Revista Brasil. Bot., V.34, n.1, p.135-140, jan.-mar. 2011 Scientific note/Nota científica Flowering and fruiting of Aulonemia aristulata: a gynomonoecious woody bamboo species from Atlantic Forest in Brazil MARIA TEREZA GROMBONE-GUARATINI1,3, ANDRESSA ALENCAR DO NASCIMENTO1 e ANA PAULA SANTOS-GONÇALVES2 (received: May 13, 2010; accepted: January 27, 2011) ABSTRACT – (Flowering and fruiting of Aulonemia aristulata: a gynomonoecious woody bamboo species from Atlantic Forest in Brazil). Aulonemia aristulata (Döll) McClure is a lignified bamboo species endemic to Brazil. This species occurs in southeastern forests and can reach high density at forest edges, dominating the understory of canopy-disturbed forest patches. The goal of this study was to describe the flowering period, floral biology, fruiting and seedling recruitment of A. aristulata in natural conditions in two areas located in a segment of the Atlantic Forest. Data on the morphology of the synflorescences and florets, timing and sequence of the anthesis events and floral visitors were recorded. Natural pollinators (open pollination or control) as well as spontaneous self-pollination were also checked. Pollen viability was estimated using the acetocarmine technique. Aulonemia aristulata is monocarpic (semelparous) with gregarious flowering. All culms in both studied areas blossomed and fruited between August and November 2007, dying subsequently between December 2007 and April 2008. Two types of synflorescences and flowers were observed: terminal with bisexual and protandric florets, with the anthesis lasting for 3-4 days; and axillary, with morphologically bisexual, but functionally female, florets and anthesis lasting for 3-4 days. The latter were also observed in the rhizome of plants whose aerial portion had been removed. The presence of axillary synflorescences with pistillate flowers is described here for the first time inAulonemia species. Moreover, this is the first report of gynomonoecy in woody bamboo. Fruiting from bisexual florets under natural conditions (35%) was superior to that obtained from bagged synflorescences (11.5%). Fruiting from functional female florets was around 20%. Pollen viability was on the average of 90%. The results suggest that Aulonemia aristulata is anemophilous. The massive bamboo seedling recruitment observed after dieback with the ability to colonize open areas could promote the regeneration of Aulonemia aristulata. Key words - floral biology, gregarious flowering, gynomonoecy, protandry, tropical forest RESUMO – (Floração e frutificação deAulonemia aristulata: uma espécie de bambu lignificado ginomonoica da Floresta Atlântica no Brasil). Aulonemia aristulata (Döll) McClure é uma espécie de bambu lignificado endêmico do Brasil. Esta espécie ocorre em florestas do sudeste e pode atingir altas densidades em bordas de floresta e dominar o sub-bosque de manchas de floresta que tiveram o dossel perturbado. O objetivo deste estudo foi descrever o período de florescimento, a biologia floral, a frutificação e o recrutamento de plântulas de A. aristulata, em condições naturais, em duas áreas localizadas em um segmento de Floresta Atlântica. Foram registrados dados sobre a morfologia das sinflorescências e das espiguetas, tempo e sequência de eventos de antese e visitantes florais. Foram também verificadas a polinização natural (polinização aberta e controle) e a autopolinização espontânea. A viabilidade do pólen foi estimada usando a técnica de acetocarmim. Aulonemia aristulata é monocárpica (semélpara) com floração gregária. Todos os colmos em ambas as populações estudadas floresceram e frutificaram entre agosto e novembro de 2007 e, subsequentemente, morreram entre dezembro de 2007 e abril de 2008. Dois tipos de sinflorescências foram observadas: terminais com antécios bissexuais e protândricos com antese de 3-4 dias e axilares com antécios bissexuais, mas funcionalmente femininos e com antese de 3-4 dias. As últimas foram observadas no rizoma de plantas das quais a porção aérea foi removida. A presença de sinflorescências axilares com flores pistiladas é descrita aqui pela primeira vez em espécies deAulonemia . Além disso, este é o primeiro relato de ginomonoicia em bambus lignificados. A frutificação sob condições naturais (35%) foi superior à obtida nas sinflorescências ensacadas (11,5%). A produção de frutos originados das flores femininas foi cerca de 20%. A viabilidade do pólen foi de cerca de 90%. O conjunto de resultados obtidos sugere que Aulonemia aristulata é anemófila. O recrutamento massivo de plântulas, observado após a morte, associado à habilidade de colonizar áreas abertas poderá promover a regeneração de Aulonemia aristulata. Palavras-chave - biologia floral, floração gregária, floresta tropical, ginomonoicia, protandria 1. Instituto de Botânica, Núcleo de Pesquisa em Ecologia, Caixa Postal Introduction 3005, 01031-970 São Paulo, SP, Brazil. 