Apple Allelopathy: Accelerating the Ripening Process

Research Questions:

• What is allelopathy and ethylene gas?
• Which fruits and vegetables ripened prematurely?
• Which fruits and vegetables did not ripen prematurely?
• What are some advantages in speeding-up the ripening process?
• Why shouldn’t unripe fruit be stored together with ripe fruit?

Allelopathy is understood to mean the influence exerted by fruit and vegetable products on other plants or plants of the same species through the gases they give off, such as ethylene (ethene, C2H4). Ethylene gas from apples can accelerate the ripening process.

Materials:

• Two unripe apricots
• Two unripe avocados
• Two unripe green bananas
• Two unripe cucumbers
• Two unripe kiwifruit
• Two unripe peaches
• Two unripe greenish tomatoes
• Two unripe grapefruit
• Two unripe zucchinis
• Two unripe apples
• 20 quart-size zip-lock plastic bags
• 10 ripe red apples

Experimental Procedure:

1. Several days before the investigation allow 10 apples to ripen.
2. Secure 20 quart-size zip-lock plastic bags.
3. Secure all or some of the following unripe fruits and vegetables: apricot, avocado, green banana, cucumber, kiwifruit, peach, greenish tomato, grapefruit, zucchini, and an unripe apple.
4. Wash and dry the items to prevent the possibility of mold and/or fungi contamination.
5. Place each item into a separate bag.
6. Add one ripe apple to one of each pair of bags.
7. When the setup is complete there will be one bag of each fruit/vegetable WITH a ripe apple and another bag with just the fruit/vegetable and NO apple (control).
8. Seal all the bags.
9. Place all bags in a dry storage area. Do not place in the refrigerator!
10. Over the next couple days observe the items for ripening.
11. Each day describe the items as being “ripe” or “unripe” and enter the results into a data table.
12. The data in the table can be visually displayed by plotting a bar graph of “Premature ripening vs. Natural ripening of Fruits & Vegetables” on graph paper or a computer equipped with Excel, by listing the number of days to ripe on the vertical axis vs the names of the fruits and vegetables (variable and control) along the horizontal axis.

Terms/Concepts: allelopathy, ethylene gas, ethane, climacteric (time of maximum respiration), plant respiration, What might be an advantage of being able to cause premature ripening of fruits and vegetables by exposing them to ethylene gas produced by ripe apples?

Reference: Ethylene Action in Plants, by Nafees A. Khan (Springer-Verlag New York, LLC, 2006).