You should also tell them that plants are wonderful at regeneration and will continue growing after parts have been cut as long as they are in a moist environment. After listing some of these considerations on the board, suggest the experiment to be carried out. A seedling will be cut approximately 0.5 inches from its top and the leaves will be placed on a moist piece of paper towel on the inside wall of the film canister, positioning the stem horizontally. Water is placed in the bottom of the cannister to provide high humidity and to wet the piece of paper so the leaves stick to it. Tell the students that under these moist conditions, the stem will continue growing.
Water also exhibits adhesive qualities.
Some students will predict that the stem will bend downwards if the cells are sensing gravity. Others may guess that the stem will grow straight out if the cells cannot sense gravity and others might think that it will bend upwards if the cells are acting more like a stem than a root, trying to orient the leaves opposite gravity. Put each possibility on the board and discuss it. After the discussion is done, take a vote on each hypothesis to determine which is the most popular. Next, hand out the supplies to the students so they can set up their experiments.