The document discusses the various ecological factors, particularly light, temperature, wind, and fire, that influence plant growth and adaptations. It categorizes ecological factors into climatic, physiographic, and biotic types, highlighting how plants adapt to varying light conditions, temperatures, and fire regimes. Additionally, it explains the effects of these factors on plant morphology, physiology, and distribution across different habitats.

1. PLANT ECOLOGY
Light, temperature, wind and fire - Variations;
adaptations of plants to their variation
By
N. Sannigrahi, Associate Professor
Department of Botany
Nistarini College, Purulia (W.B) India

2. FACTORS OF ECOSYSTEM
• Ecosystem is the delicate interaction among the different biotic and
abiotic factors to maintain a dynamic and sustainable system for the
smooth passage of life. The different factors play a very regulating
role in this regard. The ecological factors that affect the growth of
plants and determine the nature of plant communities are divided
into three types.
• The three types of ecological factors are:
• (1) Climatic factors which include rainfall, atmospheric humidity,
wind, atmospheric gases, temperature and light
• (2) Physiographic factors which include altitude, effect of steepness
and sunlight on vegetation and direction of slopes (3) Biotic factors
which include interrelationship between different plants of a
particular area, interrelationship between plants and animals
occupying the same area and interrelationship between soil
microorganisms and plants.

3. LIGHT
• Light, the sole source of energy derived from the sun is an
important ecological factor for the regulation of species
composition and vegetation. It is the primary factor in
photosynthesis, flowering and many other physiological
process in plants. It plays a vital role directly or indirectly in
regulating the growth, metabolism, development and the
distribution of plants.
• The sun not only emits the light rays used for assimilation but
in addition thermal rays and UV rays, both of which influence
many other biological process of plants. The light has dual
properties- wave and particle. The amount of energy is
inversely proportional to the wavelength of the light
.Depending upon the nature of wavelength corresponding to
energy content, light can be divided under following
categories along with their effect on vegetation.

4. RADIATION, WAVELENGTH & PLANTS
Radiation Wavelength(µ) Action in plants
Roentgen 0.00001-0.00018 Extremely harmful
Ultra-violet 0.012-0.40 Very harmful in
large quantity
Violet, blue 0.40-0.49 Phototropism
Morphological
effect
Green, red 0.49-0.70 Photosynthesis and
flowering
Infra red 0.70-1.00 Temperature effects,
photosynthesis and
flowering

5. LIGHT-ENERGY SOURCE

6. VARIATION IN LIGHT
Color Wavelength
Violet 370-430 nm
Indigo 430-470 nm
Blue 470-500 nm
Green 500-580 nm
Yellow 580-600 nm
Orange 600-650 nm
Red 650-700 nm

7. LIGHT QUALITY
In general, there exists no sharply defined distinction between
the action of the different rays. All rays that the plant absorbs
exert a definite heat effect. Yellow and red rays are photo-
tropically active, though to a much smaller degree than the
‘blue-violet rays. Growth, differentiation and tropic
movements are influenced chiefly by the blue-violet and ultra-
violet rays. This sensitiveness to the blue-violet part of the
spectrum has only been proved for phototropic reactions.
• Light has a two-fold influence upon growth. One part of the
spectrum provides the energy for carbon assimilation, and
hence for the production of raw material, while another part
acts as a stimulus, and influences directly the rate of growth
and differentiation. Even the form of the plant is determined to
a certain degree by light. Phytochromes, the photo
morphogenetic hormones play a crucial role in this regard.

8. LIGHT DURATION
• Initiation of flower buds in plants is another factor affected by
light period. Plants are grouped according to their response to
day length into what are called Short-day plants(SDP), Long-
day plants(LDP) and day-neutral(DN). The short-day plants in
general develop flowers when the days are less than 13 to 14
hours long (e.g., Chrysanthemum, Xanthium, Salvia, Maryland
Mammoth tobacco). The long-day plants develop flower when
the days are longer than 13 to 14 hours (e.g., Hordeum,
Petunia, clover, radish, lettuce etc.). The day neutral plants are
insensitive to day length (e.g., Tomato, tobacco, cotton, roses
carnation, sunflower etc.).Actually, the hypothetical flowering
hormone called Florigen is responsible for the initiation of the
flowering in course of the transformation of vegetative bud to
reproductive twig.

