Beatriz Appezzato-da-Glória

Characterization of electrical penetration graphs of the Asian citrus psyllid, Diaphorina citri, in sweet orange seedlings.

Detailed information on probing behavior of the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is critical for understanding the transmission process of phloem‐limited bacteria (Candidatus Liberibacter spp.) associated with citrus ‘huanglongbing’ by this vector. In this study, we investigated stylet penetration activities of D. citri on seedlings of Citrus sinensis (L.) Osbeck cv. Pêra (Rutaceae) by using the electrical penetration graph (EPG‐DC system) technique. EPG waveforms were described based on amplitude, frequency, voltage level, and electrical origin of the observed traces during stylet penetration into plant tissues. The main waveforms were correlated with histological observations of salivary sheath termini in plant tissues, to determine the putative location of stylet tips. The behavioral activities were also inferred based on waveform similarities in relation to other Sternorrhyncha, particularly aphids and whiteflies. In addition, we correlated the occurrence of specific waveforms with the acquisition of the phloem‐limited bacterium Ca. Liberibacter asiaticus by D. citri. The occurrence of a G‐like xylem sap ingestion waveform in starved and unstarved psyllids was also compared. By analyzing 8‐h EPGs of adult females, five waveforms were described: (C) salivary sheath secretion and other stylet pathway activities; (D) first contact with phloem (distinct from other waveforms reported for Sternorrhyncha); (E1) putative salivation in phloem sieve tubes; (E2) phloem sap ingestion; and (G) probably xylem sap ingestion. Diaphorina citri initiates a probe with stylet pathway through epidermis and parenchyma (C). Interestingly, no potential drops were observed during the stylet pathway phase, as are usually recorded in aphids and other Sternorrhyncha. Once in C, D. citri shows a higher propensity to return to non‐probing than to start a phloem or xylem phase. Several probes are usually observed before the phloem phase; waveform D is observed upon phloem contact, always immediately followed by E1. After E1, D. citri either returns to pathway activity (C) or starts phloem sap ingestion, which was the longest activity observed.

Comparative leaf morphology and anatomy of three Asteraceae species

ABSTRACT The objective of this paper was to describe and compare the morphology and anatomy of mature leaves of Mikania glomerata Spreng., Porophyllum ruderale Cass. and Vernonia condensata Baker (Asteraceae) species that have different habits emphasizing their secretory structures. Longitudinal and transversal sections of mature leaf blades of the three species were analyzed at the apex, base, and medium third part of the midvein of the leaf blade and of the margin. M. glomerata had uniseriate glandular trichomes and secretory ducts; P. ruderale had hydathodes and secretory cavities; and V. condensata had idioblasts and uni- and biseriate glandular trichomes. Key words: Mikania glomerata, Porophyllum ruderale, Vernonia condensata, secretory structures, medicinal plants * Author for correspondence INTRODUCTION The Asteraceae family consists of approximately 25000 species (Barroso, 1986) included in over 1100 genera. These species frequently present herbaceous habits, although arboreous and voluble herbaceous habits also occur (Cronquist, 1981). Because of this variety of habits, the family presents various anatomical structures and in some cases ecological specialization may occur (Metcalfe and Chalk, 1950). Secretory structures are of great taxonomical interest and their restricted distribution has an important diagnosis value (Metcalfe and Chalk, 1950; Fahn, 1979). Frequently, in Asteraceae, they occupy distinct positions in different organs of the plant occurring in all, some or in only one organ (Solereder, 1908). Castro et al. (1997) reviewed the types of secretory structures in the leaves of seventy two representatives of the Asteraceae family from the cerrado vegetation in the Reserva Biologica de Mogi Guacu, Sao Paulo, Brazil. When analyzed together these secretory structures presented diagnosis value at genus level. Eight types of leaf secretory structures were mentioned: ducts, cavities, idioblasts, laticifers, hydathodes, extrafloral nectaries, trichomes and glandular appendixes. According to Metcalfe and Chalk (1950), anatomical diversity is commonly observed in the structure of leaves of species belonging to the Asteraceae. Among the features that vary are: (a) stomata distribution on leaf surfaces; (b) guard-cell positioning in relation to ordinary epidermal cells; (c) hypoderm development on the upper side of the leaf surface; (d) mesophyll and fibrovascular system differentiation; and (e) wax secretion on leaf surface (Solereder, 1908). The anatomical features that can be observed in Asteraceae are: (a) presence of various types of glandular or covering trichomes; (b) papillae on

In vitro shoot regeneration from roots and leaf discs of Passiflora cincinnata mast.

