In this chapter discussed with role of sugars in plants and different abiotic stress occurs in plants. During abiotic stress occurs in plant metabolism - how sugars act as a mitigating strategical tool.

1. ROLE OF SUGARS FOR COMBATING PLANT
ABIOTIC STRESS

2. ❖Introduction
❖Plant growth and development
❖Physiological role of sugars in plants
❖Oxidative stress and anti-oxidant system
❖Effect of sugars on proline accumulation
❖Sugars as osmo – protectants
❖Relationship between sugars and abiotic stress in plants
➢Salt stress
➢Cold stress
➢Drought stress
❖Targeting sugars to develop abiotic stress tolerant crop varieties
❖Research evidences
❖Conclusion
Flow of presentation

3. INTRODUCTION
❖ Sugars – Vital energy rich biomolecules present in every
cell of the body.
❖ Role in primary as well as secondary metabolites of plant

4. ❖ Sugars classification
➢ carbohydrates commonly referred as sugar

5. ❖ Plants – Autotrophic and Photosynthetic organisms
❖ photosynthesis – light energy is converted into chemical energy
– resulting in the formation of energy-rich sugar molecules.
that both
Produce and consume sugars

6. Water soluble sugars
➢ sugars such as sucrose, glucose and fructose
➢ Stress response
➢ Interact with reactive oxygen species (ROS)
signalling pathways
➢ Sensory metabolite
❖ WSS – highly sensitive to environmental stress
❖ Sugars
➢ Up regulation of growth related genes
➢ Down regulation of stress related genes
role
Plays dual function

7. Role of sugars
❖ Regulation of growth and metabolism,
❖ Photosynthesis,
❖ Carbon partitioning,
❖ Carbohydrate and lipid metabolism,
❖ Osmotic homeostasis, and Protein synthesis,
❖ Gene expression during various abiotic stresses
(Hara et al., 2013)

8. plant growth and development
❖Glucose and fructose - cell division
❖Sucrose favors - differentiation - maturation & gene
regulation. (Koch, 2014)
❖Trehalose regulates growth but higher concentration affects
organ functions
➢ inflorescence,
➢ leaf tuber,
➢ seed development. (Paul and Dijck, 2011)
❖ In developing plant embryos - glucose and sucrose
➢ cell division,
➢ cell expansion and
➢ accumulation of reserve carbohydrate
regulate
(Yaseen et al., 2013)

9. ❖ Soluble sugars in plants trigger
➢ proliferation of organs,
➢ produce larger and thicker leaves,
➢ increases the size and number of tubers and
➢ adventitious roots.
Eg.
➢ High concentration of sugar leads to increase the number of
potato tubers.
➢ In Arabidopsis thaliana, high concentration of sugars
stimulate formation of adventitious roots.
(Gibson, 2005)

10. Eg.
➢ Young seedlings of Arabidopsis, exposed higher
concentration of glucose and sucrose which leads to
cotyledon expansion, true leaf formation and
root growth.
➢ Same phenomenon was observed under lower
concentration of mannose.
(Gibson, 2005)
inhibition
➢ Glucose - highly active in
✓ non-differentiated cells
✓ Cell division
➢ Sucrose - highly active in
✓ starch synthesis
✓ cell division

11. Physiological role of sugars in plants
❖ Sugars - Regulates many physiological processes such as
➢ photosynthesis
➢ seed germination
➢ flowering
➢ Senescence

12. High concentration
Low concentration
Inhibits photosynthesis
Delays seed germination
Delays flowering
Accelerates senescence
Exogenous glucose
Stimulate photosynthesis
Promotes seed germination
Promotes flowering
Delays senescence
(Fareen et al., 2016)

13. ❖ Application of Exogenous glucose in high concentration
➢ Inhibits - photosynthesis
➢ Promote - Carbohydrate storage and growth
❖ Application of Exogenous glucose in low concentration
➢ Enhances - Photosynthesis
➢ Reserve – Mobilization and export
Rolland et al., 2002
Photosynthesis
❖ Vital process associated with the production of sugars
for growth and development of plants

14. Seed germination
❖ In rice, exogenous application of 1% glucose
seed germination
❖ But, 3 and 6% of glucose significantly delay seed
germination.
(Zhu et al., 2009)
❖ Exogenously applied glucose in higher concentration
the enhancement of ABA production resulting delay of
seed germination.
(Heurtero et al., 2000)
not prevent
leads to

