This section addresses the specialized functions of lateral branches. These include photosynthesis, duplication of the main axis, protection against predators, and vegetative propagation. Sometimes lateral shoots may develop as flowers or inflorescences and serve strictly reproductive functions.

Long vs. Short Shoots

      Often lateral branches may form a system of long and short shoots. While a lateral branch may extend with long internodes, its lateral buds may have very short internodes. In such a system, a long branch will appear to have clusters of leaves (short shoots) along its sides. The leaves that develop on the long shoot may differ from those on the short shoot.

      The short shoots have very little internodal expansion. Short shoots may bear photosynthetic organs, (leaves or needles), or may be specialized for a reproductive function as in the case of flowers. Short shoots may be determinate, as in Pinus, where a specific number of needles is produced (based on the species) per leaf cluster or short shoot. If the needles are detached from the fascicle, a new needle does not grow to take its place. In other plants, such as Ginkgo, the short shoots are indeterminate. Although the leaves abscise each autumn, new leaves are produced on the same short shoot the following spring.

Axillary Tubers or Bulbils

      Lateral shoots, in some plants like Dioscorea bulbifera, develop into storage organs, also called broodshoots. The main shoots of this plant produce serial axillary buds, one of which enlarges greatly and stores food in the form of carbohydrates. This enlarged lateral bud, or bulbil, eventually abscises from the parent plant and serves as a vegetative propagule.

Runners or Stolons

      Stolons are lateral shoots that extend plagiotropically (horizontally) and serve as a means of vegetative reproduction. At a certain distance from the mother plant, they form a new plant. A set number of leaves will be produced on the runner before a new plant will be established. The spider plant, a common house plant, provides a great example of this type of lateral shoot. At the terminus of the elongated shoot, a new plant forms, develops roots, and if it makes contact with a substrate, it will take root and begin to grow independently of the parent plant. Sometimes the shoot between the new plant and the parent plant withers and dies. The developing plant at the shoot tip then falls away. Once again, the new plant makes contact with a substrate and begins to grow on its own.

Thorn Shoots

      Thorn shoots are also highly modified lateral shoots and they are usually found in the leaf axil. Thorns may be branched or unbranched, and may or may not bear any foliar appendages. Thorns are a means of protection against herbivores and sometimes assist in anchoring a plant to a wall.