Anatomical features of ecological importance and taxonomic value revealed by scanning electron microscopy and light microscopy in Camonea umbellata (L.) A.R. Simões & Staples (Convolvulaceae).

This article describes detailed and novel data on the anatomy and histochemistry of leaves, stems, and roots of Camonea umbellata (L.) A.R.Simões & Staples in different environments for the identification of characters with taxonomical value and of ecological importance, with provision of light and scanning electron microscopy images. To analyze the characters, we collected samples of the vegetative organs of three individuals in each of three populations, which were in a grazing area, an urban environment, and a biological reserve. The main diagnostic anatomical markers for the identification of C. umbellata include amphistomatic leaves, tetracytic and brachyparatetracytic stomata, peltate trichomes, long simple trichomes, epidermis with striated cuticle ornamentation, mesophyll with acute borders, presence of druses, secretory channels, angular collenchyma, fibrous pericycle in the stem, intraxylary phloem in the vegetative organs, oil bodies throughout the midrib, petiole, stem and root, and epicuticular waxes of the crust and coiled rodlet types. Since the characters above did not show variation in the environments evaluated, we consider these characters taxonomically useful for the identification of C. umbellata. RESEARCH HIGHLIGHTS: The anatomy of the aerial vegetative organs of Camonnea umbellata retains common Convolvulaceae characters. The sinuosity of the epidermal cell walls and the density of trichomes in the epidermis of the petiole were visually variable characters among the analyzed individuals. Amphistomatic leaves, tetracytic and brachyparatetracytic stomata, peltate trichomes, epidermis with striated cuticle ornamentation, dorsiventral mesophyll with border acute, presence of druses, secretory structures, angular collenchyma, fibrous pericycle in the stem, intraxillary phloem, presence of oil bodies in all organs, and epicuticular waxes of the crust type and coiled rods were considered important anatomical markers for the recognition and correct identification of Camonea umbellata.

Tolerance to mild shading levels in cattail as related to increased photosynthesis and changes in its leaf area and anatomy.

Shading is an environmental factor that has been little investigated regarding its effects on emergent aquatic plants. Typha domingensis Pers. is an emergent macrophyte that demonstrates some plasticity for self-shading, and as it can shade other species in the same area, the effect of shading on its traits deserves further investigation. The objective of the present study was to evaluate the gas exchange, leaf anatomy, and growth of T. domingensis cultivated under increasing shading intensities. The plants were collected and propagated in a greenhouse, and the clones were subjected to four shading intensities: 0% (unshaded), 35%, 73%, and 83% shading created by black nets. Growth traits, clonal production, photosynthesis, transpiration, and leaf anatomy were evaluated. The 73% and 83% shading promoted the death of all plants, but all plants survived in the 35% and unshaded treatments. Compared with the unshaded treatment, the 35% shading treatment promoted a higher photosynthetic rate and greater transpiration, supporting increased growth and production of clones. The increase in the photosynthetic rate in the 35% shading was related to the increase in leaf area which increased the photosynthesis of the whole plant. The 73% and 83% treatments inhibited the development of photosynthetic parenchyma and stomata in T. domingensis, leading to a drastic reduction in photosynthesis and energy depletion. Therefore, T. domingensis does not tolerate intense shading, but its photosynthetic characteristics and growth are favored by mild shading, a factor that may be of great importance for its competitiveness and invasive behavior.

A stomata classification and detection system in microscope images of maize cultivars.

