Plant stem stems are asparagus, bamboo shoots, cactus pads or nopalitos, kohlrabi, and water chestnut. The spice, cinnamon is bark from a tree trunk. Gum arabic is an important food additive obtained from the trunks of "Acacia senegal" trees. Chicle, the main ingredient in chewing gum, is obtained from trunks of the chicle tree. Medicines obtained from stems include quinine from the bark of cinchona trees, camphor distilled from wood of a tree in the same genus that provides cinnamon, and the muscle relaxant curare from the bark of tropical vines. Wood is used in thousands of ways, e.g. buildings, furniture, boats,
Bark beetle economic impact. In undisturbed forests, bark beetles serve the purpose of hastening the recycling and decomposition of dead and dying wood and renewing the forest. A few species are aggressive and can develop large populations that invade and kill healthy trees and are therefore known as pests. Bark beetles of the family Scolytidae feed and breed between the bark and the wood of various tree species, including spruces. More than 20 species feed on weakened, dying, or dead spruce, fir, and hemlock. Most restrict breeding area to one part of the tree: twig, branch, stem, or root collar. Some breed