Video Transcript
In high concentrations, what effect
do auxins have on cells in the root? (A) Auxins have no effect on the
growth of root cells. (B) Auxins stimulate cell
elongation and growth in the root. Or (C) auxins inhibit cell
elongation and growth in the root.
Let’s first remind ourselves what
auxins are and what they do. Auxins are plant hormones that
control cell elongation, among their many other functions. Auxins are typically produced in
the cells at the tip of plant stems and roots. When auxins are in a high
concentration in the cells of a plant stem, this will cause those cells to elongate,
often resulting in the plant stem growing upward or sometimes bending toward a light
source. However, auxins will generally have
the opposite effect on the cells in a root, where high concentrations of auxins tend
to inhibit cell elongation, thus preventing those cells from growing.
In this way, auxins can promote
positive geotropism, which is sometimes called positive gravitropism. This term describes the growth of
the roots downward into the Earth, toward the direction of the pull of gravity. But how do auxins achieve this in
the roots? By accumulating in and inhibiting
the growth of the cells on the lower side of the root while the other side grows
normally, auxins promote a turn in the root growth downward in the direction of
gravity. This can help the roots fulfil
their main function, which is to burrow deep down into soil where more water and
minerals are usually found so that they can absorb more of these essential
substances.
Now we know the effect that high
concentrations of auxins have on cells in the root. So we can answer this question
correctly. The correct answer must be (C). Auxins inhibit cell elongation and
growth in the root.
