Lecture #10 Plant Water Status Flashcards
When pressure in cell walls is below atmosphere the cells will….
shrink moderately
Under positive turgor pressure, large change in ¥w or ¥s result in
small change in cell volume
How do cacti cope with drought?
water taken from water storage cells in drought. solute concentration decreased by polymerization of soluble sugars into starch granules in water storage cells
The rate of water transport into cell depends on…
water potential difference and the hydraulic conductivity of the cell membrane
cell characteristics that favour fast equilibration (short t1/2)
cells with large A/V ratio
high membrane hydraulic conductivity
Stiff cell walls (large €)
Plant response to drought
Cell expansion decreased
Shoot growth decreased
Root growth stimulated
Xylem built to withstand negative pressure
Energy used for salt 2 maintain turgor pressure
Halophytes
Plant adapted to saline environment
low ¥s and therefore lower ¥w to help draw water and maintain turgor pressure
What happens under low RH (relative humidity)
high vapor pressure gradient between cells within leaf and surrounding atmosphere
water transpired fast from soil by roots
What happens when soil dries?
soils hydraulic conductivity decreases rapidly
soil water farther away is transmitted slower
Plans wilt, loss of turgor, leaves angle away from sun
Permanent Wilting point (PWP)
the soil water content at which 50% of seedlings wilt irrecoverably
Plant response to PWP
collapse of cell wall (Cytorrhysis), plants shrink
roots shrink, loss of hydraulic connection
root hairs irreversibly damaged
Physiological response to PWP
outer layer of root cortex (hypodermis) covered in suberin (lipid that blocks water flow into roots)
cavitation in xylem decreases water transport to leaves
What happens when water deficit plant gets re watered?
slower growth rate
m and Y decreased
m decreased cause of increase in cell wall pH
What happens when plant flooded
deficit of O2
anaerobic bacteria grows
plant respiration affect by (H2S)
