1. Plant Anatomy

2. Basic plant anatomy
Root - anchor plant in soil, absorb minerals & water, & store food
Shoot (stem) – transport water up to the leaves and transport sugars down to roots
Leaves – photosynthesis, gas exchange, transpiration

3. Roots 1 2 3 Different types of roots (you do not need to know this!)
fibrous roots (1)
mat of thin roots that spread out
tap roots (2)
1 large vertical root
root hairs (3)
increase absorptive surface area 2 3

4. stolons (strawberries)
Modified shoots
stolons (strawberries)
rhizome (ginger)
tuber (potato)
bulb (onion)

5. Leaves
simple vs. compound

6. colored leaves (poinsetta)
Modified leaves
tendrils (peas)
spines (cacti)
succulent leaves
colored leaves (poinsetta)

8. Summary Question
Why are the leaves, shoots, and roots considered “interdependent” structures?
sugars
water & minerals

9. Plant Tissues Dermal Ground Vascular
single layer of tightly packed cells that covers & protects plant (the “skin”)
Ground
bulk of plant tissue
Sugar storage
Vascular
transport system in shoots, roots, and leaf veins
Two types: xylem and phloem

10. Vascular tissue
Xylem
Move water and minerals (ex: nitrogen, phosphorus, and sulfur) up from roots towards the leaves
Dead cells at functional maturity
only cell walls remain
need empty pipes to efficiently move H2O

11. Phloem: food-conducting cells
Carry sugars from the leaves down the shoot and throughout the plant

12. Phloem Living cells at functional maturity cell membrane, cytoplasm
control of diffusion
lose their nucleus, ribosomes & vacuole
more room for specialized transport of liquid food (sucrose)
Cells
sieve tubes
sieve plates — end walls — have pores to facilitate flow of fluid between cells
companion cells
nucleated cells connected to the sieve-tube
help sieve tubes

14. Water & mineral absorption in roots
Water absorption from soil
osmosis
aquaporins
Mineral absorption
active transport
aquaporin
root hair
proton pumps
H2O

15. Mineral absorption in roots (ctd.)
Proton pumps
active transport of H+ ions out of cell
creates membrane potential difference
difference in charge
drives cation uptake
creates an H+ gradient
Enables cotransport of other solutes against their gradient
The most important active transport protein in the plasma membranes of plant cells is the proton pump , which uses energy from ATP to pump hydrogen ions (H+) out of the cell. This results in a proton gradient with a higher H+ concentration outside the cell than inside. Proton pumps provide energy for solute transport. By pumping H+ out of the cell, proton pumps produce an H+ gradient and a charge separation called a membrane potential. These two forms of potential energy can be used to drive the transport of solutes.
Plant cells use energy stored in the proton gradient and membrane potential to drive the transport of many different solutes. For example, the membrane potential generated by proton pumps contributes to the uptake of K+ by root cells.
In the mechanism called cotransport, a transport protein couples the downhill passage of one solute (H+) to the uphill passage of another (ex. NO3−). The “coattail” effect of cotransport is also responsible for the uptake of the sugar sucrose by plant cells. A membrane protein cotransports sucrose with the H+ that is moving down its gradient through the protein.
The role of proton pumps in transport is an application of chemiosmosis.

16. Mycorrhizae increase absorption
Symbiotic relationship between fungi & plant
symbiotic fungi greatly increases surface area for absorption of water & minerals
increases volume of soil reached by plant
increases transport to host plant

17. Water Movement Through Xylem – Transpiration
Xylem moves water / minerals up to the leaf ; then water evaporates through the stomata (transpiration)
Transpiration by the lower water potential of air (compared to the plant roots), which creates negative pressure to pull water up from roots to shoots
Water moves up the xylem tube by capillary action… refresh my memory… what forces cause capillary action? What property of water are these forces related to?

18. How do plants control the rate of transpiration?
Turgor pressure in guard cells controls water loss through stomata (holes on the bottom surface of the leaf)
When K+ is transported into guard cells, water follows… why? (use the term osmolarity in your response)
Turgid cell = stomata open
Loss of K+ and water makes guard cells Flaccid = stomata close

19. Leaf cross-section with open stomata

20. Control of transpiration
Balancing stomate function
always a compromise between photosynthesis & transpiration
leaf may transpire more than its weight in water in a day…this loss must be balanced with plant’s need for CO2 for photosynthesis

21. Sugar Movement Through Phloem
Phloem sap (in the form of sucrose!) moves from source (where it’s made – leaf cells ) to sink (where it’s stored/used – root cells)
Driven by positive pressure
Companion cells help move sugars by active transort from leaf cells into the sieve tube elements
What does a high sugar content do to the water potential in the sieve tubes? What should water do? (move in or out of the sieve tube?)

22. Sugar Movement Through Phloem (ctd.)
Water pressure in the sieve tube moves sap down
What does removal of the sugar at the “sink” do to the water potential in the sieve tubes? What should water do? (move in or out of the sieve tube?)