Forest trees are often affected by smoke. It is reasonable to presume that the primary effect of a disease is on the water status of the cells, which reflects in the various derangements in metabolism functions, leading to a progressive degeneration of vital activities, culminating in death. The ring necrosis of discoloured tissue occurs in the peripheral region, net necrosis of blackened small areas are rather scattered through­out, and blotch type usually comprises irregular areas of various sizes and colour- opaque grey to black in the tubers. It also helps one understand the useful substances from plants and animals which are used for medicine. The first group comprises of parasitic causal agencies (with the exception of Virus, may be) and the disease produced is the parasitic disease. 366-373 . Necrosis may be ring necrosis; net necrosis and blotch type of necrosis. The dying backward from the tip of twigs or branches of trees and shrubs during the growing season is the symptom of plants and their branches caused by definite interference with water supply, either by tissue disintegration or by inducing gum formation in the xylem region. Ø The pathogen survives in the collateral hosts present in the fields.. Ø Favourable weather conditions promote the production of conidia.. Ø The conidia help in the rapid spread of the disease.. Control measures. This disease is spread by air-borne sporangia which produce zoospores which invade the leaf or stem through stomata. Plant Pathology (Phytopathology) deals with the cause, etiology, resulting losses and control or management of the plant diseases. When feeding on roots, nematodes can cause several types of injury: Necrotic lesions, induce formation of hypertrophic cells, and suppression of cell division of apical meristem of roots. Essay on Plant Diseases: Classification of Plant Diseases, Myxomycota: Features and Occurrence | Fungi. Premature casting of leaves may occur in trees -when subjected to high-temperature. A student gets an idea of what the body is made of, its physiology, etc. In the former kind, the disease incidence depends mainly on the varia­tions of the climatic conditions. With the advent of favourable environmental conditions the pathogen becomes active and there starts the active phase and the perennating organs produce primary inoculum. Different approaches may be used to prevent, mitigate or control plant diseases. It covers basic and applied research, which focuses on practical aspects of disease diagnosis and treatment. Prolonged mechanical stress (MS) causes thigmomorphogenesis, a stress acclimation response associated with increased disease resistance. Continued shortage of water eventually results in cessation of growth and decrease in the production of auxins. This assignment requires conducting an in-depth study of a scientific topic that could take a lot of time. the non-living entities and the environmental conditions that cause disorders in plants; iii. Six-mark questions are often the questions that people find the most difficult. To start with, a water-soaked appearance of tissue is visible which is followed by rapid desi­ccation leading to the formation of sunken areas which ultimately turn grey in green fruits and yellow in ripe ones. Molecular Definition of a Gene 3. The epiphytotic disease is usually very responsive to variations of environmental conditions which actually control its incidence. (iv) Diseases classified on the basis of hosts affected: The classification of plant diseases on the basis of hosts affected is simply a matter of convenience. BIOL 120. are partial root parasites of sugarcane, cereals, maize and millets. The following table illustrates the major plant diseases caused by virus −, The following table illustrates the major plant diseases caused by Bacteria −, The following table illustrates the major plant diseases caused by Fungi −, The following table illustrates the major plant diseases caused by Nematodes −. The introduction of biotechniques in breeding programs for woody plants was motivated by the search for pest and disease resistance and to fulfill the demands of the consumer market. Like endemic disease, the pathogen may be more or less constantly present but to ensure disease development environmental conditions must be favourable. Types of Plant Breeding. This happens due to excessive loss of water from the plant body. Two types of Punnett squares are commonly used. (vi) Diseases classified on the nature of causal agencies: The diseases of plants may be attributed to one or more of the following causal agencies: (e) Parasitic angiosperms (Fig. Whereas in others, the secondary disease cycle may be absent. In apples due to boron-deficiency light brown spots of dead tissue appear in the fruits, and in trees rosette and die back. The gaconfines its effect to the chlorophyll-bering or green parts of plants, woody tissues are not directly affected. Of the various ways of classification of plant diseases stated above, only the one classified on the nature of causal agencies gives adequate information about the cause of the disease develop­ment and related facts. List of Plant Diseases Caused by Bacteria. The general pattern of disease cycle is presented in Figure 345. Why mitochondria is called as the power house of the cell? What are the characters Mendel selected for his experiments on pea plant? 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