Resprouting from roots in four Brazilian tree species

Previous studies pointed out that species richness and high density values within the Leguminosae in Brazilian forest fragments affected by fire could be due, at least partially, to the high incidence of root sprouting in this family. However, there are few studies of the factors that induce root sprouting in woody plants after disturbance. We investigated the bud formation on root cuttings, and considered a man-made disturbance that isolates the root from the shoot apical dominance of three Leguminosae (Bauhinia forficata Link., Centrolobium tomentosum Guill. ex Benth, and Inga laurina (Sw.) Willd) and one Rutaceae (Esenbeckia febrifuga (St. Hil.) Juss. ex Mart.). All these species resprout frequently after fire. We also attempted to induce bud formation on root systems by removing the main trunk, girdling or sectioning the shallow lateral roots from forest tree species Esenbeckia febrifuga and Hymenaea courbaril L. We identified the origin of shoot primordia and their early development by fixing the samples in Karnovsky solution, dehydrating in ethyl alcohol series and embedding in plastic resin. Serial sections were cut on a rotary microtome and stained with toluidine blue O. Permanent slides were mounted in synthetic resin. We observed different modes of bud origin on root cuttings: close to the vascular cambium (C. tomentosum), from the callus (B. forficata and E. febrifuga) and from the phloematic parenchyma proliferation (I. laurina). Fragments of B. forficata root bark were also capable of forming reparative buds from healing phellogen formed in callus in the bark’s inner side. In the attempt of bud induction on root systems, Hymenaea courbaril did not respond to any of the induction tests, probably because of plant age. However, Esenbeckia febrifuga roots formed suckers when the main trunk was removed or their roots were sectioned and isolated from the original plant. We experimentally demonstrated the ability of four tree species to resprout from roots after disturbance. Our results suggest that the release of apical dominance enables root resprouting in the studied species. Rev. Biol. Trop. 57 (3): 789-800. Epub 2009 September 30.

Estudios anteriores señalaron que la alta riqueza de especies de Leguminosae en fragmentos de bosques afectadas por el fuego podría deberse, al menos parcialmente, a la alta incidencia de brotes de raíz en esta familia. Sin embargo, existen pocos estudios. Investigamos la formación de brotes en tres Leguminosae (Bauhinia forficata Link., Centrolobium tomentosum Guill. ex Benth, e Inga laurina (Sw.) Willd) y una Rutaceae (Esenbeckia febrifuga (St. Hil.) Juss. ex Mart.). Todas estas especies suelen rebrotar después de los incendios. También hicimos cortes experimentales en árboles forestales: Esenbeckia febrifuga e Hymenaea courbaril L. Observamos tres orígenes: cerca del cambium vascular (C. tomentosum), desde el callo (B. forficata y E. febrifuga) y de parénquima (I. laurina). Hymenaea courbaril no respondió a ninguna de las pruebas de inducción, probablemente debido a la edad de la planta. Sin embargo, las raíces de Esenbeckia febrifuga forman retoños tras retirar el tronco o separar sus raíces. Hemos demostrado experimentalmente la capacidad de las cuatro especies de árbol de rebrotar a partir de sus raíces tras una perturbación grave.

Diurnal and seasonal carbon balance of four tropical tree species differing in successional status / Balanço de carbono diurno e sazonal de quatro espécies tropicais arbóreas de diferentes grupos sucessionais

This study addressed some questions about how a suitable leaf carbon balance can be attained for different functional groups of tropical tree species under contrasting forest light environments. The study was carried out in a fragment of semi-deciduous seasonal forest in Narandiba county, São Paulo Estate, Brazil. 10-month-old seedlings of four tropical tree species, Bauhinia forficata Link (Caesalpinioideae) and Guazuma ulmifolia Lam. (Sterculiaceae) as light-demanding pioneer species, and Hymenaea courbaril L. (Caesalpinioideae) and Esenbeckia leiocarpa Engl. (Rutaceae) as late successional species, were grown under gap and understorey conditions. Diurnal courses of net photosynthesis (Pn) and transpiration were recorded with an open system portable infrared gas analyzer in two different seasons. Dark respiration and photorespiration were also evaluated in the same leaves used for Pn measurements after dark adaptation. Our results showed that diurnal-integrated dark respiration (Rdi) of late successional species were similar to pioneer species. On the other hand, photorespiration rates were often higher in pioneer than in late successional species in the gap. However, the relative contribution of these parameters to leaf carbon balance was similar in all species in both environmental conditions. Considering diurnal-integrated values, gross photosynthesis (Pgi) was dramatically higher in gap than in understorey, regardless of species. In both evaluated months, there were no differences among species of different functional groups under shade conditions. The same was observed in May (dry season) under gap conditions. In such light environment, pioneers were distinguished from late successional species in November (wet season), showing that ecophysiological performance can have a straightforward relation to seasonality.

Este estudo considerou algumas questões sobre como um adequado balanço de carbono foliar pode ser obtido por diferentes grupos funcionais de espécies tropicais arbóreas sob contrastantes ambientes luminosos em uma floresta. O estudo foi realizado em um fragmento de floresta estacional semidecidual localizada no município de Narandiba, Estado de São Paulo. Plântulas com dez meses de idade de quatro espécies, Bauhinia forficata Link (Caesalpinioideae) e Guazuma ulmifolia Lam. (Sterculiaceae) como espécies pioneiras, e Hymenaea courbaril L. (Caesalpinioideae) e Esenbeckia leiocarpa Engl. (Rutaceae) como espécies secundárias, cresceram em um ambiente de clareira e um de sub-bosque durante nove meses. Cursos diários da fotossíntese líquida (Pn) e transpiração foram medidos com um medidor portátil de trocas gasosas por infravermelho nas estações seca e chuvosa. A respiração no escuro (Rd) e a fotorrespiração (Pr) foram também avaliadas nas mesmas folhas utilizadas para as medidas de Pn após um período de adaptação ao escuro. Nossos resultados mostraram que a respiração integrada ao longo do dia foi similar entre as espécies dos dois grupos sucessionais. Por outro lado, a fotorrespiração das espécies pioneiras foi freqüentemente maior do que nas espécies secundárias em condições de clareira. Todavia, a contribuição relativa de Pr no balanço de carbono nas folhas foi similar em todas as espécies em ambos os ambientes. Independentemente da espécie, a fotossíntese bruta, considerando os valores integrados ao longo do dia, foi significativamente maior na clareira que no sub-bosque. Nas duas épocas avaliadas, não foram observadas diferenças significativas em nenhum dos parâmetros avaliados entre as espécies crescidas no ambiente de sub-bosque. O mesmo foi observado no mês de maio sob condições de clareira. No mês de novembro, as espécies pioneiras apresentaram uma performance ecofisiológica significativamente distinta das espécies secundárias no ...