Transport, Transpiration, & Translocation Flashcards
What do you call the pathway or water moving from the soil through the plant to the atmosphere?
Soil-Plant-Atmosphere Continuum
What do you call a complex medium with solid, liquid, and gas phases?
Soil
Soil structures vary in composition, which are different due to their particle size. Arrange sand, clay, silt, and coarse sand in increasing particle size.
Clay < Silt < Sand < Coarse Sand
What are the factors that affect soil structure?
- Porosity
- Water Retention
- Aeration
This refers to the interconnected channels between soil particles.
Porosity
When can you say that the soil is in its water holding capacity?
When air has been displaced and the soil is saturated with water.
When can you say that the soil is in its field capacity?
When what’s left in the capillary pores of soil is gravitational water.
What type of soil must be used to maintain optimal plant growth? Why?
Loam soil, which is a combination of sand (40), silt (40), and clay (20). This type of soil ensures the balance between aeration and water retention.
What type of water is considered to be available and the principal source in the soil? Why?
Capillary water because the attractive forces are not too strong and the roots could absorb water.
This type of water occurs as a thin film on soil surfaces and cannot be absorbed by the plant.
Hygroscopic water
This is tied to the percentage of water remaining in the soil when a plant wilts because the remaining water in the soil is held too strongly for the plants to absorb it.
Permanent Wilting Point
Water potential in plants drives the uptake of water from the soil. This is driven by what type of gradient?
Pressure Gradient
Describe how the root absorbs water from the soil.
It first absorbs capillary water from the macropore since attractive forces are not very powerful here. As water becomes scarce, it recedes to micropores and this causes the surface of the water to have a meniscus. Such meniscus is a result of surface tension and it generates a negative tension that pulls water. Hence, as more water is removed, the radius of the curvature becomes very small. A more acute meniscus means greater tension.
In the root, where does most of the water absorption take place?
In the root hair zone (region of maturation).
What must be the conditions in order for absorption to take place in the roots?
When water potential in roots is more negative in the soil, which is possible when:
> more solutes in root cells
> decrease in turgor pressure
How does the root uptake ions from the soil?
Ions are included in the water the the roots absorb from the soil. It moves through the SYMPLASTIC AND APOPLASTIC PATHWAY but only the FORMER when traveling through the endodermis and the stele because of the presence of the casparian band. This hindrance is important because it allows the ions to accumulate in the xylem so that it would have a negative osmotic potential that could pull water towards the interior root cells.
Does the root push water to the stem or do leaves pull water from the roots to each of the stem?
Water primarily moves because of a pulling force caused by transpiration. Root pressure does not supply sufficient magnitude to push water at a height reached by most trees. Also, root pressure is absent in conifers.
