Dear friends;
in general when plants reflect drought symptoms, how can we differ between these symptom which might caused by pathogens and drought stress ?
regards,
Dr. Salem Elshatshat
Drought and pathogen stress often occurs concurrently under fields. The major symptoms of drought are: 1. Wilting of the leaves (usually starts at the top of the tree) 2. Chlorosis (yellowing of the leaves) 3. Thinning of the canopy 4. Marginal necrosis (the leaves turn brown from the outside moving inward).
In case of pathogenic attack the greater parts of the plants may be wilting, yellowing and dwarfing. Primary symptoms are visible on the invaded tissue for example swallen clubs in the clubroot of cabbage. One can localize the area of infected pathogen to the site of invasion. Pathogenic attack may be any part of the plants/trees.
Plants can suffer drought stress (and may be wilted) because of insufficient soil moisture or because of inability of the plant to absorb water from the soil and transport the water through the plant as a result of a disease affecting the roots or the stem vascular system.
A diseased plant may have brown roots (instead of more whitish, healthy roots), reduced root mass, or root deformation (e.g., root-knot nematodes). Some vascular diseases can be detected by making a cross section of the stem; the affected area shows browning/necrosis of the vascular system.
Also, plant diseases may occur randomly in the field, while plants wilted due to low soil moisture conditions may show a more generalized wilting pattern in the field.
How plant distinguishes between two different types of stresses , one being biotic stress and another being abiotic in nature...
Dear Anoop,
Biotic stress related to pathogens goes through three important steps: recognition, signal transduction and defense response by the plant. Pathogen molecules are the ones that induce recognition as a biotic stress and indeed, the molecules involved in the signal indicate that the stress is biotic, whereas in the case of abiotic stress, it is other physiological change and Moleculars that intervene.
Excellent, any distinguishing metabolites synthesized or involved I identifying the type of stimulus..?? Appreciate your response .
I have only general ideas, but for example, a high proline level indicates salt stress, the measurement of stomatal pores may indicate hydric stress, and the same think for temperature (temperature stress proteins). Whereas, increased levels of phytoalexins, Patogenisis Related Proteins (PR proteins) indicate rather a biotic stress.
In my opinion (I have been studying oak decline for decades) your question has not a single or universal answer. You have to know those pathogens can affect your plant species. There are very few generalist pathogens and the most common situations is a certain or even a high specificity between pathogen and plant.
So, you have to determine those pathogen potentially affecting your plant species. After that, you can exclude the presence or not of such pathogens in your case.
In fact, the wilting in oaks may be explained by pathogens or water stress. However, parhogens can be isolated when are the cause of such wilting in the different organs of the tree.
thanks a lot for every body for your nice comments and answers..
Regards,
Salem
I was talking about the signal g molecules involved in response to plant response to abiotic stress versus pathogenic response...
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