Lab-Structure of Herbaceous Stems

Name: ______

Partner: ______

Materials -Microscope -Prepared Monocot/Dicot Slide

Procedure

In monocots, the outermost, protective layer of cells is the epidermis. Just under the epidermis is a layer of photosynthetic cells and fiber cells. This is comprised of parenchyma, made up of large thin-walled cells. Scattered throughout the tissue are the vascular bundles, each made up of the conducting tissues, xylem and phloem.

Dicots are more complex than monocots. The epidermis is the outside layer. Underneath the vascular bundles can be found, comprised of xylem and phloem. There is a layer of tissue called the vascular cambium which forms a continuous ring of tissue within the bundles. Cells are produced by the cambium to each of its sides – those to the outside differentiate into phloem, and those to the inside differentiate into xylem. Continuous layers of xylem and phloem are produced.

Part A – Monocot Stem

Observe a prepared slide of a monocot stem under high power. Draw and label the epidermis and the vascular bundles (xylem and phloem).

Hint: Xylem cells are large in diameter. Phloem cells are much smaller in diameter and occur in a clump adjacent to the xylem.

Part B - Dicot Stem Observe a prepared slide of a dicot stem under high power. Draw and label the epidermis, vascular cambium, xylem and phloem.

Questions 1. Where are the xylem and phloem found in herbaceous stems? 2. How does the arrangement of the vascular bundles differ in monocot and dicot stems? 3. How does the position of the cambium layer make it possible for stems to grow in diameter? 4. How does the location of the cambium layer make it possible for new xylem and phloem to form in the area of the vascular bundles? 5. What is the function of xylem and phloem?