Chapter 38, 39 - Learning Objectives Transpiration, Transport, and Nutrition in Plants

1.     Describe the stepwise process of water movement through a plant.

1.)   water is absorbed by the roots through root hairs, which increases surface area

2.)   then it moves through the epidermis and cortex via 2 pathways: the aplastic route (outside cells) and the symplastic route (inside cells).

3.)   the casparian strip in the endodermis forces water to enter the cells before reaching the xylem, ensuring selective uptake 

4.)   water is then pulled up through the xylem vessels by transpiration from the leaves

 

What role does water play in photosynthesis and maintaining cell integrity? Why is there a constant demand for water?

-       water provides hydrogen needed for photosynthesis and maintains turgor pressure, which keeps plant cells rigid.

-       it's needed to sustain photosynthesis and cell structure, as well as to replace water lost through transpiration.

1.  What is dissolved in the water that roots selectively remove from soil?

Dissolved inorganic ions such as potassium, calcium, and magnesium.

What are the paths to xylem and vasculature? Describe how a plant can selectively put necessary things into the xylem.

- water and solutes move through the apoplastic and symplastic pathways until reaching the endodermis 
- here the casparian strip forces selective entry into cells, this ensures that only necessary nutrients pass through the plasma membrane into the xylem

Explain how the design of mesophyll cells promotes photosynthesis but also gas exchange.

- the palisade mesophyll has many chloroplasts and is positioned for maximum light absorption, promoting photosynthesis 
- the spongy mesophyll has air spaces that facilitate the exchange (CO2 and O2) of gases and water vapor

Explain how cohesion and adhesion properties of water aid in transpiration.

- cohesion: the water molecules are sticking to each other 
- adhesion: water molecules are sticking to xylem walls
this creates a continuous water column, allowing water to be pulled upward from the roots to the leaves as water evaporates

Describe how guard cells regulate transpiration; know the three main signals influencing guard cell activity.

guard cells regulate the opening and closing of stomata
- light signal causes guard cells to accumulate potassium and open
- low CO2 levels in the leaf cause the stomata to open
- an internal biological clock maintaining a daily rhythm of stomatal movement.

Define source and sink. Define photosynthate.

- source: an organ that produces or stores sugars (leaves) 
- sink: an organ that consumes or stores sugars (roots or fruits)

 

refers to the sugars and products made during photosynthesis

How does phloem transport photosynthates depending on a plant’s needs?

- phloem transports sugars from sources to sinks based on a plants needs
- the direction can vary, and its controlled by sugar concentration gradients and pressure differences within the phloem

Understand and explain the pressure slow mechanism: where are sugars loaded into the phloem, what happens to the solute concentration and thus the pressure? Explain what happens at the sink – how do sugar and water move?
Know the directionality in xylem and phloem.

 

 

- sugars are loaded into the phloem at the source, raising the solute concentration and drawing water into the sieve tubes by osmosis, increasing pressure 
- at the sink sugars are unloaded, lowering solute concentration and allowing water to exit back into the xylem, decreasing pressure and maintaining the flow

 

- xylem moves water and minerals upward from the roots to leaves
- phloem moves sugars bidirectionally from sources to sinks, depending on where they are needed

Demonstrate how fungi form mycorrhizae around plant roots and how this benefits both the plant and the fungus.

- mycorrhizal fungi form networks around plant roots, increasing the surface area for nutrient and water absorption
- the fungi receives carbohydrates from the plant, while the plant benefits from enhanced nutrient uptake and protection against soil pathogens

Describe how plants require the activity of nitrogen-fixing bacteria.
How do root nodules promote the symbiotic relationship between plants and nitrogen-fixing bacteria?

 

- nitrogen fixing bacteria in soil or root nodules convert atmospheric nitrogen into ammonium, which plants absorb 
- this symbiotic relationship supplies the necessary nitrogen for plant growth

 

 root nodules provide a habitat for nitrogen fixing bacteria, supplying them with carbohydrates from the plant 
- in return bacteria convert atmospheric nitrogen into ammonium, which the plant can use

Explain what happens when nutrient deficiencies occur; how do they manifest as different symptoms?

 

 

 

- nitrogen deficiency causes yellowing leaves and stunted growth 
- potassium deficiency results in poor stem growth and leaf curling
- magnesium deficiency leads to chlorosis between leaf veins

What do plants need nitrogen for and why can they not use atmospheric N2?

- for amino acid and protein synthesis 
- they can't use atmospheric N2 because its a stable gas; they need soil bacteria to convert it into usable forms like ammonium (NH-4) or nitrate (NO-3)

Describe how plants require the activity of nitrogen-fixing bacteria.
How do root nodules promote the symbiotic relationship between plants and nitrogen-fixing bacteria?

- nitrogen fixing bacteria in soil or root nodules convert atmospheric nitrogen into ammonium, which plants absorb 
- this symbiotic relationship supplies the necessary nitrogen for plant growth

 

 root nodules provide a habitat for nitrogen fixing bacteria, supplying them with carbohydrates from the plant 
- in return bacteria convert atmospheric nitrogen into ammonium, which the plant can use

Demonstrate how fungi form mycorrhizae around plant roots and how this benefits both the plant and the fungus.

- mycorrhizal fungi form networks around plant roots, increasing the surface area for nutrient and water absorption
- the fungi receives carbohydrates from the plant, while the plant benefits from enhanced nutrient uptake and protection against soil pathogens

Macronutrients

-       carbon
- hydrogen
- oxygen
- phosphorus 
- sulfur
- nitrogen
- calcium 
- potassium 
- magnesium

Micronutrients

- chlorine 
- iron 
- manganese 
- boron
- zinc
- copper
- nickel 
- molybdenum