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1. EPIPHYTES- The Air Plants
Lexile: 990L
Publication: Horticulture(Oct/Nov2007)
Author: Lynch, Meghan
An epiphyte is a plant that derives its moisture and nutrients from the atmosphere. In the wild, these
plants usually grow on tree trunks, tree branches, or rocks. Many epiphytes are native to rain forests,
where the frequent rains and humid air allow them to easily absorb plenty of water. They are also
typical of cloud forests (rain forests at high elevations). Cloud forests are frequently immersed in low
clouds, creating a cool atmosphere with 100 percent relative humidity. Although epiphytes live on
trees, they do not lake anything away from them. The host plant is simply a perch for an epiphyte.
Epiphytes have evolved special features to allow them to survive "unplanted." Many have a
pronouncedly cupped shape; water and debris collects in the center of the cup, for the plant's use.
Others are able to trap dust particles in tiny scales on their leaves and absorb nutrients from these.
Epiphytes are not without roots, though they do not rely on them in the usual way. Some, such as some
Tillandsia species, have "holdfast roots.' which only serve to fasten them to their host. Other epiphytes'
roots primarily serve as anchors but also have the ability to take water and nutrients from soil if the
plant happens to land in some.
Familiar epiphytes include staghorn fern (Platycerium bifurcatum); Dendrobium and Phalaenopsis
orchids, certain bromeliads, including the urn plant (Aechmea fasciata);
By Meghan Lynch
Staghorn fern
Spanish Moss
Urn plant
What is an epiphyte?
Lexile: 1180L
Publication: Horticulture(Dec91)
Author: Albright, T.D.
Epiphytes, or "air plants," are plants that depend on other plants for physical support. Unlike parasites,
they do not derive any nourishment from their host. The term comes from the Greek words epi,
meaning "upon," and phyton, meaning "plant." Epiphyte does not refer to a plant family or a genus;
rather it denotes an ecological group of plants with similar habits, requirements, and habitats.
Most epiphytes are native to Central and South America, the Caribbean and South Sea islands, and
tropical Asia and Africa--in other words, the tropical and subtropical regions of the world. These plants
generally fasten themselves high up in forest trees, although some have been known to settle on stone
walls, roofs, fence posts, and even utility wires.
Epiphytes like high places where they can emerge from the lush growth of the forest and get the
sunlight and rainwater they require for survival. Some take nourishment from rain, mist, and dust in
the air through their "air roots," a process that still is not well understood. Apparently most air roots do
not contain or manufacture chlorophyll. They have a spongy texture and are often a pale-white or waxy
color. The plants' anchoring roots, which may be woody or wiry, generally twine into textured bark or
into crotches in the host tree, where moss or debris provides a base. Although an epiphyte perched in
the tree canopy may get first crack at falling rain (which sometimes fails to reach the forest floor),
there are dry periods even in tropical regions, and the hot sun can shrivel exposed leaves. For this
reason, many epiphytes have thick water-retaining stems or leaves, like those of succulents. Others,
particularly a number of bromeliads, reserve water in the cup-like crowns of their leaves.
Gardeners can raise many of these interesting plants in their homes or greenhouses by mimicking the
conditions found in the plants' native habitats. An epiphyte needn't be potted in soil. Most prefer a fastdraining medium such as osmunda fiber or fir-bark mixtures, but some can simply be wired or tied to
tree branches or other supports. Generally speaking, these plants prefer high humidity and warm
temperatures. Some epiphytes have dormant periods, but when well accommodated, many will bloom
for months at a time.
Poachers are plundering the forests for epiphytes, so buy only nursery-propagated plants. "Gardeners
ought to have a chance to be part of the solution, not part of the problem," says Selby's director, Larry
Pardue.
By Teri Dunn
2. Orchids: Trickster Flowers.
Lexile: 850L
Publication: Odyssey(Mar2003)
Author: Kowalski, Kathiann M.