9. LIGHT INTENSITY
• Light intensity is very important in plant morphogenesis. It is
subject to cyclic fluctuations in intensity, depending upon the
altitude, latitude, season, and climatic conditions. One of the
most striking effects of light intensity is poor growth of
grasses when shaded by trees with dense foliage. The
undergrowth of flora may be almost entirely absent in
extremely dense forests, where trees grow very closely
together. Many species of plants are shade tolerant
(Heliophobous plants or Sciophytes), they are capable to
survive and grow in low light intensity, while others are shade
intolerant (photophilous plants or heliophytes) which require
high light intensity for growth and survival. In certain cases 50
per cent of full sunlight is needed. Shade tolerance plays a
significantly important role in forest plants where their
seedlings must become established in very poor light
conditions on the floor of the forest

10. LIGHT & PLANT ADAPTATION
• Adaptation the urge to adapt in the growing changing
surroundings. Plants adapt to light by a number of ways and
on different levels of organization-either whole plant, cellular
part or in molecular level. The systematic character of
adaptations simply broadens the adaptability range while the
low molecular adaptations balance the energy capture rate and
the distribution into the photo systems. The long term
adaptations modulate the short term strategies. There is a
coherence between the long term light adaptation and short
term adaptation to the light quality, since under limiting light,
the highly abundant mobile part of LHC II antennae will
ensure the maximum alteration in the cross section of photo
system I & II. The maximum extent of NPQ at light saturation
is also dependent on the plant growth conditions, mainly the
type of light and temperature environment and the type of
plant species.

11. LIGHT IN RELATION TO PLANTS
• Light directly or indirectly affects the plants as follows:
• Chlorophyll production-Light require for chlorophyll synthesis
• Heating action- Exposure to light raises the temperature ,
• Effect on transpiration rate-Light indirectly control the
opening and closure of stomata for transpiration,
• Distribution on plants- Light conditions are different in polar
and equatorial regions; the distribution of plants varies with
the light exposure.
• Vegetative development- The vegetative development of
plants are of different types – Heliophytes (Plants of full sun
light intensity), Sciophytes ( low light intensity),
• Photoperiodism- Total length of the day that control
reproductive biology of plants.
• Succession- The plant development along the different seres
are regulated by light.

12. LIGHT & PLANT ADAPTATION
• Several features of plant form, physiology and resource
allocation vary with the level of irradiance to which plants are
acclimatized or ecologically restricted .Variations in
adaptations to a specific level of irradiance is based on-
convergence and correlation with photosynthetic impact.
Convergence among species from different families of a given
trait in plants restricted to grow or grown under , a specific
level of irradiance is a result of natural selection.
• A second approach to identifying traits as adaptation to
irradiance level is based on the photosynthetic response of
leaves acclimatized to different light levels , together with an
analysis of how various features of their morphology and
physiology contribute to photosynthetic performance under
those levels( Bjorkman, 1984).

13. TEMPERATURE
• Temperature is also an important abiotic factors that play a
very crucial role in any ecosystem. It is the degree of the
hotness of any surroundings. The radiant energy received from
the sun is converted into heat energy. Heat is measured in
calorie or Kcal.The temperature at which the physiological
processes are maximum is called optimum temperature. The
minimum, maximum and optimum temperatures are called
cardinal temperature. The cardinal temperature varies from
species to species and the same individual from organ to
organ. The distribution of plants arte also influenced by the
temperature. The temperature has multidimensional affect
upon the vegetation and it effects from the cellular level toi
morphological level along with the output from the desired
surroundings like productivity of the plants.

