Plants need four things: sunlight, water, minerals, warmth. Leaves are the food factories for plants. In a process called photosynthesis, sunlight triggers a chemical reaction between water and minerals, absorbed by the roots, combine with chlorophyll, a remarkable chemical that gives plants their green color, in the leaves that produce starches and sugars (food for the plants) and oxygen.
Water is absorbed through tiny hairs and rootless that extend from the plant's roots. The water is supplied to the leaves trough tubes in the stems, barnacles and/or trunk. If the soil is fertile nutrients are carried to the leaves in the water. In rainforest that roots are often shallow because water is abundant. In the desert the roots often extend deep into the earth, often to all the way to the water table, many feet below the surface.
Roots are near the surface so the plants can absorb rain water before other plants do. The surface is also where most of the nutrients from decaying leaves is located. Buttress help hold the tree up. During a severe drought the water column system breaks down. In these conditions the tree is so stressed it produces a clicking sound analogous to a person gasping for air.
Websites and Resources: Rainforest Action Network ran.org ; Rainforest Foundation rainforestfoundation.org ; World Rainforest Movement wrm.org.uy ; Wikipedia article Wikipedia ; Forest Peoples Programme forestpeoples.org ; Rainforest Alliance rainforest-alliance.org ;Rainforest Portal rainforestportal.org ; Prince’s Rainforest Project rainforestsos.org/about-rainforests ; Nature Conservancy nature.org/rainforests ; National Geographic environment.nationalgeographic.com/environment/habitats/rainforest-profile ; Rainforest Books:
Book: The Private Life of Plants: A Natural History of Plant Behavior by David Attenborough (Princeton University Press, 1997); Portraits of the Rainforest By Adrian Forsythe.
Photosynthesis Websites and Resources on Rainforest Animals: Rainforest Animals rainforestanimals.net ; Rainforest Animal Photos mongabay.com ; Rainforest Plant Photos rain-tree.com/plantimages ; Rainforest Animal Photos leslietaylor.net/gallery/animals ; Rainforest Plants wheatonma.edu/rainforest ; Enchanted Learning enchantedlearning.com/subjects/rainforest ; Amazon Plants junglephotos.com ; Plants plants.usda.gov ; Biology of Plants .mbgnet.net/bioplants ; Botany.com botany.com ; Life Cycle of Plants /www2.bgfl.org ; Scientific American articles on plants scientificamerican.com ; Dave’s Garden davesgarden.com/guides ;Wikipedia article Wikipedia ; Picture Gallery in German pflanzenliebe.de
Simple photosynthesis Photosynthesis takes place inside special kidney-shaped cells called chromoplasts. Inside these are tiny flattened sacs that are stacked on top of one another like pancakes,. These sacs contain pigments, the foremost of which is chlorophyl, which absorbs light energy. Light energy absorbed in the pigment and breaks down water (with two hydrogen atoms and one oxygen atom) and carbon dioxide (with one carbon atom and two oxygen atoms) with the released atoms recombining to produce carbohydrate molecules (with one carbon atom, two hydrogen atoms and one oxygen atom) and oxygen, whish is discarded.
The carbohydrates produced by photosynthesis are the basic building blocks of all life on earth. Through various complex chemical reactions involved minerals and nutrients such as nitrogen and phosphorous, these carbohydrates can be converted into sugars, cellulose and amino acids. The food we eat, the fuel we burn and the wood we used to make our homes all are ultimately derived from photosynthesis and carbohydrates. On top of that the oxygen we breath and the oxygen that fills the atmosphere were all produced by photosynthesis. Today it helps combat global warming by absorbing carbon dioxide.
Rainforest Plant Leaves
The purpose of leaves is to absorb as much sunlight as possible from the sun. Many plants angle their leaves towards the sun and jockey with other leaves for position. Time lapse film shows them following like the sun like a head following the ball at a tennis match and move around like people in a crowd trying to catch a glimpse of a film star. Leaves can not absorb water. Rain water on a leaf in fact can disrupt photosynthesis. Most leaves have channels that direct the water off the leaves
Why leaves of different species found in same habitats form different patterns is unknown. Some of the largest leaves in the plant kingdom belong to plants that live near the ground in the rainforest. The largest undivided leaves belong to a member of the arum family of Southeast Asia and Borneo. They can reach a length of ten feet and have an area of 30 square feet.
Other species of the arum family contain a purple pigment on the underside of the leaf that catches sunlight and distributes it to food-producing parts of the leaf. Begonias that grow on the floor of Asiatic rainforests employ a similar trick. They have transparent pigment patches on the surface of their lives that serve as lenses that focus the little light it receives to food-producing parts of the plant.
