Ch.34-36 Exam Flashcards
Where does most of the mass of a plant come from? (Hint: Where does it NOT come from?)
- Most mass of a plant comes from atmosphere and water, not soil
Define essential nutrient.
An element or compound required for normal growth and production
Define macronutrients. What are macronutrients major components of in plants?
- Elements in the soil that plants require in large quantities.
- Major components of nuclei acids, phospholipids, and proteins
What three macronutrients make up 96% of the dry weight of a plant?
C,H, and O 96% of dry weight of a plant
What are the three limiting macronutrients found in plants? (Hint: They are major ingredients of all fertilizers!)
- Nitrogen (N)
- Phosphorous (P)
- Potassium (K)
What are some examples of micronutrients? What are some of their functions?
- Iron, zinc, copper, and nickel
- Function as cofactors of specific enzymes
What are the three sources nutrients can be obtained from? In which source is oxygen, carbon, and hydrogen obtained from? In which are the other macronutrients obtained
from? The micronutrients?
- From water, air, and soil
- Oxygen: O2, H2O
- Carbon: CO2
- Hydrogen: H2O
- Micronutrients: soil
- Macronutrients: soil
Explain how anions and cations behave differently. Which is more readily available for plant absorption, and why?
- Anions tend to dissolve in soil water —> readily available for plant absorption
- Cations tend to interact with negative charges of organic matter and clay —> harder for plants to absorb
Explain cation exchange. What produces the H+ ions to help cation exchange?
- Cation exchange occurs when protons (H+) bind to negative charges on soil particles —> release bound cations for uptake
- Plant roots release CO2, which interacts with H2O forming carbonic acid, which releases H+, enabling uptake of cations
Define the zone of maturation.
- Zone of maturation —> region just above the growing root tip
Define root hair’s function.
- Contain root hairs —> increase the surface area available for nutrient and water absorption
Explain how proton pumps generate an electrochemical gradient. What is the net charge both outside of the cell and inside of the cell?
- Active transport —> requires ATP
- Protons are pumped out of the cells —> outside of the cell becomes more positive
- In comparison, the inside of the cell becomes more negative
The electrochemical gradient encourages cations to enter the cell. Explain how anions must enter the cell through cotransporters.
- So much energy is released when a proton enters the cell along its electrochemical gradient that anions can be co-transported against their electrochemical gradients
Explain mycorrhizal fungi’s role in helping nutrient uptake in plants.
- Increase the plant’s surface area!
- provide nitrogen and phosphorous (limiting factors)
- Fungi receives sugar from the plant
Explain the interaction between nitrogen fixing bacteria and plants.
- Certain bacteria are able to perform nitrogen fixation —> convert N2 into ammonia, nitrates, and nitrites
- Bacteria takes up residence inside plant roots —> nodules
- Bacteria provides plant with nitrogen in exchange for sugar and protection
Name and describe the two plant vascular tissues.
Xylem: conducts water and dissolved ions from the root system to the shoot system
Phloem: conducts sugar, amino acids, chemical signals and other substances back and forth between the root system and the shoot system
What is the xylem composed of?
Tracheids and vessel element
What is the phloem composed of?
Sieve-tube elements and companion cells
How does water flow through areas? (Hint: Low water potential to high? Or high to low?)
Water always flows from areas of high water potential to areas of low water potential
Define solute potential and pressure potential.
Solute potential —> tendency of water to move by osmosis
Pressure potential —> tendency of water to move due to pressure
What is the equation for potential energy of water?
W= Wp + Ws
Explain how water is transported from the roots and the shoots, specifically through water potential.
- Soil and roots have a high water potential
- Warm and dry air has a low water potential
- This relative difference creates a water-potential gradient
- As transpiration (loss of water via evaporation) occurs —> water moves down its water-potential
Define translocation.
The movements of sugars (sucrose) through a plant from sources to sinks via phloem
Define source and sink. Give examples of sources and sinks on a plant.
Source —> a tissue where sugar enters the phloem
- Ex: Flowers, young leaves, lateral meristems, roots
Sink—> a tissue where sugar exits the phloem
- Ex: Mature leaves, vascular tissue
