Allelopathic potential of bark and leaves of Esenbeckia leiocarpa Engl. (Rutaceae)

Flaviana Maluf Souza,Sergius Gandolfi,Ricardo Ribeiro Rodrigues,Sonia Cristina Juliano Gualtieri De Andrade Perez Perez

doi:10.1590/s0102-33062010000100016

Abstract

We investigated the inhibitory potential of aqueous extracts of bark and leaves of Esenbeckia leiocarpa Engl. on lettuce germination and early seedling growth. We compared the effects of four concentrations (100, 75, 50 and 25%) of each extract to water and polyethylene glycol (PEG 6000) solution controls for four replicates of 50 seeds for germination and four replicates of ten seedlings for seedling growth. The inhibitory effects of E. leiocarpa extracts on the percentage of germination and on the germination speed seemed to be more than simply an osmotic effect, except for the percentage of seeds germinated in bark extracts. When compared to water control, both bark and leaf extracts delayed germination, and leaf extracts also affected the percentage of germinated seeds. Leaf extracts of all concentrations strongly inhibited the development of seedlings and caused them some degree of abnormality; bark extracts also caused abnormalities and reduced seedling growth. Root development was more sensitive to the extracts than hypocotyl growth. The negative effects of leaf extracts on germination and seedling growth were more pronounced than those of bark extracts, and the overall effects of both extracts were positively correlated with extract concentrations.

Highlights

Tropical forests are known for their high diversity, and the countless interactions of all organisms with biotic and abiotic factors in these forests still make the understanding of the processes responsible for community organization a complex and intriguing subject.Among the factors that determine community structure and dynamics are the positive and negative plant-plant interactions (Callaway & Walker 1997; Lortie et al 2004; Michalet et al 2006)
The germination speeds of the seeds in the 75, 50 and 25% leaf extracts and in the 100 and 75% bark extracts were lower than those observed in the water control (F = 87.50; d.f. = 7; p < 0.001; Fig. 2); the value recorded in the 100% leaf extract (0.18 days-1) was lower than the lower limits of the confidence
The differences in the percentages of germination and germination speed between the 100% leaf extract and PEG 6000 suggest that the inhibition of germination was an effect of the osmotic potential

Summary

Introduction

Among the factors that determine community structure and dynamics are the positive and negative plant-plant interactions (Callaway & Walker 1997; Lortie et al 2004; Michalet et al 2006). One of the several ways by which plants can interact is through the release of secondary metabolites in the environment, which may cause direct or indirect interference of one plant on another, by a process called allelopathy (Rice 1984). Some authors suggest that allelopathic effects can contribute to promote shifts in density, dominance and spatial patterns of plant populations (Rice 1984; Wardle et al 1998; Chou 1999; Ridenour & Callaway 2001). Allelopathic plants may have a differential role in species coexistence (Inderjit & Callaway 2003) and in forest succession (Peng et al 2004). Allelopathy is a poorly studied mechanism among tropical tree species, and the relevance of this process has probably been underestimated in the theories about the driving forces of ecological processes in tropical forests

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Conclusion