PSS 1411 Exam 3 Actual Questions with
Answers| Latest Updat
PSS 1411 – Principles of Horticulture
Exam 3 Practice Questions & Verified Answers (2026/2027 Update)
SECTION 1: WATER MANAGEMENT & TRANSPIRATION
1. List four environmental factors that increase the rate of transpiration.
A) High temperature, high humidity, low wind speed, low light intensity
B) High temperature, low humidity, high wind speed, high light intensity
C) Low temperature, high humidity, high wind speed, low light intensity
D) Low temperature, low humidity, low wind speed, high light intensity
Correct Answer: B. High temperature, low humidity, high wind speed, and high
light intensity. Rationale: Each of these factors increases the vapor pressure
gradient between the leaf interior and the surrounding air or increases stomatal
opening, both of which accelerate water vapor loss .
2. Why do plants transpire even though it can lead to water stress?
A) Transpiration is unnecessary but unavoidable
B) Transpiration is a necessary consequence of keeping stomata open to allow CO₂
uptake for photosynthesis
C) Transpiration only occurs at night
D) Transpiration is a defense mechanism against pests
Correct Answer: B. Transpiration is a necessary consequence of keeping stomata
open to allow CO₂ uptake for photosynthesis. Rationale: The stomata that allow
carbon dioxide to enter for photosynthesis inevitably also allow water vapor to
,escape, making transpiration an unavoidable trade-off of gas exchange.
Transpiration also helps cool the leaf and drive nutrient transport upward .
3. What is the "cohesion-tension theory" of water movement in plants?
A) Water is pushed upward by root pressure alone
B) Water is pulled upward through the xylem as a continuous column, held
together by cohesive forces between water molecules, in response to tension
created by transpiration
C) Water moves through the phloem by active transport
D) Water is absorbed directly by leaves from the air
Correct Answer: B. Water is pulled upward through the xylem as a continuous
column, held together by cohesive forces between water molecules, in response
to tension created by transpiration at the leaf surface. Rationale: As water
evaporates from leaf cells, it creates negative pressure (tension) that pulls the
cohesive water column upward through the xylem from the roots, without
requiring active pumping .
4. What is evapotranspiration (ET)?
A) The loss of water only through plant transpiration
B) The combined loss of water from a landscape through evaporation from soil
and plant surfaces and transpiration from plant tissue
C) The absorption of water by plant roots
D) The condensation of water on leaf surfaces
Correct Answer: B. The combined loss of water from a landscape through
evaporation from soil and plant surfaces and transpiration from plant tissue.
Rationale: ET is used to estimate total crop water use and is a key value in
calculating irrigation scheduling and water requirements for a field .
, 5. How is evapotranspiration data typically used in irrigation management?
A) To calculate how much water a crop has used so that an equivalent amount of
irrigation water can be applied to replace it
B) To determine soil pH
C) To measure nutrient levels in the soil
D) To predict pest outbreaks
Correct Answer: A. To calculate how much water a crop has used over a given
period so that an equivalent (or adjusted) amount of irrigation water can be
applied to replace it. Rationale: By matching irrigation to actual crop water use
estimated from ET, growers can avoid both under-watering (causing stress) and
over-watering (wasting water and leaching nutrients) .
6. What is drip irrigation and what is its main advantage?
A) Applies water in large volumes to the entire field
B) Applies water slowly and directly to the root zone through emitters, minimizing
water loss to evaporation and runoff
C) Uses sprinklers to simulate rainfall
D) Floods the field periodically
Correct Answer: B. Applies water slowly and directly to the root zone through
emitters, minimizing water loss to evaporation and runoff. Rationale: Because
water is delivered precisely where roots can use it and at a slow rate, drip
irrigation achieves very high water use efficiency compared to overhead methods .
7. What is the difference between water-stress wilting and disease-induced
wilting?