The starch and sugars found in leaves supplies food for animal, mostly insects who are work around the clock munching leaves. Many plants have thorns, spines, hooks, stings, and poisons on the leaves to keep animals form eating them.
Large Rainforest Trees
Growing to a great height is a great advantage for trees because it allows them out competes other plants to reach sunlight. Plants that do not grow risk being overshadowed by taller plants and not receiving enough sunlight to survive. Some of the tallest trees in rainforest are members of the pea and bean family.
tree buttress Large trees can loose hundreds of gallons of water a day to transpiration on a hot day. So that their leaves don’t wilt the same amount of water that is lost has to be replaced. How is such a great volume of water moved up trunk? The trunk is made of dead tubes filled with a column of water that rises as water transpires from the leaves. Water has a high surface tension and can be drawn upwards through capillary action without breaking into small pieces.
If the trees have enough sun and water they can grow quite large. Some survive for centuries until they begin having trouble lifting sap to their crowns and branches which have been weakened by tunneling insects and the weight of algae, moss and epiphytes. Sometimes the end comes when a large branch falls off and tree loses it balances topples over. More often than not large trees come down in strong winds or a large storm.
Most tropical tree species are broad-leaf evergreens with smooth tapered leaves that allow rain to run off so branches don't break off from being waterlogged. The leaves are angled to collect the maximum amount of sunlight. Many have special joints in their stalks that allows them to twist as they track the sun as it moves across the sky. These leaves are covered with a glossy wax that prevents algae, moss or there plants from growing on them.
At ground level many trees are supported by triangular buttresses (partly above-ground roots jutting out from the trees) that help support large trees in the shallow soil and keep them from being knocked over by heavy winds. Banging on the buttresses with a log sometimes produce a sound that can be heard for miles. The roots in the thin soil are shallow and sometimes above the ground so that nutrients can be absorbed quickly. Poisonous snakes, ants, rodents and other small animals often live in the cavities around the base of the tree.
Most of the trees depend on flowers and fruit to reproduce. Since they cannot depend on wind to assist in pollination they produce flowers with bright petals that are fertilized by beetles, wasps, butterflies, other and insects. Those that count on nectar-drinking insects are nearly always red, while those that are pale and have a fetid smell are visited by bats. Fruits with seeds housed in tough coverings are consumed by creatures such as parrots, monkeys, and deer that disperse the seeds in their excrement.
Rainforest Fruiting Cycles
flowering canopy Tropical rainforest trees don't follow seasonal cues like temperate tree in flowering, fruiting and shedding the leaves. Some drop their leaves every six months. Some every 12 months and 21 days. Other do it in a piecemeal fashion, with different branches shedding at different intervals. Because many trees grow at the same rate all year, without winter and summer fluctuations, they don't have rings and thus it is difficult to determine their age.
Flowering and fruiting patterns are even more irregular. Ten-month and 14-month cycles are common. Some species only flower once a decade. In regions with pronounced wet and dry seasons the fruiting period is usually takes place right before the wet season, a time when trees are under the most stress.
In some places there sometimes seems to be no discernable pattern in the way that trees flower and fruit. Some Asian tree communities, for example, go long intervals without flowering, then suddenly burst into fruit over a large area---an unpredictable phenomena known called "masting." What stimulates them to flower on cue like this is a mystery.
Many rainforest trees reproduce with seed-bearing fruits like figs, durian, jackfruit and avocado. The ease and speed in which many of these fruits are digested by animals who can’t afford to have large stomach poses some problems for the plant. Some birds excrete the remains of fruit that they had only eaten five minutes earlier. As a result the fruit are largely deposited in the same places they would be if they just fell from the tree. Even so enough remains in the animals so that they are deposited in new places when the animals move on.
Different Kinds of Rainforest Trees
If all rainforest trees look alike to you, you are not the only one that feels this way. Botanists often have difficulty telling trees and plants apart. Variations between plants are often subtle and only apparent for a short period of time when a species bears flowers or fruit, which is not coincidently is when scientists prefer to collect specimens and make identifications.
Three quarters of all tropical rainforest tree species are considered rare. Generally only a few trees of a specific species but many different species can be found in a 100 acre area.
Dipterocarp rainforests of Borneo and Southeast Asia are taller and have fewer lianas connecting trees than the more broken canopy of Amazonian forests.
Giant kapok, or silk cotton trees, are fixtures of Latin American forest. Similar tree are found in Africa and Southeast Asia. Kapok seeds have cottony tufts that allow them to be carried by the wind. The seeds in the similar trees in Africa and Southeast Asia have wings that causes them to spiral downwards and sometimes be carried away by winds.