15. Senescence
❖Whole plant senescence
❖Monocarpic senescence
❖ The entire plant dies after the
development of flower and seeds.
Eg. (Annuals)
Paddy, wheat, soyabean
❖ High carbon and low nitrogen - accelerates - senescence.
Arabidopsis plants – dark situation delays - leaf senescence
(Weaver and Amasino, 2011)
observed

16. Fig. Various factors interacts with glucose and affects leaf
senescence

17. ❖ Treatment of Arabidopsis plants with 2% glucose combined
with low nitrogen concentration induces leaf senescence.
(Wingler et al., 2006)
❖ In tobacco, sugar accumulation in leaves leads to senescence
enhances.
(Wingler et al., 2012)
❖ Elevated CO2, accumulation of more sugars and reduced
nitrogen and rubisco content
Acceleration in senescence
(Xu et al., 2015)

18. Flowering
High levels of glucose low level of glucose
delayed stimulates
flowering flowering
Arabidopsis
Elevation of endogenous sucrose level
❖ Arabidopsis thaliana, - Endogenous sucrose levels in leaves
and shoot apex is increased by high radiation.
King et al., 2008
Exogenous application of sucrose
❖ Chrysanthemum indicum,- Spraying 50 mM sucrose
promotes flowering compare to 100 mM sucrose level
Sun et al., 2017

19. Losses
❖ Reduce average global crop yield by >50%
❖ Affect >90% of the total global land area
❖ Only 10% of land free from stress.
(Cramer et al., 2011)
Biotic stress Abiotic stress
Stress
Abiotic Stress
“The negative impact of non-living factors on the
living organisms in a specific environment”

20. ‘‘Overall Effects of abiotic stress toPlant’’
Air pollution
Salinity stress
Drought stress
Light stress
Mechanical
damage
Cold stress
Vickers et al., (2009)
Temp. stress

21. Crop Abiotic stress Yield reduction References
Rice
Drought 53-92 % Lafitte et al., (2017)
Heat 50 % Li et al., (2010)
maize
Drought 63-87 % Kamara et al., (2013)
Heat 42 % Badu-apraku et al.,(2013)
wheat
Drought 57 % Balla et al., (2011)
Heat 31 % Balla et al., (2011)
Crop Abiotic stress Yield reduction
Chickpea
Terminal drought 30-60 %
Salinity (ESP > 10) 22-50 %
Lentil
Terminal drought 16-54 %
Salinity (ESP > 15) Upto 50 %
Faba bean Terminal drought Upto 70 %
Field pea Terminal drought 21-54 %
Yield losses in major Pulses (Kumar et al., 2016)
Yield losses in major cereals crops

22. Oxidative stress and anti-oxidant system
❖ ROS are containing highly reactive forms of oxygen
➢ superoxide ion radical,
➢ hydroxyl radical,
➢ hydrogen peroxide,
➢ singlet oxygen.
(Karuppanapandian et al., 2011)
❖ ROS are by-products of the aerobic metabolism,
➢ Cell signaling
➢ homeostasis (Kwak et al., 2006)
role

23. ❖Exposure of the plant to abiotic stress increases the
production of ROS in the cell,
➢disruption of the cellular homeostasis and
➢degradation of biomolecules (lipids, proteins)
❖ This condition in plant cells is termed as oxidative stress.
(Torres et al., 2006)
How to reduce ROS production in plants
❖ Antioxidant
❖ It is normally present in plants.
Ex.
➢ Ascorbic acid (vitamins C) and E, sugars
➢ Phytochemicals (flavonoids, terpenoids, carotenoids) and
➢ enzyme (catalase, superoxide dismutase, and peroxidases)
(Gangola et al., 2013)
leads to

24. Eg.
❖ wheat seedlings that low concentration of glucose (0.1 mM
and 0.5 mM)
➢ activity of antioxidant enzymes, such as peroxidase,
catalase and superoxide dismutase.
(Hu et al., 2012)
enhance

25. Sugars as Osmo – protectants
❖ Abiotic stresses induce dehydration of plant cells, causing
osmotic stress
➢ hydrophilic interaction,
➢ degradation of biomolecules structure (especially
protein denaturation),
➢ collapse of organelles, and
➢ destabilization of cell membranes.
lead to disrupted

26. Salt stress
❖ Induces the toxicity of specific ions such as Na+ and Cl-,
➢ uptake of crucial minerals
❖ Na+ toxicity also disturbs the Na+/K+ ratio in the plant cell,
- crucial for normal cellular operations.
(Singh et al., 2015)
reduces

27. How to cell avoid stress
❖ protect cells from increased dehydration - during abiotic
stress,
➢ osmo-protectants, or osmolyte concentrations
✓ maintain the turgor pressure of the cell and
✓ enhance stress tolerance in plants.
❖ Osmo-protectants naturally present in plants,
➢ sugars, including sucrose, trehalose, RFO, and
fructans.
(Slama et al., 2015)
with the help of
need to
Eg.

