Biotic stress (mujahid hussain 127)

a comprehensive presentation of physiology

1. Biotic stress

2. Stress Difficulty that cause worry Or an Environmental damage to plants  Biotic  abiotic Resist ance ： The adaptability of plants to adverse environment ◇Stress avoidance ◇ Stress tolerance

3. Plants are sessile and must deal with stresses in place Plants cannot avoid stress after germination How plants deal with stress has implications in Ecology: Stress responses help explain geographic distribution of species Crop science: Stress affects productivity Physiology and biochemistry: Stress affects the metabolism of plants and results in changes in gene expression

4. Plants are sessile and must deal with stresses in place From engineering, stresses cause strains (responses of stressed objects) = changes in gene expression and metabolism in plants Biological stress difficult to define/quantify:

5. Types of stress

6. Types of resistance

7. Biotic Stress and Plant Defense Responses Pathogen Strategies Necrotrophic – plant tissue killed and then colonized; broad host range e.g., rotting bacteria ( Erwinia ) Biotrophic – plant cells remain alive, narrow host range (1 plant species) e.g., viruses, nematodes, fungal mildews

8. What causes a plant to be stressed?   As with humans, stresses can originate from the surrounding environment (called  abiotic , or nonliving stresses); or, they can come from living organisms that can cause disease or damage (caused  biotic  stresses).

9. Biotic stress Biotic Stress  is  stress  that occurs as a result of damage done to plants by other living organisms, such as bacteria, viruses (although they are not considered to be living organisms, also cause biotic stress to plants), fungi, parasites, beneficial and harmful insects, weeds, and cultivated or  native plants .

10. Biotic stress The damage caused by these various living and nonliving agents can appear very similar. [2]  Even with close observation, accurate  diagnosis  can be difficult.

11. Biotic stress For example,  browning  of leaves on an  oak tree caused by drought stress may appear similar to leaf browning caused by oak wilt, a serious vascular disease, or the browning cause by  anthracnose , a fairly minor leaf disease.

12. Agriculture It is a major focus of agricultural research, due to the vast economic losses caused by biotic stress to cash crops.

13. Agriculture The relationship between biotic stress and plant yield affects economic decisions as well as practical development.

14. Agriculture   Plants are exposed to many stress factors, such as drought, high salinity or pathogens, which reduce the yield of the cultivated plants or affect the quality of the harvested products.  Arabidopsis thaliana  is often used as a model plant to study the responses of plants to different sources of stress. [5]

15. Biotic stresses Fungi cause more diseases in plants than any other biotic stress factor. Over  8,000 fungal species  are known to cause plant disease. On the other hand, only about  14 bacterial genera  cause economically important diseases in plants,

16. Biotic stresses  According to an Ohio State University Extension publication . Not many plant pathogenic viruses exist, but they are serious enough to cause  nearly as much crop damage worldwide as fungi , 

17.  Microorganisms can cause plant wilt, leaf spots, root rot, or seed damage. .  Insects  can cause severe physical damage to plants, including to the leaves, stem, bark, and flowers. Insects can also act as a vector of viruses and bacteria from infected plants to healthy plants.

18. Biotic stresses The method by which weeds, considered as unwanted and unprofitable plants, inhibit the growth of desirable plants such as crops or flowers is not by direct damage, but by competing with the desirable plants for space and nutrients. Because weeds grow quickly and produce an abundance of viable seed, they are often able to dominate environments more quickly than some desirable plants.

19. Plant defenses Physical barriers: cuticle, thorns, cell walls Constitutively produced chemicals (e.g., phytoalexins ) and proteins (e.g., Ricin ) 3) Induced responses (a.k.a., the Plant Defense Response )

20. Plant defense

21. Ephemeral plants Ephemeral plants avoid stress in US desert Only bloom after wet winter Die before summer returns

22. Alfalfa & CAM plants Avoidance also possible by morphological adaptations Deep tap roots in alfalfa allow growth in arid conditions Desert CAM plants store H2O in fleshy photosynthetic stems . Adaptation : heritable modifications to increase fitness CAM plants’ morphological and physiological adaptations to low H2O environment

23. Ferns Stress resistant plants can tolerate a particular stress Resurrection plants (ferns) can tolerate dessication of protoplasm to <7% H2O  can rehydrate dried leaves Plants may become stress tolerant through

24. Cold hardy plants Acclimation : non heritable physiological and biochemical gene expression Cold hardening induced by gradual exposure to chilling temps, cold- hardy plants

25. Pathogen invasion

26. Pathogen invasion Apoptosis : Cell suiside mechanism. at invasion site to physically cut off rest of plant

27. Assignment of : physiology Submitted to : Dr. ameer Submitted by : Mujahid hussain Roll No. : 127 Class : Bs botany 6 th (S.S) UNIVERSITY OF SARGODHA THANK YOU 