Salinity stress , impact and mechanism of plant to mitigate its effects

1. JAWAHARLAL NEHRU KRISHI VISHWVIDYALAYA
JABALPUR [M.P.]
DOCTORAL SEMINAR 1
Topic- Salinity stress , impact and mechanism of plant to mitigate its effects
PRESENTED BY
SATYENDRA THAKUR (190130002)
PhD Scholar
Department of Plant Physiology Jnkvv Jabalpur

2. Introduction
•Soil Salinization is a global and dynamic problem and is projected to
increase in future under climate change scenarios, viz. rise in sea level and
impact on coastal areas, rise in soil temperature and increase in
evaporation.
•According to mandal et al (2018) recent estimates show an increasing
trend in global salt-affected area with an area of 1,128 million ha.
•20% of total cultivated and 33% of irrigated agricultural lands worldwide
are afflicted by high salinity shrivastava and kumar 2015.
•Around 85% area worldwide is only slightly to moderately affected by high
salt concentrations while the remainder 15% suffers from severe to
extreme limitations for crop cultivation wicke et al 2011
•In India, the salt-affected soils constitute nearly 5% of the net cultivated
area, spreading from Jammu & Kashmir (Ladakh region) in north to
Kanyakumari in south, and Andaman & Nicobar Islands in the east to
Gujarat in the west.

3. Extent and Distribution of Salt Affected Soils in India
Source - Based on the map prepared by NRSA Hyderabad, CSSRI Karnal, and NBSS & LUP, Nagpur

4. In India about 6.73 m ha area is under salt affected ( 2.96 m ha saline &
3.77 m ha sodic ) CSSRI 2010
State wise salt affected area in India
State Saline Sodic Total
Andhra Pradesh 77598 196609 274207
Andaman & Nicobar Island 77000 0 77000
Bihar 47301 105852 153153
Gujarat 1680570 541430 2222000
Haryana 49157 183399 232556
Karnataka 1893 148136 150029
Kerala 20000 0 20000
Madhya Pradesh 0 139720 139720
Maharashtra 184089 422670 606759
Orissa 147138 0 147138
Punjab 0 151717 151717
Rajasthan 195571 179371 374942
Tamil Nadu 13231 354784 368015
Uttar Pradesh 21989 1346971 1368960
West Bengal 441272 0 441272
Total 2956809 3770659 6727468

6. •Soil salinity is an index of the concentration of salts in soil and is usually
expressed as electrical conductivity (EC).
•Soil salinization involves a combination of processes like evaporation, salt
precipitation and dissolution, salt transport etc that build-up of salt
concentration in soil to such a level that impacts on the agricultural
production, environmental health, and economics and quality of life.
•The major soluble mineral salts are –
•Cations (Na+), (Ca2+), (Mg2+), (K+)
•Anions (Cl−), (SO4
2-), (HCO3
-), (CO3
2-) and (NO3
-).
•Hyper-salin soil water may also contain (B), selenium (Se), strontium (Sr),
lithium (Li), (Si), (Rb), (Mo), (Mn), barium (Ba), and aluminum (Al), some of
which can be toxic to plants and animals (Tanji, 1990).
Soil Salinity and Soil Salinization

7. Soil salinization may occur through both natural and anthropogenic reasons. Out of
932.2 million ha salt-affected soils worldwide, the extent of human-induced
salinization is 76.6 million ha (,Shahid et al., 2018).
Sources of Salts in Soils
Weathering of
Minerals
Saline and Shallow
water table
Flooding/ seepage Impeded
Drainage
conditions

8. • Weathering of parent material During the process of weathering of rock
minerals or salts are released and made soluble. They are transported
away from their source of origin through surface or groundwater streams
and due to high evaporation and transpiration rates they cause soil
salinization.
• Fossil salts The fossil salt deposits (e.g., marine and lacustrine deposits)
are also responsible for salinization , Fossil salts can be dissolved under
water storage or water transmission structures causing salinization
(Bresler et al., 1982).
• Transport of salts in rivers The salts brought down from the upstream by
rivers to the plains and their deposition along with alluvial materials and
weathering of rocks may also cause salinization.
Natural processes of soil salinization (i.e., primary salinization)