28. Effect of sugars on proline accumulation
❖ Soluble sugar enhance proline content under - salt stress
(Hellmann et al., 2000)
❖ Damaging effect of salt stress,
➢ Osmolyte,
➢ maintaining turgor
➢ scavenger of ROS by enhancing antioxidant activity,
➢ stabilizes the structure of biomolecules.
(Hayat et al., 2012)
proline works as a

29. Mechanism of plants during abiotic stress
❖Abiotic stress - occurs in plants facing different phases
including
sensing, - signaling, - exhaustion- regeneration
(Duque et al., 2013)
❖Sensing
➢ Plant experiences through various mechanisms - when
there is disturbance in any of the abiotic factors.

30. Signaling
❖ The plant cell senses the changes in the cell and induces the
resistance machinery.
Exhaustion
❖ This phase involves changes in the physiological functions in
the plant cells.
Regeneration
❖ It involves the partial or full normalization of plant cell
functions, (stress removing stage).

31. Water Stress
Shortage of Water Excess of Water
Drought Flood or Water Logging
Relationship between sugars and abiotic stress in plants

32. Physiological Changes during Drought
1. Decreased plant growth
2. Decreased Photosynthesis – Stomata function
affected
3. Changes in enzymes activity
4. Changes in Hormone contents
5. Accumulation of compatible osmolytes

33. ❖ Glucose induces
➢ stomatal closure and
➢ enhances plant's adaptability
(sakabe et al., 2013)
❖ In several plant species, - raffinose, stachyose, and verbascose
➢ during desiccation of seeds and
➢ Accumulate in plant – Any abiotic factor affecting plant.
(Mohammadkhani et al., 2008)
accumulates
Eg.

34. Role of sugars – Drought
➢ Membrane protection
➢ prevents the oxidation of cell membrane
➢ maintain the turgidity of leaves
➢ prevent dehydration of membranes and proteins
➢ reduces the rate of photosynthesis
➢ maintain LWC and osmotic adjustment of plants.
(Krasensky and Jonak, 2012)

35. High temperature stress – above 40°C for most plants
Highest temperature tolerant plant – Opuntia at 65°C
Temperature Stress

36. Effect of High Temperature on Membrane
High Temperature Heavy waterloss
Stomata closed
Leaf temperature ↑
Loss of membrane
compartmentation
Membrane collapse
Leakage of Ions

37. TOMATO – SUN SCALD
HEAT INJURY -APPLE

38. LOW TEMPERATURE STRESS
Freezing stress
Below the freezing point
< 0ºC
Ice formation
Chilling stress
Above freezing point

39. Damage membrane and cell due to ice formation
CellA
Cell B
Cell B
CellA
Freezing
Ice crystals
Intracellular water
Intercellular water Cell rupture
Loss in membrane integrity

40. Freezing Injury
Frost Crack

41. Freezing injury

42. Effect of low temperature - Chilling
❖ Loss of membrane compartmentation
❖ Membrane leakage
❖ Denature of enzymes
❖ Reduction of protein synthesis
❖ Decreased water absorption
❖ Inhibition of photosynthesis & Respiration
❖ Reduced growth

43. Chilling injury

44. Salts responsible for salinity
Accumulation of salts in the soil
from irrigation water is major problem
Na , Ca+ 2+
, Mg2+
, K+
, Cl , SO-
4
2-
& HCO3
-
These ions are Usually responsible for soil salinity
Na , Cl and HCO+ -
3
- -- Potentially toxic to the plants
High concentration of Na+ - Sodicity
High concentration of Total Salts – Salinity

45. Sodicity Salinity

46. ❖ Salt stress - alters the physiology of plants
➢ photosynthesis,
➢ nitrogen assimilation,
➢ cell division and
➢ Plant growth and development.
(Anjum et al., 2011)
❖ Worldwide, 800 million hectares of soil is affected by salinity
(FAO, 2008)
❖ Salinity problems are increasing at a rate of ~10% annually
worldwide, mostly in Asia.
(Ashraf and Foolad, 2007)
by reducing

