The Structure and Function of DNA

CHAPTER TEN THE STRUCTURE AND FUNCTION OF DNA

What are three ways that viruses can get into a plant? Poat bupop ch ạo punuarty

Plant Viruses

Tobacco and related plants, causing discolored spots on the leaves, was the first virus ever discovered. To infect a plant, a virus must first get past the plant's epidermis, an outer protective layer of cells. For this reason, a plant damaged by wind, chilling, injury, or insects is more susceptible to infection than a healthy plant. Some insects carry and transmit plant viruses, and farmers and gardeners may unwittingly spread plant viruses through the use of pruning shears and other tools.

Viruses that infect plant cells can stunt plant growth and diminish crop yields. Most known plant viruses have RNA rather than DNA as their genetic material. Many of them, like the tobacco mosaic virus shown in Figure Ten point twenty-six, are rod-shaped with a spiral arrangement of proteins surrounding the nucleic acid. TMV, which infects

There is no cure for most viral plant diseases, and agricultural scientists focus on preventing infection and on breeding or genetically engineering varieties of crop plants that resist viral infection. In Hawaii, for example, the spread of papaya ringspot potyvirus by aphids wiped out the native papaya. But since nineteen ninety-eight, farmers have been able to plant a genetically engineered PRSV-resistant strain of papaya, and papayas have been reintroduced into their old habitats.