Download The Control of Transpiration

Base your answers to questions 1 through 4 on
the information below and on your knowledge of biology.
The Control of Transpiration
Plants normally lose water from openings (stomates) in their leaves. The water loss typically occurs during daylight hours
when plants are exposed to the Sun. This water loss, known as transpiration, is both beneficial and harmful to plants.
Scientists believe wind and high temperatures increase the rate of transpiration, but the size of each stomate opening can
be regulated. Reducing the size of the openings during drought conditions may help reduce the dehydration and wilting that
would otherwise occur.
A leaf may lose more than its own weight in water each day. Transpiration also lowers the internal temperature of the leaf
as water evaporates. On hot days, temperatures in the leaves may be from 3° to 15°C cooler than the outside air. With
stomates open, vital gases may be exchanged between the leaf tissues and the outside environment.
Researchers have also found many plants that use another response when leaf temperatures rise. Special molecules
known as heat shock proteins are produced by plant cells and help to hold enzymes in their functional shapes.
1. Identify the specific leaf structures that regulate the opening and closing of stomates.
2. State one way transpiration is beneficial to plants.
3. Explain why it is important for plants to "hold enzymes in their functional shapes."
4. Identify two of the "vital gases" that are exchanged between leaf tissues and the outside environment.
5. In the leaf of a plant, guard cells help to
A)
B)
C)
D)
destroy atmospheric pollutants when they enter the plant
regulate oxygen and carbon dioxide levels
transport excess glucose to the roots
block harmful ultraviolet rays that can disrupt chlorophyll
production
6. When a certain plant is without water for an extended period of time,
guard cells close openings in the leaves of the plant, conserving
water. What does this illustrate?
A) cellular communication involving the action of nerve cells and
receptor sites
B) an increase in rate of growth due to a low concentration of
water
C) maintenance of a dynamic equilibrium (homeostasis) through
detection and response to stimuli
D) a response to one biotic factor in the environment
7. The diagram below shows a microscopic view of the lower epidermis
of a maple leaf.
The area indicated by letter X is known as
A) a stomate
C) xylem tissue
B) a lenticel
D) phloem tissue
8. The diagram below which represents a cross section of a leaf of a
green plant, showing an opening (stomate) in the lower surface.
A stomate in the lower surface of the leaf has a function most similar
to the function of which cell structure?
A) cell membrane
C) ribosome
B) vacuole
D) nucleus
9. Which process is most closely associated with the regulation of water
loss from the leaves of trees?
A) digestion of water within the cytoplasm in the leaf cells of the
trees
B) synthesis of protein by the chloroplasts in the leaf cells of the
trees
C) movement of water through leaf openings controlled by the
guard cells
D) absorption of nitrogen through leaf openings controlled by the
guard cells
10. Which statement is a valid inference concerning structure X
represented in the diagram below?
A)
B)
C)
D)
Structure X contains guard cells that regulate glucose intake.
Structure X carries out heterotrophic nutrition.
Structure X produces gametes for asexual reproduction.
Structure X transports materials for metabolic activities.
11. Under certain conditions, the openings of stomates in leaves
become smaller. This process enables the plant to avoid excessive
loss of
A) water
B) salt
C) methane D) nitrates