Plant stomata are essential structures (pores) that control the exchange of gases between plant leaves and the atmosphere, and also they influence plant adaptation to climate through photosynthesis and transpiration stream. Many works in literature aim for a better understanding of these structures and their role in the evolution process and the behavior of plants. Although stomata studies in dicots species have advanced considerably in the past years, even there is not much knowledge about the stomata of cereal grasses. Due to the high morphological variation of stomata traits intra- and inter-species, detecting and classifying stomata automatically becomes challenging. For this reason, in this work, we propose a new system for automatic stomata classification and detection in microscope images for maize cultivars based on transfer learning strategy of different deep convolution neural netwoks (DCNN). Our performed experiments show that our system achieves an approximated accuracy of 97.1% in identifying stomata regions using classifiers based on deep learning features, which figures out as a nearly perfect classification system. As the stomata are responsible for several plant functionalities, this work represents an important advance for maize research, providing an accurate system in replacing the current manual task of categorizing these pores on microscope images. Furthermore, this system can also be a reference for studies using images from different cereal grasses.

Leaf water relations in epiphytic ferns are driven by drought avoidance rather than tolerance mechanisms.

Opportunistic diversification has allowed ferns to radiate into epiphytic niches in angiosperm dominated landscapes. However, our understanding of how ecophysiological function allowed establishment in the canopy and the potential transitionary role of the hemi-epiphytic life form remain unclear. Here, we surveyed 39 fern species in Costa Rican tropical forests to explore epiphytic trait divergence in a phylogenetic context. We examined leaf responses to water deficits in terrestrial, hemi-epiphytic and epiphytic ferns and related these findings to functional traits that regulate leaf water status. Epiphytic ferns had reduced xylem area (-63%), shorter stipe lengths (-56%), thicker laminae (+41%) and reduced stomatal density (-46%) compared to terrestrial ferns. Epiphytic ferns exhibited similar turgor loss points, higher osmotic potential at saturation and lower tissue capacitance after turgor loss than terrestrial ferns. Overall, hemi-epiphytic ferns exhibited traits that share characteristics of both terrestrial and epiphytic species. Our findings clearly demonstrate the prevalence of water conservatism in both epiphytic and hemi-epiphytic ferns, via selection for anatomical and structural traits that avoid leaf water stress. Even with likely evolutionarily constrained physiological function, adaptations for drought avoidance have allowed epiphytic ferns to successfully endure the stresses of the canopy habitat.

Stomatal size, ploidy and polyembryony in Eriotheca Stellate Trichome Species Complex (Bombacoideae - Malvaceae) in the Cerrados of Brazil.

Geographic parthenogenesis, range expansion of apomictic plants after climate changes, has been described for Northern Hemisphere gametophytic apomicts. But similar trends have been observed for sporophytic apomicts of Cerrado, the savannas in Brazil. Eriotheca pubescens is a common Cerrado tree, an agamic complex of either hexaploid/polyembryonic apomicts or tetraploid/monoembryonic sexual individuals. Some populations have been described as a new species, Eriotheca estevesiae, all included in the Eriotheca Stellate Trichome Species Complex (ESTSC). Since breeding systems and ploidy are clearly associated with polyembryony and stomatal size, we used these ancillary features to map the reproductive and ploidy level traits of E. pubescens and E. estevesiae. Leaves and seeds were collected from individuals of 19 populations. Seeds were evaluated for the presence of polyembryony and leaves for stomatal measurements. Eight populations were monoembryonic while another eight were polyembryonic and for other three, the embryonic pattern was not readily verified. E. pubescens polyembryonic and hexaploid populations formed a homogeneous group, but monoembryonic plants were more variable. E. estevesiae populations were monoembryonic with smaller stomata. In contrast, some E. pubescens monoembryonic populations further south presented larger stomata. Despite these outliers, possibly mixed populations, stomatal size and embryonic pattern differed from northern to southern populations. Embryonic pattern and stomatal size indicated that northernmost populations of Eriotheca STSC (E. estevesiae) are diploid and sexual. Southernmost populations, mostly polyembryonic and with large stomata, are hexaploid and apomictic. This is in agreement with geographic parthenogenesis and range expansion of apomictic lineages to southern habitats available after the last glacial maximum.