14. EFFECT OF TEMPERATURE ON PLANTS

15. EFFECT OF TEMPERATURE ON PLANTS
• The temperature has multiple effect on plants that can be
addressed as below:
• EFFECT ON CELL- At low temperature, protoplasm may be
frozen and dies and in extremely high temperature, the protein
may undergo denaturation and coagulation. Generally, 10-
40℃, the maximum activity of the cells are observed.
• EFFECT ON METABOLISM-Various metabolic activities
catalyzed by the enzymes are highly affected by the change of
the temperature. Generally increase of temperature at 10℃ can
twice the turnover number of the metabolic activities. But high
increase of temperature may finally break down the active
sites of the enzymes and the rate of the metabolism are
decreased due to least catalytic activity.

16. EFFECT OF TEMPERATURE ON PLANTS
• EFFECT ON RESPIRATION-The rate of respiration usually
doubles with the increase of temperature by 10℃ as per Vent
Hoff’s law.
• EFFECT ON GROWTH & DEVELOPMENT-With the
increase in temperature, plants exhibit the elongation of the
hypocotyls, radicals by the increase of temperature. The
growth and development are regulated by the fluctuation of
temperature. Different types of vegetation like tropical,
temperate, tundra etc are some of the examples of the
vegetation across the global variation of the temperature.
• EFFECT ON TRANSPIRATION IN PLANTS-The rate of
transpiration increases with the increase of the atmospheric
temperature and vice versa. However, extremely high
temperature, the closure of the stomata takes place. Very low
temperature also exhibit the same kind of changes.

17. EFFECT OF TEMPERATURE ON PLANTS

18. ADAPTATIONS OF PLANTS
• Against thermal variation, many plants have various
adaptations to counter it. This can be addressed as follows
with respect to different variations of temperature:
• EFFECT OF LOW TEMPERATURE: during winter, the
insoluble organic reserves may transform into dissolved
substances like sugars which depress the freezing point of the
plant tissues and prevent the lethal injury. To withstand very
low temperatures, different chemical substances like sugars,
oil and resin compounds in the protoplasm greatly enhances
the ability to withstand it. The young tissues due to more water
content highly effected but the older shoot suffers least. Bud
scales, hairy envelopes are some of the features developed by
the plants to counter the low temperature in the surroundings.

19. ADAPTATIONS OF PLANTS
• EFFECTS ON HIGH TEMPERATURE
• Beside increasing the rate of the transpiration and affecting the
soil water contents, high temperature has other detrimental
effects which may cause the death of the plants. If the
temperature rises beyond the maximum limit, the plant
becomes inactive and suffer from chlorosis.Plants are
variously adapted to withstand the effect of the high
temperature. Plants extremely in humid regions become
succulent in nature and their stems modified into phylloclade
and leaves are reduced almost in the form of spines to reduce
the rate of the transpiration. The photosynthetic systems
becomes CAM pathways. The dry seeds can withstand more
than 100℃ but water soaked seeds can tolerate up to 70℃.
The effect of temperature is much more perspective in plant
geography than plant ecology.

20. ADAPTATIONS OF PLANTS
• LIMITS OF ATMOSPHERIC TEMPERATURE
• A temperature that can overall regulate the plants biology
starting from the seed germination to growth as well as
development and reproduction is called optimum temperature.
Life activities of other organisms are best during the optimum
temperature range. However, organisms can still survive
through the low efficiency, at a temperature blow minimum or
above (maximum) the optimum temperature. Most organisms
to0lerate temperature of 0℃ to 50℃ but the optimum
temperature is 25℃.
• Thus, the effect of low, high temperature directly or indirectly
effect upon the growth and development of the living
organisms and beyond the temperature ranges, the organisms
tend to develop the adaptation for the sake of the survival of
the species in the long passage of the evolution.

21. ADAPTATIONS OF PLANTS
• Both plants and animals undergo a degree of changes in order
to cope up with the temperature with the passage of evolution.
• Production of spores, cysts, eggs, seed modification as a away
of survival,
• Increase in osmotic concentration- Osmotic concentration
increase is the factor to stop freezing by enhancing the bound
water in colloidal form
• Removal of water from tissues-Dried seeds, spores avid
freezing due to lack of water content. Dry seeds able to
germinate even after exposure to -196℃,
• Homoeothermic-Body temperature maintain at constant value
through the evaporation of water from bodies in summer to
maintain constant temperature.
• Hibernation and aestivation as a part of dormancy along with
thermal migration are some of the strategies to overcome this
unavoidable issues.

