What are the general characteristics of viruses? A detailed explanation of the basic features of viruses

A virus is an obligate parasite, much smaller than bacteria, generally about 10-30 um in size, and cannot be seen under an ordinary optical microscope. Viruses do not have cell walls or nuclei and appear fibrous, rod-shaped, and so on. Under certain conditions, some viruses can be extracted from plant tissues in crystalline form. Under an electron microscope, the virus crystals contain virus particles arranged in a highly orderly and tightly packed manner. A virus is composed of two parts: nucleic acid and protein. Parasitizing in Chinaorchidsthe nucleic acid contained in viruses on plants is mostly ribonucleic acid (RNA). The viral nucleic acid is enclosed within a protein coat. When a virus infects a cell, only the nucleic acid enters the plant cell, while the protein coat is left outside. Therefore, only the nucleoprotein part is infectious, and its pathogenicity is mainly determined by its nucleic acid part. A single virus may have two different forms. Particles of different forms may have different genetic roles. Only when particles of different forms enter the host together can the virus express its full infectivity, pathogenicity, and other genetic characteristics. Orchidviruses have a very high capacity for multiplication. Their mode of multiplication differs from the reproduction of cellular organisms. They do not take up nutrients within the host cell to form a large virus and then split into small viruses; instead, they replicate in a template-like manner using ribonucleic acid (RNA). Under the direction of the viral nucleic acid, the host cell synthesizes substances identical to the viral nucleoprotein in the cell, thereby forming new viruses. The harmfulness of viruses also lies roughly in changing the metabolic pathways of the host cell and disrupting normal physiological processes. Inorchidsthe virus appears to destroy the chloroplasts within the cells, causing the cells to lose chlorophyll, creating an obstacle to the assimilation of nutrients by the cells, and causing the leaf tissue to yellow or become necrotic. Whether it is the virus particles directly acting on the cells or the toxins released by the virus that have an effect must be determined by further research. Orchid virus diseases currently confirmed in China includeCymbidiummosaic virus Cymbidium mosaic virus and Odontoglossum ringspot virus Odontoglossum ring spot virus. (Liu Zhongjian)