreasing when increasing the cypermethrin pesticide. Moreover, in stem, epidermis thickness was observed only in B. juncea xylem thickness increased in H. annuus at 20 mg /kg treatment, while in B. juncea non-significant difference was observed at this trait relative to un-treated plants. Phloem thickness raises and pith area in both species at lower concentration of cypermethrin. Leaf collenchymatous cell area was increased at both plant species at 20 mg /kg. Epidermis, spongy mesophyll and palisade mesophyll thickness increased when increased cypermethrin. Mineral uptake by H. annuus and B. juncea from cypermethrin treated soil was measured and also Pearson correlation was measured between all analyzed traits of plants. PCA clearly differentiated all treatments and growth parameters of both plant species. Thus, findings of present study confirmed that overdose of pesticides exhibited toxic effects on different growth, physiological and biochemical attributes of tested plants and pesticide also alter structural changes in plant tissues.

Effects of the Source–Sink Relationship on Walnut Nut Quality at the Scale of the Fruit–Bearing Branch

Fruit quality is known to be regulated by the balance between leaf number/area and fruit number, but less is known about the effects of fruit–bearing branch agronomic traits, particularly for walnuts (Juglans regia L.). We assessed nut quality, physiological and biochemical indexes of leaves, and microstructure of leaves and fruit stalks at various leaf–to–fruit ratios to gain insight into the relationships between branch agronomic traits and nut quality, to identify those traits that made a better contribution to nut quality and to find out the range of the leaf–to–fruit ratio and the object of fruit to be removed for thinning. We found that the top fruit on the fruit stalk had a higher longitudinal diameter and kernel weight than the bottom at the low leaf–to–fruit level, and branches with more pinnate compound leaves had a better capacity for carbohydrate assimilation and transportation to produce better quality fruits. Specifically, with the increasing leaf number, the branch diameter, total leaf area, net photosynthetic rate, chlorophyll content, fruit weight, fruit diameters, and kernel protein content also increased. Moreover, at the microscopic level, the fruit stalk vascular bundle, leaf thickness, palisade mesophyll thickness, and ratios of palisade mesophyll to spongy mesophyll thickness in the leaf also showed the same trend. Therefore, when the ratio of leaf area to the fruit number was less than 181.5 square centimeters per fruit on the branches, reducing the fruit number could improve the size and the crude fat content of fruits. While the ratio was more than 247.8 square centimeters per fruit, the fruit number had no significant effect on fruit quality, but increasing leaf area and branch diameter could improve the fruit size and yield.

Responses in Growth and Anatomical Traits of Two Subtropical Tree Species to Nitrogen Addition, Drought, and Their Interactions.

Nitrogen (N) deposition and drought are two major stressors that influence tree growth and propagation. However, few studies have investigated their interactions. In this study, saplings of the two co-occurring species Ormosia pinnata (leguminous) and Schima superba (non-leguminous) were cultivated under two N addition rates (0 and 80 kg N ha–1 year–1) with well-watered (WW, 80% of field capacity), moderate drought (MD, 60% of field capacity), and severe drought conditions (SD, 40% of field capacity). We examined their growth, as well as multiple anatomical and non-structural carbohydrate (NSC) responses, after 2 years. Results revealed that N addition significantly promoted the growth of MD-stressed S. superba, whereas no significant effect was detected in O. pinnata. Decreased leaf water potential (both Ψmd and Ψpd) was also observed with N addition for both species under MD, but not under SD. Furthermore, the application of N positively impacted drought adaptive responses in the stem xylem of S. superba, showing decreased stem xylem vessel diameter (DH), theoretical hydraulic conductivity (Kth), and increased vessel frequency (VF) upon drought under N addition; such impacts were not observed in O. pinnata. Regarding leaf anatomy, N addition also caused drought-stressed S. superba to generate leaves with a lower density of veins (VD) and stomata (SD), which potentially contributed to an enhanced acclimation to drought. However, the same factors led to a decrease in the palisade mesophyll thickness (PMT) of SD-stressed O. pinnata. Moreover, N addition increased the xylem soluble sugar and starch of MD-stressed O. pinnata, and decreased the xylem soluble sugar under SD for both species. The results suggest that N addition does not consistently modify tree growth and anatomical traits under variable water availability. S. superba appeared to have a greater capacity to be more adaptable under the future interactive effects of N addition and drought due to major modifications in its anatomical traits.

