The document discusses temperature stress in fruit plants from both high and low temperature extremes. It provides context on what stress is and defines temperature stress. It then discusses the climatic temperature requirements of various fruit crops and the physiological and biochemical responses plants have to high and low temperature stress, including effects on photosynthesis, hormones, membrane properties, antioxidant activity, and more. It also discusses mechanisms plants use to cope with temperature stress extremes, such as cold acclimation and freezing tolerance processes. Lastly, it provides some management strategies farmers can use to help mitigate temperature stress impacts.

1. Stress due to temperature: Physiological
and Biochemical responses of fruit plants
to temperature extremes
SUKHJINDER SINGH MANN
L-2016-A-39-D

2. What is Stress ?
Stress: Factors of environment interfering the complete
expression of genotypic potential.
Abiotic Stress: The negative impact of non-living factors on the
living organisms in a specific environment.
Any unfavorable condition or substance that affects or blocks a
plant’s metabolism, growth or development (Lichtenthaler 1996)
Any deviation from the optimal condition of any factor essential
for plant growth will lead to aberrant change in physiological
processes and due to this plant body will experience tension
(Purohit 2003)

3. Climatic requirements of fruit crops
Sr. No. Crop Minimum temperature oC Maximum temp oC
1 Mango 21 27
2 Banana 15 35
3 Grape 25 35
4 Papaya 25 38
5 Pomegranate 25 35
6 Sapota 11 34
7 Guava 11 34
8 Jackfruit 25 35

4. • Temperature stress: Low or high temperature, called
frost injury or heat injury, respectively.
Temperature influences most plant activities:
• Seed germination
• Maturation
• Fruit ripening
• Plant growth rate
• Crop quality

5. Effect of high temperature
Mirza et al 2013

6. High Temperature Stress
 Biochemical responses
• Destacking of thylakoid membrane
• Alteration in membrane lipid composition
• Production of secondary metabolites
• Increase in amounts of antioxidants enzymes
• Photosystem II damage (D1 protein)
• Inhibition of Oxygen Evolving Complex
• Dissociation of extrinsic proteins
• Disorganisation of Mn cluster
• Inactivation of Rubisco activase
• Enhanced cyclic electron flow around PSI
• Reactive Oxygen Species production
• Accmulation of low molecular weight
antioxidant compounds
 Physiological responses
• Water relations – reduced water
availability
• Hormonal changes
• Increased level of ABA
• Affects ethylene production
• Photosynthesis – reduced
• Accumulation of compatible osmolytes
• Cell membrane thermostability

7. Photosynthesis
• Greer and Weedon (2012) observed that average rates of photosynthesis of Vitis
vinifera leaves decreased by 60% with increasing temperature from 25 to 45 °C.
This reduction in photosynthesis was attributed to 15%–30% stomatal closure. High
temperature also greatly affects starch and sucrose synthesis.
Optimum temperature levels for the photosynthesis of some horticultural crop species

8. Hormonal changes
• Hormonal homeostasis, stability, content, biosynthesis and compartmentalization
are altered under heat stress (Maestri et al., 2002).
• High temperature stress result in increased levels of ABA (thermo tolerance).
• Temperatures up to 35◦C have been shown to increase ethylene production and
ripening of propylene-treated kiwifruit, but temperature above 35◦C inhibits
ripening by inhibiting ethylene production, although respiration continues until the
tissue disintegration (Antunes and Sfakiotakis, 2000).
• High temperature stress appears to inhibit 1-aminocyclopropane-1-carboxylate
oxidase (ACC oxidase) more than 1aminocyclopropane-1-carboxylate synthase
(ACC synthase). High temperatures causes impairment of ethylene production by
perturbing cellular membranes, resulting in inhibition of the membrane-associated
ACC oxidase.
• Many climacteric fruit are inhibited from ripening or exhibit abnormal ripening at
high temperatures.

