A field has been watered by irrigation for a number of years. The salts that were in the irrigation water have accumulated in the soil, making the solute concentration much higher than it was before. You notice that while water is still plentiful, plants in the field seem to be wilting. How would a change in water's solute concentration affect water uptake by plants?
The force that pulls water up xylem is not unlike the force that pulls water up into a syringe. The wider the diameter of the syringe, the greater the force on the sides of the syringe. Vessel elements are larger in diameter than tracheids. Which would you expect to have stronger walls—vessel elements or trachieds? The xylem of gymnosperms, such as pine trees, contains only tracheids while the xylem in angiosperms, such as oak trees, contains both tracheids and vessel elements. Relate this information to the strength of the wood in pine trees and oak trees.