As an interesting (and potentially useful) side note, the browning of apples releases ethylene gas which is known to induce flowering of many plants, including pineapples, and ripening of fruits such as tomatoes, citrus, and melons.

Flowering can be induced by placing cut apple and your plant under a clear plastic tent, such as those used to hold in humidity. Once the plant flowers, remove the apple or the flowers will wilt very quickly.

To ripen fruit, store it in a bowl or a paper bag with ripe apples or apple peels.

Don't store apples near lettuce (causes spots and wilting), broccoli, cucumbers (turns them yellow), bananas (makes them brown faster), watermelon (makes it pulpy), or leafy greens (they'll lose their colour).