THE FLORAL STRUCTURE OF THREE WEEDY SPECIES OF SIDA (MALVACEAE)

Volume: 8Start Page: 127End Page: 13

Flower morpho-anatomy in Epiphyllum phyllanthus (Cactaceae)

The aim of this contribution was to analyze the morpho-anatomical floral structure of Epiphyllum phyllanthus (L.) Haw., a widely distributed species across South America, occurring in humid forests as an epiphyte. Flowers and flower buds were collected in Maringa, Parana State, Brazil, fixed, processed, and analyzed under light microscope and scanning electron microscope. The flower is sessile and epigynous with a well-developed hypanthium. All flower whorls have uniseriate epidermis. Secretory cavities containing mucilage and calcium oxalate crystals occur throughout the floral parenchymatous tissue. The androecium has many stamens with tetrasporangiate and bithecal anthers. The wall of the young anther is formed by epidermis, endothecium, a middle layer, and binucleate secretory tapetum that eventually becomes uninucleate. The gynoecium is syncarpous with 9-10 carpels, pluriovulate, and with parietal placentation. The ovary has inverted vascular bundles in a similar pattern as in Pereskia. The nectariferous region occurs on the inner surface of the hypanthium. The stigma has 9-10 lobes with a secretory epidermis. The ovules are circinotropous, bitegmic, crassinucelate, and have long funiculus as in many other Cactaceae.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

A macro- and micromorphological survey of floral and extrafloral nectaries in the epiphytic cactus Rhipsalis teres (Cactoideae: Rhipsalideae)

Floral and extrafloral nectaries in plants favor pollination and defense against herbivory. Despite their wide distribution in plants and differences in position, structure, and topography, their biological and systematic significance has been underutilized. This study investigated the macro- and micromorphology of floral and extrafloral nectaries in the epiphytic cactus Rhipsalis teres and reports unusual bristle-like structures (bracteoles) functioning as extrafloral nectaries in the cactus family. The floral nectary is disc-shaped embedded in the hypanthial floral cup with anomocytic stomata as secreting structures present on the epidermal nectarial tissue. Small multicellular bristle-like extrafloral nectar-secreting structures, homologues to bracts, were observed on the plants stems and function as bracteolar nectaries having a relatively long and continuous secretory activity throughout several stages of the reproductive structures. Both the floral and bracteolar nectaries are functional. It is possible that in the latter nectar discharge occurs though epidermal cells, which build up pressure inside as nectar accumulates, thereby ending with rupture of the cuticle to release the liquid. The nectar in both secreting structures is scentless and colorless, and the concentration from floral nectaries is slightly lower than that of the bracteolar nectaries, 70.6% and 76.4%, respectively. The relatively higher concentration in the latter might be correlated with exposure, relative humidity and water evaporation, leading to crystallization of sugars on the stem surface in a short period of time. (C) 2011 Elsevier GmbH. All rights reserved.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Seedling structure in Asteraceae weedy species: considerations on the vasculature system

Seedling structure in Asteraceae weedy species: considerations on the vasculature system. The vasculature system of the seedling is of interest since it represents the first mature vascular coordination between shoot and root, which was foreshadowed in the procambial system of the embryo. In this study, seedlings of ten Asteraceae weedy species were analyzed focusing on the vasculature system using a morpho and anatomical approach. The roots were found to be diarch and tetrarch, the species have intermediate or high root/shoot transition, and the cotyledons develop an independent double leaf-trace and a common simple-leaf trace. The transition region of the seedlings is strikingly different when compared with other families, such as, Annonaceae, Cactaceae, Fabaceae, Myrtaceae, Amaranthaceae, Clusiaceae, and Rutaceae. In spite of the uniformity in the vascular arrangement among the Asteraceae seedlings, the conclusion attained from this study is that some essential structural details may be of diagnostic value, such as the stele arrangement, the level of the transition zone, the cotyledon sheath, and the splitting of the phloem. Further, the presence of trilacunar node in the Asteraceae can be the result of a reversal evolutionary process ( homoplasy) during the life history of the family.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq