Jose Pedro Nepomuceno Ribeiro

Potencial alelopático do extrato foliar de Annona glabra L. (Annonaceae)

A. glabra is a wetland species, occurring in dense populations. This behavior may indicate strong competition with other species or the existence of an allelopathic process involved in this distribution. In this study, we aim to: a) evaluate the allelopathic potential of extracts produced by A. glabra leaves on germination and seedling growth of other species and on wheat coleoptile growth and b) verify the presence of substance groups on the extracts and fractions studied. The qualitative test detected triterpenes, tannins and flavonoids. A Liquid:liquid partition chromatography of aqueous extract was done, using hexane and ethyl acetate. The activities of the fractions obtained were tested on germination and initial growth of Lactuca sativa, Echinochloa crus-galli, Euphorbia heterophylla and Ipomoea grandifolia. The ethyl acetate fraction reduced L. sativa germination percentage and E. crus-galli mean germination time and affected the initial growth of all species. This fraction was purified by chromatographic column which resulted in five fractions (A, B, C, D and E). Four concentrations (1000; 158; 79; 39.5 ppm) were prepared for each one. Effects caused by fractions were evaluated by wheat coleoptile tests. Fraction A stimulated elongation at all concentrations except 1000 ppm. Fraction B was inhibitory at all concentrations except for the smaller one. C was inhibitory only at the higher concentration and E did not cause a significant effect.

Allelopathic effects of Ipomoea cairica (L.) Sweet on crop weeds

Identification of species with allelopathic potential has been a target of researches aiming to use them to control crop weeds. Ipomoea cairica is considered a weed with allelopathic potential, which has already been reported. The goal of this study was to evaluate the allelopathic properties of leaf extracts from Ipomoea cairica on the germination and early development of four of the worst crop weeds in Brazil: Bidens pilosa L., Echinochloa crus-galli (L.) Beauv., Euphorbia heterophylla L. and Ipomoea grandifolia (Dammer) O´Donel. We tested the effects of leaf extracts, in four concentrations, on the germination and early development of these species. The extracts negatively affected the germination, early development and the morphology of all target species, and the phytotoxic effect was higher as the concentration of the extracts increased. The influence of the I. cairica extracts on germination, in addition to their effects on seedling development, made them more effective.

Plantae, aquatic, amphibian and marginal species, Massaguaçu River estuary, Caraguatatuba, São Paulo, Brazil

Estuaries are the buffer zones between river and ocean. Because they are under strong tidal influence, their flora must be able to cope with salinity and flooding stress. In the present study we combined results from two surveys we performed in the Massaguacu River Estuary (23°37’20” S, 54°21’25” W), with the objective of providing a full inventory of its aquatic, amphibian, and marginal flora. We reported 102 species among 77 genera and 47 families, including six Pteridophyta species.

The effects of seasonal change of water level in an estuary on Ludwigia octovalvis (Jacq.) P. H. Raven (Onograceae) growth

The Massaguacu River estuary is an irregular estuary with sandbar breaching cycles that are irregular and happen several times each year. The species Ludwigia octovalvis is a perennial weed in several places around the world, but it is seasonal in the Massaguacu River. In this survey we determined the relationship between the rain, estuary water level variation, and the spatial and temporal distribution of this species. In a laboratory we simulated the water level variation in water tanks in order to understand how this species responds to flooding. In the field, we determined the distribution of L. octovalvis in the higher pluviose season and in the lower pluviose season. This species is relatively common in the higher pluviose season and completely absent in the lower one. There is strong evidence that this happens due to the longer and deeper sandbar breaching cycles during the dry season, which induce this species to etiolation, and, therefore, mechanical fragility. The seasonality of species in aquatic environments that do not have a dry biological season is unusual and little studied.

Potencial alelopático de macrófitas aquáticas de um estuário cego

Aquatic macrophytes represent one of the most productive communities and through metabolic activity are capable of producing great interference in the environment. Allelopathic interactions are apparently increased under biotic and abiotic stress and may exist in estuaries due to competition, salinity variation and other factors. The aim of this study was to evaluate the allelopathic properties of leaf extracts of 25 aquatic macrophyte species from a blind estuary. We tested leaf extract effects in four concentrations on the germination of lettuce. We ranked and compared the donor species according to the dose-response over the variety of treatments through unique values of allelopathic indexes. Eleven of 25 species decreased the germination percentage, all of them decreased the speed of germination and increased the germination informational entropy of the target species seeds in at least one of the tested concentrations. Crinum americanum L., Sagittaria montevidensis Cham. & Schl. and Ipomoea cairica (L.) Sweet presented the highest allelopathic index values. In general, the lowest germination percentages concurred with the lowest germination speed and highest germination informational entropies of lettuce seeds, showing an assemblage of alterations occurring simultaneously with the increase of extract concentrations.

Propagação in vitro de Baptistonia pubes (Lindl.) Chiron & V.P. Castro (Oncidium pubes Lindl.) (Orchidaceae)

Baptistonia pubes is an epiphyte that grows in Brazilian Atlantic Forest, in Paraguay and northern Argentina. It is considered vulnerable and threatened with extinction. Our aim was to verify seed germination efficiency and growth at two pHs, using two culture mediums: Murashige-Skoog (modified - (MS)) and banana pulp with added NPK 20-20-20 (Plant Prood®) (BAN), with varied nutrient and pH concentrations for germination and for growth. The seeds germinated on average 15 days after the inoculation, at all conditions. The percentage of germination varied between 2.6 and 11.6 %. The highest percentage was at pH=5.2 BAN and the lowest at pH=6.2 MS/2. The banana pulp was most efficient for germination. The pHs, in each environment, altered significantly the averages of the germinated seeds. Seedling growth showed better results in the banana medium, pH = 5.2