Epidermal and anatomical studies on Chrysophyllum L. (Sapotaceae) species of South-Eastern Nigeria

The epidermal characters of leaves and anatomical characters of petioles and young stems of some members of the genus Chrysophyllum, viz. C. albidum, C. perpulchrum, C. cainito, and C. delevoyi were analyzed to determine their diagnostic features. Paracytic stomata, crystal sand, prismatic crystals, secretory canals occurred in all the species. All the species are hypostomatic except C. perpulchrum. The midribs of all species have an open semi-circular vascular system except in C. cainito with a closed system. Midrib and petiole of C. albidum and C. cainito have non-glandular T-shaped trichomes. Accessory bundles are only seen in the petioles of C. delevoyi, and in the midribs of C. albidum and C. cainito. The midrib and petiole of C. delevoyi and C. albidum have a central bundle. Laticifers, prismatic and sand crystals occur mainly in the cortical cells, pith cells, xylem, phloem, and mesophyll. Lamina of all species studied showed uniseriate epidermis except C. cainito which has two layers of the adaxial epidermis. The stomatal index, the ratio of the spongy to palisade mesophyll thickness, the ratio of cortex thickness, outline, number, and arrangement of the vascular bundles in the midrib, petiole, and young stem differ and are valuable diagnostic features in Chrysophyllum.
 Bangladesh J. Plant Taxon. 28(1): 217-231, 2021 (June)

Effects of an oil spill on the leaf anatomical characteristics of a beach plant (Terminalia catappa L.).

This study investigated the short-term impacts of an oil spill on the leaf anatomical structures of Terminalia catappa L. from crude oil leakage in Rayong province, Thailand, in 2013. Approximately 3weeks after the oil spill, leaves of T. catappa were collected along the coastline of Rayong from one affected site, five adjacent sites, and a control site. Slides of the leaf epidermis were prepared by the peeling method, while leaf and petiole transverse sections were prepared by paraffin embedding. Cell walls of adaxial epidermal cell on leaves in the affected site were straight instead of the jigsaw shape found in leaves from the adjacent and control sites. In addition, the stomatal index of the abaxial leaf surface was significantly lower in the affected site. Leaf and petiole transverse sections collected from the affected site showed increased cuticle thickness, epidermal cell diameter on both sides, and palisade mesophyll thickness; in contrast, vessel diameter and spongy mesophyll thickness were reduced. These significant changes in the leaf anatomy of T. catappa correspond with previous research and demonstrate the negative effects of oil spill pollution on plants. The anatomical changes of T. catappa in response to crude oil pollution are discussed as a possible indicator of pollution and may be used in monitoring crude oil pollution.

Limited acclimation in leaf anatomy to experimental drought in tropical rainforest trees.

