Phloem Elements Research Articles

STUDY ON ANATOMICAL CHARACTERIZATIONOF RHINACANTHUS NASUTUS (L.) KURZ

Rhinacanthus nasutus (L.) Kurz, belonging to the family Acanthaceae, is an herbaceous shrub. This plant holds significant value in traditional medicine. The leaves of R. nasutus are commercially available as tea bags, marketed as a natural remedy for various ailments. However, the conservation status of R. nasutus necessitates appropriate protective measures to ensure its sustainability. Anatomical studies provide various histological layers, including the epidermis, cortex, vascular bundles, and pith. The leaves feature numerous diacytic stomata and hypostomatic nature. The leaf midrib exhibits a narrow epidermis with numerous glandular hairs. The medulla contains arc-shaped vascular bundles and lateral accessory bundles, with the stele comprising linear xylem elements towards the inner side and phloem elements on the outer region. Transfusion tracheids are present between the palisade and spongy cells, with tissues containing large quantities of oil droplets. The petiole shows a narrow epidermis with numerous glandular hairs. The vascular region features a V-shaped stele. The stem reveals the stelar region is extensive and the inner region is rich in developed xylem elements with linear multiple vessels. The medullary ray cells are narrow, and the pith region displays intruded primary xylem with thick-walled parenchyma cells. Wood anatomical analysis shows xylem parenchyma cells that are paratracheal. The vessel elements possessing perforation plates and transverse walls with bordered pits. Tracheids have a narrow lumen, and the lateral walls contain simple pits. The wood demonstrates multiseriate ray parenchyma and the bark consists of phloem rays and narrow fibers. In conclusion, R. nasutus exhibits a variety of histological and anatomical characteristics that support its traditional medicinal uses. The detailed anatomical studies contribute to understanding the plants structural adaptations and potential environmental interactions, thereby facilitating its identification and utilization in herbal medicine. The conservation of this species is critical to preserving its medicinal value and ensuring its availability for future research and therapeutic applications.

STUDY ON ANATOMICAL CHARACTERIZATIONOF EXOTIC SPECIES AMHERSTIA NOBILIS WALL

Amherstia nobilis, known as the Pride of Burma and colloquially referred to as Simshipa-vriksham, is a remarkable and rare tropical tree celebrated in Indian mythology, especially within the context of the epic Ramayana. Often dubbed the Queen of Flowering Trees. The species was named in honour of Lady Sarah Amherst, an early collector of Asian plants, and it stands as the sole representative of its genus. This study involves microscopic examination of various parts of the plant, revealing intricate details about its cellular structure, vascular arrangements, and overall morphology. Mature leaves of A. nobilis, for instance, have been analyzed micro-morphologically, with an average leaf area calculated. The leaves are characterized by numerous rubiaceous stomata, as hypostomatic. In the leaf midrib, the vascular area appears oval and vascular elements are U-shaped. The leaf lamina flanked by highly cutinized upper and lower epidermis layers. The palisade tissue is bi-layered, while the lower leaf lamina features loosely packed spongy layers with numerous vein bundles and large air spaces and contains starch grains. Histological examination of the rachis reveals an oval shape with a slightly thick-walled epidermis and hypodermis containing air cavities. The vascular region is well-differentiated withxylem elements in linear multiples. The secondary phloem elementspossess numerous prismatic crystals and patches of phloem fibers. In the mature stem, periderm formation, with a highly reduced cortical region containing chlorenchymatous cells. The vascular region comprises phloem tissues with patches of phloem fibers. The xylem is with large vessels arranged in linear multiples. The pith is highly reduced with included phloem elements. Wood anatomy reveals the vessels displaying paratracheal parenchyma distribution, appearing as aliform or eyelet type. The vessel elements are arranged in linear multiples, and the radial longitudinal section shows large vessel elements with bordered pits separated by end plates. The bark showed uni- and multi-seriate ray cells, long and narrow phloem parenchyma, and prismatic crystal deposits in phloem ray-parenchyma cells. The parenchyma cells are traversed by numerous phloem fibers, with starch granules deposited in phloem parenchyma. In conclusion, Amherstia nobilis, the Pride of Burma, exemplifies a unique combination of aesthetic appeal and complex anatomical structure, making it a subject of significant interest in botanical and horticultural research. Detailed histological and anatomical studies provide crucial insights into the species unique adaptations and structural features, underscoring the need for continued conservation efforts to protect this majestic and rare tropical tree.

