Plant Processes

Question 1

Goal of Plant Processes

Answer 1

Obtaining and distributing water and nutrients

Plants also need CO2 and Sunlight, but they’re usually readily available

Question 2

Root Structure

Endoderm Cells

Answer 2

• a single cell layer around the vascular tissue in the root
• secrete wax on their surfaces to form casparian strip
• all fluid must pass through their cytoplasm, selectively controlling which solutes pass into the vascular tissues or out of the phloem into the cortex cells
• drive high concentrations of potassium salts and sugars from the phloem cells to the cortex cells

Question 3

Root Structure

Casparian Strip

Answer 3

• A barrier to all ion/water flow around the endoderm cells
• prevents water from flowing around the endoderm cells or back into the cortex cells

Question 4

Root Structure

Plasmodesmata

Answer 4

• small openings with intercellular cytoplasmic connections between cortex and endoderm cells
• allow entry of water into and thorugh the cytoplasm of adjacent endoderm cells

Question 5

Positive Pressure pump

Answer 5

• high concentrations of solutes in cortex cells causes water to diffuse into them osmotically from root hairs
• lignin reinforced cell wall of cortex cells resists swelling, so it pushes water through plasmodesmata, through the endoderm cells, and into the xylem
• can move water 2 meters up the xylem

Less important for movement of water

Question 6

Capilarity

Answer 6

• caused by adhesion of water molecules to sides of tubes
• especially in the vessel elements of the xylem

Question 7

Guttation

Answer 7

at night when leaves stop photosynthesizing and drawing water, leaves within 2 meters of the ground can push water out of their stomata, collecting water droplets