Table 2. Potential ability of HHPEBA in the medium to growth inhibition.

	Potential growth inhibition (%)
Position (m)	Coleoptile	Root
1	37.1	42.8
2	26.2	34.4
3	14.8	23.3
4	6.3	10.6

The potential growth inhibition on ryegrass caused by HHPEBA was calculated using the equations of logistic functions (Fig. 2) with substituting X values by the concentrations of the compound found in the bioassay medium (Table 1) as described in the text.