Crescimento inicial e resposta estomática de milho pipoca sob estresse salino / Initial growth and stomatal response of popcorn (Zea mays everta) under salt stress

A salinidade se destaca como um problema de grande importância, pois pode limitar o desenvolvimento e a produção agrícola. O estresse salino em plantas pode afetar o seu metabolismo, além de estimular o acúmulo de osmólitos. Portanto, o objetivo desse trabalho foi avaliar o crescimento, mudanças fisiológicas e estomáticas de plantas de milho pipoca submetidas ao estresse salino. O experimento foi inteiramente casualizado, com 6 vasos por tratamento, conduzido em câmera de crescimento e irrigadas com NaCl nas concentrações de 0, 100 e 200 mM por 15 dias. As concentrações de 100 mM e 200 mM de NaCl, ocasionaram reduções significavas na altura e massa fresca da parte aérea e raízes. Observamos um aumento do dano na membrana plasmática e consequentemente uma redução no teor relativo de água nas folhas, devido às mudanças ocorridas na atividade osmótica. Além disso, houve o acúmulo de prolina, aumento no teor de clorofila e um aumento significativo no número de estômatos na superfície abaxial, assim como uma redução do tamanho dos estômatos. As plantas apresentaram um conjunto de alterações morfológicas e fisiológicas que são um mecanismo de defesa contra os efeitos da salinidade. Nossos resultados demonstraram que essas características contribuíram para uma notável tolerância à salinidade, pois possuem um importante papel protetor contra os diferentes estresses ambientais.

Salinity stands out as a major problem environmental that it may limit agricultural development and productivity. Saline stress in plants can affect your metabolism, in addition to stimulating the accumulation of osmolytes. Therefore, the aim is study was to evaluate the growth and extend our understanding physiological and stomatal changes in popcorn plants submitted to salinity stress. The experiment was completely randomized, with 6 pots per treatment, conducted in a growth chamber and irrigated with NaCl at the concentrations 0, 100 and 200 mM for 15 days. 100 and 200 mM NaCl concentrations cause significant reductions in height and fresh mass of shoots and roots. We observe an increase in the plasma membrane damage and consequently a reduction in relative water content in the leaves due to changes in the osmotic activity. Accordingly, an involvement there was a proline accumulation, increase in chlorophyll content and a significant increase in a number of stomata on abaxial surface, as well as a reduction in the size of the stomata. Plants presented a set of morphological and physiological changes, triggering a defense mechanism against the effects of salinity. Finally, our results demonstrated that these characteristics contributed to a remarkable tolerance to salinity since they have an important protective role against the different environmental stresses.

Crescimento inicial e resposta estomática de milho pipoca sob estresse salino / Initial growth and stomatal response of popcorn (Zea mays everta) under salt stress

A salinidade se destaca como um problema de grande importância, pois pode limitar o desenvolvimento e a produção agrícola. O estresse salino em plantas pode afetar o seu metabolismo, além de estimular o acúmulo de osmólitos. Portanto, o objetivo desse trabalho foi avaliar o crescimento, mudanças fisiológicas e estomáticas de plantas de milho pipoca submetidas ao estresse salino. O experimento foi inteiramente casualizado, com 6 vasos por tratamento, conduzido em câmera de crescimento e irrigadas com NaCl nas concentrações de 0, 100 e 200 mM por 15 dias. As concentrações de 100 mM e 200 mM de NaCl, ocasionaram reduções significavas na altura e massa fresca da parte aérea e raízes. Observamos um aumento do dano na membrana plasmática e consequentemente uma redução no teor relativo de água nas folhas, devido às mudanças ocorridas na atividade osmótica. Além disso, houve o acúmulo de prolina, aumento no teor de clorofila e um aumento significativo no número de estômatos na superfície abaxial, assim como uma redução do tamanho dos estômatos. As plantas apresentaram um conjunto de alterações morfológicas e fisiológicas que são um mecanismo de defesa contra os efeitos da salinidade. Nossos resultados demonstraram que essas características contribuíram para uma notável tolerância à salinidade, pois possuem um importante papel protetor contra os diferentes estresses ambientais.(AU)

