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← Theoretical A

Q30 — Gibberellin Transport and Root Endodermis Suberization

Theoretical A Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Plant Hormones Root Anatomy

Gibberellin, an essential phytohormone responsible for cell wall suberization, undergoes complex transport within plants involving a variety of transporters. Below are figures depicting results from studies on different membrane transporters of gibberellin.

Bar chart of fluorescence intensity of a suberin marker in root endodermal cells across grafted wild-type and mutant plants, alongside a diagram comparing cytoplasmic and vacuolar gibberellin concentration in root cell types. Figure 1. A Fluorescence intensity (Y) of root endodermal cells in grafted plants (X, root/shoot). Samples were treated with a fluorescent marker for suberin (Nile red); asterisks indicate a significant difference from the wild type. Col-0 - wild type, ga1-3 - mutant lacking gibberellin synthesis, npf__ - mutants lacking expression of a specific type of transporter(s). B Cytoplasmic (I) and vacuolar (II) concentrations of gibberellin (arbitrary units) in the root.

On your answer sheet, indicate “T” for true statements and “F” for false ones.

A. Transport of gibberellins occurs in the following direction: root to shoot.
B. Vacuoles of the pericycle cells are involved in the regulation of threshold values of gibberellin concentration.
C. The npf3.1 mutant is vulnerable to water and mineral imbalances, as well as toxins, compared to wild type.
D. All the transporters listed are located on the plasma membrane.
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Question reproduced from IBO 2024, Theoretical Exam Part A, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)