ABSTRACT
Kielmeyera coriacea Mart. (Clusiaceae), popularly known as "pau-santo", is a typical Brazilian cerrado tree known due to its varied secondary metabolites. This study aimed to determine the allelopathic potential of the hydroalcoholic extract of leaves of K. coriacea through bioassays of seed germination, seedling growth and mitotic index of Lactuca sativa L. (lettuce). In addition it was done the tetrazolium assay and a phytochemical screening. The extract concentrations caused alterations in germination parameters, in root growth and in the mitotic index. The phytochemical screening showed the presence of triterpenes, coumarins, steroids, flavonoids and condensed tannins, compounds known to confer allelopathic characteristics upon other species. These data indicate that K. coriacea presents an allelopathic potential because its leaf extracts interfere with germination and growth without any interference of pH and osmotic potential in the results.
Kielmeyera coriacea Mart. (Clusiaceae), conhecida popularmente como "pau-santo", é uma árvore típica do cerrado brasileiro, conhecida pelos seus variados metabólitos secundários. O estudo teve como objetivo determinar o potencial alelopático do extrato hidroalcoólico de folhas de K. coriacea por meio dos bioensaios de germinação, crescimento de plântulas e índice mitótico de Lactuca sativa L. (alface). Além disso, foi feito o teste de tetrazólio e uma triagem fitoquímica. As concentrações de extrato causaram alterações nos parâmetros de germinação, no crescimento radicular e no índice mitótico. A triagem fitoquímica mostrou a presença de triterpenos, cumarinas, esteroides, flavonoides e taninos condensados, compostos conhecidos por conferir características alelopáticas sobre outras espécies. Estes dados indicam que K. coriacea apresenta potencial alelopático pois o extrato de sua folha interfere na germinação e no crescimento da planta alvo, sem qualquer interferência do pH e do potencial osmótico.
Subject(s)
Lactuca , Germination , Guaiacum , Seedlings , Allelopathy , Mitotic Index , Trees , GrasslandABSTRACT
The spatial distribution of individuals is a fundamental property of most species and constitutes essential information for the development of restoration and conservation strategies, especially for endangered plant species. In this paper we describe the spatial distribution of different size classes of the endangered tropical tree Guaiacum sanctum and the effect of canopy cover on spatial aggregation. Adult G. sanctum were located and mapped in a 50ha plot in Palo Verde National Park, Costa Rica. Seedlings, saplings and juveniles were mapped to the nearest centimetre and permanently marked in three 50x50m subplots. Within each subplot spatial aggregation was assessed using Ripley’s K statistic and canopy opening readings were performed every 5m using a densitometer. Kriging spatial interpolation and Monte Carlo simulations were used to determine if average canopy cover differed among size classes. Individuals of G. sanctum were spatially aggregated at all size classes with seedlings being the most frequent size class in all subplots. Seedlings were found predominantly in areas with significantly higher canopy cover. In contrast, juveniles were more likely found in areas with higher light availability. The high number of seedlings, saplings, and juveniles relative to adults suggests that populations of G. sanctum in PVNP are expanding. Light availability and canopy structure are important factors shaping the spatial distribution of this species. The contemporary demographic structure of G. sanctum is dependent on forest gap dynamics and changes in human disturbance during the past 25 years.
La distribución espacial es una característica fundamental de las especies y es importante para el desarrollo de estrategias de conservación y manejo. Aquí presentamos la distribución espacial de varias etapas de desarrollo del árbol tropical Guaiacum sanctum, una especie en vías de extinción. Todos los adultos de G. sanctum se geo-referenciaron en una parcela de 50ha en el Parque Nacional Palo Verde. Las plántulas, los briznales y juveniles se mapearon en tres sub-parcelas de 50x50m. En cada sub-parcela se estimó la agregación espacial de los individuos mediante la K de Ripley. Observamos que los individuos de G. sanctum se encuentran siempre agregados, sin importar en que etapa de desarrollo se encuentren. Registramos la apertura del dosel cada 5m con un densiómetro y mediante una extra-polación espacial (Krigin) determinamos que las plántulas se agregan con mayor frecuencia en áreas con abundante cobertura de dosel, mientras que es más probable encontrar juveniles agregados en áreas con una mayor incidencia de luz. Las plántulas son los individuos más abundantes, esta distribución de edades nos sugiere que esta población probablemente está en expansión. Concluimos que el régimen lumínico y la cobertura de dosel son factores que afectan significativamente la distribución espacial del Guayacán Real.