my onion blew a bubble

Question

I regrew scallions in water and sand. They grew fast and healthy. After cutting a tip off, a bubble about 1 cm big has formed and has hung on for 24 hours. Why is this?

Answer 1

Isn't that interesting? Sounds like a fun project for a kid's experiment. I don't have time to look up specific scientific explanations, but I suspect it has to do with the composition of the sap in the scallion stem, which is not only slightly sugary because of the carbohydrates dissolved in it, but also has something a bit sticky or oily in it, and then the addition of the gases that are also in the sap, and the fluid pressure which moves the sap through the plant pressing against the liquid collecting at the site of the cut, and forming a bubble.