9. Anthropogenic reasons of soil salinization (i.e., secondary salinization)
• Land clearing for cultivation Change of land use from natural forest
vegetation to annual food crops decreases evapotranspiration and
increases leaching. The presence of impermeable/less permeable sub
soil layers may intercept the percolating water resulting accumulation of
mineral or salt content at rooting zone.
• Incorrect irrigation Indiscriminate use of saline irrigation water, poor
drainage conditions, rising water tables etc. lead to secondary
salinization of land and water resources (Rao et al., 2014). Currently
worldwide 310 million ha area is irrigated, out of which 20–33% area is
estimated to be salt-affected (Shahid et al., 2018). Irrigation with sea
water causes salinization in coastal areas.
• Use of waste effluents Use of sewage sludge and/or untreated sewage
effluent, dumping of industrial brine onto the soil etc. may also cause soil
salinization. Of particular concern is the entry of heavy metals into soils.

10. • Canal water seepage It is a serious problem leading to rise in water table
and salinity development along the banks of canals. Water-logging and
soil salinization in the Indira Gandhi Nahar Priyojna (IGNP) area in India is
a glaring example of this process. Around 50% of the command area of
IGNP has experienced water-logging (Tewari et al., 1997).
• Over-use of agro-chemicals Over-use of chemical fertilizers and soil
amendments (lime and gypsum) may also lead to soil salinization.

11. Effects of salt stress on plants
Salinity stress effects on crop growth and development

12. On growth
•Decreased rate of leaf growth after an increase in soil salinity is primarily
due to the osmotic effect of the salt around the roots.
•Increase in soil salinity causes leaf cells to loose water.
•Reductions in cell elongation and also cell division lead to slower leaf
appearance and smaller final size
Physiological Effects

13. Seed germination in saline condition is affected by three ways.
• Increased osmotic pressure of the soil solution which restricts the
absorption and entry of water into the seeds.
• Certain salt constituents aretoxic to the embryo and seedlings. Anions
like chloride (Cl−), sulphate (SO4
2-), bicarbonate (HCO3
-), carbonate (CO3
2-)
and nitrate (NO3
-) are more harmful to seed germination.
• Salt stress hampers the metabolism of stored materials.
Germination

14. Vegetative growth
• During vegetative stage, salt induced water stress causes closure of
stomata leads to reduction in CO2 assimilation and transpiration.
• Reduced turgor potential affects the leaf expansion.
• Because of reduction in leaf area, light interception is reduced,
photosynthetic rate is affected which coupled with spurt in respiration,
resulting into reduced biomass accumulation.

15. Photosynthesis
• Accumulation of high concentration of Na+ and Cl- in chloroplast cause
inhibition in the rate of photosynthesis .
• Photosynthetic enzyme or the enzymes responsible for carbon
assimilation are very sensitive to the presence of NaCl.
• The key enzyme, nitrate reductase is very sensitive to NaCl .
• One of the amino acids, glycinebetaine shows increased trend with
increase in salinity in perennial halophytes and Atriplex sps.
• Proline is an α-amino acid, accumulates in large amounts as
compared to all other amino acids in salt stressed plants.
Nitrogen Metabolism

16. Reproductive growth and yield
• Under salt stress condition, the onset of flowering is delayed due to the
limitations of source size.
• The quantum of reproductive structure such as number of flowers /
panicle is very much reduced .
• This disturbance in the normal metabolism affects the mobility of
metabolites.
• Due to imbalance of nutrients under salt stress, hormone synthesis is
hampered leads to reduction in quantity as well as quality of crop
produce.