Salt stress alters root meristem definition, vascular differentiation and metabolome in Sorghum bicolor (L.) genotypes

Knowledge on salt tolerance requires further investigation, particularly in plants of agro-food interest. Sorghum is a potentially useful plant because it is a emerging food species that combines high levels of salt tolerance with interesting nutritional characteristics. In sorghum different genotypes respond differently to saline stress and the early events characterizing the salt stress tolerance are not yet fully understood. Moreover, the number of salt resistant genotypes needs to be extended. The genotypes Bianca and Tonkawa are two possible candidates for extending sorghum cultivation to soils characterized by high levels of salinity. The root is the first organ that responds to soil conditions, especially during the initial stages of plant developmental. The research aim was to analyse the root system responses to salt stress (NaCl) of Bianca and Tonkawa genotypes to identify the morpho-functional and metabolic changes that occur during the initial stages of the root system development and to use them as discriminating parameters for assessing the different plant’s susceptibility to the salt. The results showed that salt stress negatively affected many morphological and cyto-histological root parameters, from seed germination to root system establishment. The salt altered the root meristem organization and quiescent centre (QC) definition, but similarly in both genotypes. By contrast, it reduced primary root (PR) length and induced a more extended oxidative stress in the adventitious roots (ARs) and lateral root primordia (LRPs) of Tonkawa in comparison with Bianca. The stele area and the number of protoxylem and phloem elements in the ARs were more reduced in 150 mM NaCl-treated Tonkawa seedlings in comparison with those of Bianca. Moreover, the salt enhanced lignin deposition in protoxylem, early metaxylem and endodermis and changed the root metabolic profiles significantly increasing the levels of leucine, isoleucine, alanine, proline, trigonelline, allantoin and glutamine in Bianca compared to Tonkawa. Altogether, specific morpho-anatomical and metabolic differences between the genotypes were identified as discriminating markers of genotype salt susceptibility.

Nano-silicon stabilized biometric and foliar micro-morpho-anatomical traits during in vitro propagation of Cyperus rotundus L. – A model C4 ecotype

Advancements in micropropagation techniques facilitated the incorporation of nanoparticles in the propagation of many commercially important plants. Under in vitro conditions, the adventitious shoots are regenerated with undesirable structural disorders, which increase the rate of mortality of in vitro-produced propagules. In the present study, the effect of Silicon nanoparticles (SiNPs) along with the optimized plant growth regulators (PGRs) in the nutrient medium were tested for their growth-promoting effects on in vitro developing shoots of Cyperus rotundus L. Silicon NPs at 5.0 mg/L induced a higher number of shoots (23 shoots/culture vessel) with improved shoot morphology, rhizogenesis (7.0 roots with 4.0 cm root length), photopigments [(chl a - 474.0 μg/g fresh weight (FW); chl b- 509.0 μg/g FW)] and biomass (3.0 g FW), which were comparatively superior to the morphometric outcomes of the control experiments. The occurrence of morphometric and anatomical disorders in the leaves such as non-functional stomata with increased stomatal density, underdeveloped epidermal cells, undifferentiated costal and intercostal regions, and reduced mesophyll, sclerenchyma, xylem vessels, and phloem elements was observed in the controlled shoots. Silicon NPs at 5.0 mg/L in the medium reduced the in vitro-induced structural abnormalities and modulated foliar micro-morpho-structural differentiation of leaves by promoting positive structural alterations in the leaf thickness, differentiation of dermal tissues, Kranz anatomy, vascularization, stomatal complex, and mechanical tissues. These overall developmentssupported the hardening and survival of plantlets ex vitro. The present findings report the role of SiNPs as the ‘structural stabilizer’ during in vitro plantlet development of C. rotundus, as a target species and representative model for the C4 plants.

