This presentation has intended to explore water and its different attributes in general and ecology in particular.

1. PLANT ECOLOGY
Water-Importance: States of water in the
environment; Atmospheric moisture; Precipitation
types (rain, fog, snow, hail, dew); Hydrological
Cycle; Water in soil; Water table.
By
N. Sannigrahi, Associate Professor
Department of Botany
Nistarini College, Purulia (W.B) India

2. WATER, WATER-----

3. WATER
 Water is called the elixir of life which basically is the oxides
of hydrogen. Protoplasm of plant cell or animal cell consists of
more than 85% water. All the metabolic activities of the living
organisms done at the aqueous medium. In around 3000
billion years ago, remote past life originated in the aqueous
medium most probably in the primeval ocean. Water also
forms the natural environment in the living cell. It plays an
important role in the biological systems as follows:
 The transport of different kinds of nutrients and waste
products,
 Protoplasmic streaming,
 Mediating enzyme catalyzed bio-0chemical reactions,
 Transfer of chemical energy by hydrolysis

4. GROUND WATER

5. PROPERTIES OF WATER
 Water consists of large number of properties and acts as
universal solvent as stated below:
 Melting point- The melting point of water is 0℃ which is
higher than most other common liquids like methanol, ethanol,
acetone, chloroform etc due to high intermolecular forces,
 Boiling point- It is highest(100℃) in comparison all other
solvents due to strong hydrogen bonding among the different
molecules.
 The specific heat capacity- It is 1 , being the highest in most
otrher solvents that help the living organisms to keep their
body temperature constant .This is because the change in
temperature due to absorption of a given amount of heat is less
if the specific heat of the substance is more.

6. PROPERTIES OF WATER
 Heat of fusion-It is the amount of calories of heat energy that
should be given out by one gram of substance to convert it
from liquid state to solid state at its melting point. The value is
80cal/gm being the highest among all other substances except
amonia.The stability of the biological environment is due to
water’s properties.
 Heat of vaporization-The latent heat of vaporization is defined
as the amount of calories per gram required to overcome the
attractive forces between adjacent molecules in a liquid as a
result they can go away from each other to form gaseous state.
The unusual heat of vaporization (500 cal) keep the constant
temperature of the organism.
 Density-water has highest density at 4 ℃ owing to packing of
smaller association of group have high degree of biological
significance.
 Transparent, colorless, odorless,
 High degree of solubility- It enables to make an universal
solvent status

7. STATES OF WATER IN THE ENVIRONMENT
 Water exists in three states –Solid, Liquid & Gaseous
 Solid state- in the form of ice, present below 0℃, other forms
are icebergs, glaciers, snow, sleet, hailstone etc
 Liquid state- natural form of water- the temperature range is 0-
100, present in rivers, ponds, lakes, seas, oceans etc
 Gaseous state- in the state of vapor, above 100 , water is
converted into gaseous state at boiling point when it receives
540 cal heat per gram water, called heat of vaporization.
 Water also differs from most liquids bin that it becomes less
dense as it freezes, the max. density of water in its liquid
forms is 1000 gm/ meter cube.
 The exact chemical nature of liquid water are not well
understood but some theories suggest that water’s unusual
behavior is a result of its having two liquid states.

8. ATMOSPHERIC MOISTURE
 Atmospheric moisture or humidity plays a crucial role in the
vegetation and the temperature has direct effect upon the
humidity. In the atmosphere, water present in the gaseous state
in the form of water vapor is called atmospheric moisture or
humidity. Evaporation and transpiration play crucial role in the
atmospheric humidity and clouds are the visible form. It can
be measured by the following ways:
 1. Absolute humidity-total mass of water vapor present in the
given volume of air and it ranges from 0-30 gm/cubic meter
when the air is at 30℃It is expressed as AH=mH20/V net
 Mass of the water per unit volume in the equation is termed as
volumetric humidity. With the changes of the temperature and
pressure, the absolute humidity is also changed and
psychrometrics deals with all the related issues.