17. Oxidative stress
• Due to increase in salinity stress, photosynthetic rate decreases which
increases the formation of reactive oxygen species (ROS), and increases
the activity of enzymes that detoxify these species.
• Plants undergo adjustments in leaf morphology, chloroplast pigment
composition, and in the activity of biochemical processes that prevent
oxidative damage to photosystems.
• This maintains H2O2 at levels required for cell signaling.

18. Salinity stress tolerance

19. Relative tolerance of some crops to salinity (EC)

20. Crop adaptations to saltstress
• Based onthe responses to high concentration of salts, plants can be
divided into two broad groups.
1. Halophytes
2. Glycophytes
Halophyte ( salt tolerant crops)
They are native to saline soils and they are able to complete their life cycle
under saline conditions mangrove trees, thrift (Armeria), sea lavender
(Limonium), and rice grass (Spartina).
Glycophyte (Non halophytes)
• They are sensitive plants and unable to grow under saline conditions.
• Most of the cultivated crop species belong to glycophytes.

21. Mechanisms of salinity tolerance
The mechanisms of salinity tolerance fall into three categories
1. Tolerance to osmotic stress –
• This is achieved by production of some kinds of osmolytes which are
responsible for plant to prevent osmotic stress.
• Proline , Glycinebetaine , sugars and organic acids are the kinds of
osmolytes which are responsible for plant to protect from osmotic stress.

22. 2. Avoidance
• Avoidance is the process of keeping the salt ions away from the parts of the
plant where they are harmful. The way of avoidance are generally –
• Salt exclusion
• The ability to exclude salts occurs through filtration at the surface of the root.
Root membranes prevent salt from entering while allowing the water to pass
through. The red mangrove is an example of a salt excluding species.
• Salt excretion/extrusion
• Salt excreters remove salt through glands or bladders or cuticle located on each
leaf.
• Salt glands- dump sites for the excess salt absorbed in water from the soil; help
plants adapt to life in saline environments. (e.g.) Black and white mangroves

23. • Salt bladders - e.g.) Atriplex
• Secretion through cuticle – e.g.) Tamarix
• Salt Dilution
• 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.

24. 3. Tissue tolerance / Compartmentation of ions
• Tolerance requires compartmentalization of Na+ and Cl- at the cellular and
intracellular level to avoid toxic concentrations within the cytoplasm, especially
in mesophyll cells in the leaf.
• Organ level - high salts only in roots compared to shoots especially leaves .
• At cellular level- high salts in vacuoles than cytoplasm

25. Figure - Adaptive responses of plants to salt stress

26. Figure - Adaptive responses of plants to salt stress

27. Salt affected soil
Hydraulic
•Flushing
•Leaching
•Drainage
•Safe disposal of saline water
Physical / mechanical
•Scraping
•Land leveling
•Sub soiling
Biological
•Organic matter application
•Mulching
•Fallowing
•Tree plantation
•Blue green algae
•Saline agriculture
Chemical
•Amendments
•Soil conditioning
Integrated management practices for reclamation of saline soil .

28. Hydraulic method
• Flushing – Washing of surface salts by flushing water. This is especially
practicable for soils having a crust & low permeability. However this is
not sound method of practice.
• Leaching- leaching with good quality water, irrigation or rain is the only
practical way to remove excess salts from the soil. It is effective if
drainage facilities are available.
• Drainage - Removing of excess amount of salt water from the surface of
land is also helpful to prevent water logging and accumulation of salt.
• Safe disposal of saline water – Deposition of saline water apart from
cultivated land to prevent salinization of cultivated land area.

29. Physical / mechanical
• Scraping- This is the simplest & most economical way to reclaim saline
soils if the area is very small e.g. small garden lawn or a patch in a field.
This improves plant growth only temporarily as the salts accumulate
again & again.
• Land leveling- construction of the small bunds and land leveling is
require to implement a uniform leaching.
• Sub soiling - sub soiling is a technique commonly used to alleviate the
adverse effects of soil compaction and improve soil physical conditions
.Generally sub-soiler or flat lifter is used for sub soiling.