Pharmacognostical Evaluation, In-vitro Anti-Inflammatory and Anti-Arthritic Activities of Sageraea laurina Dalzell

Aim: Present investigation performed pharmacognostical evaluation, extraction, and evaluation of anti-inflammatory as well as anti-arthritic activities of Sageraea laurina Dalzell leaves. Materials and methods: Pharmacognostical evaluation was carried out for morphology and microscopy of Sageraea laurina Dalzell leaf and its powder, followed by determination of proximate values. Ethanolic (SLLE) as well as aqueous extract of leaves (SLLA) were evaluated for phytochemical screening, and in-vitro anti-inflammatory activity against MMP-2 (gelatinase-A) along with MMP-9 (gelatinase-B) by gelatin zymography as well as in-vitro anti-arthritic activity by egg albumin protein denaturation approach. Total phenolic as well as flavonoid content of extract were assessed. Percentage inhibition for protein denaturation was calculated. Results: Microscopical study of leaves showed presence of abaxial midrib, palisade parenchyma cells, phloem elements, xylem elements, spongy parenchyma, cystoliths, lithocysts, glandular trichomes, collenchyma cells thick lamina diacytic type of stomata and vessel elements. Phytochemical screening divulged existence of carbohydrates, flavonoids, steroids, alkaloids, saponin glycosides, tannins and phenolic compounds. Copious of phenolic compounds were noted in SLLE which were 89.42mg gallic acid equivalent/g (GAE/g dry weight) along 86.21mg QUE/g quercetin equivalent /g (QUE/g dry weight). Coomasie blue staining revealed proteolysis sites as translucent bands on dark blue background. Percentage inhibition for anti-inflammatory activity for SLLE against MMP-2 and MMP-9 was found to be 62% and 56% respectively, for SLLA against MMP-2 and MMP-9 was found to be 34% and 32% respectively. Egg albumin denaturation method, displayed percentage inhibition at concentration of 500µg/ml for SLLE and SLLA 74.14 and 60.30 respectively, standard drug diclofenac sodium at same concentration was found to be 84.53%. It was found that SLLE was more potent in inhibition of egg albumin denaturation than diclofenac sodium. Conclusion: Findings of present investigation revealed possession of significant in-vitro anti-inflammatory and antiarthritic activities by Sageraea laurina Dalzell leaves and serves as a natural biomedicinal remedial agent treating inflammation and rheumatism.

Ontogeny of interxylary phloem and stem anatomy of the Cuban endemic Henleophytum (Malpighiaceae)

Lianas and vascular variants have long been correlated since it is in lianas where they are most commonly found. Structurally, these vascular variants mix soft and stiff tissues allowing lianas to twist without breaking when climbing up to the forest canopies. The study of vascular variants in Malpighiaceae lianas has a long history focusing on species-diverse taxa; however, interest in understanding them in understudied, smaller taxa has unraveled vascular variants previously unknown to the family, such as the interxylary phloem of Henleophytum, a Cuban endemic, monospecific genus. Interxylary phloem in Malpighiaceae had been previously recorded in the distantly related genera Dicella, Niedenzuella, and Tristellateia. Interxylary phloem in Henleophytum derives from a cambium that in certain periods and sites produces phloem both inward and outward, similar to the pattern described for Dicella. The phloem produced outward is not equal to that produced inward. Indeed, sieve tube elements of the inner phloem are always much wider and more abundant, something likely indicative of a division of labor between both phloem types, one specializing in conduction and the other in carbohydrate storage. This constitutes a new report of a vascular variant outside the large Tetrapteroid clade, where almost all the vascular variants have been reported for the family so far, and supports the idea of the independent, multiple origins of vascular variants in Malpighiaceae.

