1. Response of Plant to Stress

2. Presented By
Abu Khairul Bashar
Roll No: 584; Session: 2011-2012
Email: abukhairulbashar@gmail.com
Department of Environmental Sciences
Jahangirnagar University,
Savar, Dhaka-1342

3. Stress
۞ Biological stress is not easily defined but it implies adverse
effects on an organism. Like all other living organisms, the plants
are subjected to various environmental stresses such as water
deficit and drought, cold, heat, salinity and air pollution etc.
۞ The concept of stress is associated with stress tolerance. Degree
of tolerance differs with different plant species.

4.  According to Levitt (1972),
``Stress is any change in environmental conditions that might reduce
or adversely change plant’s growth and development. ``
 According to Jones (1989)
``Adverse force or influence that tends to inhibit normal systems
from functioning. ``
Continuous…..

6. Types of Stress
Abiotic Stresses
 Temperature (high / low)
 Water (high / low)
 Salt
 Radiation
Biotic Stresses
 Fungi
 Bacteria
 Insects
 Herbivores
 Other plants

7. Flowchart

8. Plant Stress
۞ Plants can respond to stress in several ways. Plants may escape
the effects of stress by completing their growth during less
stressful periods or they may suffer injury if the stress is
present and they cannot cope.
۞ Stress resistant plants can tolerate a particular stress. Many
Plants have the capacity to resist stress through either stress
avoidance or stress tolerance.

9. Stress Resistant or Stress Tolerance
Plants may become stress tolerant through-
◙ Adaptation:
-Heritable modifications to increase fitness.
-CAM plants’ physiological adaptations to low H2O environment.
◙ Acclimation:
-Non heritable physiological and biochemical gene expression.
-Cold-hardy plants’ adaptation to high H2O environment.

10. Stages of Response to Stress
1. Reception
2. Transduction
3. Response
CELL
WALL
CYTOPLASM
1 Reception 2 Transduction 3 Response
Receptor
Relay molecules
Activation
of cellular
responses
Hormone or
environmental
stimulus
Plasma membrane

11. Environmental Stresses to Which Plants may be Subjected
 High Temperature (Heat)
 Low Temperature (Chilling, Freezing)
 Water Deficits (Drought, Low water potential)
 Salinity
 Excess water (Flooding, Anoxia)
 Chemical (Heavy metals, Air Pollutants)
 Radiation (Visible, Ultraviolet)
 Pathogens
 Competition

12. Respond of Plant at Different Parts

13. Water Stress
▲Water stress is a major abiotic stress. Induced by many
environmental conditions.
▲Water stress may arise through either an excess of water or a water
deficit. Water stress is primarily caused by a water deficit, such as a
drought or high soil salinity.
▲Rate of duration influence the water stress response.

14. Water Stress and Water Availability

15. ₪ Reduction in cell and leaf
expansion.
₪ Reduction in photosynthesis.
₪ Impact on Metabolism.
₪ Effect on shoot and root
growth.
Effects of Water Stress
Smaller leaves
Less light reception
Less photosynthesis

16. Temperature Stress
☼ Each plant has its unique set of temperature requirement for growth
and development. There are two types of limits of temperature-
upper limit and lower limit.
☼ Except in the relatively stable climates vary depending on the
environment. Temperature may be of two kinds-
-High Temperature
-Low Temperature

17. Growthafter1month
RED has a greater stress tolerance than Blue
High T Low T
Comparison With Temperature

18. Continuous…
The effects of Low Temperature
included the following –
A. Chilling Stress
B. Freezing Stress

19. Chilling Stress
› Chilling injury refers to an injury that is caused by a temperature
drop to below 15°C but above the freezing point.
› Plasma membrane is the most common site for chilling injury.
› The consequences of this change may lead to cell leakage or
disruption and loss of cell liquid.

20. Plant at Chilling Stress

21. Chilling Affects on Plants
Chilling injury causes several physiological dysfunctions to the plant
including-
 Disruption of the conversion of starch to sugars
 Decreased carbon dioxide exchange
 Reduction in net photosynthesis
 The destruction/degradation of chlorophyll

22. Freezing Stress
It freezes at about -2°C, depriving the plant of its source of
water. It occurs by rapid freezing of cells to a very low
temperature.
Freezing injury in plants can be from two sources:
 1. Freezing of soil water, and;
 2. Freezing of the fluids within the plant.

23. Plant at Freezing Stress

24. ▲Desiccation or Burning of foliage.
▲Freezing can rupture membranes.
▲Extracellular ice can dehydrate protoplast
▲Increase necrotic spots on leaves, stems or fruit of the plant.
▲Reveal a dead or weakened root system.
▲Increase transpirational water loss.
Freezing Affects on Plant

25. References
William G. Hopkins, 2002. Introduction to Plant Physiology, 2nd edition,
John Wiley and Sons. Inc. New York.
Chilling and Freezing Stress in Crops-ppt.
Plant Physiology by Jain.
Plant water relations by Douglas R. Cobos, Ph.D. Decagon Devices and
Washington State University.
Plant Response to Stress by Dr. W. Mclaughlin.

26. Any Question?

27. Thank Everyone