La piña, Ananas comosus (L.) Merr., es un cultivo de gran importancia comercial por la alta demanda de su fruto. Esto ha conducido a la búsqueda de nuevos métodos de propagación que permitan acelerar la producción de propágulos para la plantación en el campo, y entre éstos, cabe señalar, el cultivo in vitro de yemas que permite mejorar sustancialmente el proceso de multiplicación. En el presente trabajo se estableció y analizó un proceso de organogénesis para la clonación de plantas de piña ‘Española Roja’ mediante el uso de secciones de hojas de la planta en el establecimiento del sistema de propagación. Para comprobar la naturaleza organogénica del proceso se realizó un análisis histológico y anatómico del material vegetal cultivado in vitro. Así mismo, se evaluó, la existencia de posibles variaciones morfoanatómicas en la estructura foliar de la población clonal, obtenida mediante el proceso organogénico. Los resultados mostraron, rizogénesis directa, y formación de vástagos vía callo en el medio de cultivo que contenía 2,5 mg·L-1de 2,4-D, a la vez que hubo formación de raíces y vástagos, vía organogénesis indirecta, en el medio que contenía 5 mg·L-1de ANA y 0,25 mg·L-1 de BA. Se obtuvo el 100 % de plantas aclimatadas. Por otra parte, los cambios morfológicos y anatómicos presentados por las vitroplantas fueron revertidos durante la aclimatación y su posterior paso a condiciones de vivero. En consecuencia, se puede considerar que los mismos son cambios fenotípicos temporales, producto de las condiciones del cultivo in vitro.

The pineapple, Ananas comosus (L.) Merr., is a crop of great commercial importance due to the high demand for its fruit; this has led to the search of new methods of propagation in order to accelerate the production of propagules to plant in the field, and among them, we may mention the in vitro culture of buds that can substantially improve the multiplication protocols. In the present research an organogenesis process for cloning ‘Red Spanish’ pineapple was developed using sections of plant leaves to establish the propagation system. To check the organogenic nature of the process, it was conducted anatomical and histological analysis of the plant material growing in vitro. Moreover, it was also evaluated the existence of possible morpho-anatomical variations in leaf structure of the clonal population obtained by the organogenesis process. The results showed direct rhizogenesis, and shoot formation via callus in the medium containing 2.5 mg·L-1 of 2.4-D, while formation of roots and shoots via indirect organogenesis was found in the medium containing 5 mg·L-1 of ANA and 0.25 mg·L-1 BA. All the plants were successfully acclimatized. On the other hand, the morphological and anatomical changes observed in vitroplants were reversed during the acclimatization and subsequent nursery conditions. Consequently, it can be consider that they are temporary phenotypic changes as a result of the in vitro culture conditions.

The morphology and anatomy of the seed coat of seven species of the genus Passiflora L. were studied in order to evaluate the taxonomic value of seed characters in this genus. Three morphological types of seed coat surfaces were found and seven anatomical patterns are species specific, so that, seed coat attributes can be used to distinguish species.

Se caracterizó morfológica y anatómicamente la cubierta seminal de siete especies del género Passiflora L., con la finalidad de determinar la utilidad taxonómica de los atributos de la semilla en este género. Se encontraron tres tipos morfológicos en la superficie de la cubierta seminal y siete patrones anatómicos diferentes para cada especie. Se concluye que los atributos de la cubierta seminal permiten distinguir especies.

Nas árvores da floresta sazonalmente inundada do rio Mapire em Venezuela, a inundação cedo induz uma diminuição reversível na condutância foliar e na taxa fotossintética. Com o objetivo de encontrar uma explanação anatômica para as respostas observadas na trocas gasosas nas folhas, as características das folhas emersas desenvolvidas sob a drenagem ou após três meses de inundação foram examinadas nas espécies nas espécies arbóreas Acosmium nitens, Campsiandra laurifolia, Duroia fusifera, Eschweilera tenuifolia Pouteria orinocoensis e Symmeria paniculata, e nas folhas desenvolvidas somente sob inundação de Inga spuria e Tachigali davidsei. A anatomia foi notavelmente similar entre as espécies e as famílias e consistiu em um parênquima paliçádico bi-celular, um parênquima lacunoso de 5-6 células e grande espessura da folha inteira. A anatomia assemelhou-se também àquele das xerófitas ou das espécies sempre-verdes possuindo cutículas grossas, células epidérmicas grandes, paredes anticlinais das epidermes engrossadas e uma abundância de esclerênquima. Folhas das árvores inundadas v. não inundadas não eram qualitativamente diferentes. A área foliar específica assemelhou-se a valores de espécies decíduas em florestas secas tropicais. Nenhuma diferença quantitativa foi encontrada entre as folhas desenvolvidas em árvores não inundadas e inundadas, à exceção de uma redução na espessura da folha inteira do E. tenuifolia, P. orinocoensis e S. paniculata e uma mudança na contribuição do parênquima paliçádico a espessura foliar em E. tenuifolia. O tamanho e a densidade estomáticos nestas espécies exclusivamente hipostomáticas permanesceram não afetados pela inundação. Uma diminuição sob inundação na espessura foliar pode estar relacionado ao aumento da condutância mesofilar e conseqüentemente da taxa fotossintética.

