Very cool! My daughters and I took this experiment one step further and asked ourselves, what happens if the celery is placed in colored salt water? Will the salt make a difference? Let's see.
Nope...nothing! No colored celery. It appears that salt water made a big difference in this experiment. In addition, the rigidity of the celery differed. The celery in the tap water was still hard and firm. The celery in the salt water limped and could bend very easily. It was cool seeing the expressions on my daughters' faces when they noticed the difference in the celery.
Give it a shot!