| A | B |
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| What's a taproot? | Taproot = the primary taproot; it grows longer & thicker; it makes it difficult to remove some plants; taproots of oak & hickory trees can even reach water far below the surface. |
| What are fibrous roots? | They're threadlike, branched roots developing from a secondary root in some plants. Grass = an example; no single root grows larger than the rest, and there can be as many as 14 million secondary roots. |
| What is epidermis root tissue? | It's a thin layer of cells that take in water and nutrients. |
| What is cortex root tissue? | It transports water and nutrients inward through the root and may store sugars or starches. |
| What does vascular cylinder tissue do as part of the root? | It contains the xylem and phloem. |
| What is the function of root hairs? | It's through them that water and nutrients enter plant roots; they do this through active transport. |
| What does overwatering do to plants and how? | It kills them by preventing the plants from getting the oxygen they need. |
| How does water move from soil spaces into the cytoplasm of root epiderman cells? | It happens by osmosis. |
| Describe the functioning of the cortex. | (1) Water moves easily through and around these cells because their cell walls and membranes of these root parenchyma cells are so permeable. (2) Water in the outer cortex moves by osmosis; so, both water and nutrients move toward the center of the root. |
| What is the endodermis? | The endodermis is found at the inner boundary of the cortex; it's a single layer of cells that enclose the vascular cylinder. It's composed of individual cells that look like bricks; each is surrounded on 4 sides by a waterproof strip called the Casparian strip. (STUDY picture, pg. 497) |
| What is the Casparian strip that surrounds the endodermis? | Casparian strips are waterproof strips surrounding each endodermal cell in a root; it's involved in one-way passage of materials into the vascular cylinder in plant roots. Without it, the upper parts of a plant might not get water, as it helps create root pressure. |
| What is the key to understanding how roots work? | Knowing that water and nutrients cannot more around endodermal cells--only through them; this is because of the impermeable Casparian strip. It ends up that roots have only a 1-way passage of materials. |
| Why is the 1-way passage of materials important to plant roots? | One-way passage keeps nutrients and other materials from leaving the plant--very important! Otherwise, the minerals, water, and other nutrients could escape from plant use. |
| How is root pressure created? | Nutrients and water keep moving into the vascular cylinder, and they cannot move out; thus, root pressure increases, forcing water into the xylem, which eventually helps push water through stems to leaves. |
| How can it be proven that active transport by root cells creates root pressure? | If you poison the root or cut off the oxygen supply, sap movement stops; once the endodermal cells in the root don't pump dissolved nutrients into the vascular cylinder, water stops moving in by osmosis. |
| What are five essential plant nutrients and what role do they play? | Nitrogen, phosphorous, potassium, magnesium, calcium. See Chart on pg. 586. |
| Why are root hairs important? | The hairs provide a larger surface area through which water can enter the plant. |
| Compare a tap root to a fibrous root. | The taproot is one long, thick root with smaller secondary roots; fibrous roots are branching roots that are all about the same size. |
| What are the chief purposes of roots? | They hold the plant in the ground and absorb water & nutrients from the soil. |
| What is another name for ground tissue? | cortex (it separates the central cylinder of vascular tissue and the outside layer of epidermal cells. |
| What is the function of the root cap? | It protects & lubricates the root as it pushes through the soil. |