Comparative study on root anatomy of six species of Himalayan Dendrobium Swartz

Comprehensive knowledge of plant anatomy is an absolute necessity for accurately identifying taxa during their vegetative phase. Orchidaceae family has been extensively studied in the Himalayan region, with a focus on morphology and floristics. However, the anatomy of orchid roots has not been investigated in detail. This study examines the root anatomy of six Himalayan Dendrobium species (D. chrysanthum, D. densiflorum, D. longicornu, D. nobile, D. rotundatum, and D. transparens) using standard plant anatomy techniques. Qualitative and quantitative traits were observed and analysed, including the multi-layered velamen, stele and cortical tissue area, and number of xylem strands, which are distinct characteristics of genus Dendrobium. ANOVA and Tukey's test at 5% significance level were used to quantitatively examine cross-sections of the roots and identify significant differences. All six studied taxa possess velamen tissues with cells having spirally thickened walls, and a single-layered exodermis with cells of varying sizes. The cortex was multi-layered and contained parenchymatous water-storage cells, while a uniseriate endodermis with passage cells were observed. D. chrysanthum and D. rotundatum had xylem and phloem elements embedded in parenchymatous tissues, whereas D. densiflorum, D. longicornu, D. nobile, and D. transparens had xylem and phloem elements embedded in sclerenchymatous tissues. Cell sizes in different root tissues varied significantly. A dichotomous key based on the root anatomical traits for the identification of these Dendrobium species is provided. Future research is suggested to explore additional parameters and to conduct experiments to understand its anatomical response to epiphytism.

Effects of Phosphorus Deficiency on Ion Transport And Its Anatomical Relation in Mung Bean (Vigna Radiata L.)

Effects of phosphorus deficiency on ion transport and its relation with anatomical structure in mungbean plants were investigated. Phosphorous deficiency caused an increase in the accumulation of K+ in the root and a decrease in the stem and leaf of mungbean seedlings grown in solution culture. Na+ and NO3 - accumulation was increased in the root, stem and leaf of P-deficient plant. On the contrary, accumulation of PO4 3- was decreased in root, stem and leaf under P-deficiency treatment. The diameter of root was decreased under phosphorus deficiency. Vascular area was found to decrease and occupied less area with smaller size of metaxylem cavity in the root and stem of mungbean plant. In phosphorus deficient plant, phloem elements were poorly developed and occupied smaller area. Bangladesh J. Bot. 52(2): 381-387, 2023 (June)

Formation of inter-and intraxylary phloem in some species of Argyreia Lour. (Convolvulaceae)

The development of inter-and intraxylary phloem was investigated in nineteen species of Argyreia Lour. Among all species, differentiation of intraxylary protophloem was observed concomitant to the regular external protophloem from the procambial derivatives (except A. nervosa). However, A. nervosa, showed the formation of medullary bundles along with the regular protoxylem while the development of intraxylary phloem was observed only after the establishment of a complete ring of the vascular cambium and deposition of a few secondary xylem elements. In all the species (except A. nervosa), additional intraxylary phloem differentiated from the adjacent parenchyma and the intraxylary cambium initiated at the periphery of the pith. It divided uni-directionally and showed deposition of only phloem elements. In the transverse view, sieve elements of intraxylary phloem were oval to circular, rectangular, or multi-angled or sometimes in a cluster of three to several cells with simple and compound sieve plates oriented obliquely on their terminal ends. In the thick stems of A. cuneata, A. elliptica, A. lawii, A. mastersii, A. nervosa, A. sericea, A. sharadchandrajii and A. splendens, thin-walled unlignified axial parenchyma strands embedded within the secondary xylem divide and differentiated into isolated or groups of interxylary phloem elements. In the transverse view, these sieve elements were like regular phloem (oval to circular) in appearance but occasionally they may be narrow in diameter, tangentially flattened and arranged in clusters. In thick stems, earlier-formed sieve elements of the interxylary phloem collapse and get crushed due to the expansion of adjacent cells. The remaining species though showed the presence of parenchyma strands within the secondary xylem, no interxylary phloem was observed even in thick stems. Such parenchyma cells within islands always showed the presence of druses.

Nectar guides and floral nectary in Lamium album L. subsp. album: structure and histochemistry in light, fluorescence, and electron microscopy

