Plants actually can protect themselves from insects, animals and diseases. They have natural defenses that they use to combat these problems. You will find that plants are amazing living creations. Plants do not have any type of immune system, but they do have some elaborate structural and chemical defenses. Plants can actually survive in yard and garden in some very harsh conditions such as, loss of roots, branches, leaves and stem tissue. Many plants can survive even these destructive circumstances. If you are wondering how they can do this, let me present three types of defenses that a plant has to help them withstand some of these brutal happenings.
Plants can prevent pathogens from attacking and invading by possessing special features. The most common defense is having needles and thorns. These prevent or discourage all but the hungriest herbivores from eating them. Some types of plants may have thick hairs that can keep insects or pathogens from coming in contact with the surface of the leaves. Examples: Lamb’s ears has hairs on the foliage that protects it from insects and diseases; Cactus have spines that keep grazing animals away; Junipers have a bitter taste that keeps animals from feeding on its foliage.
It is a well known fact that plants produce chemicals. We use chemicals from plants all the time. Some of these would be: Aspirin, originally derived from the willow tree, is used for headaches; Aloe vera sap is used for burns; Taxol is a plant derived drug used to treat cancer; Coumarin is used as a blood thinner.
Other plants , such as sugar beets and sugarcane, produce sweet-tasting chemicals, while other produce bitter and unpalatable chemicals that prevent disease or stop animals from feeding on them. There are very few animals or fungi attack young sorghum because of the high levels of cyanide that is produced in the seedlings after germination.
Plants can contain thousands of different kinds of chemicals that are used to ward off insects and diseases. One such is poison ivy and poison oak. Some chemicals are released by the plant only when it becomes injured or infected in some way.
Some plants can produce structural barriers that are responses to infection. One case is when an injured cell dies, tannin, lignins, and other resins are produced and form a type of barrier. Often times the invading insect is trapped within these chemicals. This is the plants natural way to stop invasions.
Most plants, however, seem to not be effected by most diseases and insects. Plant diseases will affect a certain type of plant. For instance, a tomato hornworm will not attack an elm tree and the Dutch elm disease will not affect a tomato plant. Scientists are always trying to find and identify cultivars that are resistant to certain diseases. The resistant plants will be given to nurseryman to be produce in quantity because they are better at resisting diseases. In this way, only the best plants are distributed into the public.
Disease resistance is one factor that keeps plants from getting certain diseases, but no plant is resistant to all diseases. Some plants are grown to be tolerant of diseases instead of resistant to them. These plants may be infected with a disease but will still perform and grow well. Such plants as cucumbers, squash and melons that will tolerate powdery mildew and still grow just fine. While lilacs may become victims to a case of severe powdery mildew infection in the late summer, but produce beautiful blooms in the spring.
Plants can also avoid infections if the gardener plants them at the proper time of the year. The soil should be warm, and free of excessive moisture. If planted too early the plant will either die outright or become ridden with disease.