Question

1. You measure xylem pressure in two plants using the pressurechamber. In one, you apply 10 bars of pressure before you noticewater coming from the xylem of your sample. In the other you apply15 bars of pressure. Which plant is more water stressed? What isthe pressure potential of the water stressed plant in MPa?
   
   
   

2. If (water potentional)_P = 0.3 MPa and (waterpotentional)_S = -0.45 MPa, the resulting (waterpotentional)_W is ...

3. Briefly describe what happens in the xylem when cavitationdue to water stress occurs. Mention one structural feature of xylemin conifers that protects against cavitation. (3 - 5 sentences).

4.Solute and pressure potential is measured in two differentplaces in the same plant. Fill in the table below with plausiblenumbers (based on physiological principles). (Note: the plant ishealthy and well-watered).

	Solute (osmotic) Potential (water potentional)s (MPa)	Pressure Potential (water potentional)p (MPa)	Total water potential (water potentional)w (MPa)
Xylem in the stem	0.0
Root cell	- 1.4