30. Biological Method
• Organic matter application - It helps to increase a water holding
capacity of a soil and decreases the conductivity of the soil saturation.
Application of FYM increases solubility of applied gypsum and hastens
the reclamation process.
• Mulching - It controls evaporation and salinity build up .
• Fallowing- Keep the land fallow during the monsoon season so that salt
accumulated during the winter season are leached out making the soil
fit to grow next crop.
• Tree plantation - Fuel wood plants are more suitable than timber
species. Ex- Eucalyptus, Casuarina, Accacia.

31. • Blue green algae- Nutrient content of saline soil was enhanced by the
application of Cyanobacteria in the form of organic matter.
Cyanobacteria not only grown in saline ecosystems but it also improve
the Physico-chemical properties of soil by enriching them with carbon,
nitrogen, and available phosphorous. ( Aparna Rai , 2015)
• Saline agriculture - Possibilities for saline agriculture exist in following
three ways-
1. Making conventional (freshwater) crops more salt-tolerant
2. Use of halophytes which are already salt-tolerant by nature
3. Irrigation of crops by saltwater

32. Rice –(CSR 10, CSR 13, CSR 23, CSR 27, CSR 30, CSR 36, CSR 43, CSR 46, CSR 49,
CSR 52, CSR 56 and CSR 60)
Wheat- (KRL 1-4, KRL 19, KRL 210, KRL 213 and KRL 283)
Indian Mustard- (CS 52, CS 54, CS 56, CS 58 and CS 60)
Chick pea (gram)- Karnal Chana 1
Dhaincha (sesbania)- CSD 137 and CSD 123
Examples of some conventional crop variety released by CSSRI for saline
conditions

33. Examples of some crop plants successfully grown under irrigation with
saline water
• Ornamental flowers like Chrysanthemum, Calendula and Matricaria can
successfully be cultivated with saline water of EC up to 5 dS m-1
• The aromatic grasses such as vetiver, lemon grass and palmarosa, could
be cultivated with saline water of EC 8.5 dS m-1
• Medicinal crop psyllium (Plantago ovata) could be cultivated with saline
water EC 8.5 dS m-1
• Other crops that could be grown are Aloe barbadensis, Ocimum
sanctum, Cassia angustifolia and Lepidium sativum.

34. Chemical method
Amendments
• This types of soil can be reclaimed by replacing exchangeable sodium
with calcium.
• This is commonly accomplished by adding gypsum .
• However if the soil is naturally high in calcium carbonate (lime) , then
the elements S or sulfuric acid can be applied .
• Soil conditioner soil conditioner is a product which is added in soil to
improve the physical quality of soil . Common types of soil conditioner
are biochar , bone meal , blood meal, compost , straw, peat moss,
spahagnum moss etc.

35. • Research Findings

36. Effect of salinity stress on morpho-physiological, biochemical and yield
characters of cluster bean [Cyamopsis tetragonoloba (L.) Taub.]
Deepika et al. 2014 Indian Journal of Plant Physiology (October–December ) 19(4):393–398

39. Ranganayakulu G. S. et al. 2013 African Journal of Plant Science Vol. 7(12), pp. 586-592,
December 2013
Effect of salt stress on osmolyte accumulation in two groundnut
cultivars (Arachis hypogaea L.) with contrasting salt tolerance

42. Conclusion
• In India about 6.73 m ha area is under salt affected ( 2.96 m ha saline & 3.77 m
ha sodic ) CSSRI 2010
• Salinity have negative impact on plant growth and development process and
its affects normal physiological process of plants which alters several metabolic
activity of crop plant resulting in reduction in the yield and productivity.
• Plant have several salt tolerance mechanism to survive under these conditions
but it is not enough to prevent yield loss.
• Therefore adoption of several integrated reclamation process are required to
prevent the yield loss due to impact of salinity stress.

43. THANK YOU