Different concentrations of 6-benzyladenine (6-BA) were used in vitro to induce buds in three types of explants: leaf discs, root segments and the seedling itself obtained from in vitro seed germination of Passiflora cincinnata Mast. The 0.5 mg.L -1 6-BA concentration was most suitable for all the three explants, however, bud formation time and means (direct/indirect) were different for each type of explant. In seedlings used as explants, it had shoot regeneration from the primary root. Histological events leading to bud formation via meristemoids were described. The origin was indirect in leaf discs, with callus formation in subepidermal cells of the chlorophyll parenchyma layers. In root segments and in seedling roots, the buds were formed directly in the pericycle (in roots with some secondary structure) and in the vascular cambium (at the initial phase of secondary structure). Also, indirect buds originated from meristemoids which were formed around the callus.

Development, structure and distribution of colleters in Mandevilla illustris and M. velutina (Apocynaceae)

Development, structure and distribution of colleters in Mandevilla illustris and M. velutina (Apocynaceae)). Colleters of Mandevilla illustris and M. velutina are present on the cotyledons, shoot apices, mature leaves and on the nodal region, where they are interpetiolar and intrapetiolar. In M. velutina there are two colleters on the adaxial basal part of the leaf blade, and in M. illustris, this number varies. The differentiation of the colleters occurs in the early stages of leaf development. When colleters are mature, they consist of a long head on a short stalk. The central core of the colleter is made up of parenchymatous cells that may exhibit phenolic compounds and is surrounded by radially elongated epithelial cells. The foliar and intrapetiolar colleters can exhibit vascularization. The colleters produce a translucient sticky substance that reacts positively to polysaccharides and, before senescence, they produce lipophilic substances. The Mandevilla colleters data can give support to the taxonomy and phylogeny of the Apocynaceae. RESUMO - (Desenvolvimento, estrutura e distribuicao de coleteres em Mandevilla illustris e M. velutina (Apocynaceae)). Coleteres de Mandevilla illustris e M. velutina estao presentes nos cotiledones, apices caulinares, folhas maduras e na regiao nodal, onde estes sao interpeciolares e intrapeciolares. Em M. velutina existem dois coleteres na face adaxial da base da lâmina foliar, porem, em M. illustris este numero varia. A diferenciacao dos coleteres ocorre nos estagios iniciais do desenvolvimento foliar. Quando os coleteres estao maduros, eles consistem de uma longa cabeca sobre um curto pedunculo. A porcao central do coleter e constituida de celulas parenquimaticas que podem apresentar compostos fenolicos e e envolvida por celulas epiteliais radialmente alongadas. Os coleteres foliares e intrapeciolares podem exibir vascularizacao. Os coleteres produzem uma substância pegajosa e translucida que reage positivamente para polissacarideos e, antes da senescencia, eles produzem substâncias lipofilicas. As informacoes obtidas sobre os coleteres das Mandevilla podem fornecer subsidios aos estudos taxonomicos e filogeneticos das Apocynaceae.

The origin and anatomy of rhizophores in Vernonia herbacea and V.platensis (Asteraceae) from the Brazilian Cerrado

The aim of this work is to study the origin and anatomy of rhizophores in two Asteraceae species from the Brazilian Cerrado: Vernonia herbacea (Vell.) Rusby and V. platensis (Spreng.) Less. In both species, axillary buds from the cotyledonary node give rise to the first rhizophores. As rhizophores develop, these organs branch to form new rhizophores from their axillary buds that constitute a sympodial system of underground branches. Nodes, internodes and axillary buds, protected by cataphylls, are evident in these underground organs. The primary root degenerates and all the root system arises adventitiously from the rhizophores. Under natural conditions, the axillary buds give rise to new rhizophores, but when exposed to the light, these buds develop into aerial stems. When rhizophores are fragmented, each of these structures, which accumulate fructans, are important organs for vegetative propagation mainly in areas subjected to environmental disturbances, such as the Cerrado, where fire and drought frequently occur.

Characterization of electrical penetration graphs of Bucephalogonia xanthophis, a vector of Xylella fastidiosa in citrus

The sharpshooter Bucephalogonia xanthophis (Berg) (Homoptera: Cicadellidae) is a vector of the xylem‐limited bacterium, Xylella fastidiosa (Wells, Raju, Hung, Weisburg, Mandelco‐Paul, and Brenner), which causes citrus variegated chlorosis. Despite the importance of citrus variegated chlorosis, the probing behavior of vectors on citrus and its implications for transmission of X. fastidiosa have not been studied. Here we studied electrical penetration graph (EPG‐DC system) waveforms produced by B. xanthophis on Citrus sinensis (L.) Osbeck (Rutaceae), and their relationships with stylet activities and xylem ingestion. Electrical penetration graph waveforms were described based on amplitude, frequency, voltage level, and electrical origin of the observed traces during stylet penetration on plant tissues. The main waveforms were correlated with histological observations of salivary sheaths in plant tissues and excretion analysis, in order to determine stylet activities and their precise position. Six waveforms and associated activities are described: (S) secretion of salivary sheath and intracellular stylet pathway, (R) resting during stylet pathway, (Xc) contact of stylets with xylem vessels, (Xi) active xylem ingestion, (N) interruption within the xylem phase (during Xc or Xi), and (W) withdrawal of stylet from the plant. The sharpshooter spent 91.8% of its probing time with its stylet in the xylem, where the main activity was ingestion (Xi: 97.5%). During a probe, the most likely sequence of events is secretion of salivary sheath and pathway (S) through epidermal and parenchyma cells (all individuals), followed by contact with xylem (Xc) (67.6% of all individuals) and ingestion (Xi) (88.3% of those that exhibit waveform Xc). The mean time to contact the xylem (Xc) and initiate ingestion (Xi) after onset of the first probe was 27.8 and 34.2 min, respectively. However, sustained xylem ingestion (Xi > 5 min) was established after 39.8 min, on average. This information is basic for future studies on the transmission mechanisms of X. fastidiosa and in order to establish control strategies aimed at interfering with this process.

