Organization topic 2 Flashcards
(38 cards)
What is transpiration?
Transpiration is the loss of water vapor from the aerial parts of a plant, primarily through the stomata in the leaves.
What are the four main factors affecting the rate of transpiration?
Light intensity, temperature, humidity, and wind speed.
How does light intensity affect transpiration?
Increased light intensity causes stomata to open, increasing the rate of transpiration.
Why does temperature increase transpiration?
Higher temperatures increase kinetic energy, causing water molecules to evaporate faster from the leaf surface.
How does humidity affect transpiration?
Higher humidity reduces the concentration gradient between the leaf and air, decreasing transpiration.
Why does wind speed affect transpiration?
Higher wind speed removes water vapor around the leaf, maintaining a steep concentration gradient and increasing transpiration.
What is the function of guard cells in transpiration?
Guard cells control the opening and closing of stomata to regulate water loss.
What is the transpiration stream?
The continuous movement of water from roots to leaves via the xylem due to transpiration.
How do plants reduce water loss?
By having waxy cuticles, reduced stomata, hairy leaves, and closing stomata during hot conditions.
What is the role of the xylem in transpiration?
The xylem transports water and minerals from the roots to the leaves through capillary action and cohesion-tension forces.
Transpiration biological importance
Transporting water and mineral ions to the leaves.
• Providing turgor pressure to keep cells rigid.
• Cooling the plant via evaporative cooling.
Describe the adaptations of xerophytes to reduce transpiration.
Xerophytes (plants in arid environments) have adaptations to minimise water loss:
• Thick waxy cuticle → Reduces evaporation.
• Sunken stomata → Traps humid air, reducing the concentration gradient.
• Hairs on leaves → Trap moisture, reducing air movement.
• Rolled leaves → Protect stomata from wind, maintaining humidity.
• Reduced number of stomata → Lowers transpiration rate.
What apparatus is used to measure the rate of transpiration and how does it work?
A potometer measures transpiration rate indirectly by tracking water uptake. Method:
1. Cut a leafy shoot underwater to prevent air bubbles.
2. Seal the shoot into the potometer using a watertight seal.
3. Introduce an air bubble and measure its movement over time.
4. The faster the bubble moves, the higher the transpiration rate.
How do plants control transpiration to balance water loss and photosynthesis?
During the day: Stomata open for gas exchange but close partially if water loss is excessive.
• At night: Stomata close since photosynthesis stops, preventing unnecessary water loss.
• Abscisic acid (ABA): A plant hormone that triggers stomatal closure during drought conditions.
What is the difference between transpiration and translocation?
Transpiration: Movement of water through the plant, from roots to leaves, via xylem (passive process).
Translocation: Movement of sugars (sucrose) and amino acids via phloem using active transport (requires ATP).
What is the role of stomata in transpiration?
Stomata are pores controlled by guard cells that regulate gas exchange and transpiration. Mechanism:
1. In bright light, K+ ions actively transport into guard cells.
2. This decreases water potential, so water enters by osmosis.
3. Guard cells become turgid, opening the stomata.
4. Water exits as vapor, increasing transpiration.
What is the role of enzymes in digestion
Enzymes break down large molecules (e.g., proteins, carbohydrates, fats) into smaller molecules for absorption into the bloodstream.
What is the function of the stomach in digestion?
The stomach secretes gastric juices containing hydrochloric acid and pepsin to digest proteins and kill bacteria.
What is the function of the pancreas in digestion?
The pancreas produces digestive enzymes (amylase, lipase, protease) and secretes them into the small intestine to break down carbohydrates, fats, and proteins.
What is the role of bile in digestion?
Bile, produced by the liver and stored in the gallbladder, emulsifies fats
What is the role of the small intestine in digestion?
The small intestine is the primary site for nutrient absorption. Villi in the lining increase surface area for efficient absorption.
How are carbohydrates, proteins, and lipids broken down in digestion?
Carbohydrates are broken down into sugars by amylase, proteins into amino acids by protease, and lipids into fatty acids and glycerol by lipase.
What is the function of the large intestine in digestion?
The large intestine absorbs water and salts from indigestible food matter, forming solid waste for excretion.
What are the components of the circulatory system?
The circulatory system consists of the heart, blood vessels (arteries, veins, capillaries), and blood.
