Concept explainers
To review:
To draw out inferences for the given questions on the basis of the table that shows the water potential measurements in a 100-meter tall tree and its surroundings, with the gravity force of –0.01 MPa (megapascal) per meter of height above the ground and states the reasons for:
(a) Sufficient leaf water potential in order to draw the water to the top of the tree,
(b) Continuation of transpiration if the soil potential is decreased to –1.0 MPa, and
(c) Effect on water potential of xylem if all the stomata are closed.
Introduction:
Water potential refers to the relative measurement of the tendency of water to flow along a concentration gradient, that is, from the region of high potential to the lower potential regions. It is caused by osmosis, surface tension, and any physical pressure. It is measured in MPa (megapascals) and represented by the Greek letter “psi” (
The following table represents the region of the plant and the water potential values in these regions:
Region | Water potential (MPa) |
Soil water | –0.3 |
Xylem of root | –0.6 |
Xylem of trunk | –1.2 |
Inside of leaf | –2.0 |
Outside air | –58.5 |
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Life: The Science of Biology
- Imagine you have a plant with a water potential of -0.1 MPa in the root tissue. What would happen if you place the roots of this plant in a 0.1 M solution of sucrose (water potential is -0.23 MPa)? The net water flow would be from the tissue into the sucrose solution The net water flow would occur only as ATP was hydrolyzed in the tissue The net water flow would be from the sucrose solution into the tissue The net water flow would be in both directions and the concentration of water would remain equal The net water flow would be impossible to determine from the values given herearrow_forwardScientists studied what caused leaf shedding in a drought deciduous (=shedding leaves during the dry season) subtropical species. They quantified the quantum yield (=efficiency) of the PSII complex and the leaf hydraulic conductance (=efficiency of leaf water movement) in leaves of that species during the wet to dry transition. Please describe the results in Figure Figure 1. Changes in leaf hydraulic conductance during the wet and dry season transition of a subtropical speciesarrow_forwardThe water potential in the leaves is -30 MPa and -20 MPa in the xylem, the water moves to the _ and if the water potential in the roots is -30 MPa and -45 MPa in the xylem, the water moves to the?arrow_forward
- The xylem cell has a water potential of -45 MPa and the mesophyll cell of the leaf has a water potential of -57MPa. Which way does the water move?arrow_forwardWhat does hydraulic conductance mean in the following? The hydraulic limitation hypothesis proposes that reduced growth in taller trees is caused by decreased photosynthesis resulting from a decrease in hydraulic conductance promoted by a longer root-to-leaf flow path.arrow_forwardB) If you have a mesophyll cell in a leaf (a living, parenchyma cell in a leaf) with a slight positive turgor pressure (Yp = 0.01 MPa) and solutes (Ys = -3.0 MPa), and it is next to a xylem vessel element with very few solutes in the xylem sap (Ys = -0.01 MPa) but high physical tension (Yp = - 2.0 MPa), which way will water flow? a) from the mesophyll cell into the vessel element b) from the vessel element into the mesophyll cell c) neither direction. They are at equilibrium. Activa GoroSearrow_forward
- Considering the concepts of hydraulic lifting and water potential, which of the following statements is like not true about the figure/illustration below? * DRY DRY WET The water generally moves from wet soil patches to dry soil patches because the latter have lower water potential. A deep-rooted plant can send water to dry soil patches with lower water potential O while simultaneously absorbing water from deep soil layers with higher water potential. The plant has higher water potential than the wet soil patches, but lower water potential than the dry soil patches. The plant has lower water potential than the wet soil patches, but relatively higher water potential than the dry soil patches.arrow_forwardDescribe how the water potential of a leaf changes throughout the course of a 24-hour period. What is driving this change? How does the water potential of this leaf compare to the water potential of a root in the same plant during the same period? How does it compare to the soil underneath the plant? Please fast and properly explain.arrow_forwardExamine the sketch of the xylem elements below (they are displayed horizontally to save page space), these elements are from top to bottom A, B, C, and D. In examining the graph below provide the sequence from left to right that you would expect the vessel elements to fall on the graph. 120 100 80 60 40 20 -12 -10 -8 -6 -4 -2 2 Xylem Water Pressure (Mpa) Percent Loss in Xylem Conductancearrow_forward
- A leaf is placed in a beaker containing a salt solution with a solute potential of -0.5 MPa. Over time the leaf turgor increased to 0.8 MPa at which time the leaf comes into equilibrium with the solution. What is the: 1)Water potential of the solution: 2)Solute potential of the leaf: 3)Water potential of the leaf: 4) pressure potential of the leaf:arrow_forwardWhich of the following condition indicate a very dry soil? O Matric potential3D5 kpa O Matric potential=D0 kpa O Matric potential=-1000 kpa O Matric potential=-100 kpa O Osmotic potential= -10 pa dotermines tCarrow_forwardWhen doing a variable radius prism plot, where do we measure to on a tree to ensure accuracy when determining whether a tree is in or out? At DBH (4.5ft) The canopy To the pith (center) of the treearrow_forward
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