Lamium album is a native common plant growing in Eurasia. It is used in medicine and cosmetics and is highly valued in apiculture. The aim of the study was to investigate the structure of the floral nectary in three stages of flower development. Additionally, histochemical studies of the nectary and nectar guides present on the lower corolla lobe were carried out. No detailed analyses of nectary tissues in this species have been conducted to date. The present analyses were performed with the use of light, fluorescence, and scanning electron microscopy. The nectary gland in the flowers of Lamium album subsp. album formed an incomplete ring at the ovary base. The nectarostomata were arranged in clusters only in the adaxial epidermis of the anterior part of the nectary. During the secretory activity of the nectary (1st day of flowering), numerous small vacuoles and cells with large lobulate nuclei with surrounding plastid clusters were observed in the epidermis and glandular parenchyma cells. The vascular bundles contained xylem and phloem elements. Corolla wilting (3rd day of flowering) was accompanied by destructive changes in the nectary parenchyma, leading to the formation of empty spaces and appearance of cell remnants on the nectary surface. The histochemical analyses revealed the presence of starch and phenolic compounds as well as acidic and neutral lipids, which are characteristic of essential oils, in the nectary tissues. The nectar guides were composed of large yellow papillae containing phenolic compounds and acidic and neutral lipids, which were also present in glandular trichomes and abaxial parenchyma cells. The present study has demonstrated that the scent of Lamium album subsp. album flowers is produced with the involvement of essential oils contained in adaxial and abaxial epidermis cells, glandular trichomes, and nectary tissues.

Complexity untwined: The structure and function of cucumber (Cucumis sativus L.) shoot phloem.

Cucurbit phloem is complex, with large sieve tubes on both sides of the xylem (bicollateral phloem), and extrafascicular elements that form an intricate web linking the rest of the vasculature. Little is known of the physical interconnections between these networks or their functional specialization, largely because the extrafascicular phloem strands branch and turn at irregular angles. Here, export in the phloem from specific regions of the lamina of cucumber (Cucumis sativus L.) was mapped using carboxyfluorescein and 14 C as mobile tracers. We also mapped vascular architecture by conventional microscopy and X-ray computed tomography using optimized whole-tissue staining procedures. Differential gene expression in the internal (IP) and external phloem (EP) was analyzed by laser-capture microdissection followed by RNA-sequencing. The vascular bundles of the lamina form a nexus at the petiole junction, emerging in a predictable pattern, each bundle conducting photoassimilate from a specific region of the blade. The vascular bundles of the stem interconnect at the node, facilitating lateral transport around the stem. Elements of the extrafascicular phloem traverse the stem and petiole obliquely, joining the IP and EP of adjacent bundles. Using pairwise comparisons and weighted gene coexpression network analysis, we found differences in gene expression patterns between the petiole and stem and between IP and EP, and we identified hub genes of tissue-specific modules. Genes related to transport were expressed primarily in the EP while those involved in cell differentiation and development as well as amino acid transport and metabolism were expressed mainly in the IP.

The Physiological and Biochemical Effects on Napier Grass Plants Following Napier Grass Stunt Phytoplasma Infection

Napier grass stunt (NGS) phytoplasma, a phloem-limited bacterium, infects Napier grass leading to severe yield losses in East Africa. The infected plants are strongly inhibited in growth and biomass production. In this study, phytoplasma-induced morphological changes of the vascular system and physiological changes were analyzed and compared with uninfected plants. The study showed that the phytoplasmas are more abundant in source leaves and range from 103 bacteria/μg total DNA in infected roots to 106 in mature Napier grass leaves. Using microscopical, biochemical, and physiological tools, we demonstrated that the ultrastructure of the phloem and sieve elements is severely altered in the infected plants, which results in the reduction of both the mass flow and the translocation of photoassimilates in the infected leaves. The reduced transport rate inhibits the photochemistry of photosystem II in the infected plants, which is accompanied by loss of chloroplastic pigments in response to the phytoplasma infection stress eventually resulting in yellowing of diseased plants. The phytoplasma infection stress also causes imbalances in the levels of defense-related antioxidants, glutathione, ascorbic acid, reactive oxygen species (ROS), and-in particular-hydrogen peroxide. This study shows that the infection of NGS phytoplasma in the phloem of Napier grass has an impact on the primary metabolism and activates a ROS-dependent defense response.

