Comportamento germinativo de duas espécies de canga ferrífera: Baccharis retusa DC. (Asteraceae) e Tibouchina multiflora Cogn. (Melastomataceae)

Abstract

RESUMO -(Comportamento germinativo de duas espécies de canga ferrífera: Baccharis retusa DC. (Asteraceae) e Tibouchina multiflora Cogn. (Melastomataceae)). O objetivo desse estudo foi avaliar o comportamento germinativo de Bacccharis retusa e Tibouchina multiflora, espécies que ocorrem na vegetação de canga no Quadrilátero Ferrífero de Minas Gerais. Diásporos coletados no município de Barão de Cocais foram colocados para germinar nas temperaturas de 15, 20, 25 e 30 °C na presença de luz contínua ou no escuro. As sementes mantidas inicialmente no escuro foram posteriormente transferidas para a presença de luz, mantendo-se as mesmas temperaturas. Os diásporos das duas espécies apresentaram comportamento fotoblástico positivo, com germinação inexpressiva no escuro em todas as temperaturas testadas. Na presença de luz contínua as sementes de T. multiflora não apresentaram diferenças na porcentagem final de germinação em todas as temperaturas testadas, mas B. retusa apresentou menor porcentagem final de germinação a 30 ºC. Os diásporos das duas espécies mantidos inicialmente no escuro, germinaram rapidamente após serem transferidos para luz branca contínua. Entretanto, não foi verificado efeito significativo do tempo de permanência no escuro nos valores finais de porcentagem de germinação alcançados a cada temperatura. Esses resultados sugerem que essas duas espécies de canga apresentam potencial para a formação de banco de sementes no solo.Palavras-chave: banco de sementes, campo rupestre, fotoblastismo, luz, temperatura ABSTRACT -(Germinative behavior of two species from "canga ferrífera": Baccharis retusa DC. (Asteraceae) and Tibouchina multiflora Cogn. (Melastomataceae)). The aim of this study was to evaluate the germinative behavior of Bacccharis retusa and Tibouchina multiflora, species that occur in the "canga" vegetation of the Quadrilátero Ferrífero of Minas Gerais. Diaspores collected in the county Barão de Cocais were placed to germinate under the temperatures of 15, 20, 25 and 30 °C at continuous light or in darkness condition. The diaspores initially remained under darkness were later transferred to light presence maintaining the same temperatures. Diaspores of both species presented a positive photoblastic behavior, with inexpressive germination under darkness in all tested temperatures. In presence of continuous light, seeds of T. multiflora showed no difference in the percentage of germination in all temperatures, while B. retusa showed lower germination at 30 °C. Diaspores initially maintained under darkness germinated rapidly after transferred to continuous light. However, no indication of significant effect of the dark period was observed in values of the final germination percentage in each temperature tested. These results suggest that these two "canga" species may have potential to constitute the soil seed bank

Seed germination of Brazilian Aldama species (Asteraceae)

“…This ability may have useful consequences, because at least some seeds will germinate, whatever the environmental conditions they are submitted (Silva et al, 2002). Moreover, seed germination studies on Asteraceae species (Ferreira et al, 2001;Gomes and Fernandez, 2002;Velten and Garcia, 2005;Garcia et al, 2006;Cury et al, 2010) indicate that different species germinate differently and respond to distincts alternating temperatures with variations in germination rates. The constant or alternating temperatures between 20 and 30 °C were most efficient despite the variation in optimal temperature for seed germination for the species studied.…”

“…Few studies have investigated seed germination for Brazilian Asteraceae species (Ferreira et al, 2001;Gomes and Fernandez, 2002;Velten and Garcia, 2005;Garcia et al, 2006;Cury et al, 2010), and about the propagation strategies of Brazilian Aldama species. Germination behavior has only been reported for Aldama robusta (Gardner) E.E.Schill.…”

Rock outcrop vegetation in Brazil: a brief overview

“…A pre-requisite for seed bank formation is prolonged seed dormancy that, therefore, may not be common to many species of the "campos rupestres". Nevertheless, Garcia et al (2006) have studied seed germination of two shrubs (including one Asteraceae of the genus Baccharis) from the ferruginous canga vegetation and found potential for seed bank formation.…”

Growing Periandra mediterranea on post-mining substrate: native Fabaceae with potential for revegetation of degraded rupestrian grasslands in Brazil

“…However, many of these species are invasive and affect local biodiversity (Barbosa et al 2010;Hilário et al 2011;Fernandes et al 2015). Several studies have attempted to improve knowledge regarding the reproductive biology and establishment of native species with potential application in the revegetation of degraded areas of rupestrian grasslands (Garcia et al 2006;Negreiros et al 2009;Figueiredo et al 2012;Rodrigues & Silveira 2013). However, few studies have evaluated the establishment and growth of species on degraded substrates or in field conditions.…”