Have you seen any diseased plants in your farm
Answers
Answer:
yes
Explanation:
I have seen a disease plants in our farm
Answer:
The variety of symptoms, the internal and external expressions of disease, that result from any disease form the symptom complex, which, together with the accompanying signs, makes up the syndrome of the disease.
Generalized symptoms may be classified as local or systemic, primary or secondary, and microscopic or macroscopic. Local symptoms are physiological or structural changes within a limited area of host tissue, such as leaf spots, galls, and cankers. Systemic symptoms are those involving the reaction of a greater part or all of the plant, such as wilting, yellowing, and dwarfing. Primary symptoms are the direct result of pathogen activity on invaded tissues (e.g., swollen “clubs” in clubroot of cabbage and “galls” formed by feeding of the root knot nematode). Secondary symptoms result from the physiological effects of disease on distant tissues and uninvaded organs (e.g., wilting and drooping of cabbage leaves in hot weather resulting from clubroot or root knot). Microscopic disease symptoms are expressions of disease in cell structure or cell arrangement seen under a microscope. Macroscopic symptoms are expressions of disease that can be seen with the unaided eye. Specific macroscopic symptoms are classified under one of four major categories: prenecrotic, necrotic, hypoplastic, and hyperplastic or hypertrophic. These categories reflect abnormal effects on host cells, tissues, and organs that can be seen without a hand lens or microscope.
clubroot
clubroot
Cauliflower roots infected with clubroot.
Rasbak
Signs
Besides symptoms, the diagnostician recognizes signs characteristic of specific diseases. Signs are either structures formed by the pathogen or the result of interaction between pathogen and host—e.g., ooze of fire blight bacteria, slime flux from wetwood of elm, odour of tissues affected with bacterial soft rot.
Technological advances in the identification of pathogenic agents
Developments in microscopy, serology and immunology, molecular biology, and laboratory instrumentation have resulted in many new and sophisticated laboratory procedures for the identification of plant pathogens, particularly bacteria, viruses, and viroids. The techniques of traditional scanning microscopy and transmission electron microscopy have been applied to immunosorbent electron microscopy, in which the specimen is subject to an antigen-antibody reaction before observation and scanning tunneling microscopy, which provides information about the surface of a specimen by constructing a three-dimensional image.
Serological tests have been made more specific and convenient to perform since the discovery of a technique to produce large quantities of monoclonal antibodies, which bind to only one specific antigen. The sensitivity of antigen-antibody detection has been significantly increased by a radioimmunoassay (RIA) procedure. In this procedure a “known” antigen is overlayed on a plastic plate to which antigen molecules adhere. A solution of antibody is applied to the same plate; if the antibody is specific to the antigen, it will combine with it. This is followed by the application of radioactively labeled anti-antibody, which is allowed to react and then washed off. The radioactivity that remains on the plate is a measure of the amount of antibody that combined with the known fixed antigen. Another highly sensitive immunoassay is the enzyme-linked immunosorbent assay (ELISA). In principle this assay is similar to the RIA except that an enzyme system, instead of radioactivity, is used as an indicator of an antigen-antibody combination.