<P> Foreign chemicals such as air pollutants, herbicides and pesticides can damage stem structures . </P> <P> There are thousands of species whose stems have economic uses . Stems provide a few major staple crops such as potato and taro . Sugarcane stems are a major source of sugar . Maple sugar is obtained from trunks of maple trees . Vegetables from 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 . </P> <P> 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 . </P> <P> Wood is used in thousands of ways, e.g. buildings, furniture, boats, airplanes, wagons, car parts, musical instruments, sports equipment, railroad ties, utility poles, fence posts, pilings, toothpicks, matches, plywood, coffins, shingles, barrel staves, toys, tool handles, picture frames, veneer, charcoal and firewood . Wood pulp is widely used to make paper, paperboard, cellulose sponges, cellophane and some important plastics and textiles, such as cellulose acetate and rayon . Bamboo stems also have hundreds of uses, including paper, buildings, furniture, boats, musical instruments, fishing poles, water pipes, plant stakes, and scaffolding . Trunks of palm trees and tree ferns are often used for building . Stems of Reed are an important building material for use in thatching in some areas . </P>

All plant organs (such as leaves roots and stems) contain tissues from all three tissue systems