Chapter Questions
One main root, formed from the enlarging embryonic root, with many smaller lateral roots branching off it is (a) a fibrous root system (b) an adventitious root system (c) a taproot system (d) a storage root system (e) a prop root system.
Root hairs (a) cover and protect the delicate root apical meristem (b) increase the absorptive capacity of roots (c) secrete a waxy cuticle (d) orient the root so that it grows downward(e) store excess sugars produced in the leaves.
Certain plants adapted to flooded soil produce aerial "breathing" roots known as (a) fibrous roots (b) pneumatophores (c) mycorrhizae (d) nodules (e) prop roots.
The waterproof region around the radial and transverse walls of endodermal cells is the (a) Casparian strip (b) pericycle (c) apoplast (d) symplast (e) pneumatophore.
The apoplast is (a) a layer of cells that surround the vascular region in roots (b) the layer of cells just inside the endodermis (c) a system of interconnected plant cell walls through which water moves (d) the central cylinder of the root that comprises the vascular tissues (e) a continuum of cytoplasm of many cells, all connected by plasmodesmata.
Plants obtain positively charged mineral ions from clay particles in the soil by cation exchange, in which (a) roots passively absorb the positively charged mineral ions (b) mineral ions flow freely along porous cell walls $(c)$ roots secrete protons, which free other positively charged mineral ions to be absorbed by roots (d) the Casparian strip effectively blocks the passage of water and mineral ions along the endodermal cell wall (e) a well developed system of internal air spaces in the root allows both gas exchange and cation exchange.
The cell layer from which lateral roots originate is the (a) epidermis (b) cortex (c) endodermis (d) pericycle(e) vascular cambium.
Mutually beneficial associations between certain soil fungi and the roots of most plant species are called (a) mycorrhizae (b) pneumatophores (c) nodules (d) rhizobia (e) humus.
Which of the following statements about soil is true? (a) pore spaces are always filled with about $50 \%$ air and $50 \%$ water (b) a single teaspoon of fertile agricultural soil may contain up to several hundred living microorganisms $(c)$ the texture of a soil is determined by the soil's $\mathrm{pH}$ (d) a soil's organic mat. ter includes litter, droppings, and the dead remains of plants, animals, and microorganisms (e) soil formation is unaffected by a region's climate or topography.
Carbon, hydrogen, oxygen, nitrogen, potassium, calcium, mag. nesium, phosphorus, sulfur, and silicon are collectively known as (a) micronutrients (b) microvilli (c) micronuclei (d) macronu. clei (e) macronutrients.
Draw a simple sketch illustrating the relationships of the following in a cross section of a primary root: remnant of primary xylem, vascular cambium, secondary phloem, secondary xylem, and periderm.
A mesquite root is found penetrating a mine shaft about $46 \mathrm{m}$ $(150 \mathrm{ft})$ below the surface of the soil. How could you determine when the root first grew into the shaft?
You are given a plant part that was found growing in the soil and are asked to determine whether it is a root or an underground stem. How would you identify the structure without a microscope? with a microscope?
Explain why, once secondary growth has occurred, that portion of the root is no longer involved in absorption. Where does absorption of water and dissolved minerals occur in plants that have roots with secondary growth?
A barrel cactus that is $60 \mathrm{cm}$ tall and $30 \mathrm{cm}$ in diameter has roots more than $3 \mathrm{m}$ long. However, all the plant's roots are found in the soil at a depth of 5 to $15 \mathrm{cm}$. What possible adaptive value does such a shallow root system confer on a desert plant?
What is the agricultural value of research to understand the control of root hair development? of the interactions leading to the development of mycorrhizal associations?
When soil has become polluted with hazardous materials such as heavy metals, it is sometimes cost-effective to construct an artificial marsh around the site. Water is pumped through the contaminated soil, picking up the hazardous material, and then the water is passed through the artificial wetland. In one experiment scientists compared the effectiveness of the tools of two different ryarsh planets (cattails and common reeds) in absorbing the heavy metal selenium. Which plant's roots removed the most selenium? What should be done to the plants after they have absorbed selenium?