Palms grow primarily in tropical areas but are also found in the highlands of the Himalayas and the Andes, in mangrove swamps and in the desert. Members of a diverse plant group that also includes grasses and orchids, they range in height from six inches to 200 feet. Some palms are trees. Some are bushes. Rattan palms, which grow as a vine, can reach lengths of 600 feet or more.
Palm trees do not branch. They generate all their growth from a huge bud at the apex of the tree, which is called the palm heart. It produces leaf after leaf as the plant grows. The palm heart is often very tasty and animals like to eat it. If something happens to it the plant can die. Many palms have sharp spines for protection.
Palm trunk have a pith center but no bark or growth rings. Leaves called fonds fan out from a crown at the top. Some leaves are 30 to 45 feet long and 4 to 8 feet wide. African raffia palms have the world’s largest leaves, reaching 75 feet in length.
Palms bear flowers and fruit. The fruits have hard kernels containing tiny germs. Some kernels, such as dates, are surrounded by a fleshy pulp. The world’s largest seed, a double coconut from the Seychelles, comes from a palm. Most palms begin flowering when they five or six and mature when they are 10 to 15 years old. Some palms live 150 years or more.
Uses and Kinds of Palms
There are several thousand species of palms. Valuable kinds of palm include coconut palms, date palms, sago palms, betel nut palms. Some palms produces a sweet sap that is made into candy, sugar and wine. The nuts of the tagua palm yields vegetable ivory. Carnauba palm leaves produce wax.
Palm tree trunks are used in the construction of houses, boats and bridges that cross canals. They are used to make grids and fences. Elastic fibers that the cover the trunks are used to make camel and horse saddles. Parts of the leafstalk are used as trowels by mason and as beaters by washerwomen. Mats, plates and baskets are made with stalks. Among the other things made with palms are dye, paper, surfboards, and wax.
See Coconuts, Dates, Palm Oil, Palm Hearts, Food
bamboo forest Bamboo is a kind of grass that can grow to size of a tree. The stems are, hollow, polished and jointed and sometimes reach three feet across. Some flower and seed every year; other only do so one every 60 years or so. Some species of bamboo die off en masse after a single flowering. One such die off killed hundred of giant pandas in China in the 1980s. Depending on the species, the die off can occur everywhere from one every dozen year or so to once every century.
In the short term bamboo reproduce by sending up new stems rather than by producing seeds. A single root may produce as many as 100 stems. These stems breaks the soil with it nodes already formed and can grow as much as a meter in a single day. Bamboo doesn't have rings like a tree. The hollow nodes are already developed when they emerges in the spring and grows like an uncoiling party favor.
There are more than 500 species of bamboo. Some species of bamboo’such as Bambusa Arundinacea of India and Phyllostacys and China---reach heights of 100 feet. Bamboo is both flood- and drought resistant. Hikers who run out of water in the Malaysian rainforest can get about a canteen's worth by boring a hole right above the joint of large stalks of bamboo.
Bamboo is used for all kinds of things: homes, musical instruments, food, scaffolding, Bamboo has been made into a fabric used to make denim trousers. Surprisingly soft, it is naturally antimicrobial and odor resistant.
Some plants have entire ecosystems with a variety of animals living in them. At Peru's Manu Biosphere Reserve, scientists have discovered a species of thick guadua bamboo that supports large populations of ants, beetles and roaches and even snakes and frogs, that actually live within the bamboo's stalks. [Source: Adele Conover, Smithsonian magazine]
The bamboo is dived into sections, called nodes, which collect water that is naturally pumped through the plant. The females of a particular kind of katydid digs holes in the bamboo with long knifelike ovipositors so that they can squeeze their abdomen into the bamboo to lay eggs. Guanda bamboo grow at amazing speeds’sometimes a meter a day---and as it grows the holes made by the katydids expand and elongate creating entry points for rainforest creatures.
Mosquitos, crane flies and other aquatic insects enter the stalks and lay eggs in the water. Their larvae feeds off rotting bamboo sediments and katydid eggs. Birds like the rufous-headed woodpecker drill rectangular holes into the stalks to extract insects, and monkeys "unzip" the elongated katydid cavities to gather food. Eventually the openings are large enough for poison-arrow frogs, finger-size rhinoceros beetles and lizards to enter and feed on the insects and larvae, and lay their eggs. Last but least are tree snakes which climb into the holes to feed on frogs and lizards.
Image Source: Mongabay mongabay.com ; Wikimedia Commons
Text Sources: The Private Life of Plants: A Natural History of Plant Behavior by David Attenborough (Princeton University Press, 1997); National Geographic articles. Also the New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Natural History magazine, Discover magazine, Times of London, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.
© 2009 Jeffrey Hays
Last updated March 2011