Plants In Extreme Conditions

.. lf prevents the surface of the leaves from drying out and the stumpy branches which are coated in a fine white powder, reflects the suns rays.

The trunk and branches of the tree are filled with a soft fibre, which can hold a large mass of water but in the most severe drought the quiver tree takes a more excessive step. The leaves must have pores for gaseous exchange, which is vital to their manufacture of food, but these pores risk moisture being evaporated, so in extreme situations, the tree amputates itself. At a point just beneath the leaves, a branch will narrow so it can no longer hold the leaves; these then will fall off.The stump then seals itself and protects the water within it.

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The stumps never regrow their leaves but the trees water needs have been reduced and other leaves saved, and the tree can survive the drought with its meagre supply until the rains come. In forests, occasional destruction by fire started by natural causes, usually lightning, can have devastating effects. Temperatures of over 1000oC can be reached in these wooded areas, due to the ready source of fuel and assistance from the winds. Regular burning whether it is natural or started by man to regenerate the soil can eliminate many fire sensitive plants but also encourage species, which are adapted to fire. Features of these species include the possession of thick resistant bark and an ability to regenerate quickly after the passage of fire.Certain conifers have cones that are serotinous, that is they require the heat of the fire to bring about the separation of the cone scales and release the seed. Forest fires often bring about the domination of such species to the specific areas in which they occur, the eucalyptus of Australia being another example. So plants, by various means, solve the problem of surviving in extreme conditions.

Living in intense heat, with minimum water has been accommodated to, but heavy daily drenchings can just as equally cause problems. In South America, where Venezuela, Guyana and Brazil all meet, stands a group of massive rectangular, plateaux.Their flat tops rise above the clouds and their vertical rock walls are cascading with surging waterfalls. The biggest of these is Roraima, nine thousand feet tall and ten miles long, it is sometimes called, the Lost World.

It arouses images of a prehistoric place and indeed the mountain contains species that can be found nowhere else on earth, but the Roraima does not house survivors from a past age but unique species, isolated on its summit that have evolved extraordinary abilities to enable them to exist in an environment with the worlds heaviest rainfall. For simple plants like algae, Roraima provides an excellent habitat but for more complex ones, life on the water-drenched rocks proves more difficult. The sodden earth supplies very little in the way of nutrients, so the plants must find other ways of finding food.Bladderworts flourish here, they are water plants that are found in wetlands all over the world and they are so expert in trapping animals that they do not grow roots at all.

Their traps, little translucent capsules are able to absorb water and as they do they create a partial vacuum inside. The entrance is lined with sensitive bristles and if a small water creature touches one of these it acts as a lever, collapsing the entrance of the capsule. In then rushes the water bringing with it the creature and imprisoning it within a fraction of a second. The bladderwort then releases a digestive acid and within two hours it will have dissolved and consumed its victim and set its trap again. Another plant that prospers below the surface is water celery, they absorb all the oxygen and carbon dioxide they need from the water around them and it also utilises the water to pollinate.

The female flower opens its petals underwater, then rapidly moves to the surface.The male flower makes its journey to the surface even more quickly and on its way breaks its stem, at the surface it unfurls its petals and using the stamens as sails, heads towards the anchored female and they collide so violently that the pollen is knocked out of its anthers. Once the female flower has reached fertilisation, it closes, and its stem tightens into a corkscrew, recoiling back under the surface and there safely under water it develops its seed.

Most of the worlds surface is covered by seawater and most of it is beyond the reach of flowering plants. The only plants that can prosper here are floating single-celled algae, the simplest of all plants. They have all of the four fundamental needs in abundance. The water never drops more than a degree or so in temperature, there is always available sunlight and they are never in short supply of nourishment as rich flow of nutrients float up from the seabed.

They are the basis of all life in the sea and perhaps the least considered by humanity, tiny creatures of the sea consume them. Among these consumers are corals and crustaceans, molluscs and fish (plankton), which in turn feed the rest of the seabed. And more importantly we land animals depend on them, for they are the main factor in maintaining the balance of gases in earths atmosphere and they produce the majority of the oxygen we breath. Plants have colonised almost the earths entire surface; in fact only about 6% of the earth has no vegetation cover. They exist in the most extreme temperatures and survive and evolve in the strangest of environments. Yet they have one adversary, man who poses a greater threat than any other living thing.

In a relatively short period of time man has plundered the earth, leaving about 10% of the flowering plants close to extinction. We must begin to realise that this action threatens our fragile ecosystem that we ultimately depend on. It is time for us to cherish our green friends and instead of destroying them, start to feel privileged to co-inhabit this planet with them, for without them we will certainly perish. Science Essays.