Germination and growth response of four plant species to different allelochemicals and herbicides

Laboratory bioassays were conducted to test the phytotoxicity of 6 allelochemicals (ferulic acid, p-hydroxybenzoic acid, 2-benzoxazolinone, L-mimosine, juglone, trans-cinnamic acid), 6 allelochemicals mixture and 2 herbicides (pendimethalin and S-metolachlor) on germination and seedling growth of 4 plants species (Rumex acetosa L., Lolium perenne L., Lactuca sativa L. and Dactylis glomerata L.). Data obtained were used to compare four germination indices viz., (total germination index (GT), speed of germination index (S), accumulated speed of germination index (AS), and coefficient of rate of germination index (CRG). The allelochemicals 2-benzoxazolinone and trans-cinnamic acid inhibited the total germination index of L. perenne L. at 1 μM concentration. The L- mimosine and six allelochemicals mixture (1 μM concentration) inhibited GT, S, AS, in L. perenne and also inhibited GT, S, AS in D. glomerata at 1 μM and 0.1 μM concentration. L- mimosine also inhibited the CRG in R. acetosa at 0.01 μM and in D. glomerata at 0.001 μM concentration. The six allelochemicals mixture (1 μM concentration) inhibited the speed of germination (S) of D. glomerata L. while trans-cinnamic acid inhibited the S in R. acetosa at 0.001 μM concentration. All other allelochemicals at 0.1, 0.01, 0.001 μM concentrations showed non-significant behavior to S all four plant species. Juglone inhibited GT of L. perenne at 1 μM concentration and in D. glomerata at 1 μM, 0.01 μM and CRG in R. acetosa at 0.01 μM concentration. The application of both herbicides strongly inhibited GT, S, AS, CRG in L. perenne L. and D. glomerata at concentration of 10⁴ μM. These results indicate that each index led to a different interpretation of allelochemicals effect on germination.