22. PLANTS AND TEMPERATURE VARIATION
• Depending upon the response of plants to temperature variation of
environment, the entire vegetation of the earth can be divided under
the following categories.
• MEGATHERMS-Plants require more or less constant high
temperature throughout the year for their growth and development
like vegetation of tropical rain forests.
• MESOTHERMS- Plants are capable of enduring lower temperature
during some period of the year followed by high temperature. Many
plants of tropical and subtropical regions of the world belongs to
the categories like vegetation of tropical deciduous forests.
• MICROTHERMS- Plants of temperate regions of the earth need
lower temperature for their optimum growth and development.
These plants can are capable of enduring high temperature even for
a few months of the year. All high altitude plants up to 3600 mts of
the temperate and sub-temperate like mixed coniferous forests
belong to this category.

23. PLANTS AND TEMPERATURE VARIATION
• HEKISTOTHERMS- These are cold-tolerant plants of polar
regions . According to A.L.P. de Candolle(1874), the plants are
restricted only to arctic and alpine regions above 3600 mts in
the temperate zones of the world. These plants have lowest
t5hermal needs and they are also adapted to short summer
season which prevail in the extreme temperate regions of the
world. They can withstand long and extremely cold winter
months without any permanent injury like Alpine vegetation.
• Thermal stratification observed and according to this three
different vegetations are found-
• Epilimnion- Vertical gradient of gradually decreasing
temperature from the surface,
• Thermo cline-Short zone rapidly falling temperature
• Hypolimnion- Bottom cold zone

24. PLANTS AND TEMPERATURE VARIATION

25. WIND AND PLANTS
• Wind is also one of the important factors that regulate the
plants different morphological attributes. Violent winds have
direct effects upon the vegetation. It often break off twigs or
branches of plants and sometimes even uproot the trees and
shrubs. The vegetation of such area have prostrate habit of
growth and extensive root network to hold thy plants upon the
soil.
• ADAPTATION OF PLANTS TO WIND
• Larger plants often exposed to violent winds have following
adaptations-
• Trunks and branches are often bent,
• The branching is irregular,
• The crown has definite morphological shape,
• The leaves are smaller than usual type , cushioned growth like
Androsae sp.

26. WIND AND PLANTS
• In the area of strong winds, the plants develop special shapes
that often resistance to wind,
• Growth is restricted on the side of the plant von which the
wind effect is higher.
• Indirect effect of wind: Wind velocity has great impact upon
the rate of transpiration
• Variation in altitude: Plants growing in the higher altitudes
show stunted growth because of the effects of wind and also of
lower light intensity. The plants growing at the lower altitudes
have less chances of being put to the effects of violent winds
and undergoing excessive transpiration due to wind action. On
account of the wind action, the height at which a plant can
grow depends on its ability to absorb and transport water
rapidly enough to replace the loss of water due to
transpiration. Besides these, Compression wood, desiccation,
dwarfing, deposition are some of the effects of wind factors on
plants.

27. FIRE-ECOLOGICAL FACTOR
• Fire is an important ecological factor and fire ecology is
concerned with natural processes involving fire in an
ecosystem along with its impact on the ecosystems. Many
ecosystems like prairie, Savanna, Chaparral and Coniferous
forests have evolved with fire as an important contributor to
habitat. Many of the plant species require fire to germinate ,
establish or to reproduce . Suppression of wild fire indirectly
effects the growth and survival of the different species. Fire is
an integral component of the function and biodiversity of the
many natural habitats. Fire is now thought to be as natural
disturbances along with flooding, wind storms, landslides that
has driven the outcome of the different species in the passage
of the biological evolution. Frequency, intensity and area
associated with fire are some important in this regard.