Dry periods are predicted to become more frequent and severe in the future in some parts of the tropics, including Amazonia, potentially causing reduced productivity, higher tree mortality and increased emissions of stored carbon. Using a long-term (12 year) through-fall exclusion (TFE) experiment in the tropics, we test the hypothesis that trees produce leaves adapted to cope with higher levels of water stress, by examining the following leaf characteristics: area, thickness, leaf mass per area, vein density, stomatal density, the thickness of palisade mesophyll, spongy mesophyll and both of the epidermal layers, internal cavity volume and the average cell sizes of the palisade and spongy mesophyll. We also test whether differences in leaf anatomy are consistent with observed differential drought-induced mortality responses among taxa, and look for relationships between leaf anatomy, and leaf water relations and gas exchange parameters. Our data show that trees do not produce leaves that are more xeromorphic in response to 12 years of soil moisture deficit. However, the drought treatment did result in increases in the thickness of the adaxial epidermis (TFE: 20.5 ± 1.5 µm, control: 16.7 ± 1.0 µm) and the internal cavity volume (TFE: 2.43 ± 0.50 mm3 cm−2, control: 1.77 ± 0.30 mm3 cm−2). No consistent differences were detected between drought-resistant and drought-sensitive taxa, although interactions occurred between drought-sensitivity status and drought treatment for the palisade mesophyll thickness (P = 0.034) and the cavity volume of the leaves (P = 0.025). The limited response to water deficit probably reflects a tight co-ordination between leaf morphology, water relations and photosynthetic properties. This suggests that there is little plasticity in these aspects of plant anatomy in these taxa, and that phenotypic plasticity in leaf traits may not facilitate the acclimation of Amazonian trees to the predicted future reductions in dry season water availability.

Leaf morphological and anatomical traits from tropical to temperate coniferous forests: Mechanisms and influencing factors.

Leaf traits may reflect the adaptation mechanisms of plants to the environment. In this study, we investigated leaf morphological and anatomical traits in nine cold-temperate to tropical forests along a 4,200-km transect to test how they vary across latitudinal gradients. The results showed that leaf dry weight decreased (P < 0.05), while specific leaf area (SLA) increased (P < 0.05) with increasing latitude. Stomatal length and stomatal density did not change significantly, while stomatal pore area index increased (P < 0.05) with increasing latitude. The palisade-leaf mesophyll thickness ratio increased (P < 0.01), while the spongy-leaf mesophyll thickness ratio decreased, with increasing latitude (P < 0.01). Climate and leaf nutrients were the main factors that regulated leaf morphological and anatomical traits. Furthermore, we identified positive correlations between leaf area and leaf dry weight, leaf thickness and palisade mesophyll thickness, but negative correlations between stomatal length and stomatal density (all P < 0.01). The observed negative correlations represented the adaptive mechanisms of leaves through their morphological and anatomical traits. These findings provided new insights into the responses of leaf morphological and anatomical traits to climate changes and important parameters for future model optimization.

Leaf anatomical and photosynthetic acclimation to cool temperature and high light in two winter versus two summer annuals

Acclimation of foliar features to cool temperature and high light was characterized in winter (Spinacia oleracea L. cv. Giant Nobel; Arabidopsis thaliana (L.) Heynhold Col-0 and ecotypes from Sweden and Italy) versus summer (Helianthus annuus L. cv. Soraya; Cucurbita pepo L. cv. Italian Zucchini Romanesco) annuals. Significant relationships existed among leaf dry mass per area, photosynthesis, leaf thickness and palisade mesophyll thickness. While the acclimatory response of the summer annuals to cool temperature and/or high light levels was limited, the winter annuals increased the number of palisade cell layers, ranging from two layers under moderate light and warm temperature to between four and five layers under cool temperature and high light. A significant relationship was also found between palisade tissue thickness and either cross-sectional area or number of phloem cells (each normalized by vein density) in minor veins among all four species and growth regimes. The two winter annuals, but not the summer annuals, thus exhibited acclimatory adjustments of minor vein phloem to cool temperature and/or high light, with more numerous and larger phloem cells and a higher maximal photosynthesis rate. The upregulation of photosynthesis in winter annuals in response to low growth temperature may thus depend on not only (1) a greater volume of photosynthesizing palisade tissue but also (2) leaf veins containing additional phloem cells and presumably capable of exporting a greater volume of sugars from the leaves to the rest of the plant.