Salinity stands out as a major problem environmental that it may limit agricultural development and productivity. Saline stress in plants can affect your metabolism, in addition to stimulating the accumulation of osmolytes. Therefore, the aim is study was to evaluate the growth and extend our understanding physiological and stomatal changes in popcorn plants submitted to salinity stress. The experiment was completely randomized, with 6 pots per treatment, conducted in a growth chamber and irrigated with NaCl at the concentrations 0, 100 and 200 mM for 15 days. 100 and 200 mM NaCl concentrations cause significant reductions in height and fresh mass of shoots and roots. We observe an increase in the plasma membrane damage and consequently a reduction in relative water content in the leaves due to changes in the osmotic activity. Accordingly, an involvement there was a proline accumulation, increase in chlorophyll content and a significant increase in a number of stomata on abaxial surface, as well as a reduction in the size of the stomata. Plants presented a set of morphological and physiological changes, triggering a defense mechanism against the effects of salinity. Finally, our results demonstrated that these characteristics contributed to a remarkable tolerance to salinity since they have an important protective role against the different environmental stresses.(AU)

In situ warming in the Antarctic: effects on growth and photosynthesis in Antarctic vascular plants.

The Antarctic Peninsula has experienced a rapid warming in the last decades. Although recent climatic evidence supports a new tendency towards stabilization of temperatures, the impacts on the biosphere, and specifically on Antarctic plant species, remain unclear. We evaluated the in situ warming effects on photosynthesis, including the underlying diffusive, biochemical and anatomical determinants, and the relative growth of two Antarctic vascular species, Colobanthus quitensis and Deschampsia antarctica, using open top chambers (OTCs) and gas exchange measurements in the field. In C. quitensis, the photosynthetic response to warming relied on specific adjustments in the anatomical determinants of the leaf CO2 transfer, which enhanced mesophyll conductance and photosynthetic assimilation, thereby promoting higher leaf carbon gain and plant growth. These changes were accompanied by alterations in the leaf chemical composition. By contrast, D. antarctica showed no response to warming, with a lack of significant differences between plants grown inside OTCs and plants grown in the open field. Overall, the present results are the first reporting a contrasting effect of in situ warming on photosynthesis and its underlying determinants, of the two unique Antarctic vascular plant species, which could have direct consequences on their ecological success under future climate conditions.

Structural and functional changes in coffee trees after 4 years under free air CO2 enrichment.

Background and Aims: Climate forecasts suggest that [CO2] in the atmosphere will continue to increase. Structural and ecophysiological responses to elevated air [CO2] (e[CO2]) in tree species are contradictory due to species-dependent responses and relatively short-term experiments. It was hypothesized that long-term exposure (4 year) to e[CO2] would change canopy structure and function of Coffea arabica trees. Methods: Coffee plants were grown in a FACE (free air CO2 enrichment) facility under two air [CO2]: actual and elevated (actual + approx. 200 µL CO2 L-1). Plants were codified following the VPlants methodology to obtain coffee mock-ups. Plant canopies were separated into three 50 cm thick layers over a vertical profile to evaluate their structure and photosynthesis, using functional-structural plant modelling. Key Results: Leaf area was strongly reduced on the bottom and upper canopy layers, and increased soil carbon concentration suggested changes in carbon partitioning of coffee trees under e[CO2]. Increased air [CO2] stimulated stomatal conductance and leaf photosynthesis at the middle and upper canopy layers, increasing water-use efficiency. Under e[CO2], plants showed reduced diameter of the second-order axes and higher investment in the youngest third to fifth-order axes. Conclusions: The responses of Arabica coffee grown under long-term exposure to e[CO2] integrated structural and functional modifications, which balanced leaf area loss through improvements in leaf and whole-plant photosynthesis.

Size matters: point pattern analysis biases the estimation of spatial properties of stomata distribution.