Morphoanatomy of three Indigofera species (Leguminosae-Papilionoideae) in Java, Indonesia

Abstract. Fugarasti H, Muzzazinah, Ramli M. 2020. Morphoanatomy of three Indigofera species (Leguminosae-Papilionoideae) in Java Indonesia. Biodiversitas 21: 5531-5538. This study aimed to explore the morphological and detailed anatomical features of the stems, leaves, and roots from three Indonesian Indigofera species. Morphological-anatomical studies of three Indonesian Indigofera species were carried out using embedded microscopic preparations. The anatomical characters of the specimens were observed using a compound optical microscope with magnification 40x, 100x, and 400x. The observation showed the anatomical cross-section of I. tinctoria stem was rectangular, I. suffruticosa was hexagonal, and I. arrecta was rounded. The tissue structures of Indigofera species, from the outside layer, were the epidermis, thin cortex, secondary phloem (narrow or wide), thick secondary xylem, and conspicuous pith in the middle. Whilst, the corner of I. suffruticosa stem contained thick collenchyma. The vascular bundles were the open collateral. The leaves of Indigofera species are made up of the upper epidermis, mesophyll (palisade parenchyma, spongy parenchyma), and the lower epidermis. The vascular bundles were located in the middle, with five or six segments of the xylem elements and small groups of phloem elements, all in the parallel lines. The primary stele type of the roots is actinostele, cambium activity pushed him aside. The vascular bundle of the roots consisted of a dense and tight secondary xylem composed of thick-walled circular vessels (mostly tightly arranged). Data about the morphoanatomy structure of three Indonesian Indigofera species could complement the novelty of the morpho-anatomy information records obtained by previous researchers.

Pharmacognostic characteristics and phytochemical profile of various parts of Parthenium hysterophorus

Parthenium hysterophorus L. (Congress grass, family Asteraceae) is found throughout the global agricultural and vacant lands. In the present work, the pharmacognostic, pharmacological and allelopathic traits of various parts (root, stem and leaves) of P. hysterophorus grown in Pakistan were investigated. P. hysterophorus growing/flowering season starts from March–April till August–September. The plant has tap root with numerous rootlets and root hairs. Stem is straight, with light groove, covered with hairs and numerous profusely branches, wherein the stem reaches up to 150 cm in height. The leaves are simple, dull green in color, alternate, leaflets with profusely dissected regions and hairs are present on the lower surface of leaf. Transverse section (TS) of root revealed epidermis, cortex, endodermis, xylem, phloem and medullary rays running from endodermis towards the center. TS of stem was circular in outline with shallow ridges covered with hairs. TS of leaf consisted of epidermis, which is intermitted by simple, glandular, branched and multicellular trichomes. Powder drug microscopy of roots revealed the presence of epidermal cell, phloem elements, fiber, cluster/group of fibers, root hairs, xylem vessels and medullary rays. The stem powder drug microscopy showed the presence of trichomes, fibers, parenchymatous cells, lignified vessel, group/cluster of vessels, secretory gland with epidermal cells, prismatic crystal of Ca oxalate and phloem elements with parenchyma cells. Phytochemical screening of diethyl ether, ethanol and aqueous extracts of root, stem and leaves showed the presence of amino acids, fixed oils, alkaloids, flavonoids, phenols, carbohydrates, proteins and triterpenoids, while steroidal glycosides, gum and mucilage were absent in all plant parts. Chemical composition showed that moisture, lipids, protein contents and total gross energy were higher in plant grown in summer season as compared to winter season. On the other hand, ash, fibers and carbohydrate contents were higher in winter and declined in summer season.

Changing Host Photosynthetic, Carbohydrate, and Energy Metabolisms Play Important Roles in Phytoplasma Infection.

Phytoplasmas parasitize plant phloem tissue and cause many economically important plant diseases. Jujube witches'-broom disease is a destructive phytoplasma disease of Chinese jujube (Ziziphus jujuba). To elucidate the influence of phytoplasma on host photosynthetic, carbohydrate and energy metabolisms, four types of jujube tissues showing disease symptoms with different severity were investigated at the structural, physiological, and molecular levels. Quantitative real-time PCR and high-performance liquid chromatography results showed that the down-regulation of genes related to photosynthesis and the lower contents of chlorophyll in diseased leaves. This clearly inhibited the light-harvesting and photosystem II activity of photosynthesis; however, overexpression of genes related to starch, sucrose and glucose synthesis led to higher contents of these carbohydrates. Meanwhile, transmission electron microscopy images revealed that dense amounts of phytoplasmas accumulated in the sieve elements of diseased petiole phloem, and the structure of the grana and stroma lamellae of chloroplasts in the diseased leaves was destroyed. Phytoplasma infection inhibited photosynthesis and led to abnormal carbohydrate accumulation in the diseased leaves. Furthermore, comparative metabolite analysis indicated that phytoplasma infection also stimulated amino acids and energy metabolisms of the diseased leaves. Continually inhibiting the photosynthetic process and stimulating carbohydrate and energy metabolisms of diseased trees may exhaust their nutrients. Our results highlight the importance of changing host metabolisms during the pathogenic process.

