COMPARATIVE ALLELOPATHY of Macaranga tanarius and Macaranga grandifolia against the AGRICULTURAL WEEDS Amaranthus spinosus, Corchorus olitorius, and Euphorbia heterophylla

john paul acedo camino (jp.camino@yahoo.com)
Natural Science and Mathematics Cluster, Ateneo de Davao University
June, 2014
 

Abstract

Abstract Macaranga tanarius has been shown to be allelopathic against a number of plants while other Macaranga species in the Philippines have been largely ignored in allelopathic studies despite their ubiquity and the burgeoning prospect of allelopathy as a weed management tool. This study aimed to compare the allelopathic activities of M. tanarius and M. grandifolia against the weeds A. spinosus, C. olitorius, and E. heterophylla. A series of leaf suspension concentrations (10%, 5%, and 1%) was applied regularly to different batches of weeds which were then assessed for reduction in juvenile parameters (germinant abundance, radicle length, and seedling shoot length) taken from two-day old weed seedlings, and adult parameters (height and biomass) taken from the weeds at their respective onset of flowering. Results attested to the allelopathic capabilities of both trees, with as little as 1% concentration capable of significantly reducing the germinant abundance, radicle length, height, and biomass of A. spinosus, indicating the allelopathic vulnerability of the said weed from early stage to maturity. C. olitorius, meanwhile, could only be inhibited by at least 5% concentration as juveniles but showed complete resistance to both trees at adulthood. Finally, E. heterophylla was totally resistant to both trees in all its juvenile parameters but was unusually susceptible to both trees as adult. All these indicate that allelopathy is stage- and species-specific against its target plant. Furthermore, the determination of the allelopathically susceptible stages of the target weeds can be exploited as a strategy in their control.