Stomata distribution is an example of biological patterning. Formal methods used to study stomata patterning are generally based on point-pattern analysis, which assumes that stomata are points and ignores the constraints imposed by size on the placement of neighbors. The inclusion of size in the analysis requires the use of a null model based on finite-size object geometry. In this study, we compare the results obtained by analyzing samples from several species using point and disc null models. The results show that depending on the null model used, there was a 20% reduction in the number of samples classified as uniform; these results suggest that stomata patterning is not as general as currently reported. Some samples changed drastically from being classified as uniform to being classified as clustered. In samples of Arabidopsis thaliana, only the disc model identified clustering at high densities of stomata. This reinforces the importance of selecting an appropriate null model to avoid incorrect inferences about underlying biological mechanisms. Based on the results gathered here, we encourage researchers to abandon point-pattern analysis when studying stomata patterning; more realistic conclusions can be drawn from finite-size object analysis.

Physiological differences and changes in global DNA methylation levels in Agave angustifolia Haw. albino variant somaclones during the micropropagation process.

KEY MESSAGE: Global DNA methylation changes caused by in vitro conditions are associated with the subculturing and phenotypic variation in Agave angustifolia Haw. While the relationship between the development of albinism and in vitro culture is well documented, the role of epigenetic processes in this development leaves some important questions unanswered. During the micropropagation of Agave angustifolia Haw., we found three different phenotypes, green (G), variegated (V) and albino (A). To understand the physiological and epigenetic differences among the somaclones, we analyzed several morphophysiological parameters and changes in the DNA methylation patterns in the three phenotypes during their in vitro development. We found that under in vitro conditions, the V plantlets maintained their CAM photosynthetic capacity, while the A variant showed no pigments and lost its CAM photosynthetic ability. Epigenetic analysis revealed that global DNA methylation increased in the G phenotype during the first two subcultures. However, after that time, DNA methylation levels declined. This hypomethylation correlated with the appearance of V shoots in the G plantlets. A similar correlation occurred in the V phenotype, where an increase of 2 % in the global DNA methylation levels was correlated with the generation of A shoots in the V plantlets. This suggests that an "epigenetic stress memory" during in vitro conditions causes a chromatin shift that favors the generation of variegated and albino shoots.

Leaf epidermis images for robust identification of plants.

This paper proposes a methodology for plant analysis and identification based on extracting texture features from microscopic images of leaf epidermis. All the experiments were carried out using 32 plant species with 309 epidermal samples captured by an optical microscope coupled to a digital camera. The results of the computational methods using texture features were compared to the conventional approach, where quantitative measurements of stomatal traits (density, length and width) were manually obtained. Epidermis image classification using texture has achieved a success rate of over 96%, while success rate was around 60% for quantitative measurements taken manually. Furthermore, we verified the robustness of our method accounting for natural phenotypic plasticity of stomata, analysing samples from the same species grown in different environments. Texture methods were robust even when considering phenotypic plasticity of stomatal traits with a decrease of 20% in the success rate, as quantitative measurements proved to be fully sensitive with a decrease of 77%. Results from the comparison between the computational approach and the conventional quantitative measurements lead us to discover how computational systems are advantageous and promising in terms of solving problems related to Botany, such as species identification.

Leaf morphophysiology of a Neotropical mistletoe is shaped by seasonal patterns of host leaf phenology.

