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Abstract
Phytotoxins include a variety of secondary metabolites which are released from plants into the environment by means of four ecological processes such as volatilization, leaching, root exudation and decomposition of plant residues in soil. And these influence growth, development and metabolism of plants. This phenomenon is known as allelopathy. While the ecological importance of allelopathy in weed-crop interaction has caught the attention of several workers, very little effort has been directed towards allelopathic studies of weeds on their associated counterparts. Therefore, the purpose of this investigation is to screen out the phytotoxicity of leaf extracts and leaf leachates of a vigourously growing weed Eupatorium odoratum L. on its associated weed Mimosa pudica L. And the allelopathic effect was measured in terms of seed germination behaviour field emergence capacity, seedling growth and some reliable biochemical indices. The present study reveals that seed pretreatment of Mimosa pudica with various concentrations of Eupatorium leaf extracts and leaf leachates for 24 reduced percentage germination and increased the time required for 50% germination (T50) of Mimosa seeds. Seedling performance of Mimosa was found to be much poor when they were raised from seeds which underwent pretreatment with the leaf extracts and leachates of Eupatorium. This was measured in terms of root, shoot and internodal length, leaf number and leaf area per plant, as well as fresh and dry weight of seedlings. Decreased seedling potential in the leaf extract and leaf leachate pretreated samples was evidenced from the lower level of chlorophyll and protein, as well as reduced activity of catalase enzyme. Leaf extract and leaf leachate – induced retarded germinability, suppressed activity of catalase enzyme and increased levels of soluble carbohydrate being the important allelopathic indices, it can be concluded that Eupatorium can potentially render allelopathic action on Mimosa.