plant response to environmental stress

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plant physiology lecture 31

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Presentation Transcript

Generalize Plant response to environmental factors : 

Generalize Plant response to environmental factors Lecture 31 Ma. Chrischelle Ferreras

Objective: : 

Objective: To know the concept of biological stress and how plants generally respond to stressful conditions

Slide 3: 

“Biological stress is not easily defined , but it implies adverse effects on an organism.”

Biological stresses : 

Biological stresses adverse force or influence that tends to inhibit normal systems of functioning(Jones and Jones, 1989)

Principal environmental stresses: : 

Principal environmental stresses: Biotic herbivores, insects pathogens, parasites

Abiotic : 

Abiotic High temperature (heat) Low temperature (chilling, freezing) Excess water (flooding anoxia) Water deficit (drought, low water potential) Salinity Radiation (visible, ultraviolet) Chemical (pesticides, heavy metals, air pollutants)

Slide 7: 

MECHANISMS : Plant stress responses Stress recognition Signal transduction Gene expression Altered cell metabolism Physiological and developmental response

Plant response to stress : 

Plant response to stress Ephemeral plants germinate, grow, and flower very quickly following seasonal rains complete their life cycle during a period of adequate moisture and form dormant seeds before the onset of the dry season stress escapers

Slide 9: 

Stress avoidance reduce the impact of a stress, even though the stress is present in the environment Alfalfa(Medicago sativa) Cactus

Slide 10: 

Stress tolerance requires the plant to come to thermodynamic equilibrium with the stress internal conditions are in equilibrium with conditions outside of the plant

Slide 11: 

Adaptation heritable modifications in structure or function which increases the fitness of the organism in the stressful environment

Slide 12: 

Acclimation nonheritable physiological modifications that occur over the life of a plant hardening hardy

Slide 13: 

Strategy manner in which a plant responds successfully to a particular stress

Water stress : 

Water stress may arise through either an excess of water or a water deficit Water deficit stress Drought stress Dessication stress

Slide 15: 

Plant membrane Photosynthesis

Slide 16: 

Stomatal response

Slide 17: 

Osmotic adjustment net increase in solute concentration due to metabolic processes triggered by stress sugarbeet cowpea

Slide 18: 

Leaf area adjustment mechanism for reducing leaf area and transpiration during times of limited water availability

Temperature stress : 

Temperature stress Chilling stress reduced leaf expansion, wilting, chlorosis Metabolic dysfunction Impaired protoplasmic streaming Reduced respiration Photosynthesis and protein synthesis Altered patterns of protein synthesis

Slide 20: 

Corn Tomato Cucumber Soybean Cotton Banana Apple Potato Asparagus

Slide 21: 

Freezing stress commonly encountered by tress and shrubs overwintering in north temperate, subarctic, and alpine regions

Slide 22: 

High temperature stress Assuming a more vertical orientation of leaves Reflective leaf hairs Waxy surfaces

Salt stress : 

Salt stress refers only to an excess in ions, particularly, but certainly not limited to, sodium and chlorine ions Halophytes -plants that grow in high-salt soils -salt regulators -salt glands

Slide 24: 

Glycophytes - sensitive nonhalophytes - can tolerate very little salt

Insects and disease : 

Insects and disease Phytoalexins Synthesized by plants to help ward off insects and disease Hypersensitive reactions biosynthesis of secondary metabolites that serve to isolate and limit the spread of the invading pathogen and necrotic lesions at the site of invasion commonly activated by viruses, bacteria, fungi, and nematode that occurs principally in plants outside specificity range

Slide 26: 

Avirulence gene a gene that encodes any determinant of the specificity of the interaction with the host Systemic acquired resistance a phenomenon in which plants react to the initial infection by slowly developing a general immune capacity Jasmonates mediate insect and disease resistance

Environmental pollutants : 

Environmental pollutants Heavy metals Cadmium Lead Arsenic Copper Nickel Zinc

Slide 30: 

Accumulator species plants that take up metals and accumulate them to levels that would be lethal to nontolerant species Astragalus Stanleya pinata

Slide 31: 

Air pollution Ozone CO₂ CO SO₂ Nitrogen oxides