If you thought orchids were just pretty flowers, think again. With about 35,000 wild species, orchids
may be Earth's biggest family of green plants. Most species live in tropical rain forests, but orchids
thrive on every continent except Antarctica. And orchids have evolved some amazing survival tricks.
Orchids produce flowers for one purpose: to reproduce. Most species must combine DNA (the genetic
blueprint) from two parent plants. But, like most plants, orchids are rooted in one place. Plus, there
often isn't another orchid close by for cross-pollination. To spread their pollen, many orchids rely on
specific pollinator insects. Often, that's more efficient than attracting insects that visit many kinds of
flowers.
“It would be like having your own private mail courier service rather than relying on an inefficient post
office that might lose your mail, your gametes,” explains Mark Whitten at the Florida Museum of
Natural History's Orchid Identification Center. After all: “That's the future of the species right there. If
that pollen gets wasted, then that plant might as well not have produced a flower that year.”
Many orchids attract pollinators through deception. “As many as 400 to 500 species produce insect
pheromone,” notes Florien Schist at the Geobotanical Institute in Zurich, Switzerland. Normally,
pheromones are chemicals released by one species that cause certain behaviors in other members of the
same species (see our February 2003 issue, on “Love at First Whiff: The Nature of Smell”).
The Orphrys sphegodes orchid, for example, emits a counterfeit version of the Andrena nigroaenea
bee's sex pheromone. The shape and color of its flower make it look like the female bee, too. When
male bees see and smell the orchid, they think a female bee is nearby and ready to mate. Instead, the
orchid's pollen rubs off on the male. If the orchid is lucky, another Orphrys orchid's fake pheromone
will fool the bee again. Then it will leave the pollen on that flower's column. (An orchid's column is a
fused structure containing both the female pistil and male, pollen-producing stamens.)
Phony pheromones aren't the only tricks orchids use to get pollinators. One attractive tropical lady's
slipper uses sight and smell tricks to fake an aphid infestation. That tricks female sweat flies into
believing the orchid is a good place to lay eggs, since their maggots eat aphids. The flower gets an
unwitting pollinator.
Other species go for the gross approach. Some orchids mimic rotting flesh. Their brown and purple
flowers are really ugly, and they stink. Female flies try to lay eggs on the orchids so that their maggots
will have food to eat. Meanwhile, they pick up the flowers' pollen.
Still other orchids may offer a real reward. Male euglossine bees collect a waxy substance from
Coryathes speciosa orchids. They put it in “cargo pockets” on their hind legs. The substance may make
the male more attractive when it courts a mate. Or, it may provide some nutrient the bee needs. Either
way, the orchids get pollinated during the bees' visits.
Some orchids' elaborate structures trap pollinator insects and make them crawl through tight tunnels to
escape. Such mechanisms let the orchids put their pollen in specific places — a bee's forehead, its
thorax, or whatever. That way, several species can share the same pollinator.
Orchids don't just make seeds after successful pollination. They make tots of them. Some make “just”
3,000 to 5,000. Other species make millions.
“One is on record at around 10 million seeds for a single fruit,” says John Beckner at Marie Selby
Botanical Gardens in Florida. “The seeds of course are very tiny to compensate, and they're blown by
the wind in almost all species.”
Because the seeds are so small, they have basically no food reserves. To germinate, they must land
where particular fungi grow. The fungi infect the orchid seeds. Then the germinating orchids pull a
switcheroo. They start feeding on the fungi. Later on, most orchids start making their own food by
photosynthesis. But some species rely on the fungi their whole lives.
While orchids share many common features, they also vary enormously. Vanilla planifolia -the source
of natural vanilla beans — grows on long vines. Renanthera storei grows to be six meters tall.
Mystacidium coffrum is barely as big as a thimble. Flowers and foliage come in many sizes, colors,
and patterns.
Some orchid species grow on the ground. Others, especially in the tropics, are epiphytic — they grow
in the treetops of the rain forest.
Still other orchids have double-duty plant parts. Florida's ghost orchid, for example, has no separate
leaves. Its roots do photosynthesis, in addition to the job of absorbing water.
