Temperature stress in crops

Temperature stress is one of the important abiotic stress that considerably influence crop production

1. Temperature stress in plants Harithalekshmi V 2018-11-067 Dept. Agrl . Meteorology

2. Significance of temperature on organic life Physical and chemical process within the plants are goverened by temperature The diffusion rate of gases and liquids Solubility of different substances Rate of reactions Stability of the enzyme system Normally the growth permitting range of temperature – 10 ℃ - 45 ℃ - Biokinetic zone

3. Cardinal temperature The three temperature points viz . minimum ,optimum and maximum temperature called as cardinal temperature Crops Maximum ℃ Minimum ℃ Optimum ℃ Cool season cereals ( Wheat,barley,oats ) 0-5 25-31 31-37 Warm season cereals ( Rice,maize,sorghum ) 15-18 31-37 40-50 ( Mavi , 1994)

4. Classification of organisms based on temperature tolerance

5. Temperature stress Low temperature High temperature Chilling Freezing Heat stress Stress stress

6. Heat stress Heat stress is defined as the rise in temperature beyond a threshold level for a period of time sufficient to cause irreversible damage to plant growth and development (Singh, 1973)

7. Effect of heat stress

8. Effect on photosynthesis Most heat sensitive physiological processs C3 plants will be more affected than C4 plants

9. How photosynthesis is reduced? Reduces amount of photosynthetic pigment Closure of stomata lead to reduced CO 2 uptake Leaf water status is affected Chlorophyll function is affected Reduced transcription and activity of RuBP Case Altered structural organization of thylakoids Lipid peroxidation of thylakoids and chloroplast membrane

10. (MHRD, 2017)

11. Reduction in plant growth Germination is affected the most Loss of cell water content Reduced net assimilation lead to reduced relative growth rate Reduced germination – Thermoinhibition - increased ABA Abnormal seedlings Poor seedling vigour Ambient temperature Heat stressed

12. Effect on r eproductive development Reproductive tissues are more sensitive P ollen and spikelet sterility Impared pollen germination Reduced pollen viability S plitting of locule at apical part of theca

13. Effect on plant metabolism

14. Yield Increase in temperature by 1 ℃ will reduce yield of the cereals by 4.1% to 10% Reduced photosynthesis Increased respiration Reduced assimilatory capacity

15. Anatomical changes Reduced cell size Closure of stomata Increased stomatal and trichomatous density Greater xylem vessels Damaged mesophyll cell and increased permeability of plasma membrane

16. Phenological changes The crop duration was reduced under elevated temperature (Rani, 2013) Temperature Duration Ambient + 4 ℃ 96 Ambient + 2 ℃ 102 Ambient 108

17. Effect of heat stress in various phenophase Growth stage Threshold temp ( C) Symptoms Emergence 40 Delay &decrease in emergence Seedling 35 Poor growth of seedling Tillering 32 Reduced tillering & height Booting - Decreased no.of pollengrain Anthesis 33-34 Poor anther dehiscence &sterility Flowering 35 Floret sterility Grain formation 34 Yield reduction Grain ripening 29 Reduced grain filling

18. Effect on mineral n utrition High temperature stress causes reduction in absorption and subsequent assimilation of nutrients Absorption of calcium is reduced at temperature of 28 ℃ in Maize Nutrient uptake is affected by both soil and air temperature in rice Nitrate reductase activity decrease under high temperature

19. Scorching of leaves Sun burn Morphological symptoms

20. Leaf senescence High soil temperature causes stem scorches at the ground level E g : cotton

21. Sun sclad Strangulation sickness Death of yong seedlings when temp exceeds 46 ℃

22. Effect on produce quality High temperature stress during post-flowering stage increases the proportion of gliadins to glutelins and decreases the proportion of starch hampering the quality of wheat flour and the grain yield (Ashraf, 2014 )

23. Mitigating heat stress Avoidance Mechanisms for surviving which include log term evolutionary, phenological and morphological adaptations and short term avoidance or acclimation mechanisms Tolerance Ability to grow and produce yield under HT

24. Avoidance Leaf rolling Closure of stomata Increased stomatal and trachomatous densities Larger xylem vessels Waxy cuticle