Underground systems of Asteraceae species from the Brazilian Cerrado1

Abstract Underground systems of Asteraceae species from the Brazilian Cerrado. The aim of this study was to describe the underground systems structure, the origin of the shoot buds, and to identify the storage reserve of seven Asteraceae species in order to understand the adaptive strategies of these species in burned Cerrado areas and their higher frequency in the floristic surveys for herbaceous and undershrub layers of this biome. The subterranean systems types—diffuse underground system, rhizophore, tuberous roots, and xylopodium—varied among the studied species, but all of them have high shoot bud-forming potential. Fructans of the inulin type were detected as storage substances. The presence of these characteristics on the underground systems could explain the frequency of these species in the floristic surveys from the Brazilian Cerrado, in which fire and seasonal drought are frequent. It is possible that the belowground bud banks in the Cerrado biome are as important as demonstrated in North American prairies where fire is also frequent. However, in the Cerrado, as demonstrated here, there are types of underground systems other than rhizomes that are usually described in the prairie. Understanding the anatomical features of these plants is one of the steps to appropriate conservation management of these species in the Cerrado.

Micropropagation of Pothomorphe umbellata via direct organogenesis from leaf explants

The establishment of a micropropagation protocol for Pothomorphe umbellata was carried out using leaf segments cultured on 1/4 strength Murashige and Skoog medium supplemented with 0.5 mg l-1 6-benzyladenine, 0.1 mg l-1 gibberelic acid added with 10 g l-1 sucrose. Rooting was achieved using MS medium devoid of growth regulators. An anatomical study confirmed shoot regeneration via direct organogenesis.

The developmental anatomy of the subterranean system in Mandevilla illustris (Vell.) Woodson and M. velutina (Mart. ex Stadelm.) Woodson (Apocynaceae)

The developmental anatomy of the subterranean system in Mandevilla illustris (Vell.) Woodson and M. velutina (Mart. ex Stadelm.) Woodson (Apocynaceae)). Two species of Mandevilla from the savanna area of Sao Paulo State, Brazil were studied. These species have been prescribed as folk medicine as infusions or alcoholic extracts of the underground system for treatment of venomous snake bites. To explain the morphological nature of such a system, its ontogeny was described to determine which parts are involved in its formation. In both Mandevilla species examined, the underground system consists of a xylopodium whose basal region joins a tuberous root. RESUMO - (O desenvolvimento anatomico do sistema subterrâneo em Mandevilla illustris (Vell.) Woodson e M. velutina (Mart. ex Stadelm.) Woodson (Apocynaceae)). Foram estudadas duas especies de Mandevilla que ocorrem em areas de campos cerrados do Estado de Sao Paulo, Brasil. Essas especies tem sido prescritas na medicina popular como extrato alcoolico ou infusoes do sistema subterrâneo para o tratamento de picadas de cobras venenosas. Para explicar a natureza morfologica de tal sistema a sua ontogenese e descrita visando determinar quais partes estao envolvidas na sua formacao. Em ambas as especies examinadas, o sistema subterrâneo consiste de um xilopodio cuja regiao basal une-se a uma raiz tuberosa.

Anatomy of the underground system in Vernonia grandiflora Less. and V. brevifolia Less. (Asteraceae)

This work dealt with the anatomy of the underground system in Vernonia grandiflora Less. and V. brevifolia Less. (Vernonieae; Asteraceae), two perennial geophytes, to elucidate their ability to sprout in the Brazilian Cerrado conditions. V. grandiflora , a subshrubby species, possessed a thickened under ground system constituted by a xylopodium and many tuberous roots. The xylopodium had stem and root structure and its buds were axill ary or originated from the cortical parenchyma proliferati on. The tuberous roots produced by this organ were adventitious and accumulated inulin-type fructans mainly in the cortical parenchyma. The thickened underground syst em of V. brevifolia , an herbaceous species, was a tuberous primary roo t whose buds originated from the proliferated pericycle. The occurrence of these bud-forming unde rground systems, which stored reserve compounds, en abled these plants to survive throughout unfavourable env ironmental conditions in the Cerrado, such as dry s eason and frequent fires in the winter.