A barley crop contains broad-leaved weeds. An auxin-based selective weed killer is sprayed over the crop. Which statement explains why the barley plants are largely unharmed?
The weeds absorb less auxin than the barley, so the weeds are unable to keep growing
The barley absorbs the same amount of auxin as the weeds, but its growth is much slower
The barley absorbs less auxin than the weeds, so its growth does not become uncontrolled
The barley absorbs more auxin than the weeds, so it grows strongly enough to survive
87 exam-style questions on AQA GCSE Biology 5.4 Plant hormones, covering 5.4.1 Control and coordination and 5.4.2 Use of plant hormones (HT only). Each one has a worked solution and a mark scheme showing where the marks go.