Roots, Stems and Leaves Chapter 23 Mr. Bragg 2014

EQ: How are plant tissues organized? Objectives: Identify the main organs of vascular plants Explain the functions of the main tissues Contrast meristems with other plant tissues

A. Specialized Tissue in Plants Plants have 3 main organs a. Roots b. stems c. leaves

2. Plants have three tissue systems: a. dermal tissue b. vascular tissue c. ground tissue

3. A special type of tissue called meristematic tissue is the only plant tissue that can produce new cells by mitosis a. Found in the tips of shoots and roots

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

Stomata Function Allows for taking in of CO2 for photosynthesis Drawback = loss of water vapor (transpiration) Larger leaf area = more water loss

5. Review - Vascular Tissue a. 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

6. Ground Tissue Lies between the dermal and vascular tissues

Activity/lab Work in pairs No more than 4 people / lab table Follow handout procedure Finish lab portion in class Take home the questions- due tomorrow

Do Now - Review 1. Compare and contrast gymnosperms and angiosperms. 2. What are the 3 main tissues found in vascular plants? 3. What are the 3 main organs of plants?

EQ: How do the structure and function of the 3 main organs help a plant to carry out life processes? Objectives: Describe the different functions of the 3 main organs in plants.

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

Root Structure & Growth Root hairs – tiny projections from the epidermis that increases the surface area for absorption of water

1. Cortex – layer of ground tissue a. Cells in this layer may contain: stored carbohydrates Resins Latex Essential oils Tannins

Endodermis – layer of tissue that encloses the vascular tissue; may be important for fluid transport

Root Structure & Function Root cap – protects the root as it forces its way through the soil Apical meristem – actively growing part of root; protected by cap

Modified Roots Why are they important? Food storage and/or increases fitness (adaptations) Modified Roots

Stem Function Three important functions: Produce leaves, branches, and flowers Hold leaves up to the sunlight Transport substances between roots and leaves

Stem types: Monocots and Dicots Two types: Monocot – has vascular bundles that contain the xylem & phloem scattered randomly Dicot – have vascular bundles organized in a ringlike pattern

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

Specialized or Modified Stems Includes: Stolons Tubers Rhizomes Bulbs Why are they important? Food storage or exploiting new territory

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

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

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

Leaf Structure

Modified Leaves Why are they important? Exploiting new territory, protection, nutrient acquisition

Closing What are the 3 functions of stems? What are the 2 functions of roots? Give an example of a modified plant organ. Why did some plants evolve these modifications?

Hormones Defined: a chemical signal produced in one part of the body and transported to other parts of the body, where it can act on target cells