Exercise 6. The Stem - Worksheet PDF

EXERCISE 6 THE STEM I. Introduction The stem together with the leaves and other stem-attached above ground parts comprise the shoot system of plants. The stem mainly functions for support of aerial parts of the plant a...

EXERCISE 6 THE STEM I. Introduction The stem together with the leaves and other stem-attached above ground parts comprise the shoot system of plants. The stem mainly functions for support of aerial parts of the plant and transport of water and solutes between roots and leaves. Aside from these main functions, stems of some plants undergo modifications to perform specialized functions. Some are photosynthetic while others function for storage while others can be used for asexual reproduction. II. Materials Plant specimens to be provided by the students per group o Terminal portion of a monocot stem and a dicot stem. o Specialized stems of potato, banana, ginger, bougainvillea, cactus, any common lawn grass, and from the Cucurbitaceae family. Compound microscope Prepared cross-section slides of monocot and young dicot stems Prepared slide of stem with secondary growth III. Procedure A. External Features of the Stem 1. Examine the terminal portion of a monocot and dicot stem. Draw and label the following parts: terminal bud, node, internode, leaf axil. 2. Examine the specialized stem of each plant specimen. Draw and identify their specialized function. 1  B. Microscopic Features of the Stem 1. Examine prepared slides of the cross-section of monocot and dicot stem at LPO. Draw and label the following parts where applicable: pith, vascular bundle, xylem, phloem, sclerenchyma cells, cortex and epidermis. Identify the type of stele observed. Shift to HPO and focus on the vascular bundle. Make a separate detailed illustration with the following labels where applicable: bundle sheath cells, xylem, phloem, air space, fiber cap. 2. Examine the prepared slide of a dicot stem with secondary growth. Draw and label the following parts: primary xylem, secondary xylem, xylem ray, vascular cambium, secondary phloem, phloem ray, periderm, bark and lenticel. IV. Guide questions 1. Briefly compare the external features of the monocot and dicot stem. What external features distinguishes the stem from the roots? 2. What are axillary buds, where can they be found and give their function. 3. Define phyllotaxy and different the following phyllotaxis: spiral, distichous, opposite, decussate and whorl. 4. What are cladodes or cladophylls? Give two examples of plant species that form this structure. 5. Compare and contrast the following in tabular form: Vascular cambium and cork cambium, ray initials and fusiform initials, softwood and hardwood, heartwood and sapwood, lenticels and stomata. 6. Enumerate and differentiate the three tissues of the periderm. 2 7. What is the bark? What tissues are included here? 8. Differentiate the steles observed in this activity. 3  WORKSHEET FOR EXERCISE 6. THE STEM Name : _____________________________ Date : _______________ Section : ________________ Score : ____________/75 Group : _____________________________ I. External Features of the Stem (45 points) 1. Monocot vs Dicot Terminal Stem Monocot Dicot Common Name: Common Name: Scientific Name: Scientific Name: 4  2. Specialized stems Potato Banana Scientific Name: Scientific Name: Type of specialized stem: Type of specialized stem: Specialized Function(s): Specialized Function(s): Ginger Bougainvillea Scientific Name: Scientific Name: Type of specialized stem: Type of specialized stem: Specialized Function(s): Specialized Function(s): 5  Cactus Gramineae species Scientific Name: Scientific Name: Type of specialized stem: Type of specialized stem: Specialized Function(s): Specialized Function(s): Cucurbitaceae species Scientific Name: Type of specialized stem: Specialized Function(s): 6  II. Microscopic Features of the Stem (25 points) 1. Monocot stem Cross-section Bundle sheath Total Magnification : Total Magnification : 2. Dicot stem Cross-section Bundle sheath Total Magnification : Total Magnification : 7 Dicot stem with secondary growth Total Magnification : 8