A gardener investigated the effect of different concentrations of a synthetic auxin herbicide on daisy plants growing in a lawn.
The table below shows the gardener's results three weeks after applying the herbicide.
| Concentration of synthetic auxin herbicide (%) | Number of daisy plants in a 1 m2 plot | |
|---|---|---|
| Before treatment | Three weeks after treatment | |
| 0 (Control) | 12 | 12 |
| 10 | 11 | 11 |
| 20 | 13 | 9 |
| 30 | 10 | 4 |
| 40 | 12 | 0 |
State and explain the conclusions the gardener can make from these results.
