Obviously, the plants grow, but more importantly, children's interest in plants, ecosystems and the world grows. And what you have is a science center that gets more focus in the classroom as the children want to investigate and experiment and are motivated to use the science process skills naturally. The growth of your science center will also branch out and begin to vine into language, math, social studies, art, and music. The children will also have hands-on experience with concepts such as evaporation, propagation, capillary action, synthesis, biodiversity, and decomposition.
Sprouting lentils is a great start.
Then go from there. Allow freedom for the children to take risks, explore, make choices, be responsible and work together. Keep investigations and projects on-going and overlapping. Integrate in all disciplines. Learn along with the children.