This document discusses various aspects of water relations in biology. It begins by defining key terms like the hydrosphere and phases of water. It then discusses the structure of water molecules and physical/chemical properties of water. Several processes are covered including capillary action, hydrogen bonding, and the soil-plant-atmosphere continuum. Cellular concepts like turgor pressure, osmosis, tonicity and aquaporins are explained. The document also discusses water movement in plants, water potential, osmoregulation, and methods to analyze water transport.

3. Water relations
Presented by: Syeda Saba Kazmi Dated: 3/9/2015

4. OUTLINE
Water
• Hydrosphere
•Water structure
•Phases
•Properties
•Water
movement
cont ….
• Cell water related
terminologies
• SPAC
• Water potential
• Tonicity
• Aquaporins
cont ….
• Osmoregulation
• Hofler diagram
• Hydroulic
conductivity
• Psychrometry
• References

5. Earth: The Biosphere
Hydrosphere Lithosphere Atmosphere

6. %age of Water on Earth
3/4th of earth surface is
covered by Water

8. Phases of Water
Gaseous phase: vapor
and clouds in the sky
Liquid Phase: seawater
and rain etc.
Solid Phase: icebergs in
the polar oceans,
glaciers

9. Water in Cell (Cytoplasm)
•fluid like material
between the cell
membrane and the
nucleus (Cytoplasm)
•over 80 % water

10. Water in Plants
Water constitutes
80-90% of the fresh
weight of
herbaceous plants,
and more than 50%
of woody species.

11. Structure of Water
Chemical formula H2O:
one molecule of water
has two hydrogen atoms
covalently bonded to a
single oxygen atom.

12. Physical & Chemical properties of water
Taste, Odour & color Transmission of Light

13. Chemical and Physical properties of water
 Surface Tension:
 Boiling Point: 100
degrees Celsius
 Density of Water:
Liquid Phase more
dense

14. The Universal Solvent Polarity of Water:

15. Capillary action:
The tendency of water to
move up a narrow tube against
the force of gravity.
E.g. vascular plants, such as
trees.

16. hydrogen bonding
Each water molecule is
connected to another
water molecule through
weak bonding known as
hydrogen bonding

17. The Soil Plant
Atmosphere
Continuum(SPAC)
The Soil-Plant-
Atmosphere
Continuum (SPAC) is
the pathway for water
moving from soil
through plants to the
atmosphere.

18. Cell Water related terminologies
Cohesion: water
molecules stick together, a
process known as
cohesion.
Adhesion: When water
molecules form hydrogen
bonds with other
molecules.

19. Cell Water related terminologies ( cont …)
Cohesion
•The attraction
water to itself –
H bonds

20. Cell Water related terminologies ( cont …)
Adhesion
The attraction of water
to other
surfaces/substances

21. Cell Water related terminologies ( cont …)
Osmosis: Movement of
water from higher
concentration to lower
concentration through
membrane.
Active transport: Reverse
of osmosis, energy is
utilized

22. Hydrophilic- attracts water & Hydrophobic- repels water

23. Cell Water related terminologies ( cont …)
Evapotranspiration
•Transpiration is the
water vapor given off
plants
•Evaporation is the
water vapor lost from
the soil
•Evapotranspiration is
the sum of both (Et)

24. Water pathway through the leaf

25. water potential.
•Water potential is the property of water that determines
which way it will flow, which depends on the concentration
of solutes in the water.
•Greek letter psi, which looks like this: Ψ.

26. Components of Water Potential
•Pressure potential (ψp).
-Difference between pressure of the water in cell
and that of the atmosphere= turgor pressure
•Osmotic pressure (solute potential) (ψs).
-Affect of concentrations of solutes inside vs outside
the cell that influence osmosis
•Vapor potential
•Gravitational potential

27. Pressure Potential
•Turgid cell (left) have a high
positive pressure potential.
•Cells that are flaccid or
plasmolysed (right) have a
pressure potential of zero.

29. Tonicity

30. Water Movement Between Plant Cells
• The path through the
plasmodesmata is called the
symplast
• Apoplast is a path through cell
walls and intracellular spaces.

