An onion bulb begins to sprout while lying on its side in a closed, opaque box. Measurements show that cells on the upper side of each young root elongate faster than cells on its lower side. In the shoot, cells on the lower side elongate faster than cells on its upper side.
Which statement describes the auxin distribution that produced these observations?
Auxin was distributed evenly between the upper and lower sides of both organs.
More auxin was present on the lower side of both the roots and the shoot.
More auxin was present on the lower side of the roots and the upper side of the shoot.
More auxin was present on the upper side of the roots and the lower side of the shoot.
105 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.