Last time we learned that water moves through a plant due to cohesion of water molecules to each other and water to sides of vessels and tracheids. It is pulled up under considerable tension. Wood is strong because it is made up of the combined primary and secondary cell walls of many tracheids, vessels and fibers. None of this tells us why oaks get their leaves later than maples, though.
Plants are able to close stomata.
O moves into guard cells, causing them to swell 4. CO 2 taken up by Rubisco 7. O diffuses out of open stoma 2. In general, when conditions for photosynthesis are favorable, stomata are open, otherwise, they are closed. In lab, we worked with excised stems.