Name: Plant stems and leaves (p. 1 of ) Introduction: Plants have a variety of configurations but the same basic structures. The three main parts of a plant are the roots, stems, and leaves. The tracheids are types of plants that have vascular tissues that carry fluids throughout the plant. We will be examining these kinds of vascular plants. Photosynthesis is performed in the leaves of the plants. The requirements for photosynthesis are carbon dioxide, water, and sunlight. Sunlight is absorbed by chloroplasts in the leaf tissues. Water is absorbed in the roots and transported to the leaves through vascular tissue, which appears in bundles on the leaf surface. Several processes, including transpiration, are used to move water upwards from the roots to the leaves. In order for transpiration to occur, water must leave the leaf through evaporation. This occurs when water moves through openings in the leaf called stomata. The stomata are surrounded on two sides by guard cells that control when they open and close. Carbon dioxide also moves through these openings. Plant growth only takes place in certain locations and only by the reproduction and differentiation (specialization) of tissues called meristem. When the meristem is at the base of a root or the ends of a stem, it is called apical meristem. The roots of plants have a root cap that protects the root as it elongates into the soil. Leaves grow from tissue on the stem that is called a node. Some plants can also grow wider, especially a type of plant called a dicot. In larger plants this process creates wood. In a cross section of the stem of such plants, rings represent growing cycles with dark rings representing latewood that has smaller cells due to the colder, shorter growing season. The light circles represent earlywood, which grows in the spring or early summer when conditions are favorable. The dark center of the tree ring is called pith and it is surrounded by heartwood, which is vascular tissue that is no longer functioning. The outer portion of the wood is called sapwood because it is vascular tissue that is actively transporting materials. Surrounding this is the bark, which consists of phloem (vascular tissue), cork, and outer bark. Objectives: 1. Observe several types of stems and leaves and identify the stem, petiole, bud, node, blade, and leaf veins. Draw and label at least two examples. 2. Observe a cross section of a woody stem. Draw and identify the pith, heartwood, sapwood, inner bark, and outer bark. Identify and label one ring making sure to indicate earlywood from latewood. 3. Using a microscope, view a cross section of a leaf. Identify, draw, and label a vein, epidermis, palisade mesophyll, spongy mesophyll, guard cells and stomata. 4. Using a microscope, view a longitudinal section of an onion root. Draw and label the root cap and apical meristem. Draw and label the vascular cylinder. Draw and label root hairs.
Name: Plant stems and leaves (p. 2 of ) Part 1. Materials: two plant examples, pencil, colored pencils Methods: 1. Carefully draw the plant example. 2. Color code and label the following: Apical meristem Bud Node Leaf Petiole Shoot system Root system
Name: Plant stems and leaves (p. 3 of ) Part 2 Materials: wood cross section, colored pencils 1. Method: Carefully draw the plant example. 2. Color code and label the following: Pith Heartwood Sapwood inner bark outer bark. 3. Identify and draw one ring. Use colors to Indicate earlywood and latewood.
Name: Plant stems and leaves (p. 4 of ) Part 3 Materials: Leaf cross section slide, microscope, Colored pencils Method: 1. Examine the leaf cross section under all magnifications. 2. Draw, identify, color code, and label the following structures: Epidermis spongy mesophyll palisade mesophyll vein (vascular tissue), guard cells stomata air pockets
Name: Plant stems and leaves (p. 4 of ) Part 4 Materials: onion root slide, microscope, Colored pencils Method: 3. Examine the onion root under all magnifications. 4. Draw, identify, color code, and label the following structures: Vascular cylinder Endodermis Xylem Endodermis Root hairs (if visible) Apical Meristem Root cap VASCULAR CYLINDER Xylem