Exercise 32 Plant Anatomy Vegetative Structures of Vascular Plants Handout PDF

Exercise 32. Plant Anatomy: Vegetative Structures of Vascular Plants Handout The structure of plants varies greatly among species; compare, for example, an oak tree with a cactus. However, these structural differences are typically quantitative rather than qualitati...

Exercise 32. Plant Anatomy: Vegetative Structures of Vascular Plants Handout The structure of plants varies greatly among species; compare, for example, an oak tree with a cactus. However, these structural differences are typically quantitative rather than qualitative; that is, the differences among roots, stems, and leaves result not from tissues unique to one species or another, but rather from different arrangements and proportions of the same tissues. These differences among plants represent a variety of adaptations to achieve the universal evolutionary goals of survival and reproduction. This exercise will concentrate on the structure of roots, stems, and leaves of vascular plants. ROOTS During seed germination, a radicle or young primary root emerges from the seed and grows down. The primary root soon produces numerous secondary roots and forms a root system that absorbs water and minerals, anchors the plant, and stores food. Root systems have different morphologies. For example, a taproot system has a large main root and smaller secondary roots branching from it (e.g., carrot). In a fibrous root system, the primary and secondary roots are similar in size (e.g., roots of many grasses). Root Apex The cone of loosely arranged cells at the root cap perceives gravity and protects the root apical meristem. The root cap protects the root by secreting mucilage and sloughing cells as the root grows through the soil. The root apical meristem is behind the root cap and produces all of the new cells for primary growth. Primary Tissue of the Root The root apical meristem produces cells that differentiate into primary tissues of the root. The outer layer of cells is the epidermis. Just inside the epidermis is the cortex, whose cells contain numerous amyloplasts, which are starch-containing plastids. The inner layer of the cortex is the endodermis, which regulates water flow to the vascular tissue in the center of the root. Immediately inside the endodermis is the pericycle, which can become meristematic and produce secondary roots  In the center of the buttercup root is the vascular (fluid- conducting) cylinder composed of xylem and phloem. Xylem transports water and minerals; phloem transports water and most organic compounds in the plant, including carbohydrates. Water-conducting cells in the xylem of angiosperms are called tracheids and vessel elements and are dead and hollow at maturity. Tracheids are long, spindle-shaped cells with thin areas called pits where the cell walls of adjacent cells overlap STEMS Stems are often conspicuous organs whose functions include support and the transport of water and solutes. Some stems (e.g., cacti) also photosynthesize and store food. The Shoot Apex The dome-shaped shoot apical meristem is not covered by a cap as was the root. The shoot apical meristem produces young leaves (leaf primordia) that attach to the stem at a node. An axillary bud between the young leaf and the stem forms a branch or flower. External Features of a Mature Woody Stem A terminal bud containing the apical meristem is at the stem tip and is surrounded by bud scales. Leaf scars from shed leaves occur at regularly spaced nodes along the length of the stem. The portions of stem between the nodes are called internodes. Vascular bundle scars may be visible within the leaf scars. Axillary buds protrude from the stem just distal to each leaf scar. Primary Tissue of Stem An epidermis covers the stem. The epidermis is coated with a waxy, waterproof substance called cutin. Below the epidermis is the cortex, which stores food. The pith in the center of the stem also stores food. In sunflower stems, the cortex is not uniform. Rather, the three to four cell-layers of the cortex just below the epidermis are smaller, rectangular cells with unevenly thickened cell walls. These are collenchyma cells; they support elongating regions of the plant Secondary Growth of Stems Between the xylem and phloem and each vascular bundle in eudicot stems is a meristematic tissue called vascular cambium. The vascular cambium is a secondary meristem that produces secondary growth (i.e., growth in girth). The vascular cambium is cylindrical and produces secondary xylem to its inside and secondary phloem to its outside. Bark Bark includes all tissues outside of the vascular cambium, including the secondary phloem. When viewed in cross section, secondary phloem consists of pyramidal masses of thick- and thin-walled cells. The thin-walled cells are the conducting cells. The increase in stem circumference resulting from activity of the vascular cambium eventually ruptures the epidermis. The ruptured epidermis is replaced by a tissue called the periderm that, like the epidermis, functions to minimize water loss. Periderm consists of cork cells produced by another secondary meristem called the cork cambium. LEAVES With few exceptions, most photosynthesis occurs in leaves, although some may occur in green stems. Leaves typically consist of a blade and a petiole. The petiole attaches the leaf blade to the stem. Simple leaves have one blade connected to the petiole, whereas