9. Biochemical responses
 Destacking of thylakoid membrane
• Increasing fluidity of membrane lipids, the strength of hydrogen bonds, and
electrostatic interactions between polar groups of proteins within the aqueous
phase of the membrane decrease. As a result, integral membrane proteins tend
to associate more strongly with lipid phase and nonbilayer lipids of the
thylakoid membrane form aggreagates of cylindrical inverted micelles.
 Photosystem II damage (D1 protein)
• PSII is more sensitive to elevated temperatures than PSI.
• Major alterations occur in chloroplasts like altered structural organization of
thylakoids, loss of grana stacking and swelling of grana

10.  Inactivation of Rubisco activase
• Deactivates Rubisco by inhibiting the enzyme Rubisco activase
• Enzyme was completely inactivated at 45°C
• Inactivation of Rubisco appears to be the primary constraint on the rate of net
photosynthesis at temperature above 30°C.
• Photosynthetic rate declined at a temperature lower than that caused denaturation of
carboxylating enzymes.
 Reactive Oxygen Species production
• Generation and reactions of activated oxygen species (AOS) including singlet
oxygen, superoxide radical (O2-), hydrogen peroxide (H) and hydroxyl radical
(OH-)
 Accumulation of low molecular weight antioxidant compounds
• Decrease in antioxidant activity in stressed tissues results in higher levels of AOS
 Increase in amounts of antioxidants enzymes

11. Adaptation to high temperature stress

12. Mechanismto copewithhightemperaturestress:

13. Mechanism in development in Heat tolerance in plants

15. Sunburn in apple

16. Low temperature stress
 Chilling stress- When plants are exposed to a low
temperature above 0°C.
Chilling stress results from temperatures cool enough to
produce injury without forming ice crystals in plant
tissues.
 Freezing stress- When plants are exposed to a low
temperature below 0°C.
Freezing stress results in ice formation within plant
tissues.
 Low temperature may affect several aspects of crop
growth; viz., survival, cell division, photosynthesis, water
transport, growth, and finally crop yield.

17. Stress by low temperature
Low temperature Stress
T > 0ºC: Chilling
T < 0ºC: Frost
Stress by Freeze dehydration
•Membrane viscosity
•Retarded metabolism
•Delayed energy dissipation, leading
to radical formation and oxidative
stress
•Protoplast volume shrinkage upon
extracellular ice formation
•Negative turgor (tension)
•Concentration of cellular solutes
•Abolition of metabolic processes
•Change of membrane potentials
•Disintegration of membrane bilayer
by freeze dehydration

18. Freezing injury
Two types of freezing occur in plant cells and tissues
• Vitrification : Solidification of the cellular content
into non-crystalline state (amorphous state) .It occurs by
rapid freezing of cells to a very low temperature.
• Crystallisation / ice formation : Crystallisation of ice
occur either extracellularly or intracellularly

19. Mechanism of Chilling injury
- Primary effect of temperature on plant cell membrane is on the fluidity of
membrane lipids.
-Membrane lipids, which are in a more or less fluid or mobile condition at high
temperature, enter in a gel- like state and become immobile below a critical
temperature
-It affect the property of membrane, particularly the activities of the membrane
associated enzymes involved in energy production and protein synthesis.
-Two events:
a) primary events by which the plants cell sense the lowered temperature
b) secondary events on long term responses that ultimately leads to death of
cell.

20. Effects of freezing stress
 Ice formation:
• Intercellular ice formation:
• Intracellular ice formation: it is most lethal may be due to physical disruption of
sub cellular structure by ice crystals.
 Membrane disruption:
• Freezing causes disruption and alter the semi permeable properties of plasma
membrane.
• Loss of solutes from the cells occur
• Cells remain plasmolyzed even after thawing
 Super cooling
• In plants cooling of water below 0ºC with out ice crystal formation is called super
cooling
• In plants water may cool down to -1 to -15ºC
• It is possible because internal ice-nucleators are absent
• This is regarded as important mechanism of freezing avoidance

