Assignment on Heat Stress on Plant

Response and Mechanisms of plant to Heat Stress

1. ADJIBOGOUN Rodrigue : 10704544 DIAW Faty : 10747923 ABAH Simon Peter: 10747927 HEAT STRESSES ON PLANT Presented by Group Two Course Title/Code : Physiology of Abiotic stresses (WACI704)

2. Introduction Effects of heat stress on plant Perception of plant to high temperature Response to heat stress Mechanism of heat stress Conclusion OUTLINE

3. INTRODUCTION Heat stress can also be called high temperature stress Heat stress (HS) is a major environmental stress that limits plant growth, metabolism, and productivity worldwide (Hasanuzzaman et al. , 2013) Plant growth and development involve numerous biochemical reactions that are sensitive to temperature.

4. HS is a major concern for crop production and approaches for sustaining high yields of crop plants under HS stress are important agricultural goals. Plant responses vary with the degree and duration of HS and the plant type. Plants possess a number of adaptive, avoidance, or acclimation mechanisms to cope with HS situations Plant survival under HS depends on the ability to perceive the HT stimulus , generate and transmit the signal , and initiate appropriate physiological and biochemical changes . INTRODUCTION

5. INTRODUCTION 0 – 10 C 10 – 30 C 30 – 65 C Classification of plant according to temperature of growth by Laucher 1995

6. Ranges of temperature for seed germination of different crops

7. Major effects of high temperature on plants Effect of high temperature on plant Plant can operate most of its physiological process normally in the range of 0-40 C High temperature stress > 40 C causes injury to the plant The degree and duration of exposure also increase the effect on plant.

8. Heat stress affects various biomolecules Plants are static poikilotherms Plant can sense mild change in the ambient temperature. Effect of high temperature on plant

9. Effect of high temperature on plant Photosynthesis and growth C 3 plant are more susceptible to high temperature stress than C 4 plants High temperature cause injuries to chloroplast by: Altering structural organization of thylakoids Swelling of grana. Impairing grana stacking ability

10. Effect of high temperature on plant Photosynthesis and growth High temperature stress affects Photosynthetic pigments Activity of photosystem II Leaf water potential Stomatal conductance Intercellular CO 2 concentration Transcription and activity of RuBPCase and RuBPCase activase

11. Effect of high temperature on plant Photosynthesis and growth High temperature stress affects Leaf area Stalk length Total biomass Number of tillers

12. Reduce flower buds production Increase flower abortion Impaired fruit and seed set Plant reproductive development Effect of high temperature on plant

13. Effect of high temperature on plant Generation of Reactive Oxygen Species (ROS) Oxidation of protein, poly unsaturated fatty acids, and DNA Activation of programmed cell death Plant metabolism

14. Perception of high temperature on plant

15. Plant Responses to Heat stress Morphological Physiological Molecular Anatomical changes Phenological changes Water relations Osmolytic reaction Hormonal changes Oxidative stress

16. Scorching of leaves and twigs Sunburns on leaves branches and stems Leaf senescence and abscission Shoot and root growth inhibition Fruit discolouration and damage Reduction in the internodes length Reproductive phase most sensitive to high temperature are gametogenesis (8 – 9 days before anthesis) and fertilization (1 – 3 days after anthesis) in various crop plants ( Foolad , 2005). Morphological Symptoms

17. Morphological Symptoms Scorching of leaves Sunburns on leaves Desiccation tolerance Fruit discolouration and damage Leaf senescence Leaf abscission

18. Reduced cell size Closure of stomata and curtailed water loss Increased stomatal and trichomatous density Greater xylem vessels of both root and shoot Damaged the Mesophyll cells and increased permeability of plasma membrane. R educed photosynthesis by changing the structural organization of thylakoids (Karim et al., 1997) Loss of grana stacking or its swelling. Anatomical Changes

19. H igh temperature can damage leaf gas exchange properties during vegetative stage increase flowers abortion during reproduction Impairment of pollen and anther development Decrease in days to ear emergence, anthesis and maturity in wheat Grain filing duration is also decreased. Phenological changes

20. Plant - w aters relations: distrubed the leaf water relations and root hydraulic conductivity (Morales et al., 2003) Enhanced transpiration induces water deficiency in plants causing a decrease in many physiological processes ( Tsukaguchi et al., 2003). High temperature causes water loss in plant more during day time than night time. PHYSIOLOGICAL RESPONSES

21. Plant species may accumulate osmolytes such as: Accumulation of compatible Osmolytes

22. MOLECULAR RESPONSES Heat stress may induce oxidative stress Activated oxygen species = autocatalytic peroxidation of membrane lipids and pigments = loss of membrane semi-permeability and modifying its function. Super oxide radical (O 2- ) Hydrogen peroxide (H 2 O 2 ) Hydroxyl radical (OH - ) The scavenging of O 2 - by superoxide dismutase (SOD) results in the production of H 2 O 2 , which is removed by Ascorbate peroxides. Note: Protection against oxidative stress is an important component in determining the survival of a plant under heat stress.

23. Different adaptation mechanisms of Plant to Heat Stress Avoidance Mechanisms Under HS conditions, plants exhibit various mechanisms for surviving which include: long-term evolutionary phonological and morphological adaptations and short term avoidance or acclimation mechanisms Tolerance Mechanisms The ability of the plant to grow and produce economic yield under HT MECHANISM OF HEAT TOLERANCE: How do plants overcome heat stress?

24. Avoidance Mechanisms Tomentose leaves Rolling of leaves

25. Schematic diagram showing the molecular regulatory mechanism of heat shock proteins based on a hypothetical cellular model. Entry of monomeric heat shock factors (HSFs) to nucleus Trimerization of HSF monomers Binding of active trimer to the specific genomic region Transcription, translation and post-translational modification Production of functional HSPs Tolerance Mechanisms

26. In general, heat stress is responsible for the up-regulation of several heat inducible genes , commonly referred as “ heat shock genes ” (HSGs) which encode HSPs and these active products are very much necessary for plant’s survival under fatal HT ( Chang et al., 2007) . This help to protect intracellular proteins from being desaturated and preserve their stability and function through protein folding; thus it acts as chaperones ( Baniwal et al., 2004) Molecular regulatory mechanism of heat shock proteins

27. Summary of adaptation to heat stress

28. Conclusion HT is one of the major abiotic stress Affect plant photosynthesis, growth, development, reproduction and metabolism. Plant can adapt to high temperature: activity of antioxidant enzyme and a ntioxidant metabolite work as scavenging and protect plant from oxidative damage HSP initiate protein folding that protect protein from denaturing and restore stability under heat stress

29. Thank you