Submitted by Tyler Hardy In this week’s lab, we took a close look at the characters of woody twigs of vascular plants. It may not seem like it initially, but there is a lot going on with these complex pieces of anatomy! These multi-faceted structures play an important role in several different plant functions, including water and nutrient transport, gas exchange, structural integrity, and new growth. Each twig has a variety of different organs present to be able to perform these duties; check it out! First, lets take a glance at a few twigs from different species, then we can break down what we are looking at. At the very tip of a twig, you can find the terminal or apical bud, enclosed within bud scales for protection. This is where the newest growth of this branch or twig happens. You may find similar, smaller structures to the sides of this and along the stem in areas known as axils. These are the axillary buds; from these buds, a plant may develop smaller vegetative or reproductive shoots. Just below each axillary bud, there is the leaf scar (or a leaf, depending on the plant and time of year), on the node where the leaf once was attached to the branch. The spaces between each node are called internodes. Within each leaf scar, notice the very small pores. These are the vascular bundle scars, the remnant of the vascular structures which once ran to and from the leaf. Following a twig lengthwise, you may notice how it maybe segmented by annular rings. These rings are the bud scale scars, what’s left from last year’s apical bud, and the space between each represents one year’s growth. All along the twig, look for small pores called lenticels. These help to provide gas exchange through the thick, protective bark that covers the woody parts of plants. And that’s just on the surface! Inside each twig are layers of protective tissues, photosynthetic tissues, structural tissues, and vascular tissues, all highly organized and intricately connected for maximum efficiency. So, next time you are picking up sticks in your yard, playing fetch with your dog, or just snapping twigs while you idle, try to remember what complex pieces of biological machinery it is that you are handling!
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