ROOT STRUCTURE: EXTERNAL ROOT Material: Botany I cards #9 - #12, #13 - #18, #19 - # 23 Presentation: 1. The external parts of the root have been introduced to the children: the root hairs, the root tips, and the root caps. The presentation is found in Botany Manual 1 and in nomenclature cards #9 - #12. 2. The types of roots have been introduced to the children: the fibrous roots, the taproots, the lateral roots, the specialized roots, and the adventitious roots. The presentation is found in Botany Manual I and in nomenclature cards #13 - #18. 3. The shapes of taproots have been introduced to the children: conical-shaped, napiform-shaped, fusiform-shaped, and tuberous-shaped roots. The presentation is found in Botany Manual I and in nomenclature cards #19 - #23. 4. Reintroduce the presentations to the children. The Botany nomenclature level I cards #9 - #12, #13 - #18, and #19 - #23 have been mastered by the children. Review the Botany level I cards with the children. Montessori Research and Development 2013 62
INTERNAL PARTS OF THE ROOT - LONGITUDINAL SECTION Material: The Internal Parts of the Root: Longitudinal Section Nomenclature cards Large carrots Knife. Cutting board Drawing paper, pencils, colored pencils Microscope and slides and hand-held magnifiers Presentation1: Key Experience 1. Examine the carrots. Discuss the parts of the root and the functions of each part: root hairs, root tips, and root caps. 2. Cut the very top part off the carrots. Slice the carrots lengthwise (longitudinally) down the center. 3. Give each child a longitudinal section of a carrot. 4. Say, What do you see? Examine with the hand magnifiers. Say, Do you remember from the parts of the root nomenclature what the tip of the root is called? Group discussion of the different parts: the root cap, the region of cell division (the apical meristem), the region of cell elongation, and the region of cell maturation. 5. The children define the parts by what they observe. If the children cannot define some of the parts, read the definitions from the cards. Montessori Research and Development 2013 63
6. Discuss the functions of the internal parts of the longitudinal section of the root: A. Internal Parts of the Root: Longitudinal Section The longitudinal section of the root is the cut along the length of the root. The longitudinal section of the root has four regions: the root cap, the region of cell division (the apical meristem), the region of cell elongation, and the region of cell maturation. These regions are related to the growth of the root. There is a gradual transition from one region to another. B. The Root Cap The root cap is located on the tip of the root. The root cap protects the apical meristem from injury as the root grows deep into the soil. A slimy substance produced by the root cap helps the downward growth of the root. The root cap is where the root grows. C. The Region of Cell Division (The Apical Meristem) The region of cell division occurs in the apical meristem. The region of cell division is located between the root cap and the region of cell elongation. The apical meristem in the region of cell division produces new root cap cells. The rapid growth of the cells in the apical meristem pushes the root cap deeper into the soil. The new cells are called primary tissue. Montessori Research and Development 2013 64
D. The Region of Cell Elongation The region of cell elongation is located between the region of cell maturation and the region of cell division (the apical meristem). In the region of cell elongation, cells that are produced in the apical meristem simply grow longer. The elongation of cells increases the length of the root. E. The Region of Cell Maturation The region of cell maturation is located near the top of the root and above the region of cell elongation. In the region of cell maturation, cells begin to develop into tissues with specialized functions. The outermost cells form the epidermis of the root. Root hairs develop and extend out from the epidermis. Presentation 2: The Microscope 1. Cut a very thin longitudinal section of the root and place it on a microscope slide. Examine under a microscope. 2. Group discussion of observations. 3. The children may draw what they observe. Montessori Research and Development 2013 65
Presentation 3: The Nomenclature 1. Group discussion of the internal parts of the longitudinal section of the root. Discuss the functions of each part. 2. Lay out the pictures, in order, from left to right. 3. Distribute the labels for the children to match to the pictures. 4. Distribute the definitions for the children to read and to match to the pictures. 5. Display the wall chart. 6. Check the definitions with the booklet. 7. Place the classified nomenclature, the booklet, and the wall chart on the shelf. 8. Follow-up activities for the children: A. Match the picture and the label (simple nomenclature). B. Match the picture, the label, and the definition cards (classified nomenclature). C. Make a booklet of the parts of the longitudinal section of the root. The children write the definitions in their own words. D. Make a chart of the parts of the longitudinal section of the root. E. Research the internal parts of the root. F. Examine other roots such as radish, beet, parsnip, etc. Montessori Research and Development 2013 66