A) They are the same condition
B) Water-stress wilting recovers once adequate water is available, whereas
disease-induced wilting does not recover even with adequate soil moisture
Answers| Latest Updat
PSS 1411 – Principles of Horticulture
Exam 3 Practice Questions & Verified Answers (2026/2027 Update)
SECTION 1: WATER MANAGEMENT & TRANSPIRATION
1. List four environmental factors that increase the rate of transpiration.
A) High temperature, high humidity, low wind speed, low light intensity
B) High temperature, low humidity, high wind speed, high light intensity
C) Low temperature, high humidity, high wind speed, low light intensity
D) Low temperature, low humidity, low wind speed, high light intensity
Correct Answer: B. High temperature, low humidity, high wind speed, and high
light intensity. Rationale: Each of these factors increases the vapor pressure
gradient between the leaf interior and the surrounding air or increases stomatal
opening, both of which accelerate water vapor loss .
2. Why do plants transpire even though it can lead to water stress?
A) Transpiration is unnecessary but unavoidable
B) Transpiration is a necessary consequence of keeping stomata open to allow CO₂
uptake for photosynthesis
C) Transpiration only occurs at night
D) Transpiration is a defense mechanism against pests
Correct Answer: B. Transpiration is a necessary consequence of keeping stomata
open to allow CO₂ uptake for photosynthesis. Rationale: The stomata that allow
carbon dioxide to enter for photosynthesis inevitably also allow water vapor to
,escape, making transpiration an unavoidable trade-off of gas exchange.
Transpiration also helps cool the leaf and drive nutrient transport upward .
3. What is the "cohesion-tension theory" of water movement in plants?
A) Water is pushed upward by root pressure alone
B) Water is pulled upward through the xylem as a continuous column, held
together by cohesive forces between water molecules, in response to tension
created by transpiration
C) Water moves through the phloem by active transport
D) Water is absorbed directly by leaves from the air
Correct Answer: B. Water is pulled upward through the xylem as a continuous
column, held together by cohesive forces between water molecules, in response
to tension created by transpiration at the leaf surface. Rationale: As water
evaporates from leaf cells, it creates negative pressure (tension) that pulls the
cohesive water column upward through the xylem from the roots, without
requiring active pumping .
4. What is evapotranspiration (ET)?
A) The loss of water only through plant transpiration
B) The combined loss of water from a landscape through evaporation from soil
and plant surfaces and transpiration from plant tissue
C) The absorption of water by plant roots
D) The condensation of water on leaf surfaces
Correct Answer: B. The combined loss of water from a landscape through
evaporation from soil and plant surfaces and transpiration from plant tissue.
Rationale: ET is used to estimate total crop water use and is a key value in
calculating irrigation scheduling and water requirements for a field .
, 5. How is evapotranspiration data typically used in irrigation management?
A) To calculate how much water a crop has used so that an equivalent amount of
irrigation water can be applied to replace it
B) To determine soil pH
C) To measure nutrient levels in the soil
D) To predict pest outbreaks
Correct Answer: A. To calculate how much water a crop has used over a given
period so that an equivalent (or adjusted) amount of irrigation water can be
applied to replace it. Rationale: By matching irrigation to actual crop water use
estimated from ET, growers can avoid both under-watering (causing stress) and
over-watering (wasting water and leaching nutrients) .
6. What is drip irrigation and what is its main advantage?
A) Applies water in large volumes to the entire field
B) Applies water slowly and directly to the root zone through emitters, minimizing
water loss to evaporation and runoff
C) Uses sprinklers to simulate rainfall
D) Floods the field periodically
Correct Answer: B. Applies water slowly and directly to the root zone through
emitters, minimizing water loss to evaporation and runoff. Rationale: Because
water is delivered precisely where roots can use it and at a slow rate, drip
irrigation achieves very high water use efficiency compared to overhead methods .
7. What is the difference between water-stress wilting and disease-induced
wilting?
A) They are the same condition
B) Water-stress wilting recovers once adequate water is available, whereas
disease-induced wilting does not recover even with adequate soil moisture
