MYCORRHIZAL SYMBIOSIS DEFINITION

MYCORRHIZAL SYMBIOSIS DEFINITION

The terms symbiotic and mutualistic have been used interchangeably to describe mycorrhizal associations. Symbiosis was originally used to define both lichens and parasites, but many scientists now use this term to describe beneficial associations only. Fungal symbioses have been defined as ‘all associations where fungi come into contact with living host from which they obtain, in a variety of ways, either metabolites or nutrients’. However, this definition excludes associations of myco-heterotrophic plants that are entirelysupported by a fungus. Only the broadest definition of symbiosis (e.g. ‘living together of two or moreorganisms’) applies universally to mycorrhizal associations.

THE TERM OF MYCORRHIZA

The term mycorrhiza (meaning fungus-root) was originated by Frank (1885), who was fairly certain that these symbiotic plant-fungus associations were required for the nutrition of both partners. More recently, mycorrhizas have been defined as associations between fungal hyphae and organs of higher plants concerned with absorption of sub stances from the soil. Broader definitions have also been published, but are of little value as they do not exclude pathogenic associations. Mycorrhizas are now considered to differ primarily from other plant-fungus associations because they are intimate associations with a specialised interface whereexchange of materials occurs between living cells.

 

MOST MYCORRHIZAS OCCUR IN ROOTS

Most mycorrhizas occur in roots, which evolved to house fungi, but they also occur in the subterranean stems of certain plants and the thallus of bryophytes. Pathogenic associations also involve intimate plant-fungus contact, but differ from mycorrhizas because they lack fungus to plant nutrient transfer, and are highly detrimental to their host plants – resulting in disease symptoms. Pathogenic fungi are typically not specialised for efficient mineral nutrient acquisition from soil. A new, broader definition of mycorrhizas that embraces the full diversity of mycorrhizas while excluding all other plant-fungus associations is presented here.

DEFINITON OF MYCORRHIZA

Definition of Mycorrhiza is a symbiotic association essential for one or both partners, between a fungus (specialised for life in soils and plants) and a root (or other substrate-contacting organ) of a living plant, that is primarily responsible for nutrient transfer. Mycorrhizas occur in a specialised plant organ where intimate contact results from synchronised plant-fungus development.

THE IMPORTANCE OF FUNGI | Fungi play a major role in a number of foods and Some molds produce antibiotics.

The Importance of Fungi. 

Fungi break down complex animal and plant matter into simple compounds. This process of decomposition enriches the soil and makes essential substances available to plants in a form they can use. Through decomposition, fungi also return carbon dioxide to the atmosphere, where green plants reuse it to make food.

Fungi play a major role in a number of foods. 

For example, mushrooms and truffles are considered delicacies by many people. Cheese manufacturers add molds to Camembert and Roquefort cheeses to ripen them and provide their distinctive flavors. Yeasts cause the fermentation that produces alcoholic beverages. In the fermentation process, yeasts break down sugar into carbon dioxide and alcohol. Baker's yeast causes bread to rise by producing carbon dioxide from the carbohydrates in the dough. The carbon dioxide gas bubbles up through the dough and causes it to rise. Someday, yeasts may become an important new source of food. Some people already eat yeasts as a rich source of protein and B vitamins.

Fungsi Pictures

Some molds produce important drugs called antibiotics. 

Antibiotics weaken or destroy bacteria and other organisms that cause disease. Penicillin, the first and most important antibiotic, was discovered in 1928 by Sir Alexander Fleming, a British bacteriologist. Penicillium notatum is one of several green molds that produce penicillin, which physicians use in treating many diseases caused by bacteria.

Penicillin is a powerful drug used to treat infections caused by bacteria. It was the first antibiotic (drug produced by microbes) used successfully to treat serious diseases in human beings. Sir Alexander Fleming, a British scientist, discovered penicillin in 1928. Various forms of the drug, called penicillins, have become widely available for medical use since the mid-1940's. Penicillins have played a major role in treating pneumonia, rheumatic fever, scarlet fever, and other diseases. The development of penicillins had a tremendous impact on medicine and encouraged research that led to the discovery of many other antibiotics.

Tree Damage by Fungi

Some fungi cause great damage. 

Parasitic fungi destroy many crops and other plants. Important parasitic fungi that attack plants include mildews, rusts, and smuts. Others produce diseases in animals and people. Some mushrooms are poisonous and can cause serious illness or death if eaten. Molds spoil many kinds of food. In damp climates, mildews and other fungi can ruin clothing, bookbindings, and other materials. Fungi may also cause wood to decay or rot.

FUNGI DEFINITION | Fungi are organisms that lack chlorophyll.

FUNGI DEFINITION

Definition of Fungi are organisms that lack chlorophyll, the green coloring matter that many plants use to make food. Fungi cannot make their own food. Instead, they absorb food from their surroundings. There are over 70,000 species of fungi. Yeasts and other one-celled fungi are too small to be seen without a microscope. But most types can be seen with the unaided eye. Some of the most common fungi include mildews, molds, mushrooms, and plant rusts.

