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A plant can manipulate Ψ p via its ability to manipulate Ψ s and by the process of osmosis. If a plant cell increases the cytoplasmic solute concentration, Ψ s will decline, Ψ total will decline, the ΔΨ between the cell and the surrounding tissue will decline, water will move into the cell by osmosis, and Ψ p will increase. Ψ p is also under indirect plant control via the opening and closing of stomata. Stomatal openings allow water to evaporate from the leaf, reducing Ψ p and Ψ total of the leaf and increasing ii between the water in the leaf and the petiole, thereby allowing water to flow from the petiole into the leaf.

 Left photo shows a wilted plant with wilted leaves. Right photo shows a healthy plant.
When (a) total water potential (Ψ total ) is lower outside the cells than inside, water moves out of the cells and the plant wilts. When (b) the total water potential is higher outside the plant cells than inside, water moves into the cells, resulting in turgor pressure (Ψ p ) and keeping the plant erect. (credit: modification of work by Victor M. Vicente Selvas)

Gravity potential

Gravity potential (Ψ g ) is always negative to zero in a plant with no height. It always removes or consumes potential energy from the system. The force of gravity pulls water downwards to the soil, reducing the total amount of potential energy in the water in the plant (Ψ total ). The taller the plant, the taller the water column, and the more influential Ψ g becomes. On a cellular scale and in short plants, this effect is negligible and easily ignored. However, over the height of a tall tree like a giant coastal redwood, the gravitational pull of –0.1 MPa m -1 is equivalent to an extra 1 MPa of resistance that must be overcome for water to reach the leaves of the tallest trees. Plants are unable to manipulate Ψ g .

Matric potential

Matric potential (Ψ m ) is always negative to zero. In a dry system, it can be as low as –2 MPa in a dry seed, and it is zero in a water-saturated system. The binding of water to a matrix always removes or consumes potential energy from the system. Ψ m is similar to solute potential because it involves tying up the energy in an aqueous system by forming hydrogen bonds between the water and some other component. However, in solute potential, the other components are soluble, hydrophilic solute molecules, whereas in Ψ m , the other components are insoluble, hydrophilic molecules of the plant cell wall. Every plant cell has a cellulosic cell wall and the cellulose in the cell walls is hydrophilic, producing a matrix for adhesion of water: hence the name matric potential. Ψ m is very large (negative) in dry tissues such as seeds or drought-affected soils. However, it quickly goes to zero as the seed takes up water or the soil hydrates. Ψ m cannot be manipulated by the plant and is typically ignored in well-watered roots, stems, and leaves.

Movement of water and minerals in the xylem

Solutes, pressure, gravity, and matric potential are all important for the transport of water in plants. Water moves from an area of higher total water potential (higher Gibbs free energy) to an area of lower total water potential. Gibbs free energy is the energy associated with a chemical reaction that can be used to do work. This is expressed as ΔΨ.

Questions & Answers

Hydra reproduce through which process
Saint Reply
who is the father of mycology
Sagar Reply
Heinrich Anton de Bary
Delissa
describe the similarities and differences between cytokinesis mechanism found in animal cells versus in plant cells
hiro Reply
are humans beings considered to have the eukaryotic cells
success Reply
yes.....
Delissa
eukaryotes are organisms that possess cells with a nucleus enclosed in a membrane, humans, and all complex organisms are eukaryotes.
Delissa
so humans and animals also have cell membranes.... cause I did this test prep and they said plants...I just want to be sure
success
and thank you for your reply it was helpful👍✌
success
eu= "perfect", "good", karyon= nut, amound, nucleus
Tiago
you're welcome. Plants are also eukaryotes.
Delissa
plants, like animals, possess a nucleus bound by a membrane.
Delissa
similarities and differences between cytokinesis mechanism found in animal cell vs cell division
Raymark Reply
what is the name of a male flower?
Ikeomu Reply
staminate means flower containing only stamen
Falak
what is the definition of evolution in a population?
Homero Reply
the slow changing of a species to adapt to any changes in the environment or how it feeds/hunts. im not good at explaining things lol.
Eclipse
the organ which is sensitive to light in euglena
Fatimah Reply
the organ which is sensitive to light in euglena is
Fatimah
all chlorophyll containing motile cells are sensitive to light
Himangshu
there is no more other chapter
Sandeep Reply
Give tow examples for nutritional deficiency Diseases-
Singampalli Reply
How does a plant cell look like
Sang Reply
in a sleepers form
David
what do you mean ? I could not understand
Gul
they have a regular shape and a large vacoule
Fatimah
I thought it looked like rectangle
Abrahán
a stage in mitosis wherein in spindle fibers begin to shorten to pu the sister chromatids away from each other towards the opposite ends of the cell
Earl Reply
a stage in interphase where chromosome s are duplicated
Earl
What is biodiversity
Sp Reply
Hmm
Hele
Name two secretions of Golgi apparatus
Daniel Reply
What contribute to evolution of eukaryotes
Chiquita Reply
hi
Nubia
hello
surya

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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