1 / 3

A plant cell has an osmotic (or solute) potential of -2.1 MPa. Neglecting the changes

A plant cell has an osmotic (or solute) potential of -2.1 MPa. Neglecting the changes in volume due to turgor pressure, what will its internal pressure be when allowed to come into equilibrium with each of the following solutions:

jocelyn-cleveland
Download Presentation

A plant cell has an osmotic (or solute) potential of -2.1 MPa. Neglecting the changes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A plant cell has an osmotic (or solute) potential of -2.1 MPa. Neglecting the changes • in volume due to turgor pressure, what will its internal pressure be when allowed • to come into equilibrium with each of the following solutions: • Water (Answer: cells internal pressure after incubation in water is Ψp = 2.1) • -2.1 MPa mannitol (Answer: Ψp = 0) • -2.5 MPa mannitol (Answer: Ψp = -0.4; plasmolysis will likely occur) • -1.0 MPa triethyl citrate to which the cell is highly permeable (Answer: Ψp = 2.1)

  2. A wind-borne pollen grain with an osmotic (solute) potential of -1.5 MPa has been • drying out while aloft. Thus, it has lost all turgor pressure. It lands on a stigma, • whose cells have an osmotic potential of -2.0 MPa and an internal pressure of • 0.8 MPa. In answering the following questions, assume that the stigma is massive • compared with the pollen grain: • In which direction will water flow? Why? • What will be the internal pressure of the pollen be after it has been on the stigma • for quite some time? • A fresh pollen grain with the same osmotic potential but an internal pressure of • -1.3 MPa is placed on the same stigma. In which direction will water flow? Why? • Answers: • Ψw of stigma = Ψs + Ψp (Ψw = -2.0 MPa + 0.8 MPa; Ψw = -1.2 MPa • Ψw of pollen in air = Ψs + Ψp (Ψw = -1.5 MPa + 0 MPa; Ψw = -1.5 MPa • Water will flow from stigma (Ψw = -1.2 MPa ) to pollen (Ψw = -1.5 MPa) because • the water in the stigma has more energy (more free water in stigma) than in • the pollen. • b. At equilibrium, Ψw of pollen will be equal to that of the stigma (Ψw = -1.2 MPa). • Ψw of pollen on stigma = Ψs + Ψp (-1.2 MPa = -1.5 MPa + ? MPa); Ψp = 0.3 MPa • c. Ψw of fresh pollen = Ψs + Ψp (Ψw = -1.5 MPa + 1.3 MPa; Ψw = -0.2 MPa • Water will flow from pollen (Ψw = -0.2 MPa) to stigma (Ψw = -1.2 MPa ) because • the water in the pollen has more energy (more free water in fresh pollen) than in • the stigma.

  3. A plant 47 meters tall is transpiring at a rate of 14 liters per hour. Suddenly, the rate drops to 7 liters per hour. What factors could have caused the rate to decrease? Give as many factors as you can. Answers could include: cloud cover increased (reduced temperature-lower driving force); wind speed decreased (increased boundary layer and increased resistance); reduced photosynthetic rate in guard cells- to affect solute production and water potential In guard cell, which affects size of stomatal opening and decreases conductivity; Increase in humidity (rain), which reduces driving force

More Related