An investigation into the coordination of growth in plants was carried out using decapitated oat (Avena) coleoptiles kept in complete darkness. The experimental setups and the corresponding growth results are shown in the diagram below:
Which of the following statements is a valid conclusion or explanation based on these results?
Treatments Q and R demonstrate that the asymmetric growth causing curvature is driven by vertical auxin transport down the side of placement rather than lateral diffusion across the midline.
Treatment S is a control showing that the mechanical pressure of the agar block is the primary stimulus for asymmetric cell elongation.
Treatment P demonstrates that auxin acts as a growth inhibitor unless it is distributed asymmetrically.
Treatment R shows that the vertical mica sheet actively blocks the synthesis of auxin in the elongation zone of the coleoptile.
