Mix of multiple choice, true/false, and fill-in-the-blank
Instant feedback after each question
Unlimited attempts for practice
Estimated time: 15–20 minutes
QUESTION 1
Which property of water allows it to move upward in plant xylem vessels against gravity?
✅ Correct! Cohesion (water molecules sticking to each other) and adhesion (water sticking to xylem walls) work together in the cohesion-tension theory to move water upward. High heat capacity helps buffer temperature, solvent properties help dissolve nutrients, and surface tension affects droplet behavior.
QUESTION 2
What are the four major classes of biomolecules?
✅ Correct! The four major classes of biomolecules are carbohydrates, lipids, proteins, and nucleic acids. Water is essential but not a biomolecule. Sugars, fats, enzymes, and DNA are examples within these classes. Carbon, hydrogen, oxygen, nitrogen are elements that make up biomolecules.
QUESTION 3
True or False: Temporary wilting occurs when soil moisture is below the permanent wilting point.
✅ Correct! It's False. Temporary wilting occurs on hot days when transpiration exceeds water uptake, even with adequate soil moisture. Plants recover overnight. Permanent wilting occurs when soil moisture is below the point where roots can extract water.
QUESTION 4
The enzyme responsible for browning in cut apples and potatoes is called ________.
✅ Correct! Polyphenol oxidase (PPO) is the enzyme that catalyzes the browning reaction when plant tissues are damaged. It oxidizes phenolic compounds to form brown melanins.
QUESTION 5
Why does sprinkler irrigation help protect crops from frost?
✅ Correct! When water freezes, it releases latent heat of fusion (about 80 calories per gram). This heat keeps plant tissues near 0°C (freezing point) rather than dropping to damaging lower temperatures.
QUESTION 6
Which type of soil requires the most frequent irrigation due to low water-holding capacity?
✅ Correct! Sandy soils have large particles and large pore spaces, so water drains quickly due to gravity. They have low adhesion and capillarity, resulting in low water-holding capacity and requiring more frequent irrigation.
QUESTION 7
True or False: Water is called the "universal solvent" because it dissolves every known substance.
✅ Correct! It's False. Water is called the "universal solvent" because it dissolves more substances than any other liquid, but it does not dissolve everything. For example, water does not dissolve oils and fats (non-polar substances).
QUESTION 8
The measure of sugar content in fruits and vegetables is called ________.
✅ Correct! Brix (symbol °Bx) measures the sugar content in an aqueous solution. One degree Brix is 1 gram of sucrose in 100 grams of solution. It's widely used in horticulture to assess fruit quality and harvest timing.
QUESTION 9
Why do leafy greens need higher humidity storage than apples?
✅ Correct! Leafy greens have high surface area relative to volume and thin cuticles (waxy layer), so they lose water rapidly through transpiration. Apples have thicker cuticles that reduce water loss, so they can tolerate lower humidity.
QUESTION 10
What causes fruit cracking (e.g., tomatoes, cherries) after heavy rain?
✅ Correct! After a dry period, fruit skins become less elastic. Heavy rain causes rapid water uptake through roots, increasing internal pressure. The cells expand faster than the skin can stretch, causing cracking. Consistent soil moisture prevents this.
📊 Quiz Complete!
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Great job! Review the explanations for any questions you missed.
📌 Section 1.1 Complete!
You have completed all units in Section 1.1: Chemical Building Blocks. You should now be able to:
Explain the four major classes of biomolecules
Describe water's unique properties and their importance for plants
Apply water biochemistry to irrigation, frost protection, and post-harvest storage
Understand the role of enzymes in horticultural processes like browning and ripening
👉 Next: In Section 1.2, we'll explore carbohydrates and lipids in detail.
Plant Biochemistry for Horticulture · HORT 202 · Dilla University · Last updated March 2026