| Photo Information |
Copyright: Francine Malo (NinaM)
![Gold Star Critiquer/Gold Note Writer [C: 566 W: 0 N: 1388]](http://i1.treknature.com/misc/g-n-g.gif) (4593) |
| Genre: Plants |
| Medium: Color |
| Date Taken: 2007-11-10 |
| Categories: Lichens |
| Camera: Canon EOS 40 D, Canon 100 f2.8 Macro |
| Exposure: f/16, 15 seconds |
| Photo Version: Original Version |
| Date Submitted: 2007-11-10 11:48 |
| Viewed: 501 |
| Points: 22 |
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| [Note Guidelines] Photographer's Note |
Hi everyone, today I didn't go out even though it is sunny and beautifully November out there. I might take a peak later. But I have found this small piece of wood in the backyard the other day and picked it up because I thought it was beautiful. It's about 1 inch x 3/4 inch and I decided to "macro" it. The sun was beautiful on the kitchen table, weak and low at that time of year. I had to do quickly because light was moving so fast accross the table where my set up was installed: a bean bag for the camera, a little plastic holder for the wood and I was relying on the orange of the table to make a nice background. Not that simple at that scale to follow the sun!
To my delight, I picked this photo because it looks like coral reefs in the ocean. I am always prone to play with different scales in nature, it's incredible how you find one pattern in one scale and the same at another one: I am always amazed to grasp in "real life" what they call fractal theory. That is why I find macro photography so exciting, it's like exploring the whole universe by going small. Hope you like it even though I am not an expert at macro: I have fun! Have a good week-end!
Francine
WIKIPEDIA on lichen:
Lichens must compete with plants for access to sunlight, but because of their small size and slow growth, they thrive in places where higher plants have difficulty growing.
A major ecophysiological advantage of lichens is that they are poikilohydric (poikilo- variable, hydric- relating to water), meaning that though they have little control over the status of their hydration, they can tolerate irregular and extended periods of severe desiccation. Like some mosses, liverworts, ferns, and a few "resurrection plants", upon desiccation, lichens enter a metabolic suspension or stasis (known as cryptobiosis) in which the cells of the lichen symbionts are dehydrated to a degree that halts most biochemical activity. In this cryptobiotic state, lichens can survive wider extremes of temperature, radiation and drought in the harsh environments they often inhabit.
Lichens do not have roots and do not need to tap continuous reservoirs of water like most higher plants, thus they can grow in locations impossible for most plants, such as bare rock, sterile soil or sand, and various artificial structures such as walls, roofs and monuments. Many lichens also grow as epiphytes (epi- on the surface, phyte- plant) on other plants, particularly on the trunks and branches of trees. When growing on other plants, lichens are not parasites; they do not consume any part of the plant nor poison it. Some ground-dwelling lichens, such as members of genus Cladina (reindeer lichens), however, produce chemicals which leach into the soil and inhibit the germination of plant seeds and growth of young plants. Stability (that is, longevity) of their substratum is a major factor of lichen habitats. Most lichens grow on stable rock surfaces or the bark of old trees, but many others grow on soil and sand. In these latter cases, lichens are often an important part of soil stabilization; indeed, in some desert ecosystems, vascular (higher) plant seeds cannot become established except in places where lichen crusts stabilize the sand and help retain water.
Lichens may be eaten by some animals, such as reindeer, living in arctic regions. The larvae of a surprising number of Lepidoptera species feed exclusively on lichens. These include Common Footman and Marbled Beauty. However, lichens are very low in protein and high in carbohydrates, making them unsuitable for some animals. Lichens are also used by the Northern Flying Squirrel for nesting, food, and a water source during winter.
Although lichens typically grow in naturally harsh environments, most lichens, especially epiphytic fruticose species and those containing cyanobacteria, are sensitive to manufactured pollutants. Hence, they have been widely used as pollution indicator organisms. When growing on mineral surfaces, some lichens slowly decompose their substrate by chemically degrading and physically disrupting the minerals, contributing to the process of weathering by which rocks are gradually turned into soil. While this contribution to weathering is usually benign, it can cause problems for artificial stone structures. For example, there is an ongoing lichen growth problem on Mount Rushmore National Memorial that requires the employment of mountain-climbing conservators to clean the monument.
Many lichens produce secondary compounds, including pigments that reduce harmful amounts of sunlight and powerful toxins that reduce herbivory or kill bacteria. These compounds are very useful for lichen identification, and have had economic importance as dyes or primitive antibiotics. Extracts from many Usnea [2] species were used to treat wounds in Russia in the mid-twentieth century. Orcein and other lichen dyes have largely been replaced by synthetic versions [3].
The European Space Agency has discovered that lichens can survive unprotected in space. In an experiment led by Leopoldo Sancho from the Complutense University of Madrid, two species of lichen – Rhizocarpon geographicum and Xanthoria elegans – were sealed in a capsule and launched on a Russian Soyuz rocket on 31 May 2005. Once in orbit the capsules were opened and the lichens were directly exposed to the vacuum of space with its widely fluctuating temperatures and cosmic radiation. After 15 days the lichens were brought back to earth and were found to be in full health with no discernible damage from their time in orbit.
Lichens are informally classified by growth form into:
* crustose (paint-like, flat), e.g., Caloplaca flavescens
* filamentose (hair-like), e.g., Ephebe lanata
* foliose (leafy), e.g., Hypogymnia physodes
* fruticose (branched), e.g., Cladina evensii, C. subtenuis, and Usnea australis
* leprose (powdery), e.g., Lepraria incana
* squamulose (consisting of small scale-like structures, lacking a lower cortex), e.g., Normandina pulchella
* gelatinous lichens, in which the cyanobacteria produce a polysaccharide that absorbs and retains water.
Paleontology
The extreme habitats that lichens inhabit are not ordinarily conducive to producing fossils.[3] Though lichens may have been among the first photosynthesizers to colonize land, the oldest secure fossil lichen that has been recovered is in thin sections of Early Devonian Rhynie chert, about 400 million years old. |
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