Internal Parts of the Root: Longitudinal Section Montessori Research and Development 2013 67
INTERNAL PARTS OF THE ROOT - CROSS SECTION Material: The Internal Parts of the Root: Cross Section Nomenclature Large carrots Knife Cutting board Drawing paper, pencils, colored pencils Microscope and slides and hand-held magnifiers Presentation 1: Key Experience 1. Examine the carrots. Discuss the parts of the root and the functions of each part: root hairs, root tips, and root caps. 2. Review the longitudinal lesson, naming the parts and their functions. 3. Slice the carrots across the width of the root. Give each child a cross section of the carrot. 4. Say, What do you see? Examine with the hand magnifiers. Discuss the different layers. 5. Beginning with the outside layer, name each layer. Ask the children what they think might be the function of each layer. Group discussion. Give the children the information from the definition cards if they have no knowledge of the functions. Montessori Research and Development 2013 68
6. Write the names and the definitions that the children generated in the discussion. 7. Discuss the functions of the internal parts of the cross section of the root: A. Internal Parts of the Root: Cross Section - The cross section of the root is the cut along the width of the root. The cross section of the root has three parts: the epidermis, the cortex, and the vascular tissue. The cross section of the root reveals the storage and movement of food, water, and minerals in the root. B. The Epidermis The epidermis is the outer layer of cells that covers the root. One type of epidermal cell produces root hairs. The other type of epidermal cells is hairless. The root hairs absorb water and minerals from the soil. C. The Cortex The cortex is the layer of cells between the epidermis and the vascular tissue. The cortex stores food. The cortex has three parts: the cortex tissue, the endodermis, and the pericycle. The lateral root begins its growth in the pericycle and grows through the endodermis and the cortex tissue. D. The Cortex Tissue The cortex tissue is the outermost layer of the cortex. The cortex tissue is cell tissue that stores food for the plant. The cortex tissue has many air spaces for aeration of the root cells. E. The Endodermis The endodermis is the middle layer of cells of the cortex between the cortex tissue and the pericycle. The cells of the endodermis are compact and waxy. The endodermis controls the flow of water and minerals between the cortex tissue and the vascular tissue of the root. Montessori Research and Development 2013 69
F. The Pericycle The pericycle is the innermost layer of the cortex. The pericycle surrounds the vascular tissue. Lateral root growth begins in the pericycle. G. The Vascular Tissue The vascular tissue is at the center of the root. The vascular tissue is made up of the phloem, the cambium, and the xylem. The vascular tissue allows for the transport of food, water, and minerals throughout the root system and all the parts of the plant. H. The Phloem The phloem is vascular tissue located at the outer layer of the vascular tissue. The phloem transports food from the leaves to all parts of the root system and to all the parts of the plant. From the leaves, the flow through the phloem is downward. I. The Cambium The cambium is vascular tissue between the phloem and the xylem. The inner cambium cells, in time, become parts of the xylem. The outer cambium cells, in time, become part of the phloem. J. The Xylem The xylem is vascular tissue located at the center of the root. The xylem transports the water and the minerals from the root system to all parts of the root system and the shoot system. From the root, the flow through the xylem is upward. 8. The children draw and label their cross section of the root. They define each part in their own words. Montessori Research and Development 2013 70
Presentation 2: The Microscope 1. Take a very thin cross section of the root and place it on a microscope slide. Examine under a microscope. 2. Group discussion of observations. 3. The children may draw what they observe. Presentation 3: The Nomenclature 1. Group discussion of the internal parts of the cross section of the root. Discuss the functions of each part. 2. Lay out the pictures, in order, from left to right. 3. Distribute the labels for the children to match to the pictures. 4. Distribute definitions for the children to read and to match to the pictures. 5. Display the wall chart. 6. Check the definitions with the booklet. 7. Place the classified nomenclature, the booklet, and the wall chart on the shelf. 8. Follow-up activities for the children: A. Match the picture and the label (simple nomenclature). B. Match the picture, the label, and the definition cards (classified nomenclature). C. Make a booklet of the parts of the cross section of the root. The children write the definitions in their own words. D. Make a chart of the parts of the cross section of the root. E. Research the internal parts of the root. F. Examine other roots such as radish, beet, parsnip, etc. Montessori Research and Development 2013 71