Scientists still have lots to learn about orchids. Unfortunately, people are destroying rain forests so fast
that many species may soon be lost. “There's still a lot out there that needs to be completely described
or discovered for the first time,” says Whitten. “It's a race against time.”
Orphrys sphegodes orchid
Ghost Orchid
Coryathes speciosa orchids
3. FATAL ATTRACTION.: Carnivorous Plants
Lexile: 1190L
Publication: National Geographic(Mar2010)
Author: Zimmer, Carl
They lure insects into death traps, then gorge on their flesh. Is that any way for a plant to behave?
A hungry fly darts through the pines in North Carolina. Drawn by what seems like the scent of nectar
from a flowerlike patch of scarlet on the ground, the fly lands on the fleshy pad of a ruddy leaf. It takes
a sip of the sweet liquid oozing from the leaf, brushing a leg against one tiny hair on its surface, then
another. Suddenly the fly's world has walls around it. The two sides of the leaf are closing against each
other, spines along its edges interlocking like the teeth of a jaw trap. As the fly struggles to escape, the
trap squeezes shut. Now, instead of offering sweet nectar, the leaf unleashes enzymes that eat away at
the fly's innards, gradually turning them into goo. The fly has suffered the ultimate indignity for an
animal: It has been killed by a plant.
THE SWAMPY PINE savanna within a 90-mile radius of Wilmington, North Carolina, is the one
place on the planet where Venus flytraps are native. It is also home to a number of other species of
carnivorous plants, less famous and more widespread but no less bizarre. You can find pitcher plants
with leaves like champagne flutes, into which insects (and sometimes larger animals) lose themselves
and die. Sundews envelop their victims in an embrace of sticky tentacles. In ponds and streams grow
bladderworts, which slurp up their prey like underwater vacuum cleaners.
There is something wonderfully unsettling about a plant that feasts on animals. Perhaps it is the way it
shatters all expectation. Carl Linnaeus, the great 18th-century Swedish naturalist who devised our
system for ordering life, rebelled at the idea. For Venus flytraps to actually eat insects, he declared,
would go "against the order of nature as willed by God." The plants only catch insects by accident, he
reasoned, and once a hapless bug stopped struggling, the plant would surely open its leaves and let it
go free.
Charles Darwin knew better, and the topsy-turvy ways of carnivorous plants enthralled him. In 1860,
soon after he encountered his first carnivorous plant--the sundew Drosera--on an English heath, the
author of Origin of Species wrote, "I care more about Drosera than the origin of all the species in the
world." He spent months running experiments on the plants. He dropped flies on their leaves and
watched them slowly fold their sticky tentacles over their prey. He excited them with bits of raw meat
and egg yolk. He marveled how the weight of just a human hair was enough to initiate a response. "It
appears to me that hardly any more remarkable fact than this has been observed in the vegetable
kingdom," he wrote. Yet sundews ignored water drops, even those falling from a great height. To react
to the false alarm of a rain shower, he reasoned, would obviously be a "great evil" to the plant. This
was no accident. This was adaptation.
Darwin expanded his studies from sundews to other species, eventually recording his observations and
experiments in 1875 in a book, Insectivorous Plants. He marveled at the exquisite quickness and power
of the Venus flytrap, a plant he called "one of the most wonderful in the world." He showed that when
a leaf snapped shut, it formed itself into "a temporary cup or stomach," secreting enzymes that could
dissolve the prey. He noted that a leaf took more than a week to reopen after closing and reasoned that
the interlocking spines along the margin of the leaf allowed undersized insects to escape, saving the
plant the expense of digesting an insufficient meal. Darwin likened the hair-trigger speed of the Venus
trap's movement--it snaps shut in about a tenth of a second--to the muscle contraction of animals. But
plants don't have muscles and nerves. So how could they react like animals?