21. Physiological responses of plants to low temperature
• Decrease in photosynthetic activity
• Cessation of protoplasmic streaming
• Loss of membrane semi-permeability
• Leakage of ions
• Decrease in the activity of a number of enzymes
• Increase in the metabolites (alanine, ethanol, acetaldehydes and keto acids)
 Inhibition of the chlorophyll synthesis
 Post chilling increase in respiratory rate
 Abnormal patterns of ethylene production in fruit
 Inhibition of starch to sugar conversions
• Inhibition of development of flavor components in fruit

22. Biochemical responses of plants to low temperature
 Increased level of lipid desaturation
• Plant membrane lipids have tendency to change from gel to liquid-crystalline phase
which is caused by increased lipid desaturation.
• Modifications of lipid unsaturation, controlled by key desaturases, lipases and invertases,
account for a fraction of acquired freezing tolerance
 Disorganization of cytoskeletal structure
• The ER structure reveals relative stability evenin the absence of cytoskeletal structures
during cold stress that manifests a certain organizational independence of this membrane
organelle.
• ER membranes might provide cytoskeletal monomers with the information important for
their spatial organization during cold and also during subsequent recovery of actin
filaments and microtubules at optimal temperatures
 Segmentation of central vacoule
• contribute to enhancement of freezing tolerance.
• plays role in calcium influx elicited by cold shock where the immediate rise in
cytosolic free calcium concentration occurred. Vacuole served as an intracellular
source of calcium.
 Reduced efficiency of both photosystem (PSI & PSII)
• Reduces the capacity to assimilate carbon, photosynthetic electron flux from photosystem
I (PSI) to oxygen can increase and result in increased production of potentially damaging
superoxide, hydrogen peroxide and hydroxyl radicals

23.  Changes in rigidification, protein and nucleus acid conformation, specific
metabolic and/or redox status
• Perception occurs through low-temperature induced changes in membrane fluidity,
protein and nucleic acid conformation, specific metabolite-and/or redox status.
• Activation of calcium channels or secondry signals such as ABA or ROS leads to cold-
induced Ca2+ increase in the cytosol and calcium signal amplification, and possibly
phospholipid signaling are triggered.
 Reversible coupling, decrease in protein content and accumulation of stress
related proteins in mitochondria
• Plant mitochondria posses alternative enzymes enabling oxidizing of both external
NAD(P)H and internal NAD(P)H independently of complex I, providing additional
flexibility to the mitochondrial metabolism during cold stress.
 Modifications in pectin content and their methyl esterification degree in
plasma membrane
• Suspension-cultured cells of grape and apple the cold acclimation was the result of
increase in the cell wall strength and a decrease in the cell wall pores
 Accmulation of proline and carbohydrates

24. A model to explain symptoms of chilling injury
in chilling-sensitive plants.

25. Lipid liquefaction
liquid-crystalline state
Low temperature
Solid-gel state
High temperature
liquefaction

26. Model illustrating the freezing process in acclimated
and non-acclimated plant cells.

27. Mechanism of freezing tolerance
 Freezing avoidance:
• The ability of plant tissues/ or genes to avoid ice formation at sub zero
temperature
Super cooling is a mechanism of freezing avoidance which is controlled by
• Lack of ice nucleators
• Small cell size
• Little or no intercellular space
• Low moisture contents
• Barriers against external nucleators
 Freezing tolerance:
Ability of plants to survive the stress generated by extra cellular ice formation
and to recover and re grow after thawing
• Components of freezing tolerance
1. Osmotic adjustment
2. Amount of bound water
3. Plasma membrane stability
4. Cell wall components properties
5. Cold responsive proteins e.g. ABA

30. Chilling Injury In Mango And Apple

31. Management of temperature stress
• Use of mulches
• Use of anti transpirants
(Kaolin, PMA, Liquid
paraffin's
• Use of shade net houses and
poly tunnels
• Plant training and pruning
procedures.
• Regular irrigation intervals
• Use of reflective white coating
substances
• Use of high speed wind fans
• Burning of grasses trash in
surrounding of orchards
• Use of poly tunnels
• Use of anti freezing
chemicals
• Use of low chilling varieties
• Harvesting at right mature
time