RESUMEN
The leaf architecture, defined as the tri-dimensional organization of the leaves on the stem axis, influences the plant capacity to intercept sun light. This study investigated the leaf architecture of Impatiens walleriana, a species of the understorey of forests, to evaluate the existence of variation among distinctive positions of the leaves and identify the morphological characteristics that influence the leaf overlapping and, consequently, the process of light capture. Thirty plants, under the same light condition, were collected in a remnant of Floresta Ombrófila Mista (25º25S e 49º17W), in Curitiba, Paraná. Leaf width, leaf length, lamina thickness, leaf area, petiole length, leaf angles, and divergence angles were measured. The mean values of leaf angles, divergence angles, and petiole length varied significantly in relation to leaf position. Apparently, leaf overlapping is minimized by the synergic effect of leaf angles, divergence angles, elliptic form of the lamina, and long petioles, which, together, allow for a spatial organization around the stem axis, where most leaves can receive the difuse light at the understorey forest. These morphological characteristics, associated with reproductive strategies, appear to be responsible for this species´ success on the colonization of disturbed understorey, replacing native vegetation.
A arquitetura foliar, definida como a organização tridimensional das folhas no caule, influencia a capacidade da planta em interceptar a luz solar. Este estudo investigou a arquitetura das folhas de Impatiens walleriana que ocorre nos subosques de Floresta Ombrófila Mista para avaliar se existe variação na arquitetura em relação à posição das folhas no eixo caulinar, identificar as características morfológicas que influenciam a sobreposição das folhas e, consequentemente, o processo de captura de luz. Foram coletados 30 indivíduos na mesma condição luminosa, num fragmento de Floresta Ombrófila Mista, Curitiba, Estado do Paraná. Largura, comprimento, espessura, área foliar, comprimento do pecíolo, ângulo foliar e ângulo de divergência foram mensurados. Os valores médios do comprimento do pecíolo e dos ângulos foliares e de divergência variaram significativamente com a posição foliar. Aparentemente, o auto-sombreamento foliar é minimizado pelo efeito sinérgico do ângulo de divergência, do ângulo foliar, da forma elíptica da lâmina e dos pecíolos longos, que, em conjunto, permitem que a maioria das folhas possa receber a luz difusa disponível no interior da floresta. Essas características morfológicas, juntamente com as estratégias reprodutivas, parecem influenciar o sucesso da espécie na colonização de subosques perturbados, substituindo a vegetação nativa.
RESUMEN
In forest remnants of Maringá, Paraná, Brazil, there is abundance of the liana species, with little studied reproductive structures, morphologically and anatomically. Among these species occurs Dalechampia stipulacea Müll. Arg., which is the object of the present study. It is a Euphorbiaceae with pseudanthium and trichomes that cause irritation of the skin. The fruits and seeds were fixed and cut freehand and in a rotation microtome, according to the usual techniques. The fruit is a schizocarp tricocca with loculicidal and septicidal dehiscence. The mature pericarp presents sclerenchymatous middle mesocarp and endocarp that originate from meristems installed in the ovary mesophyll and epidermis. The inner mesocarp is constituted by a layer of macrosclereids of subepidermic origin. The seed originates from anatropous, bitegmic and crassinucelate ovule; it is exotegmic and albuminous. The seed presents structural characteristics verified in Acalyphoideae, except for the mesotegmen vascularization