Part 2: Plant Structure—Stem

The stem is a plant’s primary structural support system above ground. In addition to supporting all of the plant’s shoot organs (leaves, buds, flowers, cones, fruit, etc.), the stem allows the plant to grow tall and increase its exposure to sunlight. Receiving adequate amounts of sunlight is critical for plants because it is the energy source that powers the process of photosynthesis. Much like roots, stems are usually branched to provide as much space as possible for leaf formation and the growth of reproductive structures such as flowers and fruits.

Inside of the stem is held the plant’s conducting system made up of two main types of conducting tissues: the xylem and the phloem. The xylem’s main function includes moving the water and minerals absorbed by the roots up throughout the rest of the plant. The phloem transports products made during photosynthesis (especially sugars) from the leaves to the rest of the plant where they are needed for further chemical reactions. The stem is also an important storage site for the sugars produced during photosynthesis and excess nutrients that have been absorbed from the soil. To accommodate its many functions, most stems are composed partially of lignin, a durable compound that gives flexibility, waterproofing properties, and compression resistance to the plant’s structure.

Cinnamon and cassia are examples of essential oils that are isolated by distillation from the inner bark, while Sandalwood is an essential oil that is distilled from the wood chips of the innermost part of the tree, the heartwood. On the other hand, frankincense and myrrh essential oils are carefully isolated from the resins that seep out from damaged parts of the wood and bark of their trees.