Question

Ethylene gas \(\left(\mathrm{C}_{2} \mathrm{H}_{4}\right)\) is emitted by fruits and is known to be responsible for their ripening. Based on this information, explain why a bunch of bananas ripens faster in a closed paper bag than in an open bowl.

Short answer

Bananas ripen faster in a closed paper bag due to trapped ethylene gas, increasing its concentration.

Step-by-step solution

Understanding Ethylene Gas

Ethylene ( C_2H_4 ) is a plant hormone that acts as a signaling molecule to regulate fruit ripening processes. When bananas produce ethylene, it accelerates their ripening and that of nearby fruits.

Closed Environment in Paper Bag

Placing bananas in a closed paper bag traps the ethylene gas emitted by the bananas, creating a concentrated environment. This higher concentration of ethylene leads to faster ripening.

Open Environment in Bowl

In an open bowl, ethylene gas can easily dissipate into the surrounding air, reducing its concentration around the bananas. This lower ethylene concentration results in slower ripening compared to when the gas is trapped.

Conclusion

In a closed paper bag, the ripening process is expedited because the ethylene concentration is kept high, whereas in an open bowl, the gas dissipates, slowing the ripening.

Key concepts

Fruit Ripening

Fruit ripening is a natural process that allows fruits to become sweeter, softer, and more palatable. This transformation is essential for the plant's reproductive process. Ripening involves several changes, like the conversion of starches to sugars, breakdown of acids, and changes in color, texture and aroma.

These changes not only make the fruit more appealing to animals, encouraging them to eat the fruit and disperse the seeds, but also prepare the seeds inside the fruit to grow into new plants. Ripening is a complex process controlled by both genetic factors and environmental conditions. The role of ethylene gas in accelerating this process makes it an important topic in studying plant biology.

Plant Hormones

Plant hormones, known as phytohormones, are naturally occurring compounds that regulate various processes in plants. These chemical messengers are essential for plant growth, development, and responses to environmental stimuli. One of the key plant hormones involved in fruit ripening is ethylene.

Ethylene is unique because it is a gaseous hormone.

• It regulates a variety of functions beyond fruit ripening, such as leaf shedding (abscission), flower blossoming, and stress responses to environmental changes.
• Ethylene influences cell growth and differentiation, impacting how the plant changes and adapts over time.

Ethylene production increases when fruit is stressed or injured, meaning it can also trigger in response to physical damage, further accelerating ripening.

Banana Ripening

Bananas, like many other fruits, produce ethylene gas naturally as they mature. Ethylene signals the banana cells to begin converting stored starches into sugar, which is why bananas get sweeter as they ripen. Their peel changes color from green to yellow, and they become softer and more aromatic.

Banana ripening can be influenced by surroundings. For example, placing bananas in a closed paper bag traps ethylene gas, creating a micro-environment where the gas can't escape. This increases the concentration of ethylene around the bananas, speeding up the ripening process significantly faster than if they were in an open-air environment like a bowl, where the ethylene concentration is diluted.

Therefore, understanding the relationship between ethylene and banana ripening can help you manage how quickly your bananas become ready to eat.

Gas Concentration

Gas concentration refers to the amount of a particular gas within a specific volume. In the context of fruit ripening, the concentration of ethylene gas around the fruit is crucial.

• When bananas or other fruits are placed in a closed container, their emitted ethylene gas accumulates, increasing the local concentration.
• This high concentration enhances the hormone's effect, driving the ripening process more swiftly.
• On the other hand, in an open space, the ethylene dissipates, leading to a lower concentration and therefore a slower ripening process.

Understanding gas concentration helps explain why fruits ripen at different rates under various conditions and can be applied to manage the timing of fruit ripening efficiently.