Final answer:
Freshly cut celery remains fresh in water due to osmosis, where water moves into the cells across semipermeable membranes, ensuring the cells stay turgid and the celery crisp. This is similar to food preservation methods that use high osmotic pressure to prevent microbial growth.
Step-by-step explanation:
Freshly cut celery in a container of water is able to maintain its freshness due to osmosis, which is the movement of water from an area of low solute concentration to an area of high solute concentration across a semipermeable membrane. In this case, the water moves into the celery cells, which are in a hypotonic environment relative to the surrounding water. This influx of water helps keep the cells turgid, resulting in crispness.
When celery becomes limp, it's because it has lost water, leading to a loss of turgidity in its cells. By placing it back in water, we reverse this process, as water re-enters the cells, restoring their turgidity and the celery's crispness. This is similar to how certain preservation methods, such as adding high amounts of salt or sugar to foods like jams and cured meats, create an environment of high osmotic pressure that prevents microbial growth.
Celery's ability to maintain freshness in water also relies on its semipermeable membranes, which allow water to pass through while solute molecules are retained, creating the necessary conditions for osmosis. This natural preservation technique is due to how plants regulate water intake and loss, ensuring cellular health and structural integrity.