In classic experiments on the translocation of organic solutes performed by the Italian anatomist Marcello Malpighi in 1686, the bark of a tree was removed in a ring around the trunk. This experiment, called girdling, was also done by T. G. Mason and E. J. Maskell in 1928. The following were the observations:
I. It has no immediate effect on transpiration.
II. Sugars accumulate above the girdle—that is, on the side toward the leaves—and are depleted below the treated region.
What conclusion/s can be drawn from the above observations?
A: Water moves in the xylem, interior to the bark.
B: Sugar is transported in the bark of the tree and that the sieve elements are the cellular channels of sugar transport.
1. Only A | 2. Only B |
3. Both A and B | 4. Neither A nor B |
Trace the correct path of water from the soil through the plant to the atmosphere:
1. | endodermis- cortex - epidermis - vessel elements - intercellular spaces in mesophyll - stomata. |
2. | epidermis - cortex - Casparian strip - endodermis - sieve cells - intercellular spaces in the mesophyll - stomata. |
3. | Casparian strip - root hairs - epidermis - cortex - xylem - endodermis - intercellular spaces in mesophyll - stomata. |
4. | root hairs - cortex - endodermis - vessel elements - intercellular spaces in mesophyll - stomata. |
Closure of stomata occurs as the guard cells:
1. lose water.
2. begin photosynthesis reducing internal concentration.
3. pick up chloride ions.
4. gain potassium ions.
Guttation is:
1. deposition of dew drops on the leaves in the morning.
2. shrinking of protoplast away from the cell wall.
3. evidence of root pressure.
4. cavitation in the water column.
A column of water in the xylem even in a tall tree normally does not sink because of its weight due to:
1. | the exceptionally large diameter of vessels. |
2. | bubbles too large to be transported even through the pits. |
3. | the presence of strong ion concentrations near the top of the tree. |
4. | the tensile strength of a column of water. |
The apoplast pathway in plants includes all the following except:
1. the lumen of a xylem vessel
2. the lumen of a sieve tube
3. the lumen of tracheids
4. the cell wall of a root hair
Osmosis in plants would not be affected by:
1. water potential gradient
2. a difference in solute concentrations
3. type of cell membrane receptor proteins
4. number of aquaporins
Active transport of substances does not involve:
1. transport of solute along the concentration gradient.
2. use of a specific membrane transport protein.
3. hydrolysis of ATP.
4. transport of solute against a concentration gradient.
The direction of water movement in plants can always be predicted by measuring:
1. pressure potential
2. number of aquaporins
3. proton gradients
4. water potential (ψ)
Give = 0.25 MPa and = -0.50 MPa,what will be the resulting Ψ:
1. +0.75 MPa.
2. -0.75 MPa.
3. -0.25 MPa.
4. +0.25 MP