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.

Investigations on the morpho-anatomy and histochemistry of Aconitum napellus L.

Aconitum napellus L. is a popular medicinal plant extensively used in homeopathy. This article provides detailed morphology and microscopy, including the anatomical and histochemical features of the herb, to aid authentication and quality control. In cross-section, the root in secondary growth shows the phloem surrounded by pericyclic fibers and a well-developed xylem. The stem is irregular in outline, displaying unicellular trichomes and many free collateral vascular bundles encircling the pith. The leaf is dorsiventral, hypostomatic with anomocytic and anisocytic stomata, and shows non-glandular trichomes. The floral parts are characterized by uniseriate epidermises, homogeneous mesophyll, anomocytic stomata on the abaxial surface, trichomes, and oval pollen grains. The tissue fragments in powdered herbs show these characteristics and have numerous starch grains with thimble-shaped, linear or star-shaped hilum. The detailed macroscopic and microscopic analysis provided in this study can help in the authentication and quality control of A. napellus raw materials. RESEARCH HIGHLIGHTS: Key anatomical, micromorphological, and microchemical features of Aconitum napellus are described. The results of the study can support the taxonomy of the genus Aconitum. Morphological standardization of the species reported here is helpful in the quality control of this herb.

Leaf and stem micromorphology of Byrsonima sericea DC. by light and scanning electron microscopy.

Micromorphological studies were carried out using multiple microscopic techniques on the leaves and stem bark of Byrsonima sericea DC. (Malpighiaceae), a species popularly known as "murici" and used medicinally, in order to identify both qualitative and quantitative features of leaf and stem anatomy and histochemistry as differential parameters to support both the quality control of its ethnodrugs and the taxonomy of the genus. The study was conducted using traditional techniques of plant anatomy, histochemical tests, and the stomatal index (SI). Byrsonima sericea has hypostomatic leaves, anomocytic stomata, and its epidermal walls are anticlinal and straight on the adaxial and curved on the abaxial faces. T-shaped trichomes were observed mainly on the abaxial surface. The leaf epidermis showed waxes syntopism on both surfaces, with the occurrence of different crystalloid forms on a single phylloplane. The mesophyll is dorsiventral, with 3-4 collateral vascular bundles. Phenolic compounds, starch, and proteins were identified in the petiole and stem. The SI was 14.5 ± 0.53% (p < .05), but did not showed significant variations. A set of characters were found to be distinctive for the studied species, however, constituting parameters that could be used to separate B. sericea from other species of the genus.

Foliar anatomy and microscopy of six Brazilian species of Baccharis (Asteraceae).

We report for the first time the presence of cluster crystals of calcium oxalate within the glandular trichomes and oil bodies in the mesophyll for Baccharis species. Moreover, the comparative leaf anatomy and micro-morphology of six species of Baccharis, namely B. illinita, B. microdonta, B. pauciflosculosa, B. punctulata, B. reticularioides, and B. sphenophylla is investigated by light and scanning electron microscopy. The studied species exhibited differences in their leaf anatomical features such as the morphology of the cuticle, type and occurrence of the stomata, presence or absence of glandular trichomes, shape of the flagelliform trichomes, and the arrangement of the mesophyll tissues. These differences can be helpful in the species identification and classification and could represent informative characters for the reconstruction of the evolution of the genus.

Perianth organs in Nymphaeaceae: comparative study on epidermal and structural characters.

The perianth organs of six species of Nymphaeaceae, representing Euryale, Nymphaea and Victoria, were studied on the basis of macroscopical, micromorphological, and anatomical characters. The aims were to determine whether perianth is differentiated among tepal whorls considering the presence of sepaloid and petaloid characters, and to evaluate the occurrence of both features in individual tepals. Selected perianth series were examined macroscopically, with light microscopy, and scanning electron microscopy. Osmophores were detected using neutral red and Sudan. In all tepals examined, stomata and hydropotes were present on the abaxial and adaxial surfaces. These are anomocytic or stephanocytic; hydropotes of irregular type are also present. The outer series of tepals display morpho-anatomical characters in most part related with photosynthetic and protective functions. Osmophore activity is very scarce and petaloid epidermal morphology is present only in N. lotus, thus allowing interpretation of this whorl as primarily sepaloid. The second series exhibits both petal-like and sepal-like characters; in N. amazonum and N. gardneriana sepaloid and petaloid group of cells are present on the abaxial surface of individual tepals. Therefore, this whorl is transitional between the outer and the innermost ones. Both the morpho-anatomy and presence of osmophore activity indicate that the innermost series is entirely petaloid. Inner tepals of E. ferox, N. alba, and V. cruziana share the presence of epidermal cells with predominantly smooth cuticle, whereas those of N. amazonum, N. gardneriana, and N. lotus share a cuticular ornamentation consisting of numerous papillae on each cell. Morphological characters of the perianth epidermis are in some respects congruent with the molecular phylogeny of Nymphaeaceae. Our results support the co-expression of sepaloidy and petaloidy within individual tepals and the mosaic model of perianth evolution proposed for the angiosperms.