Several mistletoe species are able to grow and reproduce on both deciduous and evergreen hosts, suggesting a degree of plasticity in their ability to cope with differences in intrinsic host functions. The aim of this study was to investigate the influence of host phenology on mistletoe water relations and leaf gas exchange. Mistletoe Passovia ovata parasitizing evergreen (Miconia albicans) hosts and P. ovata parasitizing deciduous (Byrsonima verbascifolia) hosts were sampled in a Neotropical savanna. Photosynthetic parameters, diurnal cycles of stomatal conductance, pre-dawn and midday leaf water potential, and stomatal anatomical traits were measured during the peak of the dry and wet seasons, respectively. P. ovata showed distinct water-use strategies that were dependent on host phenology. For P. ovata parasitizing the deciduous host, water use efficiency (WUE; ratio of photosynthetic rate to transpirational water loss) was 2-fold lower in the dry season than in the wet season; in contrast, WUE was maintained at the same level during the wet and dry seasons in P. ovata parasitizing the evergreen host. Generally, mistletoe and host diurnal cycles of stomatal conductance were linked, although there were clear differences in leaf water potential, with mistletoe showing anisohydric behaviour and the host showing isohydric behaviour. Compared to mistletoes attached to evergreen hosts, those parasitizing deciduous hosts had a 1.4-fold lower stomatal density and 1.2-fold wider stomata on both leaf surfaces, suggesting that the latter suffered less intense drought stress. This is the first study to show morphophysiological differences in the same mistletoe species parasitizing hosts of different phenological groups. Our results provide evidence that phenotypical plasticity (anatomical and physiological) might be essential to favour the use of a greater range of hosts.

Anatomical, morphological, and phytochemical effects of inoculation with plant growth- promoting rhizobacteria on peppermint (Mentha piperita).

Plant growth-promoting rhizobacteria (PGPR) generally exert their effects through enhancement of plant nutrient status and/or phytohormone production. The effects of PGPR on aromatic plant species are poorly known. We measured plant growth parameters, chlorophyll content, trichome density, stomatal density, and levels of secondary metabolites in peppermint (Mentha piperita) seedlings inoculated with PGPR strains Bacillus subtilis GB03, Pseudomonas fluorescens WCS417r, P. putida SJ04, or a combination of WCS417r + SJ04. The treated plants, in comparison with controls, showed increases in shoot biomass, root biomass, leaf area, node number, trichome density, and stomatal density, and marked qualitative and quantitative changes in monoterpene content. Improved knowledge of the factors that control or affect biosynthesis of secondary metabolites and monoterpene accumulation will lead to strategies for improved cultivation and productivity of aromatic plants and other agricultural crops without the use of chemical fertilizers or pesticides.

Effects of stomatal density and leaf water content on the ¹8O enrichment of leaf water.

Leaf water isotopic composition is imprinted in several biomarkers of interest and it is imperative that we understand the isotopic enrichment of leaf water. Here, we test the effect of stomatal density and leaf water content on the oxygen isotopic composition of leaf water in transgenic Arabidopsis plants expressing different stomatal densities, and several other species showing a range of stomatal density. We grew Arabidopsis plants hydroponically and collected other species in the field. Stomatal density and leaf water content were determined for each plant. We measured transpiration and extracted leaf water for isotopic determination. Using these measurements and the current leaf water isotope model, we calculated several of the parameters related to leaf water isotopic enrichment. High stomatal density promoted leaf water isotope enrichment. No conclusion, however, can be drawn regarding the effect of leaf water content on leaf water isotope enrichment. Factors such as transpiration might mask the effect of stomatal density on leaf water isotopic enrichment. We propose a method by which stomatal density can be incorporated in the current Peclet model of leaf water isotope enrichment. These findings have important applications in the use of plant-based metabolic proxies in paleoclimate studies.

Extrafloral nectaries in neotropical Gentianaceae: occurrence, distribution patterns, and anatomical characterization.

