The most commercially valuable member of this family is the common pineapple,
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
, 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
is produced. Each
gives rise to
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
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
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
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
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
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