Bromelaid vs Aizoaceae (living stone) doc module 1

Bromelaid vs Aizoaceae (living stone) doc module 1 - The...

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The most commercially valuable member of this family is the common pineapple, Ananus comosus. A native of South America, the pineapple has been widely planted as a cash crop throughout tropical and subtropical regions. The pineapple is a biennial plant , that is, it usually lives for only two years. In the first year this species produces a dense growth of sharp-pointed, overlapping leaves. During the second year a short stalk with many flowers is produced. Each flower gives rise to fruits that are technically berries, but then the stalk bearing the fruit begins to swell. This results in the development of a thick, sweet, fleshy mass, within are embedded the fruits. This whole thing is the "pineapple," which is therefore an aggregation of fruits within an accessory structure (the thickened stem). When you buy a pineapple at the market you notice at the top of the "fruit" a tuft of prickly, reduced leaves or bracts, and a cleanly cut-off base. This may lead you to believe that the pineapple was cut off from the plant at ground level, but this was not the case. Pineapples grow at the end of shoots, two to four per plant, so they are cut off from an underlying, large-leafed shoot. Bromeliads are xerophytes and possess many of the usual, water-conserving adaptations of such plants: a thick epidermis covered with wax, water-storage cells Single swamp cypress covered with spanish moss. Photograph by Chris Sharp. Photo Researchers, Inc. Reproduced by permission. that cause the leaves to appear succulent (that is thick and fleshy), and sheathing leaf bases. One of the notable characteristics of bromeliads is the distinctive, water-absorbing scales on their leaves and stems. These thin scales occur in grooves in the epidermis, and they resemble opened umbrellas. Their thinness and large surface area make the scales ideal for rapidly absorbing water . Equally important in terms of water economy are the shape and arrangement of the leaves of bromeliads. In many species the leaves are wide and deeply U-shaped where they join the stem, forming a series of vessel-like compartments. When it rains, water flows down the leaves and pools in the compartments, where it can be absorbed by the umbrella scales. Especially remarkable are the "tank plants," such as Nidularium and Billbergia. In these species the stem is greatly reduced and the densely packed leaves have broad, overlapping bases, resulting in a pitcher or vase-like center-the tank. Rainwater fills the tank, where some of the moisture is absorbed by the umbrella A bromeliad growing on the bole of a cypress tree in Everglades Page 1 of 10
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National Park, Florida. Photograph by E.R. Degginger. Photo Researchers, Inc. Reproduced by permission. scales. Because the tank is shaded by the dense crown of leaves around it, the water does not evaporate quickly and can persist, enabling the plant to survive periods of drought . Interestingly, some species of
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Bromelaid vs Aizoaceae (living stone) doc module 1 - The...

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