Flower vascularization and fruit developmental anatomy of quinoa (Chenpodium quinoa Willd) Amaranthaceae

The floral anatomical structural and developmental features of seeds and fruits of quinoa (Chenpodium quinoa Willd) cv. Hualhuas were studied using light microscope with the purpose to elucidate their structure and to contribute ecological studies of the species. The plants produce panicle inflorescences having hermaphrodite and pistillate flowers. The hermaphrodite flower possesses: 5 imbricate sepals; 5 antisepalous stamens; its filaments extend laterally forming a ring of nectariferous tissue surrounding the ovary having modified stomata. The gynoecium is bicarpellate with unilocular ovary having a single campylotropus ovule. The basal part of the ovary contains two dorsal carpellary bundles one is small towards the posterior side the other is large towards the anterior side. Whereas the ventral carpellary bundles of the two carpels occurring in the center of the ovary base and consist the vascular supply of the ovule. The dorsal posterior bundle terminates with the appearance of the locule. The ovule attach with the basal placenta on the anterior side of the ovary. The posterior carpel is sterile and reduced whereas the anterior one is fertile. The nutrients movement into the seed takes place through the high selectivity phloem elements embedded in the vascular strand of the funiculus. The collapsed outer layer of the pericarp in mature fruit could reshaped and regain turgor pressure after soaking in water, this may help for rapid germination. Although quinoa has thin seed coat layers however it have thick cell walls could maintain the moisture of embryo and perisperm and increase seed hardness as response to the arid habitats.

Regulatory networks controlling the development of the root system and the formation of lateral roots: a comparative analysis of the roles of pericycle and vascular cambium.

The production of a new lateral root from parental root primary tissues has been investigated extensively, and the most important regulatory mechanisms are now well known. A first regulatory mechanism is based on the synthesis of small peptides which interact ectopically with membrane receptors to elicit a modulation of transcription factor target genes. A second mechanism involves a complex cross-talk between plant hormones. It is known that lateral roots are formed even in parental root portions characterized by the presence of secondary tissues, but there is not yet agreement about the putative tissue source providing the cells competent to become founder cells of a new root primordium. We suggest models of possible regulatory mechanisms for inducing specific root vascular cambium (VC) stem cells to abandon their activity in the production of xylem and phloem elements and to start instead the construction of a new lateral root primordium. Considering the ontogenic nature of the VC, the models which we suggest are the result of a comparative review of mechanisms known to control the activity of stem cells in the root apical meristem, procambium and VC. Stem cells in the root meristems can inherit various competences to play different roles, and their fate could be decided in response to cross-talk between endogenous and exogenous signals. We have found a high degree of relatedness among the regulatory mechanisms controlling the various root meristems. This fact suggests that competence to form new lateral roots can be inherited by some stem cells of the VC lineage. This kind of competence could be represented by a sensitivity of specific stem cells to factors such as those presented in our models.

Identification of Passiflora spp. genotypes resistant to Cowpea aphid-borne mosaic virus and leaf anatomical response under controlled conditions

