THE POTENTIAL EFFECTS OF ALLELOPATHIC MECHANISMS ON PLANT-SPECIES DIVERSITY AND DISTRIBUTION DETERMINED BY THE WHEAT ROOTLET GROWTH-INHIBITION BIOASSAY IN SOUTH-AMERICAN PLANTS

Phytotoxicity of aqueous extracts from 60 plant species from tropical and temperate communities was tested by wheat rootlet growth inhibitio n assay. Differences in the inhibition and stimulation of the growth o f the wheat rootlets were observed among both communities. 26.7% of th e total sample belonging to the tropical community showed considerable allelopathic activity in this bioassay, while 23.3% of the total samp le stimulated rootlet growth. On the other hand, 71.9% of the temperat e plants studied presented this activity, while none of the species sh owed stimulating effects. The possible influence of allelopathic effec ts on the coexistence of a particular mixture of plant species in a de termined area is discussed.