Importance of germination indices in interpretation of allelochemical effects.

Sunflower cv. Suritross 42 and wheat cv. Inqalab 91 were evaluated for their natural allelopathic potential against Rumex dentatus. A germination test was conducted using leaf extracts (5, 10, 15, 20, 25 and 30%) of wheat and sunflower, and these were applied on seeds of R. dentatus. The germination indices used were: total germination (GT), number of days required for germination of 50% of the total seed number (T₅₀), number of days for 50% of the total number of seeds germinated (T₅₀), germination speed (S), speed of accumulated germination (AS) and coefficient of rate of germination (CRG). The germination index AS was the most sensitive among the 6 indices, while CRG was the least responsive. The aqueous extracts of sunflower and wheat at concentrations higher than 20% significantly reduced the total germination of tested seeds. Sunflower extracts even at 10 and 15% showed significant reduction in the germination speed and speed of accumulated germination.