PREMISE OF THE STUDY: Extrafloral nectaries (EFNs) are structures that secrete nectar and protect plants against herbivores and pathogens. In Gentianaceae, these structures have been described in species of Calolisianthus, Fagraea, and Anthocleista and are important morphological markers for taxonomic and phylogenetic studies. To establish a foundation for further studies, we investigated the occurrence, distribution patterns, and anatomy of EFNs on leaves of 27 species belonging to 13 genera and three tribes of neotropical Gentianaceae. • METHODS: Leaf samples were diaphanized, stained with basic fuchsin, and mounted in glycerinated gelatin. Cross sections were obtained from material embedded in methacrylate or paraffin, stained, and mounted in Permount. Polysaccharides were histochemically stained with periodic acid-Schiff stain. Samples were also examined with scanning electron microscopy. • KEY RESULTS: Unusual EFNs, visible only with light microscopy, were formed of modified epidermal cells. Each EFN consisted of 2-5 secretory cells encircling a central cell. The EFNs varied in size and in the shape and arrangement of the adjacent cells surrounding the secretory cells. EFNs occurred in all analyzed species as isolated units distributed throughout the leaf blade or as aggregates; aggregates were generally visible to the naked eye. Based on their occurrence as aggregates or isolated units and on their location on the leaf blade, six distribution patterns were identified. • CONCLUSIONS: This is the first comprehensive study of EFNs on the leaves of neotropical Gentianaceae. The data suggested that NEFs evolved from isolated units for NEFs in aggregates. The results represent a new source of data for future ecological, systematic, and phylogenetic studies in Gentianaceae.

Plasticity of stomatal distribution pattern and stem tracheid dimensions in Podocarpus lambertii: an ecological study.

BACKGROUND AND AIMS: Leaf and wood plasticity are key elements in the survival of widely distributed plant species. Little is known, however, about variation in stomatal distribution in the leaf epidermis and its correlation with the dimensions of conducting cells in wood. This study aimed at testing the hypothesis that Podocarpus lambertii, a conifer tree, possesses a well-defined pattern of stomatal distribution, and that this pattern can vary together with the dimensions of stem tracheids as a possible strategy to survive in climatically different sites. METHODS: Leaves and wood were sampled from trees growing in a cold, wet site in south-eastern Brazil and in a warm, dry site in north-eastern Brazil. Stomata were thoroughly mapped in leaves from each study site to determine a spatial sampling strategy. Stomatal density, stomatal index and guard cell length were then sampled in three regions of the leaf: near the midrib, near the leaf margin and in between the two. This sampling strategy was used to test for a pattern and its possible variation between study sites. Wood and stomata data were analysed together via principal component analysis. KEY RESULTS: The following distribution pattern was found in the south-eastern leaves: the stomatal index was up to 25 % higher in the central leaf region, between the midrib and the leaf margin, than in the adjacent regions. The inverse pattern was found in the north-eastern leaves, in which the stomatal index was 10 % higher near the midrib and the leaf margin. This change in pattern was accompanied by smaller tracheid lumen diameter and length. CONCLUSIONS: Podocarpus lambertii individuals in sites with higher temperature and lower water availability jointly regulate stomatal distribution in leaves and tracheid dimensions in wood. The observed stomatal distribution pattern and variation appear to be closely related to the placement of conducting tissue in the mesophyll.

Structural analysis and involvement in plant innate immunity of Xanthomonas axonopodis pv. citri lipopolysaccharide.

Xanthomonas axonopodis pv. citri (Xac) causes citrus canker, provoking defoliation and premature fruit drop with concomitant economical damage. In plant pathogenic bacteria, lipopolysaccharides are important virulence factors, and they are being increasingly recognized as major pathogen-associated molecular patterns for plants. In general, three domains are recognized in a lipopolysaccharide: the hydrophobic lipid A, the hydrophilic O-antigen polysaccharide, and the core oligosaccharide, connecting lipid A and O-antigen. In this work, we have determined the structure of purified lipopolysaccharides obtained from Xanthomonas axonopodis pv. citri wild type and a mutant of the O-antigen ABC transporter encoded by the wzt gene. High pH anion exchange chromatography and matrix-assisted laser desorption/ionization mass spectrum analysis were performed, enabling determination of the structure not only of the released oligosaccharides and lipid A moieties but also the intact lipopolysaccharides. The results demonstrate that Xac wild type and Xacwzt LPSs are composed mainly of a penta- or tetra-acylated diglucosamine backbone attached to either two pyrophosphorylethanolamine groups or to one pyrophosphorylethanolamine group and one phosphorylethanolamine group. The core region consists of a branched oligosaccharide formed by Kdo2Hex6GalA3Fuc3NAcRha4 and two phosphate groups. As expected, the presence of a rhamnose homo-oligosaccharide as O-antigen was determined only in the Xac wild type lipopolysaccharide. In addition, we have examined how lipopolysaccharides from Xac function in the pathogenesis process. We analyzed the response of the different lipopolysaccharides during the stomata aperture closure cycle, the callose deposition, the expression of defense-related genes, and reactive oxygen species production in citrus leaves, suggesting a functional role of the O-antigen from Xac lipopolysaccharides in the basal response.