Physiological and anatomical changes induced by drought in two olive cultivars (cv Zalmati and Chemlali)

Photosynthetic gas exchange, vegetative growth, water relations and fluorescence parameters as well as leaf anatomical characteristics were investigated on young plants of two Olea europaea L. cultivars (Chemlali and Zalmati), submitted to contrasting water availability regimes. Two-year-old olive trees, grown in pots in greenhouse, were not watered for 2 months. Relative growth rate (RGR), leaf water potential (ΨLW) and the leaf relative water content (LWC) of the two cultivars decreased with increasing water stress. Zalmati showed higher values of RGR and LWC and lower decreased values of ΨLW than Chemlali, in response to water deficit, particularly during severe drought stress. Water stress also caused a marked decline on photosynthetic capacity and chlorophyll fluorescence. The net photosynthetic rate, stomatal conductance, transpiration rate, the maximal photochemical efficiency of PSII (Fv/Fm) and the intrinsic efficiency of open PSII reaction centres (F′v/F′m) decreased as drought stress developed. In addition, drought conditions, reduced leaf chlorophyll and carotenoids contents especially at severe water stress. However, Zalmati plants were the less affected when compared with Chemlali. In both cultivars, stomatal control was the major factor affecting photosynthesis under moderate drought stress. At severe drought-stress levels, the non-stomatal component of photosynthesis is inhibited and inactivation of the photosystem II occurs. Leaf anatomical parameters show that drought stress resulted in an increase of the upper epidermis and palisade mesophyll thickness as well as an increase of the stomata and trichomes density. These changes were more characteristic in cv. ‘Zalmati’. Zalmati leaves also revealed lower specific leaf area and had higher density of foliar tissue. From the behaviour of Zalmati plants, with a smaller reduction in relative growth rate, net assimilation rate and chlorophyll fluorescence parameters, and with a thicker palisade parenchyma, and a higher stomatal and trichome density, we consider this cultivar more drought-tolerant than cv. Chemlali and therefore, very promising for cultivation in arid areas.

LEAF STRUCTURAL DIVERSITY IS RELATED TO HYDRAULIC CAPACITY IN TROPICAL RAIN FOREST TREES

The hydraulic resistance of the leaf (R1) is a major bottleneck in the whole plant water transport pathway and may thus be linked with the enormous variation in leaf structure and function among tropical rain forest trees. A previous study found that R1 varied by an order of magnitude across 10 tree species of Panamanian tropical lowland rain forest. Here, correlations were tested between R1 and 24 traits relating to leaf venation and mesophyll structure, and to gross leaf form. Across species, R1 was related to both venation architecture and mesophyll structure. R1 was positively related to the theoretical axial resistivity of the midrib, determined from xylem conduit numbers and dimensions, and R1 was negatively related to venation density in nine of 10 species. R1 was also negatively related to both palisade mesophyll thickness and to the ratio of palisade to spongy mesophyll. By contrast, numerous leaf traits were independent of R1, including area, shape, thickness, and density, demonstrating that leaves can be diverse in gross structure without intrinsic trade-offs in hydraulic capacity. Variation in both R1-linked and R1-independent traits related strongly to regeneration irradiance, indicating the potential importance of both types of traits in establishment ecology.

Leaf structure of Syzygium spp. (Myrtaceae) in relation to site affinity within a tropical rain forest

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.

Anatomical variation in juvenile eucalypt leaves accounts for differences in specific leaf area and CO2 assimilation rates

Specific leaf area (SLA) is an important leaf attribute representing a compromise between the capture of light and CO2 and the limitations imposed by leaf structure, herbivore resistance and the mitigation of water loss. We examined three Eucalyptus L'Her. species to determine whether variation in CO2 assimilation rate was related to SLA and leaf anatomy. Seedlings were grown in a naturally illuminated glasshouse with adequate water and nutrients. Light-saturated rates of photosynthesis were measured on the youngest fully expanded leaves. Mesophyll characteristics were measured from sections thick of the interveinal leaf lamina. Significant interspecies variation in SLA corresponded to clear trends in anatomy and photosynthesis. Low-SLA leaves were thicker, having increased thickness of palisade mesophyll because of a greater number of palisade layers. E. occidentalis, E.camaldulensis and E. grandis had 3.7, 2.0 and 1.0 layers of palisade cells which corresponded to an SLA of 14.8, 17.6 and 21.8 m2 kg-1, respectively. High investment of dry mass in photosynthetic tissue was associated with higher leaf N (area and mass) concentration, chlorophyll concentration and photosynthetic capacity per leaf area. Leaf morphology affected use of the resources N, water and CO2. In contrast to the thin leaves of E. grandis, thick leaves of E. occidentalis had low N-use efficiency and high instantaneous water-use efficiency. Differences in leaf structure of these species appear to reflect the most limiting resource experienced in the environments to which they have adapted.

