Coconut (Cocos nucifera)
ARECACEAE, Palm Family
One of the most useful plants is the coconut palm, Cocos nucifera, which is grown around the world in lowland tropical and subtropical habitats. From this species come many natural products, including foods, drinks, fibers, building materials, and chemicals. This species can grown where annual precipitation is fairly low, and it does well growing near salt water, where salt spray would kill many other plants.
The plant is a feather palm, which means that its leaves are pinnately compound (like a feather); these leaves are frequently used in thatching. The long trunk of the tree, which is not formed in the same manner as that of a dicotyledon, is used for building supports, and the stem can be tapped near the top of the plant to yield a sugar, which can be fermented into an alcoholic beverage. Moreover, the shoot tip can be eaten, although this kills the plant.
Practically everyone would recognize a coconut, but most people do not understand the botany of this reproductive structure. A coconut fruit is actually a one-seeded drupe. On the outside is the husk, which is initially green but turns brown after being picked and dried. Inside the outer coat of the fruit lies the mesocarp, which is packed with vascular bundles. This fiber is called the coir and is used for making mats and rope. What we buy in the grocery store is the "stone" of this drupe, which has a hard "shell," the endocarp, and the seed, which is inside of the shell. The shell is used for containers and is widely employed by artisans to make ornaments and decorations. Next occurs the seed coat, which is thin, and then the white flesh or copra and the "coconut milk." Both the copra and the milk are the endosperm of this seed. Yes, coconut is unique among plants in having copious liquid endosperm, which bathes the young embryo. Initially the milk is fairly sweet and the copra is thin, but as the seed matures, the liquid is converted into solid endosperm rich in oils (triglycerides). The solid endosperm, copra, is harvested, dried, and then pressed to release the oil, widely used for chief ingredients of shampoo and hair conditioners.
Coconut palms are an excellent source of food for native peoples in the tropics. The plants have many fruits per plant at any time, and fruits are rich in calories and essential vitamins. A special feature of the liquid endosperm is that the liquid portion contains large quantities of a plant hormone called cytokinin. It was this plant hormone that figured greatly in the first successful attempts by experimental botanists to grow plants in test tubes from single cells. It turned out that cytokinin is the crucial ingredient to get single cells to develop into embryos.
In the wild the coconut is dispersed from one beach site to another distant beach via flotation on the water. The coir is light and thus permits this drupe to float for days, even months, without sinking. During that time, the embryo is not damaged by seawater. When the fruit washes up on a distant beach, the embryo germinates through one of the three thin areas ("eyes") in the endocarp, but the cotyledon remains within the fruit, i.e., hypogean germination, but in this case resting on the surface of the sand.
Inasmuch as this fruit is a proven expert at dispersal by floating on the ocean, there is little surprise that this Old World plant, a native of the Indian Ocean region, was growing and used in the New World before Columbus arrived. There is good evidence that the coconut palm was growing on the Pacific side of the Isthmus of Panama before the Spaniards arrived; this is also consistent with the dispersal model, because coconuts could have drifted via sea currents from the islands of the Pacific Basin to the western coastline of Central America. Nonetheless, coconuts have been intentionally carried around the world, including to some of the islands of the Pacific Basin, so that the trip to the New World from southeastern Asia very possibly was aided by humans. Coconuts, kumara (sweet potato, Ipomoea batatas), and breadfruit (Artocarpus) were three extremely important victuals on long voyages of the ocean-going Polynesians.
Knowing now that the coconut grows on beaches of tropical islands, you may like to hear the popular myth from eastern Papua about the origin of the coconut. Each day a man came home in the evening with a basket filled with large fish. Naturally, this villagers went to spy on him, to find out how he was so successful. At dawn, the man removed his head, placed it under a shrub, and then waded out into the ocean, where the fish would be attracted to him and be swallowed through his neck. The man spewed out the many fish on shore, placed his head on again, then sorted the fish to return the small ones to the water. Then next morning the jealous onlookers stole the man's head and hid it in the sand. When he could not find his head, the man changed into a fish and swam away, but his head subsequently grew into a coconut tree.