Bryophyta, Ancient and Tough

An ancient creature is waking up.  These creatures are small in stature but extremely tough.  They have been around longer than plants, although we often lump all green sessile things together.  Mosses are different though.

They have neither roots, nor vascular tissue, the plant equivalent of our circularity system.  They anchor to the substrate with little hold-fasts, somewhat like those giant algae, sea-weeds, and they drink though diffusion and osmosis.  They do well in places that are rich in airborne moisture.

Another things mosses lack is flowers and the associated seeds.  Like ferns, club-mosses, horsetails, and fungi mosses reproduce by spores.  By the millions.  They invest in quantity over quality and don’t pack any food or protection for their offspring before they cast them to the wind.  The spores will only germinate under perfect conditions.  Orchid growers are familiar with this problem, as orchids try the seed equivalent of this strategy.  Their dispersal strategy is like colonizing the galaxy by putting people in zip-lock bags and flinging them out of the solar system in the hopes that one of them eventually hit an earth-like planet.

This time of year the capsules that held the spores look like fossilized wind-socks.

Mosses are incredibly tough and individual stems from a colony can be very long lived.  A common way of judging the age of stair-step moss is the count the feather-like branches on a stem.  Five and seven year old moss stems are common and there are other mosses much longer lived than that.  An established moss colony may been in place for thousands of years.  Especially colonies in cold environments.

In the northern hemisphere we tend to think of plants and animals going dormant in response to cold.  If you can prevent the water in your tissues from freezing the danger for plants becomes one of dehydration.

Mosses, as I have said, are tough.  And Ancient.  They have some tricks they have learned over the hundreds of millions of years they have been around.  They learned these tricks before the ancestors of most of the things we see around us evolved.  Dinosaurs are latecomers to the party by the standards of the mosses.

Mosses dry up.  In a way the lessons learned as a spore transfer to the adults.  Most of their water evaporates, and as it does so the moss tissues curl in predictable ways.  The pores through which they breath close. Mosses can wait a long time like that.  Some mosses are so good at surviving this way that they grow in deserts.

Air in cold environments often contains less moisture than desert air.  Vermont has been even dryer than usual and many of the fir-cap mosses are still tightly furled, waiting for water.  Many look like the dry spires in the picture above.

Others have found enough water to wake up.

Like sponges, moss colonies trap water and fine debris.  The debris falls to the ground in the suddenly still water and becomes a nutrient supply for the mosses once they rehydrate.  Much like flowers they open as their tissues fill with water.

The growing tip opens as it hydrates revealing a tight furl of nascent microphylls (moss and clubmoss leaves) tinged a rosy hue.  Cold is well and good for living slowly, but growth requires warmth and the tips of the moss are shaped like little parabolic reflectors.  They trap both water and the sun’s light.  The reddish color may help them adsorb the long-wave understory light once the forest above leafs out.

From now through summer the new spore capsules will ripen, and come fall and winter they will scatter their spores across the landscape to drift with the wind, flow with the water, and run across the snow.

Unlike the poor fellows in zip-lock bags hurtling between the stars, the mosses have stacked the odds a little for their offspring.

Where water splashes moss may grow.  Where wind dies and lets drop what it carries moss may grow.  Where snow is late to melt moss may grow.

NOTE: The three close-in photos were taken though a 10x hand-lens held to the front camera of an iPhone4.

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2 comments on “Bryophyta, Ancient and Tough

  1. Isaac says:

    It’s nice to see bryophytes getting some love. People pay too much attention to flowers!

  2. Nice post … and nice photos from your iPhone.

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