Specialized Cells in Plants
Student Expectation B.5.B Examine specialized cells, including roots, stems, and leaves of plants. (EOC) and (Supporting Standard)
Plants Nonvascular: have no vessels, no roots, no stems or leaves. Examples: Mosses & Liverworts Vascular: have vessels to transport food and water. They have roots, stems and leaves. Example: Grass, corn, trees, flowers, bushes
Types of Roots Three Types of Roots Taproots (dicots) – the primary root grows long and thick while the secondary roots remain small. Example: Oak and hickory trees, carrots, dandelions, radishes Fibrous (monocots) – branch out so that no single root grows larger than the rest. Example: grasses Adventitious – helps to develop modified underground stems or to aid in climbing. Example: ivy Types of Roots
Cross Section of a Root
Cross Section of a Root Epidermis – outer layer of the root. Cortex – spongy layer of ground tissue. Endodermis – encloses the roots vascular system. Vascular System Xylem – transports water. Phloem – transports nutrients
Cross Section of a Root Root Hairs – increase the surface area for the root to take in water. Apical Meristem – Where roots grow in length, production of new cells. Root Cap – Protects the root as it forces its way through the soil.
Root Function Purpose of the Root -Anchor the plant to the ground. - Extract water and minerals from the soil (needs the sun to do this). How does this occur?
Root Function 1. Uptake of plant Nutrients. Along with carbon dioxide and water, flowering plants need inorganic nutrients: Nitrogen, phosphorus, potassium, magnesium 2. Active Transport of Minerals – water and minerals move from the epidermis through the cortex into the vascular cylinder (osmosis)
Root Function 3. Movement into the Vascular Cylinder – water and minerals enter the vascular cylinder and move up the plant by way of the xylem. Once in the plant, the waxy Casparian strip keeps the water and minerals inside the plant. 4. Root Pressure – the starting point for the movement of water through the vascular system of the entire plant.
Stems Function: 1. Produce leaves, branches, and flowers. 2. Hold leaves up to the sunlight. 3. Transport substances between roots and leaves.
Stems - Vocabulary Internodes - Regions between the nodes Buds – undeveloped tissue for new stems or leaves. Nodes – where leaves are attached.
Leaf Functions 1. Photosynthesis – uses the sun to make food. 2. Transpiration – loss of water 3. Gas Exchange – take in CO2 and give off O2 during photosynthesis.
Leaves
Leaves Mesophyl – the site where photosynthesis takes place. There are two types of cells in the mesophyl. Palisade Mesophyl – elongated cells, tightly packed, contain numerous chloroplasts, absorbs most of the light. Spongy Mesophyl – rounded and loosly packed, creates pockets of air space between the cells to allow CO2 and O2 to diffuse into cells and into and out of the leaf through openings in the lower epidermis called the stomata.
Leaves Guard Cells – regulate movement into and out of the leaf tissue.
Internal Feedback Loop When water pressure is abundant, the guard cells will open the stomata. When water is scarce, the opposite occurs. Water pressure in leaves drops and the guard cells respond by closing the stomata.