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PLANT PHYSIOLOGY

Az Agrármérnöki MSc szak tananyagfejlesztése TÁMOP-4.1.2-08/1/A-2009-0010

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Principal Manuals in Plant Physiology

Arteca, R.N. (1996): Plant Growth Substances. Principles and Applications. Chapman & Hall, New York, p. 332.

Davies, P.J. (Ed.) (2004): Plant Hormones. Biosynthesis, Signal Transduction, Action! Kluwer Academic Publishers, Dordrecht/Boston/London, p. 750.

Hopkins, W.G., Hüner, N.P.A. (2009): Introduction to Plant Physiology. John Wiley & Sons, Inc., Hoboken, p. 503.

Salisbury, F.B., Ross, C.W. (1992): Plant Physiology.

Wadsworth Publishing Co., Belmont, p. 682.

Taiz, L., Zeiger, E. (2010): Plant Physiology. Sinaurer

Associates Inc., Publishers, Sunderland, p. 782 + 137.

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Water and Plant Cells,

Water Potential

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Overview

1. Water in Plant Life

2. The Structure and Properties of Water

3. Water Movement by Diffusion, Osmosis and Bulk Flow

4. Hydrostatic Pressure and Osmotic Pressure are two Components of Water Potential

5. Methods for Measurement of Water Potential

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1. Water in Plant Life

1.1. Without water life could not exist

1.2. The actual water content of different plant cells, tissues and plant parts is variable

1.3. The productivity of various ecosystems depends on annual precipitation

1.4. Water loss to the atmosphere is an inevitable

consequence of photosynthesis

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Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 68.

Productivity of various ecosystems as a function of annual precipitation

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Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 97.

Water pathway through the leaf

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2. The Structure and Properties of Water

2.1. Water has unique physical and chemical properties 2.2. The thermal properties of water are biologically important

2.3. Water is the universal solvent

2.4. Polarity of water molecules results in cohesion and

adhesion

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Source: Hopkins W.G., Hüner N.P.A. (2009): Introduction to Plant Physiology. p. 2.

Some chemical properties of water compared with other molecules of

similar molecular size

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Source: Hopkins W.G., Hüner N.P.A. (2009): Introduction to Plant Physiology. p. 2.

A) Structure of a water molecule

B) Hydrogen bonds among water molecules

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Source: Hopkins W.G., Hüner N.P.A. (2009): Introduction to Plant Physiology. p. 4.

Solvent properties of water molecules

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Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 70.

A) The shape of a droplet placed on a solid surface

B) Observation of capillarity

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3. Water Movement by Diffusion, Osmosis and Bulk Flow

3.1. Diffusion is the net movement of molecules by random thermal agitation

3.2. Diffusion is effective over short distances 3.3. Osmosis is the diffusion of water across a selectively permeable membrane

3.4. Bulk flow is driven by hydrostatic pressure

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Source: Hopkins W.G., Hüner N.P.A. (2009): Introduction to Plant Physiology. p. 6.

Diffusion is accomplished through the random thermal motion of

individual molecules

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Source: Hopkins W.G., Hüner N.P.A. (2009): Introduction to Plant Physiology. p. 7.

Osmosis is the directed movement of the solvent molecules (usually

water) across a selectively permeable membrane

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Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 71.

A seal syringe can be used to create positive and negative pressures in

fluids such as water

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Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 71.

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4. Hydrostatic Pressure and Osmotic Pressure are two Components of Water Potential

4.1. The hydrostatic pressure developed by osmosis can be demonstrated using an osmometer

4.2. The plant cell is a special osmotic system

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Source: Salisbury F.B., Ross C.W. (1992):

Plant Physiology. p. 44.

a) A mechanical osmometer in a beaker

b) A cell as an osmotic system

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Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 76.

The concept of water potential and its components

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Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 76.

The concept of water potential and its components

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Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 76.

The concept of water potential and its components

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Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 76.

The concept of water potential and its components

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5. Methods for Measurement of Water Potential

5.1. Water potential can be measured in any plant tissues and organs

5.2. Methods for measurement of water potential:

psychrometer, pressure chamber, cryoscopic osmometer,

and pressure probe

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Source: Taiz L., Zeiger E. (2010): Plant Physiology. Web material, http://5e.plantphys.net

The use of isopiestic psychrometry to measure the water potential of a

plant tissue

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Source: Taiz L., Zeiger E. (2010): Plant Physiology. Web material, http://5e.plantphys.net

The pressure chamber method for measuring plant water potential

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Source: PMS Instrument Company, 1725 Geary Street SE, Albany, OR 97322 USA, http://pmsinstrument.com

The concept of a commercial water potential meter based on pressure

chamber method

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Source: PMS Instrument Company, 1725 Geary Street SE, Albany, OR 97322 USA, http://pmsinstrument.com

'Pump-up chamber': the commercial water potential meter

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Source: PMS Instrument Company, 1725 Geary Street SE, Albany, OR 97322 USA, http://pmsinstrument.com

Measuring of water potential using 'Pump-up chamber'

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Source: Taiz L., Zeiger E. (2010): Plant Physiology. Web material, http://5e.plantphys.net

A cryoscopic osmometer measures the concentration of total dissolved

solutes by measuring the freezing-point depression of a solution

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Source: Taiz L., Zeiger E. (2010): Plant Physiology. Web material, http://5e.plantphys.net

Use of the micromanometer, a pressure probe, to measure cell turgor

pressure

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Source: Taiz L., Zeiger E. (2010): Plant Physiology. Web material, http://5e.plantphys.net

Diagram of the simplest pressure probe

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Summary

Water limits both agricultural and natural

ecosystems. The hydrogen bonds give water its

unusual physical properties. Bulk flow, diffusion and osmosis are the major forces of water movement.

Concentration, pressure, and gravity contribute to

water potential in plants. Plant cells typically have

negative water potentials. Measurement of water

potential serves important data about plant and

water relationship.

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Questions

• What is the importance of water in a plant's life?

• What kind of driving forces are involved in water movement?

• What are the components of plant water potential?

• How plant water potential can be measured?

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THANK YOU FOR YOUR ATTENTION

Next lecture:

Water in plants: absorption, transport and transpiration

Compiled by:

Prof. Vince Ördög

Dr. Zoltán Molnár

Ábra

Diagram of the simplest pressure probe

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