Seasonal variation of soluble carbohydrates and starch in Echinolaena inflexa, a native grass species from the Brazilian savanna, and in the invasive grass Melinis minutiflora

Abstract

Echinolaena inflexa (Poir.) Chase is an abundant C3 grass species with high biomass production in the Brazilian savanna (cerrado); Melinis minutiflora Beauv. is an African C4 forage grass widespread in cerrado and probably displacing some native herbaceous species. In the present work, we analysed seasonally the content and composition of soluble carbohydrates, the starch amounts and the above-ground biomass (phytomass) of E. inflexa and M. minutiflora plants harvested in two transects at 5 and 130 m from the border in a restrict area of cerrado at the Biological Reserve and Experimental Station of Mogi-Guaçu (SP, Brazil). Results showed that water soluble carbohydrates and starch amounts from the shoots of both species varied according to the time of the year, whilst in the underground organs, variations were observed mainly in relation to the transects. Marked differences in the pattern of the above-ground biomass production between these two grasses relative to their location in the Reserve were also observed, with two peaks of the invasive species (July and January) at the Reserve border. The differences in carbohydrate accumulation, partitioning and composition of individual sugars concerning time of the year and location in the Reserve were more related to the annual growth cycle of both grasses and possibly to specific physiological responses of M. minutiflora to disturbed environments in the Reserve border.Keywords: biological invasion, cerrado, starch, sugars, tropical grasses. Variações sazonais de carboidratos solúveis e amido em Echinolaena inflexa, uma espécie nativa do cerrado, e na gramínea invasora Melinis minutiflora ResumoEchinolaena inflexa (Poir.) Chase é uma gramínea C3 muito abundante em áreas de cerrado e com alta produção de biomassa. Melinis minutiflora Beauv. é uma gramínea C4 de origem africana introduzida no Brasil para fins forrageiros, que se espalhou amplamente por áreas de cerrado, provavelmente deslocando espécies nativas. No presente trabalho, o conteúdo e a composição de carboidratos solúveis, o teor de amido e a biomassa aérea foram analisados sazonalmente em plantas de E. inflexa e M. minutiflora coletadas em dois transectos, a 5 e 130 m da borda da Reserva Biológica e Estação Experimental de Mogi-Guaçu, uma área restrita de cerrado (SP, Brasil). Os resultados mostraram que os carboidratos solúveis e o conteúdo de amido da parte aérea de ambas as espécies variaram de acordo com a época do ano, enquanto que nos órgãos subterrâneos as variações foram observadas principalmente em relação aos transectos. Diferenças marcantes no padrão de distribuição de biomassa aérea das duas espécies em relação à localização na reserva também foram observadas, com dois picos de produção da espécie invasora (em julho e janeiro) na borda da reserva. As diferenças observadas no acúmulo de carboidratos, partição e composição dos açúcares em relação à época do ano e localização na reserva foram mais relacionadas ao ciclo anual de crescimento de ambas as espécies e possivelmente a respostas f...

Diversity of non‐structural carbohydrates in grasses (Poaceae) from Brazil

“…In the case of tropical species, starch content in shoots of E. inflexa was lower during rainy periods, when the vegetative growth was higher. In contrast, during winter (driest season), the aerial biomass was reduced but the relative starch content increased (Souza et al ., ). This tendency was also observed for Paspalum notatum , another species growing in tropical and subtropical climate (Ribeiro et al ., ).…”

Competition with trees does not influence root characteristics of perennial grasses in semi-arid and arid savannas in South Africa

“…Contrary to our expectations we did not find any differences in the soluble sugar content in the grasses of the three sites. Sucrose is the predominant nonstructural carbohydrate in most tropical C 4 grasses (Busso et al, 1990;Souza et al, 2010;White, 1973) and reportedly aids fast aboveground growth during early wet season in dry savannas or after moderate defoliation (Danckwerts and Gordon, 1990;Souza et al, 2010). Soluble sugars are more labile than starch and can be easily broken down to simpler sugars compared to starch which can be used by plants.…”

Habitat filtering and interspecific competition influence phenological diversity in an assemblage of Neotropical savanna grasses

“…Although grass species flowered during the whole rainy season, flowering was concentrated at the middle of this period (mean date on February 7, Table 1). An explanation for this pattern is that that some species might need a buildup period to accumulates carbohydrates (Souza et al 2010) for completely vegetative growth and then flowering (Monasterio and Sarmiento 1976;Sarmiento 1992). For instance, the amount of starch in shoots of a Cerrado perennial grass Echinolaena inflexa is lower in the rainy season, when vegetative growth is higher, compared to the dry season, when vegetative growth is lower (Souza et al 2010).…”

“…Furthermore, in the dry season, the grasses go through a semi-rest phase without vegetative growth (Monasterio and Sarmiento 1976). Thus, in the rainy season they might need a build-up period to store carbohydrates and to vegetative growth (Munhoz and Felfili 2005;Souza et al 2010) before flowering.…”