 Fungi Pictures

Fungi structure : Parts of a fungus. 

Fungi structure Except for yeasts and other one-celled fungi, the main part of a fungus consists of thousands of threadlike cells called hyphae. These tiny, branching cells form a tangled mass called a mycelium. In many kinds of fungi, the mycelium grows beneath the surface of the material on which the organism is feeding. For example, the mycelium of a mushroom often grows just beneath the surface of the soil. The umbrella-shaped growth known as a mushroom is actually the fruiting body of the fungus. The fruiting body produces cells called spores, which develop into new hyphae. Spores are smaller and simpler than the seeds of plants, but both enable an organism to reproduce.

Some bread molds and microscopic species of fungi bear spores in tiny structures called sporangia. In black bread mold, the sporangia form at the tips of upright hyphae called sporangiophores. Other hyphae called stolons spread over the surface of the bread. They are anchored by rhizoids (rootlike structures). Groups of sporangia usually form above the rhizoids.

Fungi Pictures

Fungi characteristics How a fungus lives. 

Fungi characteristics  Fungi live almost everywhere on land and in water. Some fungi are parasites that feed on living plants and animals. Other fungi, called saprophytes, live on decaying matter. Still other fungi live together with other organisms in ways that are mutually beneficial. Such a relationship is called symbiotic. For example, a fungus and an organism called an alga may live together symbiotically to form a lichen. Some fungi also live with the roots of plants in a symbiotic relationship known as a mycorrhiza. The fungus takes carbohydrates from the plant. In return, the fungus helps supply the plant with water and such important minerals as phosphorus, potassium, iron, copper, and zinc. Most species of trees, shrubs, and herbs have mycorrhizal relationships with fungi.



Mycorrhiza is the symbiotic association of the mycelium of certain fungi with the roots of certain higher plants,living in close relationship with the surface cells. Ex. It is possible with many, if not all, species of plant which normally form mycorrhizas in natural conditions to grow them in artificial surroundings without their appropriate fungi.

Fungi cannot produce their own food because they do not contain chlorophyll. They take carbohydrates, proteins, and other nutrients from the animals, plants, or decaying matter on which they live. Fungi discharge chemicals called enzymes into the material on which they feed. The enzymes break down complex carbohydrates and proteins into simple compounds that the hyphae can absorb.

Fungi Pictures

Types of Fungi.

Most kinds of fungi reproduce by forming spores. Some spores are produced by the union of gametes (sex cells). Others, called asexual or imperfect spores, are produced without the union of gametes. Many fungi produce spores both sexually and asexually. Many spores are scattered by the wind, and others are transported by water or by animals. Mushrooms and some other fungi forcefully discharge their spores. A spore that lands in a favorable location germinates (starts to grow) and eventually produces a new mycelium.

Types of Fungi. Yeasts can reproduce by forming spores, but many kinds of yeasts reproduce by budding. When a yeast buds, a bulge forms on the cell. A cell wall grows and separates the bud from the original yeast cell. The bud then develops into a new cell. Budding produces a large number of yeast cells rapidly.

XINGU TRIBE IN THE MIDDLE AMAZON RAIN FOREST

Amazon forest is one of the world's tropical forests in the Americas. Amazon Tropical Rainforest is the largest tropical forest in the world with a measure of 5.2 million km2. Around two-thirds of the Amazon tropical rain forest in Brazil, most of these forests include several countries namely Bolivia, Peru, Ecuador, Colombia, and Venezuela.

Amazon forest has a variety of flora and fauna as well as have high biodiversitas. The Canopy height measuring between 20-50 m, this is starta trees on top. All Species in the amount of trees per hectare can be found more than 280 species of trees. In addition to a diverse variety of flora are also various special fauna of the Amazon jungle.

In the Amazon jungle there is a large and long river named as forested namely the Amazon River. River of life around a giant snake named "Anaconda Snake" can reach a length of 9 meters. In the cinema shown that these snakes prey on humans by means of wind up helpless prey and swallow it.

But the more interesting thing in the middle of the Amazon jungle there Xingu tribe who still live without the use of clothing. Although their lives using the technology but the culture and characteristic of this tribe still preserved.

Their day-to-day life are using advanced technology such as television, parabolic, and so forth but still no use clothing as their native culture.

Some read using glasses for blurred vision had begun. This shows that they already know and using equipment such as befits the modern man.

The ceremonies performed XINGU tribe as customs and traditions continue to be preserved and conserved.

Body tribe in the Amazon jungle is tinged with a wide range of traditional tools and materials. According to their body color is a way to give them the differences between animals, that they profess belief.

Young woman with her legs must be marked using the tools and carded to remove the blood.