Anatomical variation in juvenile Eucalyptus leaves accounts for differences in specific leaf area and CO2 assimilation rates

Specific leaf area (SLA) is an important leaf attribute representing the compromise between the capture of light and CO2, and the limitations imposed by leaf structure, herbivore resistance and the mitigation of water loss. We examined three Eucalyptus species to determine whether variation in CO2 assimilation rate is related to SLA and leaf anatomy. Seedlings were grown in a naturally illuminated glasshouse with adequate water and nutrients. Light saturated rates of photosynthesis and the response of assimilation to intercellular CO2 concentration were measured on the youngest fully expanded leaf. Mesophyll characteristics were measured from 1µm thick sections of the interveinal leaf lamina. Significant interspecies variation in SLA was observed corresponding to clear trends in anatomy and photosynthesis. Low SLA leaves were thicker having increased thickness of palisade mesophyll due to a greater number of palisade layers. E. occidentalis, E. camaldulensis and E. grandis had 3.7, 2.0 and 1.0 layers of palisade cells which corresponded to an SLA of 14.8, 17.6 and 21.8 m2 kg-1 respectively. High investment in this photosynthetic tissue increased leaf nitrogen, chlorophyll and photosynthetic capacity per leaf area. The leaf morphology affected how the leaves used these resources. Thick leaves of E. occidentalis had lowest nitrogen use efficiency and highest instantaneous water use efficiency in contrast to the thin leaves of E. grandis. Differences in leaf structure of these species appear to reflect the environments to which they have adapted and the most limiting resource.

Seedling Leaf Structure of New England Maples (Acer) in Relation to Light Environment

Abstract Seedling leaves of the genus Acer from southern New England were compared in relation to light. The species investigated were red maple (A. rubrum L.), a species tolerant of xeric and hydric sites; silver maple (A. saccharinum L.), a species restricted to riparian sites that are periodically flooded; and sugar maple (A. saccharum Marsh.), a mesic species of lower slopes and valleys. Germinating seedlings of all species were collected and grown within four shade treatments that had contrasting light quantity and quality: (1) approximately 100% of full sunlight, red:far-red ratio = 1.27; (2) 40% of full sunlight, ratio = 0.97; (3) 15% of full sunlight, ratio = 0.85; and (4) 4% of full sunlight, ratio = 0.46. Leaves, cuticles, and epidermal and palisade mesophyll cell layers were all thicker, and stomatal densities were higher for all three species in the full sun treatment. Dimensions of leaf structure (leaf thickness, palisade mesophyll thickness, lower epidermal thickness) were between 25 and 35% smaller for silver maple as compared to the other maples. Silver maple also allocated less biomass to roots (about 15% less) and more to stems. Its thin upper surface cuticle, thin leaves, and large leaf area predispose this species to desiccation. Phenotypic plasticity of leaf anatomical measures was greatest for red maple, suggesting it to be more of a generalist than its congeners. Red maple allocated greater biomass to roots in shade (17% and 27% more than sugar and silver maple respectively), with thicker leaves and cuticle, making it least prone to desiccation. Sugar maple had greater dry mass and total leaf area in the deepest shade than the other maples. Measures of leaf structure can provide useful insights into known ecological affinities of site and shade-tolerance among maples. For. Sci. 45(4):512-519.