31. Absorption of water
• Active absorption
• It is the absorption of water by
roots with the help of metabolic
energy generated by the root
respiration.(types)
• Active osmotic water
absorption
• Active non osmotic water
absorption
• Passive absorption
• This mechanism is carried out
without utilization of metabolic
energy

32. Aquaporin
• Aquaporins are integral
membrane proteins from a
larger family of major intrinsic
proteins (MIP) that form pores
in the membrane of biological
cells.

33. Discovery
•2003 Nobel Prize in Chemistry
was awarded jointly to Peter
Agre for the discovery of
aquaporin
• Roderick MacKinnon for his
work on the structure and
mechanism of potassium
channels

34. Function
• Aquaporins are "the plumbing
system for cells," said Agre.
• Also known as water channels
• Aquaporins selectively conduct
water molecules in and out of
the cell

35. Beta-Barrel
Alpha Helix
Amphipathic Helix
Fatty acid
Chain
GPI-Anchored
Peripheral
Types of Membrane Proteins

36. Structure
Aquaporin proteins are made up of six transmembrane α-
helices arranged in a right-handed bundle, with the amino and
the carboxyl terminals.

37. Aquaporins In plants
The presence of aquaporins in the cell membranes seems to serve
to facilitate the transcellular symplastic pathway for water transport

38. Types(in plants)
Aquaporins in plants are separated into five main homologous
subfamilies, or groups:
1: Plasma membrane Intrinsic Protein (PIP)
2: Tonoplast Intrinsic Protein (TIP)
3: Nodulin-26 like Intrinsic Protein (NIP)
4: Small basic Intrinsic Protein (SIP)
5: X Intrinsic Protein (XIP)

39. Hofler Diagram: Analysis of change in
torgor and osmotic potential
• Small changes in cell volume give large changes
in ψp
• Hofler slop is actually the study of elastic
modulus(rigidity) of cell wall

42. Pressure volume curve

43. Osmoregulation
Osmoregulation is the active regulation of the
osmotic pressure of an organism fluids
Regulators and conformers

44. Osmoregulation in plants
While there are no specific osmoregulatory organs in higher
plants, the stomata are important in regulating water loss
through evapotranspiration.
• Xerophytes
• Hydrophytes
• Mesophytes

45. Hydraulic conductivity
Hydraulic conductivity is a property of vascular plants, soils and
rocks, that describes the ease with which a fluid (usually water)
can move through pore spaces or fractures.

47. Methods of determination
There are two broad categories of determining hydraulic
conductivity:
• Empirical approach by which the hydraulic conductivity is
correlated to soil properties like pore size and particle size
(grain size) distributions and soil texture.
• Experimental approach by which the hydraulic conductivity is
determined from hydraulic experiments.

48. Psychrometry
Psychrometry is the science of study of various
properties of air, method of controlling its temperature
and moisture content or humidity and its effect on various
materials and human beings.

49. Composition of Air

50. Psychrometric Properties of Air
Psychrometry is the science of air.
Study of psychrometric properties of air like:
• Temperature,
• Relative humidity
• dew point temperature
• Composition of air

51. References
• http://www.tutorvista.com/content/biology/biology-iv/plant-water-relations/absorption-water-by-
plants.php
• http://www.springerlink.com/content/qw62632354v4nm77/
• http://www.ictinternational.com.au/appnotes/ICT101.htm
• http://www.jstor.org/stable/4353618
• http://www.wiziq.com/tutorial/70692-Biology-XI-11-Transport-in-plants-4-Mechanism-of-Water-Absorption
• http://www.uoguelph.ca/~mgoss/four/410_N05.html
• www.slideworld.com/.../Water-relation-Soil-Plant-Atmosphere-continu
• https://frank.itlab.us/learning/xylem.ppt
• www.prairiesoilsandcrops.ca/articles/volume-6-11-screen.pdf
• https://pilgrimapbio.files.wordpress.com/2011/11/water-potential.ppt