To reach the location of their residence should use aircraft or even pass the river far enough.
That glimpse XINGU tribe living in the middle of the Amazon tropical rain forest. They still keep their styles and traditions of their lives, as a unique case received much attention various media and is the subject of interest to the tourist.

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EQUAL CHANCE AND DISPERSAL LIMITATION OF TROPICAL FOREST COMMUNITIES

The equal chance or null community hypothesis is based on the idea that all species are equivalent in terms of their habitat requirements and growth rates, and therefore that every species has an equal chance of inhabiting openings as they become available in the forest.

Basically this hypothesis suggests that local diversity is based on the number of species contributing seeds in the local area, and that tree replacement occurs via random chance. Recent modelling studies indicate that simple null models of tropical forest communities can retain very high species diversity over long periods of time.

Although species in such a null community eventually go extinct via a ‘random walk’ process, the time to extinction is sufficiently long that speciation may act to add new species to the system. For such a null community to maintain very high levels of diversity, one more kind of process is also generally required : namely "dispersal limitation", which refers to the fact that seeds of a given species do not germinate in all possible sites that could potentially be occupied by that species.

The result of dispersal limitation is that many species fail to encounter one another. If dispersal limitation is sufficiently strong, competitive exclusion can be avoided entirely. Recent studies have shown that the absence of plant species at a given site is in fact commonly due to a lack of seed dispersal rather than their inability to compete in that particular area.

TROPICAL DEFORESTATION | Conservation And Sustainable Management Of Tropical Forests

Greatly refined estimates of tropical deforestation have recently been obtained through analyses of changes in forest cover in satellite images. For example, analyses of Landsat imagery covering the Brazilian Amazon indicated an increase in deforested area of 78.000 km2 in 1978 to 230.000 km2 in 1988, or a loss of approximately 6% of the total forested area. Tropical deforestation rates vary greatly across geographic regions, and have shown marked swings over the last decades. Through the 1980s the highest deforestation rates were observed in southeast Asia, but more recently deforestation has shifted to the neotropics and Africa.

In addition to the outright removal of forest, tropical deforestation also acts to fragment landscapes, a pattern of great conservation concern. Tropical forest fragments offer an insufficient amount of habitat for many larger or wide-ranging species of animals, and forest fragments can be seriously degraded by decreased humidity and high wind exposure near edges.

The internal fragmentation of tropical forests caused by selective logging is also a major concern. Studies suggest that low-intensity logging can allow for recovery of primary forest conditions within a couple of decades; however, heavy logging requires a much longer recovery period, and some highly degraded forests may not be able to approach pre-harvest conditions even after hundreds of years.

In many regions construction of logging roads makes forested areas far more accessible to those interested in further exploitation such as subsistence farmers, hunters and fuelwood gatherers. For example, when a commercial logger leaves the concession, subsistence farmers are able to penetrate deeper into the forest than would have previously been the case. Post-logging forest use is becoming increasingly intense due to high population growth rates in many tropical countries.

One partial answer to these difficulties is development of sustainable forestry practices in combination with improved conservation of remaining tropical forests. "Natural forest management" in which gap phase dynamics is emulated by harvesting has been advocated as a means of mitigating losses of diversity and ecosystem function while allowing continued timber harvests. Alternative harvesting practices, such as planning of harvest areas and skid trails, tree marking and directional felling, can be used to reduce the residual impacts of the harvest. Recent studies suggest that such reduced-impact logging in tropical forests can dramatically reduce post-harvest tree mortality. This results in greater retention of forest biomass, increased long-term value of the forest in terms of timber commodities, and more rapid recovery of pre-harvest forest conditions.

GAP PHASE DYNAMICS IN TROPICAL FOREST

Gap phase dynamics has been hypothesized to play an important role in the maintenance of high diversity in the tropics. When one or a few trees die, an opening in the canopy occurs, resulting in increases in light levels and other plant resources. Seedlings and saplings grow rapidly in gaps, competing for these resources; only one canopy tree ultimately will be able to occupy the space relinquished by the original gap-forming tree.

For gap phase dynamics to contribute to species diversity, one must assume that there are differences in resources (light, nutrients, etc.) associated with different parts of the gap (i.e. gap edge or
centre), and that different species are adapted to these differences. Such a pattern is referred to as "gap partitioning".


Larger gaps are expected to contain greater resource heterogeneity than smaller gaps, and thus should show higher diversity of regenerating trees. This hypothesis was recently tested by Stephen Hubbell and co-workers using data from a 50-ha mapped forest plot on Barro Colorado Island in Panama. Although gap sites were found to have greater species diversity of saplings, this was due entirely to higher stem density in the gap sites. The number of species encountered per stem did not differ between gap and nongap sites. Thus, recent evidence suggests that gap phase dynamics may not be the major mechanism for maintaining diversity in tropical forests. There is, however, clear evidence for important niche differences in tropical trees related to soil types and forest hydrology.