Ethylene Triggers the Ripening of Fruit for Many Plant Species

question 19

Multiple Choice

Ethylene triggers the ripening of fruit for many plant species but does not seem to play an important role for the ripening of grapes. Scientists hypothesized that the trigger for the ripening of grape fruits is abscisic acid (ABA) . They sprayed unripe Cabernet Sauvignon grapes with different concentrations of ABA and tracked several fruit characteristics over time: percent of fruits that are purple, concentration of anthocyanin (a purple pigment) per fruit, weight of each fruit, and total soluble solids per fruit as measured by °Brix. °Brix measurements indicate the amount of sugar in the fruit, and determine how much alcohol a wine will have. Higher values of each measurement indicate a greater degree of ripening. The scientists' results are shown in these four graphs.
Source: Wheeler, S., Loveys, B., Ford, C., & Davies, C. (2009) . The relationship between the expression of abscisic acid biosynthesis genes, accumulation of abscisic acid and the promotion of Vitis vinifera L. berry ripening by abscisic acid. Australian Journal of Grape and Wine Research, 15(3) , 195-204.
-The visual indicator for grape ripening is the color of the fruit. Does adding ABA appear to speed up the ripening of grape fruit?

• A) Yes, because fruits that were treated with ABA have more anthocyanin (purple pigment) earlier than the control.
• B) Yes, because there were always more colored fruits in both ABA treatments compared to the control.
• C) No, because fruits in all the treatments were colored by the end of the experiment.
• D) No, because fruits in all the treatments have similar amounts of anthocyanin (purple pigment) by the end of the experiment.