Dogwood trees are among the first to bloom in the spring, acting as harbingers of fair weather to come. Homeowners value the trees for their small stature and big blossoms. In nature, dogwoods nestle themselves beneath taller trees, spreading branches and roots wide to collect what they can of sunlight and water, producing their distinctive flowers and berries in order to reproduce.
Form and Function
Studying the anatomy of a plant is more than just a descriptive or taxonomic activity. It also helps you to understand the plant's particular role in its environment and how it relates to the other species around it. The small stature and distinctive flowers of the dogwood tree reveal its role in the forest ecosystem and provide clues about how it grows and reproduces. For the landscaper or gardener, this information, in turn, allows her to effectively grow the dogwood tree as a garden plant.
Dogwood trees do not grow large, reflecting their position in the forest community as an understory tree. Their small stature allows them to grow into the spaces left beneath other trees. Because of this, dogwoods often cannot tolerate extended periods of full sun. While the shade beneath the forest canopy means less light for creating energy, it also means less water loss and sun damage to the tree's leaves. Dogwoods develop extensive but shallow root systems that allow them to obtain water from a broad area surrounding the tree. Without the protective shade, the surface layer of soil from which dogwoods take their water quickly dries, dehydrating the tree.
Dogwood trees produce energy in their leaves through photosynthesis, a chemical reaction that converts sunlight into sugar. Because dogwoods are understory trees, they are blocked from receiving a lot of sunlight during the summer. Because of this, dogwood branches spread wide, often growing parallel to the ground, until some trees are wider than they are tall, enabling them to capture sunlight over a broader area. Dogwoods are deciduous trees, so they lose their leaves in the fall, protecting themselves from dehydration when the ground freezes and their roots can no longer extract water to compensate for what is lost from the leaves.
Dogwood trees produce large showy blossoms in the spring, and blossoms may be white, pink or pale yellow. However, what most people recognize as flower petals are in fact bracts, modified leaves that surround the actual flower. Four teardrop-shaped bracts radiate from a center that bristles with the tree's actual flowers, small yellow-green structures. Because the actual flowers are so small and relatively dull in color, the large bracts function to attract insect pollinators. Flowers contain both male and female parts that produce pollen and seeds, respectively. For fertilization to occur and seeds to form, pollen must be transferred to the female pistil, a task that insects help to accomplish.
Once the pollen sticks the pistil at the center of a dogwood flower, a thin pollen tube extends into the flower and releases sperm into the egg. From this, a seed forms. Dogwood trees produce one seed per flower, encapsulated in a bright red berry. Berries form from the plant's ovary, fleshing out into a pericarp or fruit coat, the color and sweetness of which attracts birds and other animals. When they ingest the seed and later expel it in their droppings, they effectively transport a new dogwood tree to a location it couldn't reach through normal dispersal methods.
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