1. Responses to Abiotic Stresses
CHAPTER 22
Responses to Abiotic Stresses

2. Introduction 22.1 Plant responses to abiotic stresses
22.2 Stresses involving water deficit
22.3 Osmotic adjustment and its role in tolerance to drought and salinity
22.4 Impact of water deficit and salinity on transport across plant membranes
22.5 Additional genes induced by water stress
22.6 Freezing stress
22.7 Flooding and oxygen deficit
22.8 Oxidative stress
22.9 Heat stress

3. What is the effect of stress in plant?
Biotic stress (chapter 21)
Abiotic Stress (chapter 22)
What is Abiotic Stress?
Environmental condition that cause damage are water logging, drought, high or low
terperatures, excessive soil salinity, inadequate mineral nutrients in the soil, and too
much or too little light…
What is the effect of stress in plant?
Stresses trigger a wide range of plant responses
- gene expression and cellular metabolism to change in growth rate and crop yields.
Some responses enable a plant to acclimate to the stress
Identifying which responses promote or maintain plant growth and
development during stress is important for understanding
the stress response process.

4. Stress tolerance crop plant
22.1 Plant responses to abiotic stresses
Plant stresses greatly diminish crop yields
Abiotic and biotic stress reduce average productivity of crop by 65% to 87%
Biotechnology +
Classical breeding
technique
Stress tolerance crop plant
= enhance food
Many factors determine how plants respond to environmental stress

5. Stress resistance mechanism -- Avoidance & Tolerance -- Acclimation
Resistance mechanisms allow organisms to avoid or tolerate stress
Photosynthetic stem
Deep root
Osmotic tolerance
Wet season life cycle
Cold hardy tree
Stress resistance mechanism -- Avoidance & Tolerance
-- Acclimation

6. 22.1.3 Gene expression patterns often change in response to stress

8. 22.2 Stresses involving water deficit
Water potential and relative water content describe the water status of plant.
Equation 22.1: Water potential
Ψw = Ψs + Ψp + Ψg + Ψm
Equation 22.2: Water potential (simplified)
Ψw = Ψs + Ψp
Ψw = water potential
Ψs = solute potential
Ψp = pressure potential
Ψg = gravitational potential
Ψm = matric potential

9. 22.3 Osmotic adjustment and its role in tolerance to drought and salinity
Osmotic adjustment is a biochemical mechanism that helps plant acclimate to dry
or saline soil.
Osmotic adjustment
; cell actively accumulates solutes
and, as ad result, Ψs drops, promoting
the flow of water into the cell

10. 22.3.2 Compatible solutes share specific biochemical attributes.
Sugar (sucrose, fructose)
Sugar alcohol (glycerol, methylated inositol)
Complex sugar (trehalose, raffinose, fructan)
Charged metabolite (glycine betaine,
DMSP, proline, ectoine)
Dae-Jin Yun, 2005

11. H2O
The hydration shells of macromolecules are not disrupted by compatible solutes

12. Osmotic adjustment in a mesophyll cell of a salt stressed spinach leaf.

13. 22.3.3. Some compatible solutes may serve protective functions
Glycine betaine prevents salt induced inactivation of Rubisco and destabilization of
the oxygen-evolving complex of Photosystem Ⅱ.
Sorbitol, mannitol, myo-inositol and proline can reduce hydroxyl radicals in vitro.
Transgenic plants can be used to test the acclimative functions of specific
osmolytes.
osmoprotectant encoding gene

14. 22.3.5. Glycine betaine accumulation is regulated by the rates of its synthesis
and transport

15. 22.3.6. In some plant species, salt stress inhibits sucrose synthesis and promotes
accumulation of mannitol
Salt stress inhibit sucrose synthesis
Salt stress also down-regulates NAD+ dependent mannitol dehydrogenase.
Transgenic plants expressing NAD+ dependent mannitol-1-phosphate
dehydrogenase(fructose 6-phosphate  mannitol 1-phosphate) accumulate
mannitol.
- Mannitol accumulating transgenic seed was able to germinate in the salt media.

16. 22.3.7. Taxonomically diverse plants accumulate pinitol in response to salt stress.
D-Pinitol
a cyclic sugar alcohol (major solute in the Pinaceae)
accumulate in salt tolerant legumes
Pinitol can contribute 70% of the soluble carbohydrate
in salt treated plant.
In leaf, pinitol localized to the chloroplast and cytosol
Increase in the concentration of pinitol in salt exposed plant,
myo-inositol 6-O-methyltransferase induced by 60-fold

17. 22.4 Impact of water deficit and salinity on transport across plant membranes

18. - Na+/H+ antiporter in PM - energized by H+-ATPases
Carriers, pumps, and channels operate to minimize the impact of perturbing ions on cell metabolism.
by the active transport of cytosolic Na+ across the plasma membrane out of cells
- Na+/H+ antiporter in PM
- energized by H+-ATPases
by the active transport of cytosolic Na+ across the tonoplast membrane into vacuole
- Na+/H+ antiporter in Vacuole

19. Chemiosmotic processes in plant cell
Energize Na+/H+ antiports
Plassma membrane H+-ATPase
Vacuolar H+-ATPase
Tonoplast membrane H+-pyro
phosphatase

20. 22.4.2 Synthesis and activity of aquaporin may be up-regulated in response to drought
Water channels
Facilitate water movement in drought
stress tissues and promote the rapid
recovery of turgor on watering
Rd28 gene encodes a member of the MIP
family

21. Expression of MIP-related genes
watering
drought
Increase or decreases of Rd28 gene

22. 22.5 Aditional genes induced by water stress
drought
heat
Oxyzen species
Water
stress
salinity
pathogens
Multiple stress-related roles

23. 22.5.1 some seed proteins may protect vegetation tissues from stress.
Lea genes
Seeds during maturation and desiccation
Vegetative tissues of plants exposed to stresses
Cytoplasmic location
Rich in alanine and glycine and lacking cysteine and tryptophan

24. Five group of LEA proteins

25. Induction of osmotin gene Induction of osmotin protein
osmotin, a tobacco protein with antifungal activity, accumulates during water deficit.
Induction of osmotin gene
Induction of osmotin protein
Ethylene
Cold
Water deficit
UV-light
Lack of water
Salinity
Fungal infection
Wounding
Fungal infection
Ethylene
Auxin
ABA
Salinity
TMV Infection

26. Model for antifungal action of osmotin1
Fungal hypha releases fungal toxins 2
Disrupt the plant membrane 3
Causing it to leak nutrients that the fungus utilizes 4
The plant cell loses turgore 5
Promotes the acumulation of osmotin 6
Osmotin from the leacking cell comes into contact with a fungal membrane receptor 7
Facilitates the formation of pores in the fungal membrane
Limit the effect of osmotin 8

27. 22.5.3 some genes induced by water stress are responsive to ABA.
ABA induced gene
Increased in response to water
deficit and low temperature
Stomatal closure
ABI1 and ABI2 gene are thought to
encode protein phosphatases
Regulating tyrosin kinase