In trees of the seasonally flooded forest of the Mapire River in Venezuela, early flooding induces a reversible diminution in leaf conductance and photosynthetic rate. With the aim of finding an anatomical explanation for the observed responses of leaf gas exchange, the characteristics of emerged leaves developed under drainage or after three months of flooding were examined in the tree species Acosmium nitens, Campsiandra laurifolia, Duroia fusifera, Eschweilera tenuifolia, Pouteria orinocoensis and Symmeria paniculata and in leaves developed only under flooding in Inga spuria and Tachigali davidsei. Anatomy was remarkably similar among species and families and consisted of a bi-layered palisade parenchyma, a 5-6-cell-thick spongy parenchyma and large whole-leaf thickness. Anatomy also resembled that of xerophytes or evergreen species by possessing thick cuticles, large epidermal cells, thickened anticlinal epidermal cell walls and an abundance of sclerenchyma. Leaves of flooded v. un-flooded trees were not qualitatively different. Specific leaf area resembled values of deciduous species in tropical dry forests. No quantitative differences were found between leaves developed in un-flooded and flooded trees, with the exception of a reduction in whole-leaf thickness of E. tenuifolia, P. orinocoensis and S. paniculata and a change in the contribution of palisade parenchyma to leaf thickness in E. tenuifolia. Both stomatal size and density in these exclusively hypostomatous species remained unaffected by flooding. A decrease under flooding in whole-leaf thickness may have resulted in an increase in mesophyll conductance and therefore photosynthetic rate.

El género neotropical Hymenocallis Salisb. es uno de los más problemáticos entre las Amaryllidaceae, debido a la frecuente superposición de los límites entre la variación intra e interespecífica. El objetivo principal de este trabajo fue explorar el potencial de los caracteres morfoanatómicos foliares en la delimitación vegetativa de las especies de Hymenocallis que crecen en Venezuela. Se trata de plantas geófitas, de follaje estacional o persistente, con láminas sésiles, subsésiles y pseudopecioladas, lineares, loriformes, oblanceoladas a elípticas; la anatomía puede ser equi- o bifacial. Con los resultados obtenidos se realizaron análisis de agrupamiento simple, utilizando el porcentaje de discrepancia (disimilitud) como método de cálculo de la matriz de distancia y el método del vecino más cercano como criterio de reunión entre los grupos de especies. Veintidós caracteres resultaron informativos para la separación de grupos discretos; los caracteres cualitativos produjeron siete grupos discretos, correspondientes cada uno a una especie, salvo uno que agrupa parcialmente a Hymenocallis lobata Klotzsch y H. venezuelensis Traub. Se presenta una clave vegetativa para la separación de las especies venezolanas basada exclusivamente en caracteres morfológicos y anatómicos de la hoja.

The Neotropical genus Hymenocallis Salisb. is known as one of the most problematic genus within the Amaryllidaceae. To define some of its species remains difficult because the limits between intra and interspecific variation are often superposed, thus, the main objective of this investigation was to explore the potential of the foliar morphoanatomy to delimit Venezuelan species. These species are geophytes, with seasonal or persistent foliage; sessile, subsessile or pseudopetiolated leaves; leaf blades are linear, lorate, oblanceolate or ellipsoid; anatomy could be equi- or bifacial. Of the evaluated characters, 22 have been selected as the most informative to form species clusters through a hierarchical clustering analysis, using percent disagreement as distance matrix calculation method and simple linkage as joining rule. Analysis of qualitative characters produced seven discrete groups that correspond to each of the studied species, except one which H. venezuelensis partially clusters Hymenocallis lobata. Based on evaluated morphological and anatomical characters, a vegetative key to separate Venezuelan species is presented.

Se realizó el estudio anatómico de la cubierta seminal en ocho especies del género Passiflora L., con el objetivo de hallar características que permitan distinguir especies y contribuyan a resolver problemas taxonómicos presentes en el género. Se encontraron ocho patrones anatómicos diferentes considerando las siguientes características: grosor de la cubierta seminal, número de capas, tipo de capa y tipo de alargamiento radial de las células. Se observó una capa de macroesclereidas y una capa de células obliteradas en todas las especies estudiadas.

The seed coat anatomy of eight species of genus Passiflora L. was studied in order to search for characteristics that would allow species distinction and resolve taxonomic problems. Eight anatomical patterns were found based on the seed coat thickness, number of coats, coat type and radial extension type of the cells. One layer of macrosclereid and one layer obliterated cells were observed in all the species studied.

Se realizó el estudio morfológico de la semilla de 51 especies del género Passiflora L., con la finalidad de encontrar caracteres que permitan el reconocimiento y la separación de especies. Fue posible distinguir 48 de las 51 especies estudiadas. Se presenta un registro microfotográfico de la semilla de 51 especies y una clave artificial.

The seed morphology of 51 species of Passiflora was studied in order to search characteristics that would allow recognition and separation of individual species. It was possible to distinguish and separate 48 of the 51 species. An overview of the seed morphology from 51 species of Passiflora and an artificial key are presented