25. Tolerence – Antioxidative response

26. Heat stress -> Expression of heat shock genes -> Heat shock proteins Tolerence – Heat shock protein

27. Agronomical method of heat stress mitigation Sowing time Indian farmers adjust sowing time of wheat in such a way, so that crop escapes to the hot and desiccating winds during grain-filling period E arly sowing of high-yielding Indian variety of wheat C306 ( Coiventry et al . 2011 ) Tillage Zero tillage, bed planting and conventional tillage with mulching ( Kajla et al . 2015 )

28. Water Management D rip irrigation also helps in maintaining adequate soil moisture and reduces soil temperature Foliar Spray P otassium fertilizer, urea, zinc, IMCP, and GA3 Application of nutrients like nitrogen, K , Ca, and Mg decreases the damaging effects of reactive oxygen species ( Almeselmani et al . 2006)

29. Protective substances Millets and wheat seeds – Pre soaked 18-24h - 0.25 M CaCl 2 ( Genkel et al ., 1955) 0.05-0.08% ZnSO 4 – Sugar beet, Potato, Sunflower ( Petinov , 1961) ZnSO 4 , CaCl 2, Ca(NO 3 ) 2 – Barley, Wheat ( Onwueme , 1972)

30. Low temperature stress

31. Chilling Stress Freezing stress Damaging effect of low temperature above the freezing point Damage due to freezing of intercellular water content into ice crystals Due to short term exposure of low temperature of 0 - 15 ℃ Temperature below ℃ Tropical and sub- tropical crops are affected All kind of crops mostly seen in crops grown in temperate regeion In rice pollen viability is affected resulting in sterility In cotton boll fails to open In castor no seed setting Field crops sensitive to frost are wheat, barley, mustard, potato, peas, winter maize, and tomato

32. Suffocation Formation of thick cover of ice/snow on the soil surface presents the entry of oxygen and crop suffers Heaving Lifting of plants along with soil from its actual position by ice, crystals. This is a mechanical lifting Physiological drought and desiccation Spring drought- coniferous trees- in cool temperate climate Decreased water absorption by plants at low temperature is the combined effect of the decreased permeability of root membrane and increased viscosity of water

33. Symptoms of chilling stress Plant growth and death

34. Surface lesions on leaves and fruits

35. Abnormal curling, lobbing and crinkling of leaves Water soaking of tissues

36. Symptoms of freezing stress in wheat Tillering 12 F (-11 ℃ ) Leaf chlorosis B urning of leaf tips Silage odor

37. Jointing  24 F (-4 C)   Death of growing point L eaf yellowing or burning lesions Splitting or bending of lower stem

38. Booting 28 F (-2 C) Floret sterility Head trapped in boot

39. Milking 28 F (-2 C ) White awns or white head S hrunkened , roughened, or discolored kernals

40. Altered date of sowing In cotton early planting increases percentage of open ball In mustard early planting reduces adverse effect of frost Selection of varieties and crops Barley and oats are more tolerant than wheat Maintaining good crop stand and spacing Use high seed rate to cover frost effect on germination Adequate inter row spaces should be maintained to allow sunlight incidence and to increase soil temperature Agro-techniques for management of Low temperature stress

41. Irrigation Keep crop well irrigated. Sprinkler irrigation increases canopy temperature Delving Using of wide blade tyne to mix deep clay soil with sandy top soil Delving reduces soil albedo, increases potential to store and release heat by soil Covers/thermal blankets for protecting high value crops Allow sunlight to penetrate during day and trap radiation at night time by covers and reduces freeze damage Nutrient management High N increases vulnerability to frost K, Cu and Mo deficiency render crop vulnerable to frost

42. Physical method Heaters to reduce temperature inversion C old acclimation E vaporation suppressors

43. Cold hardening Soil banking Wrapping

44. Sprinking •Keep plant leaf temperature at 1 to 2°C more •Increases the moisture content of the air and soil Thus slowing the rate of temperature drop •The water absorbs heat during the day which is released slowly at night

45. Fogging R etards the loss of heat from soil and plant surfaces to the atmosphere •Applying ground water with an average temperature of 21°C (70°F) to a greenhouse can create a ground fog if the ground surface is several degrees cooler than the water

46. Summary Significance of temperature High temperature stress Low temperature stress - Cold injury - Freezing injury Mitigation strategies for temperature stress

47. Thank you..