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.
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
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)
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.
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
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
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.
46.
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.
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
