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Why Do Plants Have Thorns?

Why Do Plants Have Thorns?

Michael R. Evans, associate professor of horticulture in the Dale Bumpers College of Agriculture, Food and Life Sciences, replies:

Since plants are typically anchored in place by their root system, they are not able to run awayfrom predators. Therefore, plants have developed various defense mechanisms against commonpredators such as insects and other animals that might want to eat them. Plants deploy a numberof chemical and physical defenses to protect themselves from predators. Some plants producechemicals that are poisonous or might taste bad to insects and animals. A good example of sucha plant is the milkweed, which produces cardiac glycosides – although Monarch butterfly larvaespecifically feed on milkweed. Other plants develop modified leaves, stems or epidermal cells thatchange shape and become hardened and sharp.

Officially, modified leaves are referred to as spines, modified branches are thorns andmodified epidermal cells are prickles. In most cases, people simply refer to them as thorns orspines. Examples of plants that deploy these types of defenses include roses, barberry, floweringquince and raspberries and blackberries – unless horticulturists have bred them to be thornless.Regardless of what we call them, structures such as thorns make it difficult for animals to comealong and take a bite without a painful lesson!

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