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Chapter 23 Biology – Miller • Levine

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1 Chapter 23 Biology – Miller • Levine
Roots, Stems and Leaves Chapter 23 Biology – Miller • Levine

2 Specialized Tissue in Plants
The three organs of a plant are the roots, stems and leaves The three tissue systems of a plant are dermal tissue, vascular tissue, and ground tissue A special type of tissue called meristematic tissue is the only plant tissue that can produce new cells by mitosis Found in the tips of shoots and roots

3 Dermal Tissue The outer covering of a plant
Consists of a single layer of epidermal cells Cuticle – a waxy layer that often covers the epidermis Provides protection against water loss & injury May include specialized structures such as root hairs and guard cells

4 Vascular Tissue Transports water and nutrients throughout the plant
Xylem – transports water; composed of dead cells Phloem – transports nutrients; composed of living cells called sieve tube elements

5 Ground Tissue Lies between the dermal and vascular tissues
Parenchyma – has thin cell walls and large central vacuoles Collenchyma – has strong, flexible cell walls and is found in larger plants Sclerenchyma – has extremely thick, rigid cells walls

6 Roots Types of roots: Taproot - A thick primary root that grows long and is found mainly in dicots Fibrous roots – branch extensively and are found mainly in monocots

7 Root Structure & Growth
Root hairs – tiny projections from the epidermis that increases the surface area for absorption of water Cortex – layer of ground tissue Endodermis – layer of tissue that encloses the vascular tissue Root cap – protects the root as it forces its way through the soil

8 Root Structure & Function

9 Root Function Anchor a plant in the ground
Absorb water and dissolved nutrients from the soil

10 Stem Function & Types Three important functions: Two types:
Produce leaves, branches and flowers Hold leaves up in the sunlight Transport substances between roots and leaves Two types: Monocot – has vascular bundles that contain the xylem & phloem scattered randomly Dicot – have vascular bundles organized in a ringlike pattern

11 Monocots and Dicots

12 Stem Structures Nodes – where leaves are attached
Internodes – regions between the nodes Buds – contain undeveloped tissue that can produce new stems and leaves

13 Leaf Structure Blade – thin, flattened section
Petiole – thin stalk that attaches the leaf to the stem Veins – contain the xylem and phloem

14 Leaf Structure Palisade mesophyll – tightly packed cells that absorb light Spongy mesophyll – loosely packed cells with air spaces Stomata – pore-like openings for taking in CO2 and releasing O2 Guard cells – cells that open and close the stomata

15 Leaf Structure

16 Leaf Functions Photosynthesis – takes place in the mesophyll cells of the leaf Transpiration – the loss of water from a plant through its leaves (helps to pull water up from the roots) Gas exchange – taking in carbon dioxide and releasing oxygen

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