Neco Model Questions Vol1 2017 Agricultural Science Question 35

Practice objective / multiple choice question 35 from the 2017 Neco Model Questions Vol1 Agricultural Science examination.

Neco Model Questions Vol1 2017 Agricultural Science Objective / Multiple Choice Easy Difficulty
Question 35 NECO_MODEL_QUESTIONS_VOL1 • 2017 • AGRICULTURAL_SCIENCE • objective

In a field the soil temperature rises from \(18^{\circ}\text{C}\) in the early morning to \(28^{\circ}\text{C}\) at midday, while the volumetric soil moisture declines from \(30\%\) to \(18\%\) over the same period. For a C₃ crop, explain how these simultaneous changes affect the rate of photosynthesis, and state which factor is most likely to limit photosynthesis at midday.

Answer Options

A. Both higher temperature and lower moisture stimulate photosynthetic enzymes, so photosynthesis peaks at midday with no limiting factor.
B. The temperature increase directly enhances photosynthesis, while the moisture decline has little effect; thus, temperature is the main limiting factor at midday.
Correct Answer C. Temperature rise tends to increase photosynthesis up to the optimum, but the concurrent moisture loss causes stomatal closure. At midday the water deficit is the primary limiting factor.
D. Moisture loss leads to increased leaf area, which compensates for temperature effects; therefore, neither factor limits photosynthesis at midday.
Correct Answer
C
Correct Option:
Temperature rise tends to increase photosynthesis up to the optimum, but the concurrent moisture loss causes stomatal closure. At midday the water deficit is the primary limiting factor.

About This Question

This is Neco Model Questions Vol1 2017 Agricultural Science Question 35. It is one of the objective questions from the 2017 Neco Model Questions Vol1 Agricultural Science examination.

Difficulty level: Easy .

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