Today biologists using 21st-century tools to study cells and DNA are beginning to understand how
these plants hunt, eat, and digest--and how these bizarre adaptations arose in the first place. After years
of study, Alexander Volkov, a plant physiologist at Oakwood University in Alabama, believes he has
figured out the Venus flytrap's secret. "This," Volkov declares, "is an electrical plant."
When an insect brushes against a hair on the leaf of a Venus flytrap, the bending triggers a tiny electric
charge. The charge builds up inside the tissue of the leaf but is not enough to stimulate the snap, which
keeps the Venus flytrap from reacting to false alarms like raindrops. A moving insect, however, is
likely to brush a second hair, adding enough charge to trigger the leaf to close.
Volkov's experiments reveal that the charge travels down fluid-filled tunnels in a leaf, which opens up
pores in cell membranes. Water surges from the cells on the inside of the leaf to those on the outside,
causing the leaf to rapidly flip in shape from convex to concave, like a soft contact lens. As the leaves
flip, they snap together, trapping an insect inside.
The bladderwort has an equally sophisticated way of setting its underwater trap. It pumps water out of
tiny bladders, lowering the pressure inside. When a water flea or some other small creature swims past,
it bends trigger hairs on the bladder, causing a flap to open. The low pressure sucks water in, carrying
the animal along with it. In one five-hundredth of a second, the door swings shut again. The cells in the
bladder then begin to pump water out again, creating a new vacuum.
Many other species of carnivorous plants act like living flypaper, snagging animals on sticky tentacles.
Pitcher plants use yet another strategy, growing long tube-shaped leaves into which insects fall. Some
of the largest have pitchers up to a foot deep and can consume a whole frog or even a rat unlucky
enough to fall into them. Sophisticated chemistry helps make the pitcher a death trap. Nepenthes
rafflesiana, a pitcher plant that grows in jungles on Borneo, produces nectar that both lures insects and
forms a slick surface on which they can't get a grip. Insects that land on the rim of the pitcher
hydroplane on the liquid and tumble in. The digestive fluid in which they fall has very different
properties. Rather than being slippery, it's gooey. If a fly tries to lift its leg up into the air to escape, the
fluid holds on tenaciously, like a rubber band.
Many carnivorous plants have special glands that secrete enzymes powerful enough to penetrate the
hard exoskeleton of insects so they can absorb nutrients from inside their prey. But the purple pitcher
plant, which lives in bogs and infertile sandy soils in much of North America, enlists other organisms
to digest its food. It is home to an intricate food web of mosquito larvae, midges, protozoans, and
bacteria, many of which can survive only in this unique habitat. The animals shred the prey that fall
into the pitcher, and the smaller organisms feed on the debris. Finally, the pitcher plant absorbs the
nutrients released by the feeding frenzy. "Having the animals creates a processing chain that speeds up
all the reactions," says Nicholas Gotelli of the University of Vermont. "And then the plant dumps
oxygen back into the pitcher for the insects. It's a tight feedback loop."
UNFORTUNATELY, THE ADAPTATIONS that enable carnivorous plants to thrive in marginal
habitats also make them exquisitely sensitive to environmental changes. Agricultural runoff and
pollution from power plants are adding extra nitrogen to many bogs in North America. Carnivorous
plants are so finely tuned to low levels of nitrogen that this extra fertilizer is overloading their systems.
"They eventually burn themselves out," says Ellison.
Suction Traps Bladderwort (Utricularia)
Antennae on the bladders of the aquatic plant guide tiny prey toward the trap. Touching the trigger
hairs springs open a valve--and lower water pressure inside sucks in prey. Glands absorb nutrients and
expel water.
Pitfall Traps Tropical pitcher plant (Nepenthes)
Nectar secreted on the lid and slippery rim draws insects and spiders. Losing their foothold, prey find
no traction in the waxy zone and drown in a pool of digestive juices.
Sticky Traps Sundew (Drosera)
Tentacles sparkling with sticky gel arm more than 180 sundew species. The struggle of stuck prey
stimulates other tentacles to bend toward the captive, coating it with enzymes that digest it.
