Friday, September 12, 2014

Lichens and Bryophytes - Bridge of Evolution in the Plant Kingdom.

Dr Abe V Rotor 

“Ah, but what good is rock when it loses the essence on which life rises?” - avr

Liverworts clinging on the lighted face of a rock. Like higher plant, they need sunlight to manufacture food by means of photosynthesis. The lower photo is stressed by limited moisture as summer approaches. 
Mosses make a carpet of soil which is actually the weathered surface of the rock. Bryophytes produce acidic substances that break down compounds of calcium, phosphates and other materials. It is this soil layer that invites higher plants such as isang dakot na bigas at the left.This fruticose lichen hangs on a garden fence at the Center for Ecozoic Learning and Livelihood in Silang Cavite. Actually it was transplanted from its natural habitat, and made as a natural decor. 

Fruticose lichen hangs on the trunk of tree. In spite of its epiphytic nature it does not harm its host because it is not parasitic. It shares however with the water and nutrients collected by the tree from rain and dust, as well as from the gradual wearing out of the bark tissues. 

Young colony of squamous-foliose type of lichen on the trunk on acacia. Note its spreading and coalescing growth that will soon carpet a large area. Lichen is a closely knit association of algae and fungi in a state of symbiosis. UP, Diliman, QC

Luxuriant growth of green alga on a tree trunk which is being invaded by moss. Soon the colony will be dominated and subsequently replaced by the latter. Succession in the plant kingdom is common among simple plants, more so among higher plants in forests, swamps, grasslands, and all ecosystems.

Mature foliose type of lichen, named after its leaf-like structure, grows on the trunk of pine tree in Benguet. This is the intermediate type of lichen, crustose being the simplest, and fruticose the most advanced.

Mature colony of liverwort wear down as summer approaches, drying up in the process. But come next rainfall, a new colony develops in its place. Dried liverworts and mosses are gathered as substrate for growing seedlings and orchids. 

Imagine a lowly moss as a tree, and a liverwort as a large green carpet shaped like a liver. A hornwort has pinnacles in Gothic style. It is when you are small that you see small things big, and big things present themselves as giants.

Bryophytes are the dwarfs of the plant kingdom, while the true or vascular plants are the giants. Mosses and liverworts are the early forms of plants, which botanists believe to have stopped evolving. What they were millions of years ago are what they appear today.

Observe a piece of rock covered with bryophytes. Under the magnifying lens you are looking at a miniature forest. It is thick and every space is taken by structures that look like stalks, leaves and other parts. On closer look these are not true organs because they lack vascular tissues, which in higher plants are for conduction of water and food and in providing support to the plant.

Since bryophytes are short-lived and seasonal, the soil deposit becomes thicker in each generation, while the borders extend to new frontiers. Soon whole trunks of tree, walls and rocks become covered like green carpet. As the bryophyte community reaches its peak and climax, more and more organisms become dependent on it. Insects frequent the place as a hunting ground for their prey.

Feel the softness of a carpet of mosses on the wall or rock. It is thick and spongy. Now this is important because when it rains the carpet absorbs and stores water. In the night and in the morning dew precipitates and settles down making the surroundings cool.

Months, years pass. New plants rise out in the middle of the carpet. You are witnessing plant invasion. Soon the bryophytes will lose their dominance to ferns, and ferns to tracheophytes - annuals, biennials and trees. The bryophytes have done their part.

“What good is rock when it loses the essence from which life rises?”
Ask the algae, the lichen, the moss and the liverwort.

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