47. ❖ Effect of high concentration of salt in soil
➢ reduction of leaf growth,
➢ declines stomatal conductance,
➢ ionic imbalance and
➢ photosynthesis. (Wani et al., 2013)
leads to
❖ Supplementation of low concentration of glucose
seed germination under saline conditions.
(Hu et al., 2012)
wheat seedlings promotes

48. ❖ Accumulation of low concentration of soluble sugars, such
as glucose and sucrose
➢ stimulates the activity of antioxidant enzymes
(Boriboonkaset et al., 2012)
Under salinity
Role of sugars during salinity
➢ Maintain ion partitioning
➢ Regulate homeostasis in the plant cell,
➢ Maintaining proper cell functions and
➢ enhancing the abiotic stress- tolerance.
(Nahar et al., 2016)

49. Sugar
compound
Transgene Species
Enhanced
tolerance to
Trehalose
Trehalose-6-phosphate
synthase
Lycopersicon
esculentum
Drought, oxidative
stress (ROS),
salinity
Trehalose-6-phosphate
synthase and
phosphatase
Arabidopsis
thaliana
Drought, salinity,
temperature
changes
Trehalose phosphorylase
Nicotiana
tobacum
Drought, salinity
RFOs
Galactinol
Galactinol synthase
Arabidopsis
thaliana
Oxidative stress,
chilling, drought,
salinity
Fructans
Sucrose 1-
fructosyltransferese
N. tobacum
Freezing
Fructan 6-
fructosyltransferase
oryza sativa Chilling
Mannitol
Mannitol-1-phosphate
dehydrogenase
oryza sativa Drought, salinity
Targeting sugars to develop abiotic stress tolerant crop varieties

50. RESEARCH EVIDENCES

52. Meng et al., (2015)
Impact of water deficit on plant growth Dry matter accumulation of plant

53. FIG - Impact of water deficit on carbohydrates metabolite
concentrations during a 24-h cycle 5 days after water deficit.
Sucrose concentration Starch concentrationHexose concentration
Meng et al., (2015)

55. Growth parameters of Arabidopsis thaliana cultured in vitro -
a Number of leaves. b Total leaf area.
WL- Weak light
ML - Medium light
SL - Strong light
(Aleksandra et al., 2012)

57. Salt
concentration
(Nacl) (mM)
Fresh weight
(mg)
Dry weight
(mg)
LAI (mm2)
Chlorophyll
(%)
Control (0) 750.75 76.35 32.07 30.41
30 537.85 61.88 24.76 28.15
60 402.35 43.77 17.09 24.20
90 323.00 35.95 11.99 16.61
Table - Effect of salt concentration on growth parameter (Shoot
fresh weight & shoot dry weight, LAI & chlorophyll content) in
sweet sorghum
(Almodares et al., 2018)

58. Effect of salinity on the carbohydrates content in shoot, root, leaf of sweet sorghum
d
c
ba
d
Effect of sweet sorghum carbohydrates content comparisons in salt concentration
(Almodares et al., 2018)

60. Effect of various glucose treatments on growth attributes of wheat under
normal irrigation and drought treatments
Glucose treatments- 0,5,10,25 & 50 mM
PlantheightFresh&dryweightNo.oftillers/pl
Control IrrigatedControl Drought
Reproductive stagevegetative stageseed priming
(MuhammadZahidetal.,2018)

62. Treatments
Shoot fresh
weight (g)
Shoot dry
weight (g)
Shoot
height
(cm)
Flag leaf
area
Ir.1 Ir. 2 Ir.1 Ir. 2 Ir.1 Ir. 2 Ir.1 Ir.2
Control 5.18 3.24 1.08 0.69 56.43 46.2 4.72 3.28
Maltose 10.17 8.70 1.53 1.42 74.73 74.26 8.66 8.36
Trehalose 8.54 5.25 1.61 1.59 70.5 54.17 8.36 7.70
Ir.1- Irrigation after 10 days interval
Ir. 2 - Irrigation after 20 days interval
Table - Effect of foliar spraying with maltose and trehalose on
growth parameter of wheat plants under water stress.
(Hemmat et al., 2016)

63. Conclusion
❖ Abiotic stress hinders many physiological aspects of plants,
such as normal plant growth, development, metabolism,
cell functioning, etc.
❖ Sugars have been recognized as a new class of metabolite
have innumerable functions in plants.
❖ Sugars altered developmental, physiological and
biochemical parameters of plants under abiotic stress and
increasing stress tolerance to plants.
❖ Stress mitigation strategies exogenous sugars plays a
important role for boosting the mechanisms of plant.

64. Thank you…