This is a great project. Very interesting. Imagine tomato seeds sprouting inside of a tomato. I thought the seeds had to dry out before sprouting - misconceptions I suppose. Right now I have tomatoes on my windowsill in big canning jars, doing very well, flowering with red tomatoes. I'm trying to keep it going as long as possible, I was able to get it to flower again.
Thanks. I found it interesting as well that seeds would sprout inside a tomato. Apparently, if the tomato ripens very slowly in cool conditions, the hormone preventing sprouting can expire. This tomato came from a plant left in an unheated hoop house in zone 3 into November. Here is a link to the video if you're interested. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-O2_IZMxjrlo.html
It will probably work even better for your lettuce and spinach than for my tomato plant. It is a challenge to provide enough light in the house in January for a tomato plant.
