| Notes: Shoots |
Shoots, or stems, can be vegetative or floral. This means that the shoot can end with leaves or flowers.
Stem Vocabulary.
Nodes are points where leaves are attached. Internodes are the stem segments between nodes. The auxillary bud is located at the angle formed by nodes with the main stem and is usually dormant. This bud can develop into a vegetative shoot with its own terminal bud or a floral shoot. Why? The terminal bud is the area of concentrated growth in most plants. Its own growth exhibits apical dominance, inhibiting the growth of auxillary buds. Around the terminal bud is a complex arrangement of nodes and internodes with maturing leaves.
Apical Dominance.
Apical dominance is often thought of as an evolutionary adaptation to competition for sunlight: the taller the plant is the more of the plant is exposed to light; thus, more photosynthesis can occur. Apical dominance demonstrates the rationale of pruning and "pinching back." Cut the terminal bud and the plant grows wider; cut the auxillary buds and the plant grows taller. However, it is important to remember that plants also need to increase exposure to the environment for reasons such as pollenation; therefore, branching is a very important concept as well as vertical growth.
Modified Stems.
These perform many different types of functions for the plant. The following is a list of types and functions:
Stolon: this is a horizontal stem that extends along the surface. An example would be strawberry plants.
Rhizome: this is a horizontal underground stem that often stores food with the help of tubers.
Tuber: this is often a bulby extension of a rhizome that stores food. An example would be a potato.
Bulb: this is a vertical underground stem with fleshy food-storing capabilities. An example would be an onion.
Next: "Leaves."