MCB 259: PLANT PHYSIOLOGY 1998, Quiz 3

According to van't Hoff's law the magnitude of the osmotic pressure is
a) proportional to the solute concentration
b) proportional to the inverse of the solute concentration
c) equal to the inverse of the temperature

During plasmolysis
A) the vacuole fuses with the cytosol,
B) the plasmalemma is destroyed,
C) the plasmalemma detaches from the cell wall

The waterpotential in the vacuole of a visibly plasmolyzed cell is eaqual to
a) -
b) P
c) the waterpotential of the cell after it is transferred into and equillibrated with distilled water.

Traube's cells come into existence and grow, if you place a crystal of a Cu2+ salt in a solution of K4[Fe(CN)6]. The membranes of these artificial cells are permeable/impermeable (circle the correct alternative) to water, but permeable/impermeable to Cu2+.

What causes the water uptake into Traube's cells?
a)turgor pressure, b)osmosis, c)matrix potential, d) all of the above?

What is the turgor pressure of the plant cell?
A) The difference between the hydrostatic pressure inside the cell and outside.
B) The tension of the cell wall minus the osmotic pressure.
C) the water potential of a plant cell surrounded by distilled water.

A fully turgescent cell with a 1 M concentration of osmotically active substances is transferred from destilled water into a 1 M solution of sucrose.
A) Due to other factors contributing to the water potential inside the cell, the cell will take up more water from the solution.
B) The cell will be in equilibrium with the sucrose solution and therefore neither gain nor loose water
C) Because of the turgor pressure is acting on the intracellular compartments, the cell will loose water to the sucrose solution

How high are the highest trees? (approx., circle correct answer)
approx.: 30m; 50m; 100m; 250m; 500m; 1000m; 2500m; 5000m

The endodermis is
a) the epidermis of the root
b) a layer of symbiotic fungal cells inside the root
c) a layer of cells between the cortex and the conducting tissues of the root.

Where on the way from soil => root => stem => leaves => gas phase inside the leaves => boudary layer => air surrounding the plant usually is the greatest drop in water potential? Circle region with highest drop.

Water flows (if it flows at all)
from places with positive to places of negative water potential (correct/incorrect)
from places with negative to places with more negative water potential (correct/incorrect)
always to places with a more positive water potential (correct/incorrect)

The main force that drives the flow of water through the plant is generated by
A) transpiration of water from the leaf cell wall which generates a tension (negative pressure) in that pulls up a continuous water column through xylem and root
B) osmotic water influx into the apoplast of the cells inside the endodermis which generates the root pressure
C) peristaltic movements of the stem
D) primary active water transport.

Why is in Renner's experiment a branch with leaves more effective in pulling water through a constricted piece of wood than a vacuum pump?
A) The leaves not only generate a hydrostatic but also an osmotic pressure difference
B) The leaves generate a negative hydrostatic pressure (tension), i.e., the pressure difference is larger than in the case of vacuum.

The permanent wilting point of most plants is reached at a soil water potential
A) of about -15 MPa, B) of about -13 bar, C) of about -130 bar, D) of about -1.5 MPa
E) less (more negative) than -100 bar

The outermost layer of a young root (with root hairs and before the onset of secondary thickness growth) is called A) Pericycle, B) Endodermis, C) Rhizodermis, D) Epidermis.

The water holding (or field-) capacity is an important soil characteristic.
a) The water holding capacity of sand is smaller than that of clay
b) The water holding capacity of sand is larger than that of clay
c) The water holding capacity depends on the actual water potential of the soil.

Which of the following air water interfaces can sustain a larger difference in hydrostatic pressure?
A) a surface with a radius of curvature of 5 nm (water filled pores in cell wall)
B) a surface with a radius of curvature of 75Ám (diameter of xylem vessel)
C) a flat surface