Ethylene and Fruit Ripening

Observe how ethylene gas speeds ripening and wilts flowers

Difficulty: Very Easy | Time: 2-7 days | Visual Impact: High

Historical Context

Ethylene’s role in plant biology was discovered accidentally. In the early 1900s, farmers noticed that fruit stored near kerosene heaters ripened faster. Russian scientist Dmitry Neljubow identified ethylene as the culprit in 1901, and in 1934, R. Gane confirmed that plants themselves produce ethylene.

This tiny molecule (C₂H₄) turned out to be a major plant hormone - the only gaseous hormone known in plants. It regulates ripening, flowering, leaf drop, and stress responses. The discovery revolutionized the fruit industry: today, bananas are shipped green and ripened on demand with ethylene gas, while apples are stored in low-ethylene environments to stay fresh for months.

The same hormone that ripens fruit also signals flowers to wilt and die - a response that makes biological sense (after pollination, petals are no longer needed) but frustrates florists and flower lovers.

Materials

  • Ripe banana (or apple) - 1
  • Green bananas or unripe tomatoes - 2-4
  • Fresh cut flowers (carnations work well) - 2-4 stems
  • Paper bags - 3
  • Glass jars or containers with lids - optional

Procedure

Part A: Accelerated Ripening

  1. Place one green banana in a paper bag with a ripe banana
  2. Place another green banana in a paper bag alone (control)
  3. Leave a third green banana in open air (second control)
  4. Fold bags closed loosely (don’t seal airtight)
  5. Check daily - the banana with the ripe companion ripens 2-3 days faster

Part B: Flower Wilting

  1. Place one fresh flower in a jar or bag with a ripe banana
  2. Place another flower in a bag alone (control)
  3. Keep a third flower in a vase with water (second control)
  4. Observe over 24-48 hours
  5. The flower exposed to banana wilts dramatically faster

The Science

Ethylene (C₂H₄) is a gaseous plant hormone:

Effect Mechanism
Fruit ripening Breaks down cell walls, converts starch to sugar, develops color and aroma
Flower wilting Triggers senescence (aging), causes petal drop
Leaf yellowing Breaks down chlorophyll

High ethylene producers: - Ripe bananas, apples, avocados, tomatoes - Damaged or stressed fruit

Ethylene-sensitive items: - Unripe fruit (will ripen faster) - Cut flowers (will wilt faster) - Leafy vegetables (will yellow)

This is why you should: - Store bananas away from other fruit (unless you want them to ripen) - Keep flowers away from the fruit bowl - Store apples separately from other produce

Variations

  • Quantitative version: Weigh fruit daily to track water loss and ripening
  • Temperature effect: Compare ripening rates at room temperature vs refrigerator
  • Blocking ethylene: Commercial produce uses 1-MCP to block ethylene receptors; you can test if a slightly open bag slows the effect
  • Different fruits: Test which fruits produce more ethylene (apples vs bananas vs tomatoes)

Real-World Applications

  • Commercial ripening rooms: Bananas are gassed with ethylene to ripen uniformly
  • Controlled atmosphere storage: Apples stored with low O₂ and no ethylene stay fresh for months
  • 1-MCP treatment: Flowers and produce are treated to block ethylene response
  • “One bad apple spoils the bunch”: This proverb is literally true - damaged fruit releases ethylene

Resources