9. HUMIDITY
 Relative humidity-Defined as the amount of water vapor
present in comparison with the amount of water vapor
required to saturate the water at the same temperature and
pressure, expressed as the percentage of saturation. The
relative humidity φ is also defined as the ratio of the partial
pressure of water vapor (pH2O)in the mixture to the
equilibrium vapor pressure of water over a flat surface of pure
water at a given temperature.
 It is normally expressed as percentage. A higher percentage
indicates the more humid air moisture. It is used as part of
forecasts of weather report of precipitation, dew or fog. In hot
summer weather, a rise in relative humidity increases the
apparent temperature of humans by hindering the evaporation
of perspiration from the skin.

10. HUMIDITY
 Specific humidity- It is the ratio of the mass of water vapor to
the total mass of the moist or humid air. It is approximately
equal to the mixing ratio, which is defined as the ratio of the
mass of water vapor in the air parcel to the mass of the dry air
for the same parcel. As temperature decreases, the amount of
the water vapor needed to reach saturation also decreases. As
the temperature of a parcel of air becomes lower, it will
eventually reach to the point of saturation without adding or
losing water mass. The difference in the amount of water
vapor in a parcel of air can be quite larger.
 Vapor pressure (pressure exerted by vapor in thermodynamic
equilibrium with its condensed phase at a given temperature in
a closed system), Dew point are also play an indication of
atmospheric moisture.

11. PRECIPITATION
 Precipitation indicates fall of water in different states. There
are three distinct ways of precipitation- Connective(more
intense but short duration), stratiform and orographic
stratification (occur in mountain). Phases of precipitation can
be sub-divided as below:
 LIQUID PRECIPITATION
 Drizzle-Fine drops smaller than 0.5 mm in diameter produced
from low stratified clouds
 Rain-Liquid water in the form of droplets,
 Fog-a thick cloud of tiny water droplets suspended in the
atmosphere near the earth’s surface,
 Sun shower while shower during sun shining.

12. PRECIPITATION
 FREEZING PRECIPITATION
 It may be freezing drizzle that freezes on contact with the
ground or an object or near the surface,
 Freezing rain-the rains that falls when surface temperature is
below freezing,
 Snain - combination of rain and snow, soft, translucent but
contains some traces of ice crystals.
 FROZEN PRECIPITATION
 It may be Snow-forms of ice crystals that precipitate from the
atmosphere , more than 1.0 mm in size,
 Snow grains-very small, ≤ 1.0 mm, white, opaque,
 Sleet-small, translucent balls of ice,
 Hail-consists of ball or irregular lumps of ice,
 Snow pellets-small particles of snow with a fragile crust of ice

13. TYPES OF PRECIPITATION
 Either sensible or latent heat, heat energy is involved in the
arrangement of molecules. Convection is the heat transfer due
to bulk movement of molecules within fluids. There are three
kinds of precipitations-
 Orographic, Convectional ,Cyclonic.
 OEROGRAPHIC
 It results when warm moist air moving across the ocean is
forced to rise by large mountains. Due to lower temperature,
the high elevation causes cooling of the air but it could not
hold as much moisture as warm air can do. Clouds are formed
and precipitates on the windward side of the mountain. As the
air moves down the mountain, it collects moisture from the
ground via evaporation. This side of mountain is called
leeward side having little precipitation. This uneven
distrinution of precipitation is very common feature.

14. TYPES OF PRECIPITATION
 CONVECTIONAL PRECIPITATION
 It results from the heating of the earth’s surface. As the air
warms, the air molecules move further apart. With the
increased distance between the molecules, the molecules are
less packed and the air becomes lighter and rises rapidly to the
atmosphere. Water vapors cool down and precipitates.
Convection precipitation occurs over a certain period for short
time as convective clouds have limited horizontal extent.
 CYCLONIC OR FRONTAL PRECIPITATION
 When the leading edge of a warm, moist air mass(warm front)
meets a cool and dry air mass (cold front), the molecules in the
cold air more tightly packed. Thus, the cold air is heavier than
the warm air. The warmer air mass is forced up over the cool
air. As it rises, the warm air cools, the water vapor condenses,
clouds from and undergone precipitation. Thus, frontal
precipitation falls out of nimbostratus clouds

15. MORE ON PRECIPITATION
 Different types of precipitations occur in the nature. They can
summarized as below:
 RAIN- May be normal rain, drizzle, updrafts, acid rain
 FOG-visible cloud droplets or mist formed less than dew
point; it may be radiation fog, ground fog, advective fog,
steam fog, frontal fog, ice fog, freezing fog, precipitation fog
or hail fog or other types depending upon their nature.
 HAIL-a kind of solid precipitation produced by cumulonimbus
clouds,
 DEW-liquids form of water droplets that appears on thin,
exposed objects in the morning or evening due to
condensation. When the temperature are low enough, dew
takes in the form of ice called frost.