Biometry of stomata in Blechnum species (Blechnaceae) with some taxonomic and ecological implications for the ferns.

Morphological stomatal traits, such as size, form and frequency, have been subject of much literature, including their relationships with environmental factors. However, little effort have focused on ferns, and very few in the genus Blechnum. Stomatal length, width and frequency (as stomatal index) of a number of specimens of fourteen Neotropical species of Blechnum were measured in adult pinnae. The aim of the work was to find biometrical relationships between stomatal traits and between stomatal traits and habit, habitat and ecosystem of the plants. Statistical analyses of data were conducted using Exploratory Data Analysis and Multivariate Statistical Methods. Stomatal length and width showed a very high correlation, suggesting an endogenous, genetic control, thus giving these traits a considerable diagnostic utility. With respect to the relationships between stomatal traits and environment, we found significant statistical relationships between altitude and stomatal index. We also addressed the interpretation of the ecological-selective significance of various assemblages of stomatal traits in a diverse conjunction of habits, habitats and ecosystems.

Biometry of stomata in Blechnum species (Blechnaceae) with some taxonomic and ecological implications for the ferns

Morphological stomatal traits, such as size, form and frequency, have been subject of much literature, including their relationships with environmental factors. However, little effort have focused on ferns, and very few in the genus Blechnum. Stomatal length, width and frequency (as stomatal index) of a number of specimens of fourteen Neotropical species of Blechnum were measured in adult pinnae. The aim of the work was to find biometrical relationships between stomatal traits and between stomatal traits and habit, habitat and ecosystem of the plants. Statistical analyses of data were conducted using Exploratory Data Analysis and Multivariate Statistical Methods. Stomatal length and width showed a very high correlation, suggesting an endogenous, genetic control, thus giving these traits a considerable diagnostic utility. With respect to the relationships between stomatal traits and environment, we found significant statistical relationships between altitude and stomatal index. We also addressed the interpretation of the ecological- selective significance of various assemblages of stomatal traits in a diverse conjunction of habits, habitats and ecosystems. Rev. Biol. Trop. 59 (1): 403-415. Epub 2011 March 01.

Los caracteres morfológicos estomáticos, tales como tamaño, forma y frecuencia, han sido objeto de abundante investigación, incluyendo su relación con los factores ambientales. Sin embargo, poco esfuerzo se ha realizado en esta materia en helechos y menos todavía en el género Blechnum. En este trabajo se midieron la longitud, anchura y frecuencia (como índice estomático) de estomas de pinnas adultas de un número de individuos en catorce especies de Blechnum neotropicales. El objetivo fue encontrar relaciones biométricas entre los caracteres estomáticos, y entre los caracteres estomáticos y el hábito, hábitat y ecosistema de las plantas. Se realizaron análisis estadísticos como Análisis Exploratorios de Datos y Métodos Estadísticos Multivariantes. La longitud y la anchura de los estomas mostraron una muy fuerte correlación, sugiriendo un control genético endógeno que otorga a estos caracteres un considerable valor diagnóstico. Con respecto a las relaciones entre los caracteres estomáticos y el ambiente, encontramos una relación estadísticamente significativa entre la altitud y el índice estomático. También se incluyen interpretaciones de la significación ecológico- selectiva de un conjunto de caracteres estomáticos en diferentes conjuntos de hábitos, hábitats y ecosistemas.