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.

Morphological features of different polyploids for adaptation and molecular characterization of CC-NBS-LRR and LEA gene families in Agave L.

Polyploidy has been widely described in many Agave L. species, but its influence on environmental response to stress is still unknown. With the objective of knowing the morphological adaptations and regulation responses of genes related to biotic (LEA) and abiotic (NBS-LRR) stress in species of Agave with different levels of ploidy, and how these factors contribute to major response of Agave against environmental stresses, we analyzed 16 morphological trials on five accessions of three species (Agave tequilana Weber, Agave angustifolia Haw. and Agave fourcroydes Lem.) with different ploidy levels (2n=2x=60 2n=3x=90, 2n=5x=150, 2n=6x=180) and evaluated the expression of NBS-LRR and LEA genes regulated by biotic and abiotic stress. It was possible to associate some morphological traits (spines, nuclei, and stomata) to ploidy level. The genetic characterization of stress-related genes NBS-LRR induced by pathogenic infection and LEA by heat or saline stresses indicated that amino acid sequence analysis in these genes showed more substitutions in higher ploidy level accessions of A. fourcroydes Lem. 'Sac Ki' (2n=5x=150) and A. angustifolia Haw. 'Chelem Ki' (2n=6x=180), and a higher LEA and NBS-LRR representativeness when compared to their diploid and triploid counterparts. In all studied Agave accessions expression of LEA and NBS-LRR genes was induced by saline or heat stresses or by infection with Erwinia carotovora, respectively. The transcriptional activation was also higher in A. angustifolia Haw. 'Chelem Ki' (2n=6x=180) and A. fourcroydes 'Sac Ki' (2n=5x=150) than in their diploid and triploid counterparts, which suggests higher adaptation to stress. Finally, the diploid accession A. tequilana Weber 'Azul' showed a differentiated genetic profile relative to other Agave accessions. The differences include similar or higher genetic representativeness and transcript accumulation of LEA and NBS-LRR genes than in polyploid (2n=5x=150 and 2n=6x=180) Agave accessions, thus suggesting a differentiated selection pressure for overcoming the lower ploidy level of the diploid A. tequilana Weber 'Azul'.

Microscopic Aspects of Silicon-Mediated Rice Resistance to Leaf Scald.

This study investigated the effect of silicon (Si) on the potentiation of rice resistance against leaf scald at the microscopic level. Rice plants ('Primavera') were grown in a nutrient solution containing 0 (-Si) or 2 mM (+Si) Si. The foliar Si concentration of the +Si plants (3.6 dag/kg) increased in comparison with the -Si plants (0.3 dag/kg). An X-ray microanalysis revealed that the leaf tissue of +Si plants infected with Microdochium oryzae had higher peaks and deposition of insoluble Si than that of -Si plants. The high foliar Si concentration for the +Si plants reduced the expansion of leaf scald lesions. Scanning electron microscopy revealed that fungal hyphae and appressorium-like structures of M. oryzae were more abundant in the leaf surface of -Si plants relative to +Si plants. At both histopathological and ultrastructural levels, fungal hyphae grew abundantly into the leaf tissue of -Si plants. By contrast, rice cell walls were rarely degraded and fungal hyphae were often surrounded by amorphous granular material in the leaf tissue of +Si plants. Conidiophores emerged from stomata 36 h after fungal penetration, and conidia were noticed inside the leaf tissue of the -Si plants in great abundance. The collective results of the present study showed a high concentration and deposition of Si and a considerable deposition of phenolic-like compounds in the leaf tissue of +Si plants. These results indicate that the potentiation of the phenylpropanoid pathway in these plants supplied with Si was favorable for the increase in rice resistance to leaf scald.

Microscopic characters of the leaf and stem of Lavandula dentata L. (Lamiaceae).

Lavandula dentata L. is an aromatic plant used in folk medicine for different purposes and, for this reason, phytochemical surveys have been carried out in the search for bioactive substances aiming to support its uses. Since there is little knowledge on the structural aspects of L. dentata, this work has studied the anatomical characters of the leaf and stem using light and scanning electron microscopy, in order to assist the species identification. As a result, there are different types of trichomes: capitate glandular with uni- or bicellular head, peltate glandular with multicellular head, and branched non-glandular. The leaf is hypostomatic showing diacytic stomata. The epidermis is uniseriate and coated with striate cuticle. The mesophyll is dorsiventral and the midrib is concave-convex and traversed by a single collateral vascular bundle. The stem is quadrangular and has alternating strands of collenchyma and cortical parenchyma as well as a typical endodermis in the cortex. The phloem and xylem cylinders are traversed by narrow rays and there is an incomplete sclerenchymatic sheath adjoining the phloem. These results are a novelty for the species and contribute to distinguish it from other lavenders.