16. HYDROLOGICAL CYCLE
 The water cycle scientifically known as the hydrological cycle
refers to the continuous exchange of water within hydrosphere
, between the atmosphere, soil water, surface water, ground
water and plants. It is a cyclic movement of water from the
atmosphere to the earth’s surface and through a variety of
pathways back to the atmosphere. Water moves perpetually
through each of the regions in the water cycle consisting of the
following main transfer processes.
 Evaporation-from water bodies into the air and transpiration
from plants
 Precipitation- from water vapor condensing from the air and
falling to earth,
 Infiltration
 Surface run off from the land usually reaching to the sea.

17. WATER CYCLE
 IMPORTANT FEATURES
 Most of the water vapor over oceans returns to the oceans but
winds carry water vapor the land at the same rate as run off
into the sea along with the contribution of evaporation and
transpiration.
 Runoff water flows into rivers, lakes. Seas and oceans and the
runoff shapes environment creating river valleys and deltas.
 The energy to drive the water cycle comes from the sun and
the cycle is a steady state one because the total precipitation is
balanced by the total evaporation. However, a significant
amount of water are incorporated by the ecosystems in the
protoplasmic synthesis and substantial return to the
atmosphere by the transpiration.
 Aquifers play a contributory role in the storage of water in the
ground water table.

18. PROCESS OF WATER CYCLE
 Precipitation-Condensed water vapor falls to the earth surface,
 Canopy interception-Plant foliage eventually evaporates back
into the atmosphere.
 Snowmelt-Runoff produced by snow melting,
 Runoff-water movement across the land
 Infiltration-Flow of water from ground surface to ground,
 Subsurface flow-Flow of water under ground, into the vedose
zone and aquifers,
 Evaporation- Transformation of water from liquid to gas
phases as it moves from ground water into the overlying
atmosphere,
 Sublimation-State change from solid water to water vapor,
 Deposition- changing water directly to ice,

19. PROCESS OF WATER CYCLE
 Advection-Movement of water in solid, liquid or vapor states
through the atmosphere,
 Condensation-transformation of water vapor into liquid,
 Transpiration-Release of water vapor by plants,
 Percolation-Water flows vertically through the soil and rocks
under the influence of gravity,
 Plate tectonics- water enters into the mantle via seduction of
oceanic crust and the water returns to the surface via
volcanism.
 In addition to these, there are different other minor pathways
that either directly or indirectly contribute to the hydrological
cycle to maintain a sustainable water cycle in the nature along
with to contribute different natural cycles .

20. WATER CYCLE

21. WATER IN THE SOIL
 Water present in both the atmosphere as well as soil and the
amount of water varies considerably in different soils
depending upon the nature of the soil and its porosity and
other factors. The available soil water is very important in the
growth and the development of the plants and vegetation. The
sources of water in the soil are rain, drizzle, snow, dew and
irrigation.
 HYGROSCOPICITY: The power of solid particles to adsorb
water upon their surface is called hygroscopocity.The larger
the relative surface, the large is hygroscopicity. The water
retention capacity in the clay is much more than the other
types of soil. Water retention capacity of the sandy soil is very
poor and hence, this type of soil is termed as physically dry
soil. Physiologically dry soil is the character of saline soil.

22. TYPES OF SOIL WATER
 The soil water is generally classified into four groups-
 Hygroscopic water,
 Capillary water,
 Gravitational water and
 Chemically bound water.
 HYGROSCOPIC WATER
 The water present as a thin film around the soil particles are called
hygroscopic water. Particles with great force due to which it can not
be removed easily. As the hygroscopic water id not available by
plant, it is also unavailable water. The amount of hygroscopic water
varies with soil texture, temperature and atmospheric humidity.
Hygroscopic coefficient is the a maximum amount of water
adsorbed by 100 gm of dry soil under standard conditions at the
50% relative humidity and 25℃.