Snap Traps Venus flytrap (Dionaea)
The trap closes in a tenth of a second when prey hit at least two trigger hairs-or one hair twice. Teeth
form a cage to block escape. The trap slowly tightens, releases digestive fluids, then reopens in about
ten days.
Pitcher Plant
Bladderworts
Venus Flytrap
4. Planet of the vines.
Lexile: 1170L
Publication: New Scientist(10/5/2013)
Author: Laurance, William
Climbing plants are taking over the world's forests. What's going on, asks biologist William Laurance
GAZE out over a tropical rainforest and the scene looks idyllic -- a kaleidoscope of trees festooned
with colorful vines, orchids, ferns and lichens. Don't be fooled. Myriad ecological battles are being
fought beneath this tranquil surface. None is more embittered than that between trees and their ancient
enemies, the vines.
Biologists like myself who study these jungle ecosystems are now seeing a shift in this war. Until a
decade or so ago the two adversaries were evenly matched, but vines now seem to be on the march. If
that continues, the face of our forests -- and of our planet -- could be changed irrevocably. We are left
scrabbling to unearth the root cause.
If the forest were a financial system, trees would be its old money. Deeply rooted, they grow slowly,
investing heavily over time in woody trunks and branches to support their leaves, and providing homes
for a zoo of other species. Vines, on the other hand, would be the flashy junk-bond traders.
Representing up to half of the plant species in a typical rainforest and producing up to 40 per cent of all
leaves, they are down-and-dirty competitors. They invest almost nothing in supportive tissue, instead
taking advantage of the trees' investments to scramble up to the top of the forest and produce great
flushes of leaves that bask brazenly in the full sun.
Francis Putz, a biologist at the University of Florida in Gainesville, highlighted this fraught
relationship in a 1980 paper entitled "Lianas vs trees". Lianas, or woody vines, can grow to be
hundreds of meters long, with stems over half a meter across. Trees pay a high price for their presence.
Lianas can strangle and deform a tree's branches, their dense foliage robs trees of life-giving sunlight,
and their roots scarf up vital nutrients and water. Trees bearing lianas usually grow more slowly,
reproduce less and die sooner than those without. Once lianas reach the canopy, they often climb
laterally, effectively roping trees together so that, when one falls, it can drag down others. This is why
loggers hate them: if they don't cut every liana linked to a tree before felling it, another may be yanked
down on top of them. "Loggers call them 'widow-makers'," says Putz.
There are obvious reasons why some vines are becoming more prevalent. Humans have introduced
invasive species, such as the rubber vine to northern Australia and kudzu to the south-eastern US, that
smother native forests, grasslands and waterways. Most vines are light-loving, and increase rapidly in
forests that have been fragmented by agriculture or selectively logged. Small, regenerating trees on the
edge of disturbed forests provide ideal trellises for climbing quickly into the canopy. A decade ago, my
colleagues and I revealed much higher liana abundances in fragmented than in intact Amazonian
forests. Trees in these areas are beleaguered, dying two to three times as fast as normal.
But vines are also proliferating in undisturbed forests. Oliver Phillips of the University of Leeds in the
UK and his colleagues revealed in 2002 that lianas had increased sharply at the expense of trees at sites
across western Amazonia. Something similar has been seen in nearly a dozen other intact forests in
Central and South America. "It was controversial at first," says Phillips, "but few doubt it now."
What's happening? A likely cause is that tropical forests around the globe are becoming more dynamic,
with trees dying and regenerating more rapidly -- conditions that strongly favour vines. It is possible
that global warming is intensifying windstorms that increase tree fall in the affected areas, yet there is
little evidence for such an effect.
Instead, a more subtle driver seems to be at play: rapidly rising levels of atmospheric carbon dioxide.
CO2 fuels photosynthesis, and the more there is, the faster plants grow. Faster growth creates more
competition among plants for light, space and nutrients, which in turn drives higher rates of tree death
and regeneration. Rising CO2 could also favour vines directly. Several studies over the past few years
suggest that vines, with high photosynthetic rates, an abundance of energy-producing leaves and little
costly supportive tissue, are primed to take advantage of rising CO2.
