1. SALT TOLERANCE IN
HALOPHYTES AND
GLYCOPHYTES
B. RAKAVI
(2015601709)
STRESSPHYSIOLOGY
I M.SC.(PLANT PHYSIOLOGY)
TAMILNADU AGRICULTURAL

2. • GLYCOPHYTES – Salt sensitive plants(plant growth is inhibited by
saline soil).
• HALOPHYTES can survive and complete their life cycle in salt
concentrations of 200 mM NaCl .
• Halophytes can be further categorized as euhalophytes (true
halophytes), pseudohalophytes (salt avoiders) and
crinohalophytes (salt excreters)
• One of the striking features of most of these halophytes is the
correlation between uptake of cations and whole plant
succulence.

3. SURVIVAL EXTENT
Salinity 
Growth

Glycophyte
Intolerant
Halophyt
e
Facultative
Halophyte
Obligate
Halophyte

4. Salt adaptation in halophytes
• Depend on adaptation to low
osmotic potential and high salt
concentrations in the external
solution.
• Effector molecules that lead to
salt adaptation, and regulatory
molecules, which regulate
amounts and activities of
effectors.
Atriplex Spongiosa

5. Physiology of Halophytes
• Several key enzyme systems and genetic control mechanisms
have been identified.
• Halophytes use the controlled uptake of Na+ into cell
vacuoles to drive water into the plant against a low external
water potential (through SOS).

6. Avoidance:
• Avoidance is the process of keeping the salt ions away from
the parts of the plant where they are harmful
• Salt Exclusion
• Salt Extrusion
• Salt Dilution
Tolerance
• Osmotic adjustment
• Hormone synthesis - ABA stress hormone, hardens plants
against excess salts
• Detoxification
• Growth control

7. SALT EXCLUSION
• The ability to exclude salts -occurs through filtration at the
surface of the root. (Red Mangroves)
SALT EXCRETION
• Salt excreters remove salt through glands or bladders or
cuticle located on each leaf.
• Salt bladders - Atriplex , Mesembryanthemum crystallinum L.
• Salt glands - active process, selective for sodium and
chloride.( eg) Black and white mangroves
• Secretion through cuticle – eg) Tamarix

8. Regulation of Salt Contents
• Secretion of salts
– Salt exported via active
transport mechanism
– Excretion includes Na+ and Cl- as
well as inorganic ions
Leaf surface
containing salt
gland of Saltcedar
(Tamarix
ramiosissima)
Two celled salt gland of SpartinaPhotograph and schematic diagram of salt gland of
Aeluropus litoralis

9. Chenopodium quinoa salt glands

10. SALT DILUTION
• By dilution of ions in the tissue of the plant and by
maintaining succulence.
• Plants achieve this by increasing their storage volume by
developing thick, fleshy, succulent structures.
• Succulence is mainly a result of vacuoles of mesophyll cells
filling with water and increasing in size.
• This mechanism is limited by the dilution capacity of plant
tissues.

11. RESPONSE OF SALT TOLERANCE
TOLERANCES
1. Tolerance to osmotic stress.
2. Na+
exclusion from leaf blades.
3. Tissue tolerance.

12. TOLERANCE TO OSMOTIC STRESS
• The osmotic stress immediately reduces cell expansion in
root tips ,young leaves and causes stomatal closure.
• Ensuring water usage for grain to matures
• Depends on species for desirable and undesirable
activity.

13. Na+
EXCLUSION
• Na+
exclusion by roots ensures that Na does not
accumulate to toxic concentrations within leaves.
• Premature death of older leaves.

14. TISSUE TOLERANCE
• Tolerance requires compartmentalization(Cellular
and intracellular level).
• Energy dependent transport.
• Toxicity occurs with time, after leaf Na+
increases to
high concentrations in the older leaves.
• Salt-saturated leaf fall.

16. PROCESS SPECIFIC TOLERANCE
• Growth
• Photosynthesis and Stomatal conductance
• Oxidative stress
• Cellular signaling

17. GROWTH
• Reductions in cell elongation and also cell division lead to
smaller leaf appearance.
• Cell dimensions change, with more reduction in area than
depth, so leaves are smaller and thicker.-Depends mainly on
Osmotic effect.
• Osmotic adjustment
• Effect of ABA and GA
• DELLA protein mediated growth inhibition.

18. PHOTOSYNTHESIS AND STOMATAL
CONDUCTANCE
• Stomatal response- local synthesis of ABA
• Rates of photosynthesis per unit leaf area in salt-treated
plants are often unchanged, even though stomatal
conductance is reduced.
• Feedback inhibition from sink to source may fine tune the
rate of photosynthesis to match the reduced demand arising
from growth inhibition.

19. OXIDATIVE STRESS
• The reduced rate of photosynthesis increases the formation
of reactive oxygen species (ROS).
• Increases the activity of enzymes that detoxify these species.
• The coordinated activity of the multiple forms of these
enzymes in the different cell compartments achieves a
balance between the rate of formation and removal of ROS,
and maintains hydrogen peroxide (H2O2) at the levels
required for cell signaling.

20. CELLULAR SIGNALING
• Mediated by ABA which senses the external salt
concentrations.
• The best-characterized signaling pathway specific to salinity
stress likely involves these increases in [Ca]cyt.
• Sensed by a calcineurin B-like protein (CBL4), originally
identified as SOS3
• CBL-interacting protein kinase (CIPK24, originally identified as
SOS2)
• Membrane bound Na+/H+ antiporter, SOS1
(sos – salt overly sensitive)

22. Na+
concentration

23. CONCLUSION
• Salt-tolerant genes from halophytes are
potential key players of salt tolerance in
glycophytes (2015).
REFERENCES
• Annual review of plant biology
• journal of genomics
• Halophytes-potentials review