28. FIRE REGIME
• Fire regime refers to the characteristics of natural fire and how
it interacts with particular ecosystem..It is classified as per
frequency, intensity, size, pattern, season and severity. Three
levels of fire are found-
• Ground fires burn the rich organic matter,
• Surface fires burn dead plant materials,
• Crown fires that burns the tops of shrubs & trees.
• Wild fires generally occur during the time of lightning. There
are four fire components-fuel, heat, oxygen and a sustained
chemical reaction. It is called fire tetrahedron. First three
components are called fire triangle . The energy released per
unit length of fire line is KW /m. Whatever may be, the fire
has strong effect upon the vegetation as stated below.

29. FIRE AND PLANTS

30. FIRE ON ABIOTIC COMPONENTS
• Fire, being an abiotic components has strong effect upon the
other non-living components of an ecosystem in general and
soil in particular.
• Fire can remove vegetation that leads to increased solar
radiation on the soil surface resulting greater warming and
faster cooling of the surface.
• Fewer leaves left to intercept rain to allow more moisture
retention in the soil surface.
• Fire changes the status of the soil nutrients including
oxidation, volatilization , erosion and leaching,
• Plant decaying mineral nutrients are more soluble and
available in the form of ash and promotes the erosion of
surface nutrients.
• Soil becomes more basic in pH and alter the clay content and
porosity of the soil.

31. ADAPTATIONS OF PLANTS ON FIRE
• Despite fire, plants can adapt itself by a good number of
adaptibility.Plant species can be
• Fire intolerant-Species are highly flammable and completely
destroyed by fire. However, some of these plants seeds may
germinate and grow after the fire.
• Fire tolerant- The plant species can withstand fire up to certain
degree and continue growing. These plant species are referred
as resprouters that store extra food in their roots. This provides
energy for recovery and regrowth after fire
• Fire Resistant- These type of plants suffer little damage during
characteristic fire regime. These includes large trees whose
flammable parts are high above the surface fires. Pine
ponderosa is an example of a tree species that suffers virtually
no crown damage under the naturally mild fire regime.

32. EFFECTS OF FIRE
• In addition to the direct killing effects on plants, fir has lot of
effects in the following ways.
• Some trees as a result of fire have large scars on their stems.
This scars enables a safe passage of the entry of pathogens
inside the plants for causing diseases.
• Fire brings a marked alteration of different factors like rainfall,
nutrient recycling, fertility of soil, and other indispensible
factors of the surroundings. Such alteration even may cause
long term damages of the surroundings.
• Fire tolerant species increase in abundance killing fire
sensitive species and this ultimately cause gene erosion.
• Fire has some positive roles. Cynodon sp, Paspalum sp like
herbs are stimulated by fore to produce large quantities seeds .

33. ADAPTATIONS OF PLANTS ON FIRE
• Plants have evolved different types of adaptations to cope up
with fire. Pyriscence is a part where maturation and release of
seeds is triggered in a whole or in a part by fire or smoke.
This behavior is called serotiny.All pyriscent plants are
serotinous but all serotinous plants are not pyriscent. Some
plants are smoke-0activated seeds or fire-activated buds. The
cones of Pinus contorta are pyriscent. They are sealed with
resins. The fire melts away, releasing seeds. Many plant
species including giant sequuoia ( Sequoiadendron gigantum)
require fire to make the gap in the vegetation canopy that will
left in light, allowing their seedlings to compete with more
shade tolerant seedlings of other species and to establish
themselves. Thus, plants enable to compete with fire for their
survival.

34. CONCLUSION
• The environment is a complex of so many things like light,
temperature, wind, fire etc and these factors play a very crucial
role in the dynamic nature of a sustainable ecosystem. Any
external factors of the discussed above affects the life of the
organism in any way. The sum of all these ecological factors
either living or non-living makes the environment of an
organism. The habitat indeed presents a particular set of
conditions called environmental complex . The understanding
of the different factors and their role is very significant one in
order to understand the ecology as a whole and the individual
in particular.

35. 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.