Vismia Guianensis Research Articles

Levantamento da infestação de plantas daninhas associada a uma pastagem cultivada de baixa produtividade no Nordeste Paraense

A região do trópico úmido amazônico ocupa 350 milhões de hectares, constituindo a maior área de fronteira agrícola do planeta. A pecuária como exploração do uso da terra é a principal forma de ocupação e de desmatamento na região, apesar da baixa produtividade e das conseqüências ambientais. O declínio da produtividade da pastagem está associado, entre outras, ao manejo inadequado e à elevada infestação de plantas daninhas herbáceas e arbustivas, anuais ou perenes, geralmente denominadas "juquira" na região. Se essas plantas não forem controladas adequadamente, podem levar à degradação da pastagem, resultando na completa perda de produtividade e no posterior abandono da área. Com o objetivo de identificar as plantas daninhas mais importantes que ocorrem em área de pastagem de baixa produtividade no município de Terra Alta, PA (0º 58" S e 47º 52" W. Gr.), foi efetuado um levantamento florístico em 0,33 ha de área cultivada com capim-quicuio-da-amazônia (Brachiaria humidicola). Foram registrados 4.700 indivíduos, distribuídos em 17 famílias botânicas, representadas por 36 espécies vegetais. Destacaram-se as famílias Poaceae, Rubiaceae, Fabaceae, Asteraceae e Solanaceae, sendo encontrado em cada uma delas cinco, cinco, quatro, três e três espécies, respectivamente. As plantas daninhas consideradas de maior importância na comunidade vegetal foram: Borreria verticillata, Hyptis atrorubens, Rolandra argentea, Desmodium canum, Panicum pilosum, Davilla rugosa, Imperata brasiliensis, Paspalum maritimum, Vernonia scorpioides e Vismia guianensis.

Morphology and anatomy of developing fruits and seeds of Vismia guianensis (Aubl.) Choisy (Clusiaceae).

Morphological, structural and developmental features of fruits and seeds of Vismia guianensis (Aubl.) Choisy. are here presented, with the purpose to elucidate their structure and to contribute to taxonomical and ecological studies of the family. The fruit is a berry and the "rind" is constituted by the exocarp and by the subepidermal layers which constitute the mesocarp. The reddish pulp, rich in starch, is constituted by the parenchymatic mesocarp, with branched secretory ducts and vascular bundles, joined with the endocarp, which arises from a ventral meristem. The bitegmic, anatropous ovules, provided by the endothelium, develop into anatropous, bitegmic and exalbuminous seeds. The reddish uniseriate testa shows phenolic contents. The tegmen becomes crushed resting only the uniseriate exotegmen with undulate, thick walled and lignified cells, which contain a number of calcium oxalate prismatic crystals. The embryo, rich in lipids, is straight and shows foliaceous cotyledons.

New bioactive aromatic compounds from Vismia guianensis

Five benzophenones, vismiaguianones A–E, and two benzocoumarins, vismiaguianins A and B were isolated from the CHCl 3 extract of the roots of Vismia guianensis by bioassay-directed fractionation using the DNA strand-scission assay and KB cell line. Of the isolates obtained, vismiaguianone B exhibited DNA strand-scission activity, whereas vismiaguianones D and E and vismiaguianin A were found to be significantly cytotoxic.

Plantas daninhas de uma pastagem cultivada de baixa produtividade no Nordeste Paraense

Atualmente existem 23 milhões de hectares de pastagens cultivadas em área originalmente sob floresta na Amazônia. Desse total, em torno de cinco milhões de hectares encontram-se com baixa produtividade ou em vias de degradação, infestados de plantas daninhas. Com o objetivo de identificar as plantas daninhas que ocorrem em área de pastagem de baixa produtividade em Terra Alta, PA ( 0º 58” S e 47º 52” W. Gr. ), foram efetuados levantamentos botânicos qualitativos, pelo método visual e coleta de todas as espécies presentes na área. Foram registradas 34 famílias, representadas por 118 espécies, destacando-se as famílias Leguminosae, Gramineae, Malvaceae, Myrtaceae, Cyperaceae e Asteraceae com 21, 16, 8, 7, 6 e 6 espécies, respectivamente. As plantas daninhas consideradas mais importantes foram: Borreira verticillata, Rolandra argentea, Desmodium canum, Davilla rugosa, Vismia guianensis e Imperata brasiliensis.

In vitro plant regeneration of Vismia guianensis through organogenesis

A protocol for in vitro plant regeneration through organogenesis was established for Vismia guianensis(Hypericaceae), a species that produces an anti-cancer compound. The highest mean number of shoots per gram of callus (57.33) was obtained on Murashige and Skoog medium supplemented with 4.44 μM 6-benzyl-aminopurine, 5.70 μM indole-3-acetic acid and 12.88 μM gibberellic acid. Rooting was favoured by the addition of 10 μM indole-3-butyric acid, and by sucrose concentrations higher than 1%.

Physiological Responses to Soil Moisture Stress in Two Amazonian Gap- Invader Species

1. Disturbed habitats in Amazonia, like active pastures and abandoned agricultural areas, are characterized by significant diurnal and seasonal drought stress that may restrict successful colonization by many plant taxa. Some species, however, show a remarkable capacity to withstand these water-limited conditions. We investigated, under controlled conditions, the bulk tissue-water relations and the gas-exchange characteristics in response to soil moisture stress of Solanum crinitum Lam. and Vismia guianensis (Aubl.) Choisy, two co-occurring gap-invading small trees kown to dominate, disturbed, drought-prone habitats in the eastern Brazilian Amazon region. 2. Bulk tissue-water relations of these two species were very different. Vismia guianensis had significantly higher bulk tissue elastic modulus (more rigid tissues) and lower bulk tissue osmotic potential at full hydration and at turgor loss than S. crinitum. 3. The elastic and osmotic properties could either enhance turgor maintenance or increase the ability of a plant to extract soil water. In turn, this may help explain their ability to succeed in drought-prone habitats. With more elastic tissue properties, S. crinitum is able to maintain turgor and thus leaf gas exchange over greater changes in tissue water content, whereas having relatively more rigid tissues would aid V. guianensis in developing water potential gradients from the leaves to the soil with little tissue water loss, thus enhancing water uptake from drier soils. 4. Photosynthetic capacity in S. crinitum was less affected by soil moisture stress than V. guianensis. Furthermore, because S. crinitum maintained stomatal conductance (g), but photosynthesis (A) declined under moisture stress, intrinsic water-use efficiency (A/g) actually dropped when water was limiting for this species. In contrast, V guianensis maintained high A/g under both watering regimes and was always more water-use efficient than S. crinitum. Moreover, S. crinitum had two- to fourfold higher dark respiration than V. guianensis. We believe that it is this combination of traits that leads to lower growth in S. crinitum when compared to V. guianensis in the field. 5. We suggest that the different gas-exchange responses and tissue water relations properties represent two different strategies for dealing with water deficits. Solanum crinitum, appears to be more able to cope with short-term water stress and is regarded to be a successful stress tolerator. In contrast, V. guianensis, appears to be able to cope better with chronic, long-term water stress, what we call a successful stress-avoider