2. Universidade Federal de Viçosa, Departamento de Biologia Vegetal, Bamboos are members of the Bambusoideae Campus Universitário. Av. P. H. Rolphs, s/n., 36570-000 Viçosa, MG, Brazil. (Poaceae) subfamily and they are divided into two 3. Autor para correspondência: [email protected] tribes. The first, Bambuseae, includes woody bamboos 136 M. T. Grombone-Guaratini et al.: Flowering and fruiting of Aulonemia aristulata and encompasses about 1,300 species, while the second, São Paulo, Aulonemia is represented by two species: Olyreae, includes the herbaceous bamboos, comprising Aulonemia aristulata (Döll) McClure and Aulonemia about 110 species (Clark et al. 1995, Judziewicz et al. fimbriatifolia L. G. Clark (Clark 2001, 2004). Aulonemia 1999). aristulata is one of the threatened species of the state of Brazil has the largest bamboo diversity in the New São Paulo (Mamede et al. 2007). In general, this species World, housing 89% of the genera and 65% of the known shows discontinuous and low density populations, but bamboo species (Filgueiras & Santos-Gonçalves 2004). can reach high density at forest edges and dominate Understory bamboos are a very important component the understory of canopy-disturbed forest patches. The of the Atlantic Forest (Filgueiras 1988). substantial biomass of this bamboo species, which forms Bamboos are plants that display rapid biomass large tussocks due to the voluminous underground net growth after long periods of exclusively vegetative of rhizomes, apparently has a negative effect on the growth (Griscom & Ashton, 2003, 2006), culminating survival of other arboreal species in the Parque Estadual in explosive flowering followed by widespread das Fontes do Ipiranga (PEFI). population death. The synchronized flowering and The purpose of this study was to describe not yet dieback of monocarpic bamboos normally reset the known flowering period, floral biology, fruiting, and regeneration process by creating an opportunity for seedling recruitment of A. aristulata in the Atlantic germination and growth of canopy species (Giordano Forest in Brazil. Moreover, floral visitors, natural et al. 2009). Nevertheless some studies consider the pollination (open pollination or control) and spontaneous massive bamboo seedling recruitment after reproduction self-pollination were also checked. an efficient strategy to suppress or delay the recruitment and colonization of tree species and the growth of adult Material and methods trees (Griscom & Ashton 2003). Floral characters observed in reproductive biology Study area – The study was carried out at the Parque studies have shown that in some bamboo species Estadual das Fontes do Ipiranga (PEFI), an urban isolated the gynoecium matures earlier than the androecium tropical forest fragment (ca 530 ha) located in São Paulo, (Ramanayake &Yakandawala 1998, Huang et al. 2002) SE Brazil (23°38’40” S, 46°36’38” W; 770-825 m.a.s.l.). while in others both, the gynoecium and the androecium The area is part of the São Paulo Green Belt Biosphere. The mature at the same time (John & Nadgauda 2002). regional climate is classified as Köppen’s Cwb type (1948) (i.e., temperate with a rainy summer and dry winter) (Santos Protandrous florets (the androecium matures earlier & Funari 2002). Average maximum and minimum annual than the gynoecium) are rare in bamboos (Ramanayake temperatures are 22.4 °C (February) and 15.7 °C (July), & Weerawardene 2003). The presence of seed set in respectively. Annual preciptation averages 1,540 mm, with enclosed synflorescences and embryo development in less than 100 mm of monthly precipitation from April to a few fruits indicates that apomixis is also possible in September (Santos & Funari 2002). The predominant soils bamboo species (Nadgauda et al. 1993, Ramanayake & are latosols according to the Brazilian Soil Classification Weerawardene 2003). System (Embrapa 1999). Due to the long intermast period for the mass Two non-contiguous sites within the PEFI were selected flowering of the majority of bamboo species (Janzen for this study. Past disturbances, such as logging, fire, and 1976), very few reports have investigated their sexual partial deforestation resulted in discontinuous canopy areas (Pivello & Peccinini 2002) that potentially promoted the reproduction. Among the Brazilian species, only the colonization of bamboo species into open forest patches. woody bamboos Actinocladum verticillatum (Nees) These sites exhibit a predominance of A. aristulata in the McClure (Filgueiras & Pereira 1988) and Merostachys understory (up to 4 m height), an open canopy and a low riedeliana Döll (Guilherme & Ressel