23–1 Specialized Tissues in Plants Photo Credit: Getty Images Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Seed Plant Structure Seed Plant Structure What are the three principal organs and tissues of seed plants? Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Seed Plant Structure The three principal organs of seed plants are roots, stems, and leaves. These organs perform functions such as the transport of nutrients, protection, and coordination of plant activities. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Plant Tissue Systems What are the three main tissue systems of plants? Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Plant Tissue Systems Plants consist of three main tissue systems: dermal tissue vascular tissue ground tissue Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Seed Plant Structure Leaf Stem Vascular plants consist of roots, stems, and leaves. Each of these organs contains dermal tissue, vascular tissue, and ground tissue. Root Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Dermal Tissue Dermal Tissue The outer covering of a plant consists of epidermal cells. Epidermal cells make up dermal tissue. The outer surfaces of epidermal cells are covered with a thick waxy layer, known as the cuticle. The cuticle protects the plant against water loss and injury. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Vascular Tissue Vascular Tissue Vascular tissue forms a transport system that moves water and nutrients throughout the plant. Vascular tissue is made up of xylem, a water-conducting tissue, and phloem, a food-conducting tissue. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Vascular Tissue Cross Section of a Stem Vascular tissue is made up of xylem and phloem. Xylem tissue conducts water from the roots to the rest of the plant. Phloem tissue conducts a variety of materials, mostly carbohydrates, throughout a plant. Photo Credit: Ray F. Evert, University of Wisconsin Xylem Phloem Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Ground Tissue Ground Tissue Cells that lie between dermal and vascular tissues make up the ground tissues. The three kinds of ground tissue are: parenchyma collenchyma sclerenchyma Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 23–2 Roots Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Seed Plant Structure Roots: absorb water and dissolved nutrients. anchor plants in the ground. protect the plant from harmful soil bacteria and fungi. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Types of Roots The two main types of roots are: taproots, which are found mainly in dicots, and fibrous roots, which are found mainly in monocots. Copyright Pearson Prentice Hall

Root Structure and Growth The root’s surface is covered with cellular projections called root hairs. Root hairs provide a large surface area through which water can enter the plant. Root hairs A root consists of a central vascular cylinder surrounded by ground tissue and the epidermis. Root hairs along the surface of the root aid in water absorption.

23–3 Stems Photo Credit: Getty Images Copyright Pearson Prentice Hall

Stem Structure and Function What are the three main functions of stems? Copyright Pearson Prentice Hall

Stem Structure and Function Stems have three important functions: they produce leaves, branches and flowers they hold leaves up to the sunlight they transport substances between roots and leaves Copyright Pearson Prentice Hall

Monocot and Dicot Stems The arrangemnet of tissues in a stem differs among seed plants. How do monocot and dicot stems differ? Copyright Pearson Prentice Hall

Monocot and Dicot Stems Monocot Stems Vascular bundles are scattered throughout the ground tissue. Epidermis Vascular bundles Ground tissue In a monocot, vascular bundles are scattered throughout the stem. Photo Credit: ©Ed Reschke/Peter Arnold, Inc. Monocot Copyright Pearson Prentice Hall

Monocot and Dicot Stems Dicot stems have vascular bundles arranged in a ring-like pattern. Vascular bundles Epidermis In a dicot, vascular bundles are arranged in a ring. Photo Credit: ©Ed Reschke/Peter Arnold, Inc. Cortex Pith Dicot Copyright Pearson Prentice Hall

23–4 Leaves Photo Credit: Getty Images Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Seed Plant Structure Leaves: are a plant’s main photosynthetic systems. increase the amount of sunlight plants absorb. Adjustable pores conserve water and let oxygen and carbon dioxide enter and exit the leaf. Copyright Pearson Prentice Hall

Leaf Structure Leaf Structure How does the structure of a leaf enable it to carry out photosynthesis? Copyright Pearson Prentice Hall

Leaf Functions Leaf Functions Most leaves consist of a specialized ground tissue known as mesophyll. Leaves absorb light and carry out most of the photosynthesis in a plant. Some of the most important manufacturing sites on Earth are found in the leaves of plants. The cells in plant leaves are able to use light energy to make carbohydrates. Copyright Pearson Prentice Hall

The air spaces connect with the exterior through stomata. Leaf Functions The air spaces connect with the exterior through stomata. Stomata are porelike openings in the underside of the leaf that allow carbon dioxide and oxygen to diffuse into and out of the leaf. Leaves absorb light and carry out most of the photosynthesis in a plant. Some of the most important manufacturing sites on Earth are found in the leaves of plants. The cells in plant leaves are able to use light energy to make carbohydrates. Stoma Copyright Pearson Prentice Hall

Each stoma consists of two guard cells. Leaf Functions Each stoma consists of two guard cells. Guard cells are specialized cells that control the opening and closing of stomata by responding to changes in water pressure. Leaves absorb light and carry out most of the photosynthesis in a plant. Some of the most important manufacturing sites on Earth are found in the leaves of plants. The cells in plant leaves are able to use light energy to make carbohydrates. Guard cells Copyright Pearson Prentice Hall

When water pressure within guard cells is high, the stoma open. Leaf Functions When water pressure within guard cells is high, the stoma open. Plants regulate the opening and closing of their stomata to balance water loss with rates of photosynthesis. A stoma opens or closes in response to the changes in pressure within the guard cells that surround the opening. When the guard cells are swollen with water the stoma is open. Copyright Pearson Prentice Hall

When water pressure within guard cells decreases, the stoma closes. Leaf Functions When water pressure within guard cells decreases, the stoma closes. Plants regulate the opening and closing of their stomata to balance water loss with rates of photosynthesis. A stoma opens or closes in response to the changes in pressure within the guard cells that surround the opening. Copyright Pearson Prentice Hall

Leaf Functions Plants regulate the opening and closing of their stomata to balance water loss with rates of photosynthesis. Stomata are open in daytime, when photosynthesis is active, and closed at night, to prevent water loss. In hot, dry conditions stomata may close even in bright sunlight, to conserve water. Copyright Pearson Prentice Hall