A comparison of leaf physiology and anatomy of Quercus (section Erythrobalanus‐Fagaceae) species in different light environments

Physiological and anatomical attributes of leaves were examined of three species of Quercus section Erythrobalanus. All three species occur in moist temperate deciduous forests of eastern North America. Seedlings of each species were grown in different light conditions for comparison. The attributes measured were net photosynthesis, stomatal conductivity, blade and cuticle thickness, stomatal density, thickness of upper and lower epidermis, and thickness of palisade mesophyll. The results generally demonstrate the close association between anatomical adaptations and efficiency of physiological processes; they also elucidate the distribution patterns of the three Quercus species across the forest topography in southern New England. The most drought‐tolerant and light‐demanding species, Q. velutina (Lam.), exhibited the greatest leaf anatomical plasticity, the highest net photosynthesis in the different light conditions, and the lowest stomatal area per unit area of leaf. The most drought‐intolerant species, Q. rubra (L.), exhibited the least leaf anatomical plasticity, the lowest net photosynthesis in the different light conditions, and the highest stomatal area per unit area of leaf. Quercus coccinea (Muenchh.) usually exhibited values that were intermediate between Q. rubra and Q. velutina.

A Comparison of Leaf Physiology and Anatomy of Quercus (Section Erythrobalanus-Fagaceae) Species in Different Light Environments

Physiological and anatomical attributes of leaves were examined of three species of Quercus section Erythrobalanus. All three species occur in moist temperate deciduous forests of eastern North America. Seedlings of each species were grown in different light conditions for comparison. The attributes measured were net photosynthesis, stomatal conductivity, blade and cuticle thickness, stomatal density, thickness of upper and lower epidermis, and thickness of palisade mesophyll. The results generally demonstrate the close association between anatomical adaptations and efficiency of physiological processes; they also elucidate the distribution patterns of the three Quercus species across the forest topography in southern New England. The most drought-tolerant and light-demanding species, Q. velutina (Lam.), exhibited the greatest leaf anatomical plasticity, the highest net photosynthesis in the different light conditions, and the lowest stomatal area per unit area of leaf. The most drought-intolerant species, Q. rubra (L.), exhibited the least leaf anatomical plasticity, the lowest net photosynthesis in the different light conditions, and the highest stomatal area per unit area of leaf. Quercus coccinea (Muenchh.) usually exhibited values that were intermediate between Q. rubra and Q. velutina.

Relationships between leaf anatomy and ozone sensitivity of Fraxinus pennsylvanica marsh. and Prunus serotina Ehrh.

It is well known that there are genetic differences in sensitivity of broad-leaved tree species to ozone (O 3). It would be helpful to know if individual trees in the field could be classified as sensitive or tolerant based on properties of sensitivity other than the presence/absence of foliar injury symptoms. We hypothesized that leaf anatomical characteristics allowing greater amounts of O 3 inside the leaf would be found in the leaves of sensitive individuals compared to the leaves of tolerant individuals. Light microscopy was used to examine 11 anatomical characters of leaves of field-grown Fraxinus pennsylvanica Marsh. and Prunus serotina Ehrh. trees that differed in O 3 sensitivity, as determined by injury symptoms. The characters were measured on uninjured areas of leaves collected in the field from trees classified as tolerant or sensitive. There were significant differences between sensitive and tolerant individuals of both species for several characters, including stomatal density, palisade mesophyll thickness and total mesophyll thickness, and the percentage of spongy mesophyll layer relative to total leaf mesophyll. Differences in stomatal density were inconsistent for the two species considered. The palisade mesophyll was significantly thinner by 27 and 17% in sensitive green ash and black cherry leaves compared to tolerant leaves, causing the percentage of spongy mesophyll layer relative to total leaf thickness to be 20-12% higher for sensitive compared to tolerant individuals. Consequently, the total leaf thickness was less for sensitive trees for both species. This aspect of leaf anatomy was consistent with shade leaf anatomy and may be associated with O 3 sensitivity for these two broad-leaved species.