Skip to main content
Biology LibreTexts

8.6: Shoot Morphology

  • Page ID
    33463
  • Shoots are composed of nodes. Each node has a leaf and an axillary bud, which emerges from the leaf axil. The leaf is located just below the bud, which will become either a branch or a flower. The identity of each organ is determined by its location in the node.

    In the diagram below, label the bolded features, as well as the photosynthetic part of the leaf (the blade) and the stem of the leaf (the petiole). Label the bolded features in the diagram below.

    clipboard_effae5996fce3896d53c78dc349e640d1.png
    Figure \(\PageIndex{1}\): A node

    Scars and Features of a Woody Shoot

    When a leaf or bud falls off, it leaves a scar behind. Leaf scars are crescent shaped and have small, circular bundle scars within them where vascular bundles traversed the plant tissues. A leaf scar will be located below a bud, branch, or bud scar.

    Plants that grow in temperate regions generally have a growing season. Each year, the newly emerging growth is within the terminal bud which is protected by terminal bud scales. When these scales fall off as the new growth emerges, they leave a region of terminal bud scale scars behind. Regions between terminal bud scale scars represent one year of growth.

    On woody shoots, a layer of bark has replaced the epidermis (more on this in lab 8). To continue to exchange gases with the exterior environment, the bark layer develops small tears called lenticels. These can be small circular or elongated scars.

    Label the bolded features in the diagram below. Draw in leaf scars where they are missing!

    clipboard_ed7a44951c844b3fe40fcc2f47f995698.png
    Figure \(\PageIndex{2}\): Woody twig morphology

    Leaf Arrangement

    As shoots develop, the leaves are arranged in a particular order which can differ from plant to plant. In some plant species, one leaf emerges from the branch at a time (left) so leaves appear to alternate from side to side. This type of leaf arrangement is called alternate. In other plants, two leaves are formed on either side of the stem at the same time. This type of leaf arrangement is called opposite (middle). If three or more leaves are produced at the same region on the stem, the leaf arrangement is whorled (right).

    clipboard_e485742fdd5ac31f9d9b62f46e3d367c9.png
    Figure \(\PageIndex{3}\): Leaf arrangement

    Observe the shoots available in lab and identify the leaf arrangement and age of each. Record your findings in the table below.

    Shoot

    Leaf Arrangement

    Age (years)

    Contributors and Attributions