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Q17 - ABA and Ethephon Effects on Sweet Cherry Ripening

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

To study the effect of phytohormones on fruit maturation, researchers used abscisic acid (ABA) and ethephon to treat sweet cherry fruits and afterward evaluated the expression of the PacNCED1 gene, which encodes 9-cis-epoxycarotenoid dioxygenase, a key enzyme in ABA biosynthesis. They also checked the expression of the PacACO1 gene, encoding 1-aminocyclopropane-1-carboxylic acid oxidase, an enzyme involved in ethylene biosynthesis. The transcript of PacACT1 (a beta-actin cDNA fragment) was used to standardize all expression measurements (Fig.Q17-D).

Treatment Firmness of pulp Soluble solids content/titratable acidity Anthocyanin (U.g-1)
Control 20.3a 14.4a 13.4a
Ethephon 19.6a 15.3a 14.4a
ABA 11.9b 16.8b 23.8b

(a and b indicate values that are significantly different.)

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. Both ABA and Ethephon stimulate the expression of PacACO1 and PacNCED1 genes in sweet cherry fruit.
B. The expression of PacNCED1 and ABA accumulation in pulp are higher than in the seed in the treatments of ABA
C. ABA induces the maturation of sweet cherry fruit via stimulation of ethylene production.
D. Ethephon shows lower effect on anthocyanin and endogenous ABA production than exogenous ABA does.
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Question reproduced from IBO 2016, Theoretical Paper A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)