23. TYPES OF SOIL WATER
 CAPILLARY WATER: It refers to the water present in narrow
capillaries in between the soil particles which is held due to the
capillary action of the interparticular spaces. The water held by the
capillaries is of great importance for vegetation, since it provides a
reservoir from which the plants can draw it in times of low rainfall.
Capillary water is not drawn by the gravitational force. The amount
of capillary water varies with the surface tension of the water film,
soil texture and structure, temperature and organic matter. The
highest amount of capillary water that can be held by a soil is called
its maximum capillary capacity.
 GRAVITATIONAL WATER: It is that surplus of water which, after
rain or irrigation, sinks or drains downward rapidly under the
influence of gravity. This forms ground water or water table. This
water is beyond the reach of the root systems of the plants and it is
unavailable to plants.

24. TYPES OF SOIL WATER
 CHEMICALLY BOUND OR COMBINED WATER
 This type of water occurs in the form of hydrated oxides of
iron, aluminum, silicon etc. This type of water is chemically
bound with the soil elements which are available by plants.
This type of water can not be detached from the soil elements
except strong heating. Field capacity is the total amount of
water present contributed by capillary water, hygroscopic
water, combined water and water vapor. Very often plants
begin to wilt due to loss of turgor pressure by the reduction of
capillary water and this condition is called wilting point. When
the plants do not achieve their turgidity due to the least water
availability caused permanent wilting and the % of water
present in this condition called wilting coefficient. Soil
moisture content is another issue that to be addressed.

25. WATER TABLE
 The water table is the upper surface of the zone of saturation
of the earth’s crust. The zone of saturation is that zone where
the pores and fractures of the ground are saturated with water.
 IMPORTANT FEATURES
 The water table is the surface where the water pressure head is
equal to the atmosphere pressure .It may be visualized as the
surface of the subsurface materials that are saturated with
ground water in a given vicinity.
 The ground water either from precipitation or from water
flowing develop aquifer due to zone of saturation (phreatic
zone) reached.
 The water table should not be confused with water level in a
deeper well. If a deeper aquifer has a lower permeable unit
that confirms the upward flow, then the water level in this
aquifer may rise to a level that is greater or less than the
elevation of the actual water table.

26. WATER TABLE

27. WATER TABLE
 The water table may vary due to seasonal changes such as
precipitation and evapotranspiration. In undeveloped regions
with permeable soils that receive sufficient amounts of
precipitation, the water table typically slopes toward rivers
that act to drain the ground water away and release the
pressure in the aquifer.
 SURFACE TOPOGRAPHY
 Within the aquifer, the water table is rarely horizontal, but
reflects the surface relief due to the capillary effect in soils,
sediments and other porous media. In aquifer, ground water
flows from points of higher pressure to points of lower
pressure and the direction of ground water flow typically has
both a horizontal and vertical component. The slope of the
water table is known as the hydraulic gradient which depends
on the rate at which water is added to and removed from the
aquifer and the permeability of the material.

28. WATER TABLE
 FLUCTUATIONS
 There are three types of fluctuations-
 Tidal fluctuations-On low oceanic islands with porous soil,
fresh water tends to collect in lenticular pools on top of the
denser sea water intruding from the sides of islands. Such an
island’s freshwater lens, and thus the water table rise4s and
falls with tides.
 Seasonal fluctuation-Due to seasonal variation, the water table
shows anomalous behavior. The disparity between the level of
the winter and the summer water table is known as ‘Zone of
intermittent saturation’, wherein the water table will fluctuate
in response to climatic condition.
 Long term fluctuation-Fossil water is ground water that has
remained in an aquifer for several millennia and occurs mainly
in the desert. It is non-renewable due to its depth below the
surface.

29. THANKS FOR YOUR PLEASURE
 ACKNOWLEDGEMENT
 1.Google for images
 2.Different WebPages for content
 3.Ecology & environment- P.D.Sharma
 4.Ecology & Environmental Biology- T. K.saha
 5. A text book of Ecology- S. Chand & company.
 Plant Ecology & Phytogeography- Arun Chandra
Sahu
 Disclaimer: This PPT has made as a free learning
resources for academicians, teachers, students and
others without any financial interest.