Abstract Passion fruit woodiness caused by the Cowpea aphid-borne mosaic virus (CABMV) is one of the main problems associated with the cultivation of passion fruit in Brazil. Identifying sources of resistance in Passiflora collections is the first step to develop resistant varieties. The objective of this study was to screen some Passiflora genotypes for CABMV resistance, as well as to evaluate foliar anatomical aspects associated with this viral infection. Eighty genotypes belonging to 12 Passiflora species were evaluated in a completely randomized block design with treatment in a factorial scheme (80 genotypes × 7 evaluations). Artificial inoculation with CABMV was performed twice every four days. At 55 days after inoculation (DAI), the symptoms were evaluated through a scale of scores, which was then used to estimate the severity based on the disease index (DI%). The DI values for the different genotypes were grouped using the Scott-Knott test (p ≤ .05) and multivariate analysis. The viral infections were confirmed by RT-PCR analysis. The genotypes BGP014, BGP112, BGP134, BGP143, BGP152, BGP170, BGP238, BGP077 and BGP413, belonging to the species Passiflora suberosa, P. malacophylla, P. setacea, and P. cincinnata, were considered resistant (0.00% DI). The disease caused by CABMV was more drastic in P. edulis, resulting in changes in the constitution and organization of vascular bundles of the leaf blade, with irregular arrangement of xylem and phloem elements, as well as spongy parenchyma cell hypertrophy. The wild species presented minor anatomical foliar alterations after inoculation with CABMV, particularly P. suberosa, P. setacea, and P. malacophylla, which did not present any changes after inoculation. The difference in the severity of CABMV among genotypes for resistance to the CABMV opens new perspectives for crossing these genotypes as parents in order to incorporate resistance to CABMV in passion fruit.

A structural review of foliar glands in Passiflora L. (Passifloraceae).

Extrafloral glands in Passifloraceae species have aroused the interest of many researchers because of their wide morphological diversity. The present work analyzed the foliar glands on 34 species of Passiflora from samples containing glands in the petiole and foliar blade fixed in 50% solution of formaldehyde-ethanol-acetic acid and stored in a 70% ethanol solution. For anatomical analyses, part of the material was embedded in Paraplast, longitudinally sectioned and double stained with safranin and astra blue. Scanning electron microscopy analysis was also carried out. To analyze the presence of sugars in the secretion of foliar glands, a glucose strip test was used. Based on the results of morphological, anatomical and glucose strip tests, the foliar secretory glands in Passiflora can be grouped into two categories: Type I glands, defined as nectaries, can be elevated or flattened, and can have a sugar content high enough to be detected by the glucose strip test analysis. Type II glands are elevated and did not show a positive reaction to the glucose strip test. From an anatomical viewpoint, glands characterized as extrafloral nectaries show a multistratified secretory epidermis, typically followed by two flat layers of nectariferous parenchyma with dense content. Internal to these layers, vascular bundles are immersed in the subsecretory parenchyma and terminate in phloem cells. On the other hand, type II glands show a single layer of elongated secretory epidermal cells. Internal to this single layer, parenchyma and vascular tissue with both phloem and xylem elements can be observed. The analyzed species show a wide diversity of gland shape and distribution, and the combined analysis of morphology, anatomy and preliminary tests for the presence of glucose in the exudate in different Passiflora subgenera suggests the occurrence of two categories of glands: nectaries and resin glands.

Sugary secretions of wasp galls: a want-to-be extrafloral nectar?

The most widespread form of protective mutualisms is represented by plants bearing extrafloral nectaries (EFNs) that attract ants and other arthropods for indirect defence. Another, but less common, form of sugary secretion for indirect defence occurs in galls induced by cynipid wasps. Until now, such galls have been reported only for cynipid wasps that infest oak trees in the northern hemisphere. This study provides the first evidence of galls that exude sugary secretions in the southern hemisphere and asks whether they can be considered as analogues of plants' EFNs. The ecology and anatomy of galls and the chemical composition of the secretion were investigated in north-western Argentina, in natural populations of the host trees Prosopis chilensis and P. flexuosa . To examine whether ants protect the galls from natural enemies, ant exclusion experiments were conducted in the field. The galls produce large amounts of sucrose-rich, nectar-like secretions. No typical nectary and sub-nectary parenchymatic tissues or secretory trichomes can be observed; instead there is a dense vascularization with phloem elements reaching the gall periphery. At least six species of ants, but also vespid wasps, Diptera and Coleoptera, consumed the gall secretions. The ant exclusion experiment showed that when ants tended galls, no differences were found in the rate of successful emergence of gall wasps or in the rate of parasitism and inquiline infestation compared with ant-excluded galls. The gall sugary secretion is not analogous to extrafloral nectar because no nectar-producing structure is associated with it, but is functionally equivalent to arthropod honeydew because it provides indirect defence to the plant parasite. As in other facultative mutualisms mediated by sugary secretions, the gall secretion triggers a complex multispecies interaction, in which the outcome of individual pair-wise interactions depends on the ecological context in which they take place.