Medicinal and Poisonous Plants Help
Medicinal and Poisonous Plants
Medicinal Plants: Plants Promoting Biological Disorder
Throughout recorded history, human beings have exploited plants and their products not only for food but also as sources of healing for their diseases and injuries. Many of our modern drugs are potent extracts or synthetic modifications of the parts of medicinal plants . Consider, for example, the substance called ephedrine (ih- FED -rin). This drug was named after its original natural source – a group of gymnosperms called the Ephedra (ih- FEE -druh), literally “horsetail” plants. The Ephedra (horsetail plants) are a genus of small shrubs whose long stems are jointed and wiry, making them look like (of course) horsetails! Their leaves are flat, like scales, helping them to conserve water and adapt to life in the desert regions of Asia, Europe, and North and South America. Long ago, Native Americans ground up these shrubs and used them as a food source (flour and so-called Mormon or Mexican tea). But, even more importantly, they discovered that the Ephedra were strong medicinal plants. We now know that the chief chemical was ephedrine, which is a powerful bronchodilator ( brahng -koh- DIE -lay-ter) – a “widener” ( dilat ) of the “bronchi” (branching lung airways). Ephedrine is thus often given to asthma patients, helping them to relax and open their airways during an attack. Further, ephedrine is a constrictor (kahn- STRIK -ter) or “narrower” of the blood vessels lining the nasal passages. Thus, it greatly reduces the swelling and inflammation of the nasal passages during hay fever attacks.
Poisonous Plants: Promoters of Disease and Disorder
Take a walk through any woods or field, and you are likely to encounter the exact opposite of the medicinal plants – the poisonous or toxic plants . These poisonous plants are generally classified into “Do not eat!” groups, versus “Do not touch!” groups. The “Do not eat!” category includes such species as poison hemlock, castor bean, horse chestnuts, laurel, jimsonweed, and deadly nightshade. Prominent among the “Do not touch!” group are poison ivy , poison oak , and poison sumac (Figure 9.7). Poison ivy and poison oak are vines that climb on trees and fence posts, whereas poison sumac is a stand-alone shrub-like plant. [ Study suggestion: Look carefully at Figure 9.7. What prominent anatomic feature do all three poisonous varieties of plants have in common? This will help you recognize them, so you “Do not touch!”]
These closely related plants all contain the same toxic chemical, urushiol (yew- ROO -she-ahl). Urushiol is a toxic oil that is easily rubbed off onto the human skin when the leaves of poison ivy/oak/sumac are touched. The oil frequently creates severe contact dermatitis ( der -mah- TIE -tis), a painful “inflammation of” (-itis) the “skin” (derm). The affected skin may become extremely red, itchy, and swollen, and drain watery fluid from blisters. Urushiol may also be a sensitizer, making the stricken person even more sensitive to poison ivy in the future!
Practice problems for these concepts can be found at: Plant Test
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