TRibute to the tree in its day...

The question today is What is left of the trees, these magnificent creatures that are with us and dominate our landscapes? How they have dominated the valleys and mountains of our lands, particularly in the Tropics, covering it with a green carp?

Trees provide under its canopy, countless ecosystems where life has evolved to produce an explosively rich terrestrial biodiversity. They also protect and enrich the soil and retain rain water in ecosystems, provide shade and provide food for a chain of living organisms.  Today the forests are predominantly composed of vascular plants, which means with a circulatory system to conduct water and nutrients (but without a heart), and a cellulose skeleton on which they grow to stay closer to the sun. Its leaves have green granules which capture solar energy through photosynthesis. Cellulose, a polymer (chain of molecules) the consists of rings containing carbon is one of the most abundant organic substances in the tree and is the main component of wood.

Plants, through photosynthesis, capture carbon dioxide from the air, CO2, since ancient times, trapping it to form sugars and other substances such as cellulose. It is estimated that the primitive atmosphere contained abundant CO2, that by photosynthesis was transferred to the earth, and eventually to organic deposits such as coal, oil and natural gas. Today, exists in small amount (0.035%) of carbon dioxide in the atmosphere and its presence is important to keep the hot surface because without the greenhouse effect the Earth's surface would be frozen. We know that it’s presence in excess, would make life impossible, the extreme case is the planet Venus with a 97% CO2 atmosphere and an atmospheric temperature of 900oC! (It is two times hotter than a conventional oven, and therefore no water or ice).

Another vital gas for living beings is oxygen (O2), which is not found in another part of the solar system, only on earth. It is proposed that the atmospheric oxygen, which now represents 20% of the air, is the product of photosynthesis, which captures the CO2 and release it as by-product.  All plants and animals use this oxygen for combustion of the sugars we get to eat. Our life depends on photosynthesis because it is the biological mechanism that captures solar energy directly, and introduces oxygen into the atmosphere which allows the burning of sugars when cellular respiration. Oxygen is very reactive and its abundance in the atmosphere is unusual. For this reason, NASA researchers use oxygen as a marker of life in the investigation of planetary systems outside our solar system.

Life originated in the sea and therefore we have to seek the origin of the trees in the marine ancestors, photosynthetic cyanobacteria far above the vascular plants and who were responsible for photosynthesis during most of life at the sea. Its fossils remain dating back up to 3.5 billion years ago, long before the invasion of life on earth. Cyanobacteria are bacterial cell type that developed green pigments that function as antennae to capture sunlight and bringing this energy to the synthesis of many substances.

Vascular plants are composed of other cells called eucariónicas, much larger, a core, able to trap and digest small bacteria. To visualize the difference in size, if the plant cell were of the size of a watermelon, the bacteria would be of the same size of the seeds. Studies indicate that millions of years ago cell eucariónica ingested a cyanobacterium and ended up developing a symbiotic (mutually beneficial relationship) between them, that during the evolutionary time was consolidated with the transfer of a lot of the genetic information to the core of the bacterial plant cell, now a days the ancestral bacteria, the chloroplast may not be reproduced without the cell nucleus. With a simple light microscope  we can see the clusters of green pigment called chlorophyll, within the cytoplasm of the cells in a leaf. Through this journey this wonderful plant life sprouted across the land. The invasion of the land is a recent event in the history of life, the forests are now very different to primary forests.

There is a special gift waiting a few hours from San Jose in the upper parts of the National Park Braulio Carrillo, a forest of tree ferns which takes us back through time to the forests of the Devonian, 350 million years ago. A treasure that is priceless. Thanks to Life, thanks to the trees!

Coordinator Peace with Nature, Casa Presidencial.