compound leaves have several leaflets sharing one petiole. Palmate leaflets of a compound leaf arise from a central area, as your fingers arise from your palm. Pinnate leaflets arise in rows along a central midline. Leaves are also classified according to their venation (i.e., arrangement of veins). Parallel veins extend the entire length of the leaf with little or no cross-linking. Pinnately veined leaves have one major vein (i.e., a midrib) from which other veins branch. Palmately veined leaves have several veins each having branches. Veins of vascular tissue in leaves are continuous with vascular bundles in stems. The arrangement of leaves on a stem is called phyllotaxis and characterizes individual plant species. Opposite phyllotaxis refers to two leaves per node located on opposite sides of the stem. Alternate phyllotaxis refers to one leaf per node, with leaves appearing first on one side of the stem and then on another. Whorled phyllotaxis refers to more than two leaves per node. Internal Anatomy of a Leaf The leaf is only 10–15 cells thick—pretty thin for a solar collector! The epidermis contains pores called stomata, each surrounded by two guard cells (you will study stomata again in the next exercise). Just below the upper epidermis are closely packed cells called palisade mesophyll cells; these cells contain about 50 chloroplasts per cell. Below the palisade layers are spongy mesophyll cells with numerous intercellular spaces.  Answer the following questions Use the following image and word bank to label the plant anatomy.  Q# Answer Word Bank 1. Auxillary Internode Bud Flower stalk 2. Second Node Lateral 3. Internode Shoot 4. First Node First node 5. Stem Stem Root cap 6 Tap Root Terminal 7. Terminal bud Bud Tap root 8. Flower Axillary bud 9. Flower Stalk Second node 10. Axil Root 11. Lateral Flower Shoot Axil 12. Leav Leaf 13. Petiole Petiole 14. Root 16. 15. Root Cap Give two examples of plants that are monocots. Lilies & Orchids 17. Give two examples of plants that are dicots. Roses & Dandelions 18. What is a cotyledon? A leaf-like part of a plant embryo that is found within a seed 19. What is the function of the endosperm? Surrounds the embryo and provides nutrition in the form of starch oils and proteins. 20. Label the leaf model and match with structure definition. Make sure to include the corresponding letter from the image! Letter? Term? Definition Word Bank E. Phloem transports food ( glucose) down the plant. Xylem The leaves make glucose during Stomata photosynthesis. The glucose is transported Palisade through the phloem down to the roots for Mesophyll storage. Spongy Mesophyll D. Xylem Transports water and minerals UP the plant. Guard cell Water travels from the roots up through the Epidermis tree to the leaves against gravity. A. Epidermis Protect the leaf prevent water loss. B. Palisade Upper layer of elongated cells within a Mesophyll eudicot leaf C. Spongy Lower layer of irregularly shaped cells Mesophyll within eudicot leaf-has lots of air spaces G. Stomata Modified epidermal cells which open and close for gas exchange/prevent water loss F. Guard One of the paired cells in the epidermis of a Cell plant that control the opening and closing of a stoma of a leaf. 21. Label the root tip model. Use the following word bank: xylem, phloem, Root apical meristem, Root Cap, Zone of Maturation, Zone of Cell Division, Zone of Elongation. A. PHOLEM B. XYLEM C. ROOT APICAL MERISTEM D. ROOT CAP E. ZONE OF CELL DIVISION F. ZONE OF ELONGATION G. ZONE OF MATURATION 22. The following images are cross section of stems and roots. Identify each image as either a stem or root AND as either a monocot or eudicot. (ex: Monocot Root, Monocot Stem, Eudicot Root, or Eudicot Stem) B. MONOCOT STEM A. EUDICOT STEM C. MONOCOT STEM  D. MONOCOT ROOT 23. Fill out the table below. Name Description Stolon horizontal stems that produce new plants that their nodes Rhizome underground, stems that store, food and water. Tuber modified underground, stems that store food and can produce new plants. Corn 24. What benefit does a plant derive from forming root hairs? Which zone on the root tip are root hairs found? Root hair help absorb water and nutrients from the soil. Root hair is near the root apical stem. 25. What is the function of xylem? Phloem? Transports water and minerals from roots to leaves. Pholem transports food from leaves to the rest of the plant. 26. What is the function of stomata? Stomata are tiny pores found on the underside of leaves they open and closed to regulate the exchange of gases between the plant and the atmosphere. 27. What are the functions of air spaces near the lower surface of the leaf? For gas exchange. 28. Based on the arrangement of vascular tissue, how could you distinguish the upper versus lower surfaces of a leaf? Dicot leaves have an upper surface that is like a network of vascular bundles what the lower surface has a parallel arrangement. Monica leaves typically have a parallel arrangement on both surfaces. 29. How do taproot systems and fibrous root systems help plants survive and reproduce? Taproots provide deep, anchoring and water axis while fibrosis roots create a white network for nutrition absorption. 30. What is the function of root hairs? They help absorb water and nutrients from the soil. 31. How is primary growth different from secondary growth? Primary growth is the increase in plants length. Secondary growth is the increase in plants girth.