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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