This document discusses abiotic stresses on plants. It defines abiotic stress as negative impacts from non-living factors like drought, extreme temperatures, salinity, and nutrient deficiencies. Primary abiotic stresses significantly impact global crop yields. The document outlines how these stresses affect plants physiologically by reducing growth, photosynthesis and reproduction. It also explains how plants develop resistance and acclimate to stresses through genetic adaptations like hardening off. Finally, the document notes that abiotic stresses limit biodiversity and agricultural production worldwide.

1. ABIOTIC STRESSES

2. Presented by:
Eng. Qusai Bani-Domi (Qusai Qarqz)

3. Content
■ Definition of pressure and its types.
■ Which stresses are called abiotic? And its effects on plants.
■ Stress responses in plants.
■ How plants deal with abiotic stress.
■ Adaptation and acclimation.
■ Plant stress and genetic potential.
■ The effect of abiotic stresses on agriculture.
■ The effect of changes in environmental conditions on seed
production.
■ The impact of abiotic stress.

4. Definition of Stress
Any environmental or physical pressure
that elicits a response from an organism.

5. Types of stress
1) Abiotic stress: is the negative impact of non-living
factors on living organisms in a specific environment.
2) Biotic stress: is the negative influences caused by
other living organisms.

6. Which stresses are called
abiotic?

7. Abiotic primary stresses
■ drought (water stress).
■ excessive watering (water logging).
■ extreme temperatures (cold, frost and heat).
■ salinity.
■ mineral toxicity.

8. Abiotic stresses, especially hypersalinity and drought
are the primary causes of crop loss worldwide.
Fig.1 The effect of hypersalinity and drought

9. Abiotic Secondary stresses
■ Mechanical stress.
■ lonic stress.
■ Oxidative stress.
■ Osmotic stress.

10. Drought
Drought: an extended period of deficient rainfall relative to
the statistical mean for a region.
■ Meteorological drought is qualified by any significant deficit
of precipitation.
■ Hydrological drought is manifest in noticeably reduced
river and stream flow and critically low groundwater tables.

11. Effects of drought stress on crops
■ Reduced seed germination and seedling
development.
■ Poor vegetative growth.
■ Reproductive growth is severely affected.
■ Plant height and leaf area reduced.

12. ■ Significantly reduction in leaf weight.
■ Reduced photosynthesis.
■ Reduced stomatal conductance.
■ Significantly reduction in the total dry matter.

13. Effects of flooding stress on plants
1. Decay and death of leaves.
2. Wilting.
3. Abscission.
4. Epinasty.
5. Lenticels formation.
Flooding: is any situation of excess water.
Flooding stress

14. Nutrient deficiency & Toxicity
■ Under the anaerobic condition Fe toxicity is high.
■ This leads to increase the polyphenol oxidase activity,
leading to the production of oxidized polyphenols.
■ It also causes leaf bronzing and reduced root oxidation
power.

15. Salinity
Is defined as the presence of excessive amounts of
soluble salts that hinder or affect the normal functions
of plant growth.
Fig.2 Effect salt on plants

16. Effects of salt stress on plants
1- Osmotic effect or water deficit effect:
Reduces the plant‘s ability to take up water, and this
leads to slower growth.
** This is the osmotic or water-deficit effect of salinity.
2- Salt specific effect or Ion Excess Effect:
Salts enter the transpiration stream and eventually injure
cells in the transpiring leaves, further reducing growth.

17. Effects of Heat stress on Plants
■ Seedling establishment is hampered.
■ Drying of leaf margins and scorching effect on leaves.
■ Reduction in plant growth.
■ Pollen development is affected.
■ Alteration in photosynthesis.
■ Total biomass is reduced.
■ Spikelet sterility.
■ Grain and fruit development and quality is affected.

18. Stress responses in plants
Fig.4 Effects of abiotic stress

19. Stress responses in plants
Fig.5 Effects of abiotic stress

20. How plants deal with abiotic
stresses?

21. Resistance
Is the adaptability of plants to adverse environment.
Types of Resistance
1. Stress avoidance:
In the whole growth process does not meet with the face of adversity.
2. Stress tolerance:
Plant has a capacity of environmental stress defense, and a variety of
physiological processes remain normal.

22. Adaptation and acclimation
Adaptation
is a change in both physical and chemical composition of an organism
with habitat changes.
Acclimation
is a physical reaction made in order to adjust to said changes.
Adaptation Permanent
Acclimation Temporary

23. Examples of adaptation
1- The seaweed is a plant adapted for its underwater environment.
2- Cacti are adapted for the desert environment.

24. Example of acclimation
1- Maple trees.
2- Irises.
3- Tomatoes.
**can survive freezing temperatures if the temperature
gradually drops lower and lower each night over a
period of days or weeks.

25. How acclimation allows plants to respond
to environmental fluctuations?
For example
Process known as hardening off, to speed up the growth of plants
garden often start by:
1- Growing them indoors in pots under optimal growth condition.
2- The gardeners then move the plants outdoors for part of the day
over a period long enough to acclimate or harden.

26. Define of plant stress and genetic
potential
Plant stress: is any external factor that negatively
influences plant growth, productivity, reproductive capacity
or survival.
Genetic potential: is the likelihood that a mutation to a
gene coding for the currently favored phenotype will
produce the intermediate or unfavored phenotype.

27. plant stress prevents the plant from achieving its
full genetic potential.
For example:
1- a decrease in light intensity would cause a reduction in
photosynthetic activity.
2- with a concomitant decrease in the energy supply to the plant.

28. The effect of abiotic stresses on agriculture
■ Abiotic stress management is one of the most important
challenges facing agriculture.
■ Abiotic stress can persistently limit choice of crops and
agricultural production over large areas and extreme
events can lead to total crop failures.

29. ■ Abiotic stresses adversely affect the livelihoods of
individual farmers and their families as well as
national economies and food security.
Fig.6 Crops damaged by forst

30. How do changes in environmental
condition affect seed production?
Examples
1- the transition to reproductive growth occurs only after the
vegetative adult phase completes its genetically determined
developmental program.
2- under stress conditions the vegetative growth program may
terminate prematurely and the plant may go immediately to the
reproductive phase.

31. The impact of abiotic stress on biodiversity
■ Biodiversity is determined by many things, including abiotic
stress.
■ If an environment is in a state of great stress, its biodiversity
is reduced.
■ If there is no strong presence of abiotic stress in an area, its
biodiversity increases.

32. ■ This idea leads us to understand how endangered species
are linked to abiotic stress.
■ The number of species decreases.
■ This means that these species are most vulnerable to the
threat of pollution , extinction and indeed extinction, when
and where abiotic stress is exceptionally severe.
Fig.7 Extinction

33. Thanks for listening.
I hope you have benefited from the topic.
If you have any questions you would like to ask,
we will be happy to answer everything.

34. References
https://www.sciencedirect.com/topics/pharmacology-toxicology-and-
pharmaceutical-science/abiotic-stress
https://en.m.wikipedia.org/wiki/Genetically_modified_crops
https://journals.plos.org/ploscompbiol/article?id
http://www.differencebetween.net/science