The controlling, life-supporting element of any plant is its canopy, the outer-most existing layer of foliage and vegetation. The tree canopy, compromised of leaves, fine branches, and twigs, fashions an environment which is able to function in many different, useful ways while being capable to support living organisms. Some of these functions include filtering the pollutants out of the air, dragging the wind, converting solar energy into sugar and water through photosynthesis, controlling the exchange of energy and materials such as carbon dioxide and oxygen, and many more.
Understanding the functions of the canopy is crucial in the understanding of how a tree operates and of its tolerance. Trees are perennial plants, which characterizes them as plants that are able to live through all seasons of the year. All trees possess a permanent, woody, self-supporting main stem, or a trunk as well as vascular tissue for the purpose of transporting materials to different areas of the organism. It is also characteristic of trees to grow to a height that exceeds twenty feet, or six meters.
Another important characteristic of trees are its leaves, the main inhabitants of the canopy and the functional parts of it. The specific structures of a leaf can be found below. Leaf structure is a relevant subject which needs a certain understanding. The leaf itself is comprised of several layers. From the outside in, there is the cuticle, upper epidermis, palisade mesophyll, spongy mesophyll, and then the lower epidermis. The cuticle is the waxy, protective layer that helps prevent water loss by preventing the water in the plant’s tissues from evaporating.
Right underneath the cuticle, where most of the light energy is received, is the upper epidermal layer. The upper epidermis is also the layer where the wax surface may be produced. Directly below that lies the palisade mesophyll. This important layer is the photosynthesis layer, where the majority of the photosynthesis processes occur within structures called chloroplasts. Also, because of this, this is where the carbon dioxide is utilized, as well as the production of glucose, oxygen.
The spongy mesophyll is made up of loosely packed, irregular shaped cells surrounded by air spaces. Within the spongy mesophyll are bundles of vascular tissue that make up the veins of the leaf, called the phloem and xylem. This layer is crucial in the exchange and circulation of gases and water vapor. Since this layer is also characterized as a mesophyll layer, it too carries out some photosynthesis. The lower epidermis is important in that it holds most of the stomata found on the leaf.
The stomata are tiny openings in the leaf’s skin whose size is regulated by guard cells on either end. It is here that most of the gas exchange takes place. The functions of the canopy and its structure are closely related. Bearing this in mind, does the actual position in the canopy affect the leaf morphology of the Acer saccharum, specifically blade area? There are three qualitative areas of morphology in which to choose, blade area, specific leaf weight and mass. For the purposes of this research experiment, blade area of Acer saccharum leaves was investigated.
If leaf position becomes increasingly distant from the trunk, it would be the prediction then that leaf blade area will get increasingly larger. On the contrary, it is equally possible that as leaf position becomes increasingly distant from the trunk, blade area will not be affected. Methods and Materials It was the objective of this study to determine a relationship between the leaf blade area and the canopy position. In order to better understand the relationship between blade area and canopy position, simple experimental setup was used.
Leaf collection was the first step, however, picking random leaves would leave scrambled peaces of data, so the transect approach was utilized. For each transect, a transect being an arbitrary transverse line through the canopy which the leaves will lie on, will have samples one-half meter apart with five samples total. Only a total of 6 transects were collected for this particular experiment. Each leaf was carefully picked off at the base of the petiole and then labeled T1-P1 to T6-P5 depending on the transect and placement. These labels were placed on sticky tape and positioned on the petiole.
Once this objective was accomplished, the leaves were labeled again on the actual leaf blade with permanent marker. This step was taken because the petioles were cut off next. Subsequently, the leaves were organized into transects and positions and then placed into manila envelopes for press. Once the leaves were placed in the folders, the folders were placed between two wooden slabs and squeezed together with a belt strap to flatten the leaves. Pressing the leaves will safely remove all the moisture from the leaf blades while reserving the original blade shape.