1. Soil consists of inorganic particles and organic ________.
silt
clay
humus 1 2 3 4 5

2. Layers of soil that are identified by distinct properties are called ________.
leaching
weathering
horizons
ecosystems 1 2 3 4 5

3. Topsoil is not ________.
the horizon most essential for plant growth
the horizon closest to bedrock
deeper in some places than in others
a soil with decomposed organic matter 1 2 3 4 5

4. Bacteria in root nodules produce a biologically active form of the essential nutrient ________.
nitrogen
oxygen
carbon
hydrogen 1 2 3 4 5

5. Mycorrhizae are ________.
very small roots that absorb nutrients
a bacterial infection of roots
a mutualism between roots and fungi
responsible for nitrogen fixation 1 2 3 4 5

6. Root hairs are extensions of ________ cells.
epidermal
endodermal
vascular
pericycle 1 2 3 4 5

7. endodermal transport proteins sieve tubes in phloem
The control point where plants adjust the quantity and types of solutes absorbed from soil water are the ________.
root hairs
root nodules
endodermal transport proteins
sieve tubes in phloem 1 2 3 4 5

8. The Casparian strip is a barrier to unrestricted ________ flow into the vascular cylinder.
water and gas
water and solute
solute and ATP
oxygen and ATP 1 2 3 4 5

9. Which of the following is an identifying characteristic of xylem tracheids and vessel members?
their cells are dead at maturity
they carry organic products of photosynthesis
they are discontinuous from roots to leaves
they operate under high fluid pressure 1 2 3 4 5

10. Which is not true of xylem tracheids and vessel members?
they are perforated with pectin-coated pits
they consist of dead, mature cells
they move nutrients from leaves downward
they have rigid lignin-filled walls 1 2 3 4 5

11. According to cohesion-tension theory, ________.
energy is expended to raise water from roots to leaves
negative pressure from evaporation pulls water toward the leaves
pressure from the vascular cylinder pushes water toward the leaves
tension between tracheids pushes water upward from the roots 1 2 3 4 5

12. In water conservation, the essential principle of osmosis is ________.
water follows the light
ions follow the water
water follows the concentration gradient
water follows the ions 1 2 3 4 5

13. Plant structures directly responsible for maintaining turgor include ________.
roots and periderm
cuticle and stomata
petioles and endoderm
meristem and phloem 1 2 3 4 5

14. the tracheid structure blue light carbon dioxide levels
In stomata, all of the following influence the opening and closing of guard cells except ________.
the tracheid structure
blue light
carbon dioxide levels
the hormone ABA 1 2 3 4 5

15. Smog pollution directly affects plants by ________.
clogging stomata
blocking sunlight
reducing photosynthesis
all of the choices 1 2 3 4 5

16. The primary function of phloem is to distribute ________ through the plant.
groundwater
minerals
organic products
inorganic nutrients 1 2 3 4 5

17. In translocation, companion cells in ________ load sucrose into ________.
veins, sieve-tube members
veins, tracheids
sieve-tube members, xylem
xylem, phloem 1 2 3 4 5

18. According to pressure flow theory, the mechanisms that increase fluid pressure are ________.
gravity and diffusion
gravity and osmosis
active transport and osmosis
diffusion and concentration gradient 1 2 3 4 5

19. loading by companion cells unloading at sinks decreased turgor
All of the following conditions are required to maintain a pressure gradient in phloem except ________.
photosynthesis
loading by companion cells
unloading at sinks
decreased turgor 1 2 3 4 5

20. All of the following are sink regions except ________.
flowers
photosynthetic tissues
fruits
growing roots 1 2 3 4 5