Most evidence, however, suggests Earth is heading for a viney future. This worries ecologists like
Stefan Schnitzer at the University of Wisconsin-Milwaukee. "Vines can change forests in a lot of
ways," he says. "They hit big, slow-growing trees far harder than smaller, faster-growing species,
meaning they can probably change the entire composition of the forest."
It's not just trees that are at risk. Ainhoa Magrach, a postdoctoral colleague of mine at James Cook
University in Cairns, Australia, has found that plants that live on trees, such as ferns, tend to be
excluded in regions where vines are dense. These ferns are little islands of biodiversity, sustaining
many animals in the rainforest canopy. A few species have mutualisms with aggressive ants that attack
encroaching vines, but most are not so lucky.
The biggest worry is that proliferating vines could reduce carbon storage. Forests lock up billions of
tons of carbon in woody tissue, and when vines kill or suppress trees some of that carbon is released
into the atmosphere. Studies in Panama and Amazonia suggest rampaging vines replace just a small
fraction of the carbon they cause trees to release. That could induce a positive feedback, with still more
greenhouse gases and a warmer future for us all. If that goes too far, we really could be heading for a
planet of the vines.
"Vines are down-and-dirty competitors, producing great flushes of leaves that bask brazenly in the
sun"
Vines stop at nothing in their scramble towards the light
By William Laurance
Kudzu
Wisteria
5. Xerophytes
Lexile: 890L
Publication: Monkeyshines on America(Nov98 U.S. Deserts: Flora & Fauna)
Author:
Approximately one-fifth of the earth's land surface is desert. Considering that only about one-fourth of
the total surface area of our planet is land, it isn't hard to understand why so many organisms have
adapted to live in harsh desert climates. Not all deserts are rich in plant life, but several deserts support
a wide variety of species.
The desert is an unusual biome (environment). Temperatures can soar from over 100 degrees F (38
degreesC) to below freezing in a single day. Rainfall is minimal. Some desert areas go for months, and
sometimes years, without any measurable rain. Desert plants are generally referred to as xerophytes.
Perhaps the most well-known desert plant is the cactus. Cacti, wherever they live, are an integral part
of the desert biome. These sometimes husky, sometimes tiny plants have developed some of the best
features for storing water. Most noticeable of these are the cactus's tiny leaves, sometimes known as
spines. Water can't escape through the stomata, the holes through which plants lose or take water.
These holes are kept shut constantly by guard cells. Much water is kept in these fleshy stems.
Sagebrushes have small leaves, as cacti do, to minimize water loss. Several plants shed leaves during
dry spells, and some like the brittlebush even shed entire branches to conserve water. The creosote
bush has waxy leaves to minimize water loss.
These plants also grow separated from each other, by distances up to miles, so competition for water
and minerals is reduced. Other plants which also manage to survive in the desert are the Joshua tree,
palm trees, and yuccas.
Desert plants have special survival adaptations in their seeds, too. Several annuals produce seeds which
are dormant until enough rain has fallen to penetrate the seed coat, triggering germination. Other
plants, especially trees, begin life as seeds which must be cracked open. Seeds often break during
torrential rains, when they are struck by debris. Abundant rainwater allows the plants to germinate, and
this carries the seeds far from the parent plant, reducing competition for water.
Desert plants are very important to the landscape of deserts. Vast and intricate root systems prevent
erosion from water and wind flow.
Desert flowers are always short-lived. After brief rains, or when water rises to the desert surface,
flowers spring up.
They bloom quickly, giving the desert a few days of bright color and fragrance; however, soon the
flowers wither and die. Some desert flowers are sand verbena, apricot mallow, mariposa lily, and
agave.
Plants are the primary water source for many animals.
Desert plants are the key to all desert life.
sand verbena
Sagebrushes
apricot mallow
cacti