From Seed to Seed:
Plant Science for K-8 Educators


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Introduction to stems

"... that thing that comes up from the ground that the leaves attach to"

Stems are the aboveground structures that bear the plant's leaves and flowers. The stem provides a host of services to the plant:
  • It provides a pathway for transporting water up to the leaves, and moving the sugars produced in the leaves down to nourish the roots.

  • It acts as a sturdy mast to hold up the leaves and help orient them for maximum exposure to sunlight.

  • It can act as a storage site for carbohydrates.
All stems have nodes along their length. A node is the point at which a leaf attaches to the stem. The axillary buds that we introduced you to during the photosynthesis discussion are located at the nodes. (Remember that these buds, located just above where the leaf meets the stem, sprout to form new leaves or side shoots.) The section of the stem located between two nodes is called the internode. The very tip of the stem where the most rapid growth usually occurs is called the apical bud (Gr. apex = highest point).




Many familiar garden plants' stems are soft and green; these are called herbaceous (her-BAY-shus) stems. Examples include the stems of annuals like impatiens and lettuce, and perennials such as hostas and lupine. The stems of trees and shrubs also start out soft and green, but become woody as they mature. (Recall our earlier discussion about secondary growth producing wood.)

Stems contain vascular tissues-the "circulatory system" of the plant. Similar to our blood vessels, vascular tissues form an intricate network of veins that carry fluids throughout the plant. Large cells of the xylem (ZY-lem; Gr. xylon = wood) form a conduit for transporting water up from the roots. The smaller cells of the phloem (FLOW-em; Gr. phloos = bark) primarily transport sugars produced in the leaves, but are also involved in some water movement.

In herbaceous stems, the xylem and phloem are contained in vascular bundles.

A plant's shoot system consists of its aboveground stems, plus any branches and leaves.

Now let's put it all together...























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