1. Roots, Stems, and Leaves Principles of Life Science Rainier Jr/Sr High School Mr. Taylor

2. Plant Cell Types Levels of Organization Concept Review: ◦ There are many different types of cells and plants have 3 basic types of cells ◦ Tissues are made of groups of similar cells that perform a specific function for an organism. Plants have 3 basic types of tissues. ◦ Organs are made of different tissues that do a general function for an organism. An example in plants would be a stem or a root. ◦ Organisms are made of organ systems made from different organs.

3. Plant Cell Types There are 3 basic cell types in plants: ◦ Parenchyma cells:  The most common type of cell  Thin walls and large central vacuoles  Many have chloroplasts  Many have storage vacuoles for starch and other products of photosynthesis.  Continue to divide throughout plant’s life: can heal wounds or start a new plant from a cutting.

4. Plant Cell Types There are 3 basic cell types in plants: ◦ Collenchyma cell:  Cell walls may be thin or thick, but remain flexible.  Provide support while a plant is growing.

5. Plant Cell Types There are 3 basic cell types in plants: ◦ Sclerenchyma cells:  Have a cell wall hardened by lignin so they are very strong!  Once mature, these cells do not grow; in fact they often become hollow cells connected to their neighbors  If found in the vascular system of a plant, they provide the rigid tubes that carry materials throughout the plant.

6. Roots, Stems, and Leaves are only found in vascular plants and are made of 3 basic kinds of tissue: ◦ Dermal tissue ◦ Ground tissue ◦ Vascular tissue

7. Dermal Tissue Forms on outer/external surfaces of plants ◦ Epidermis: often a single layer of flat cells. ◦ Cuticle: a waxy covering to reduce water loss. ◦ Plant hairs: on leaves it slows water loss, on roots it increases surface area ◦ Stomata: openings flanked by guard cells that allow for H 2 O and CO 2 exchange. ◦ Dead cells make the outer bark of a plant.

8. Ground Tissue A variety of thick- and thin-walled cells making up the bulk of plant tissue ◦T◦T his tissue is surrounded by dermal tissue. ◦T◦T hin-walled in leaves carry on photosynthesis ◦T◦T hick-walled often aid in support and protection (cactus spines are an example). Also serve as storage for water, nutrients, and food.

9. Vascular Tissue Cells stack end-to-end to form little pipes. ◦ Xylem: thick-walled and conduct water and minerals. The cells are dead sclerenchyma cells. ◦ Phloem: thinner-walled; transport food (sugars) and other nutrients. The cells are living parenchyma cells.

10. Vascular Tissue: Xylem Xylem moves water and dissolved minerals by the cohesion-tension theory. ◦ Water molecules are attracted to each other (hydrogen bonding): force is called cohesion. ◦ Water molecules are attracted to other materials (xylem walls; by hydrogen bonding, too); force is called adhesion. ◦ Transpiration (the loss of water through stomata in the leaves) creates a vacuum in the xylem that pulls water up into the plant.

11. Vascular Tissue: Phloem Phloem is a living tissue of mostly sieve- tube elements (a type of parenchyma cell). ◦ Movement of sugars and starches can be either from storage or to storage according to the pressure-flow model.  Loading of sugars and starches from an area of high concentration into sieve-tubes (phloem) uses plant energy.  Once loaded into the phloem, movement of the materials is by diffusion to areas of low nutrient concentration.

12. Roots Function to ◦ Anchor plants into ground ◦ Absorb water and other “raw” nutrients ◦ Store starches and sugars. Dicots have a taproot with many root hairs Monocots have a fibrous, highly-branched root system

13. Roots General cross-sectional structure: ◦ Xylem and phloem in a central vascular cylinder. ◦ Cortex of ground tissue surrounds the core ◦ Root hairs grow from epidermal cells to greatly increase surface area to both anchor the plant and increase water and nutrient absorption.

14. Roots General cross-sectional structure: ◦ Root cap covers and protects the growing tip of the root. ◦ The meristem is an active growing/dividing area of cells that “pushes” the root through the soil.

15. Stems Function to support leaves that attach to stems at nodes. Non-woody stems on herbaceous (flexible) plants have bunches of xylem and phloem called vascular bundles. ◦ Randomly scattered in monocots ◦ Arranged in rings in dicots. Pith: ground tissue surrounds vascular bundles

16. Stems Woody stems: stiff and non-green ◦ Central core of pith. ◦ Ring of xylem; as it ages it becomes filled with lignin and becomes wood. ◦ Xylem cells are larger during periods of rapid growth, smaller when slowly growing. The difference is seen as tree rings. (One cycle per year = one ring per year.) ◦ Outside xylem is phloem; as it ages it dies and becomes part of the bark.

17. Stems

18. Leaves Primary site of photosynthesis Petiole: the central stalk Blade: the flattened part of the leaf The leaf is mostly ground tissue (the site of photosynthesis) covered by an upper and lower epidermis covered with cuticle. Most stomata are on lower surface.

19. You have to be-”leaf” that it’s time to be done!