A student marks equal lengths on the upper and lower sides of a horizontal root. After several hours, the upper marked length has increased more.
Which explanation is correct?
more auxin on the upper side stimulated elongation there
more auxin on the lower side inhibited elongation there
more auxin on the upper side inhibited elongation there
more auxin on the lower side stimulated elongation there
46 exam-style questions on Edexcel GCSE Biology 6.3 Plant hormones, covering 6.3.1 Plant hormones and tropisms and 6.3.2 Commercial uses of plant hormones. Each one has a worked solution and a mark scheme showing where the marks go.