Allelopathic effects of Dicranopteris linearis debris on common weeds of Malaysia

Greenhouse experiments were conducted to study the allelopathic effects of debris of Dicranopteris linearis on emergence and growth of 10 Malaysian common weeds; 5 broad-leaved weeds (Asystasia gangetica, Melastoma malabathricum, Ageratum conyzoides, Mimosa pudica and Crassocephalum crepidioides) and 5 grasses (Echinochloa colona, Eleusine indica, Paspalum conjugatum, Dactyloctenium aegyptium and Chloris barbata) in greenhouse.

The aerial tissues (shoot mass) of D. linearis inhibited the emergence of test species more than the underground tissues (underground mass). Covering the soil surface with the debris, inhibited the seedlings emergence of test species more than debris incorporation into the soil. The shoot mass debris quantity required for incorporation into the soil to inhibit 50% emergence of bioassay species (I₅₀) was 31.51 g/kg. Among the test species grown in the soil with incorporated shoot mass, M. malabathricum was most tolerant, while, Crassocephalum crepidioides was most sensitive. The soil with incorporated shoot mass severely suppressed the growth of test species. The concentration of shoot mass debris quantity fo soil incorporation required for 50% (I₅₀) inhibition of fresh bioassay species was 5.19 g/kg. Compared to the shoot mass debris, the underground mass debris had little effect on the growth of test species covering the soil surface with shoot mass debris decreased the growth of all test spp, except M. malabathricum, rather its growth was ameliorated. Since the allelopathic effects on emergence and growth of test species were positively correlated to the total water-soluble phenolic compounds in the soil and in the debris of D. linearis, it is suggested that the allelopathic effects on the test species may be caused by phenolic compounds. shoot mass showed stronger allelopathic effects than underground mass, due to higher content of phenolic compounds in shoot mass (83.25 mg phenolic compounds/g tissue) than underground mass (1.13 mg phenolic compounds/g tissue).