[pf] seed speed

· Last Wednesday we three came back from a day-and-a-half on our farm,
pruning trees that we had helped plant in July (winter) 1996.

· I had worn some thick woollen socks, and after getting home here in our
Auckland suburb I spent more than 40 minutes pulling some long grass-seeds
out of them.

· One of the main concerns about global warming (greenhouse gases) is the
speed - such a great change in only a few decades, maybe a century.

· The time-scale for tolerable change is how fast plants of various kinds
can move, to keep up with the pole-ward movement of the climate they can
survive in. Our current climate change is too fast for almost all plants,
which can only travel roughly a hundred metres a decade.
  Parent plant produces seed, often just dropped, sometimes on the end of a
long stem which lays it down a couple of feet away, sometimes carried by
the wind (maple spinners), and sometimes carried by animals including humans.
  The seed (or the daughter "clone"-plant, if it's asexual vegetative
reproduction) will only produce a new parent plant if the conditions are
suitable. This is one reason why humans should leave uncleared corridors
between wild copses and forested areas; so not only ground-travelling
animals but also plants can travel north (in the northern hemisphere).

· The grass seeds I removed from my socks had travelled 180 km in 2 hours.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

· One little feature, that could be considered "design" if you have little
idea how long a billion years is, or the difference between a near
infinitesimal probability and a zero probability.

· These seeds each had two curved strong hairs or fibres at the tail, and
just back from the sharp point at the front they had backward-facing
spines, so small as to be hardly visible.

· Over a day-night cycle of humidity and temperature, the two curved fibres
straighten then curve again, pushing against whatever they're touching,
like the soil. The sharp point at the front is pushed through most
obstacles (my socks, a sheep's wool, the soil), and is held there by the
ratchetting effect of the backward-facing spines.
  So the seed digs itself deeper, day by day.

David.
David MacClement davd @ ihug.co.nz (remove spaces)
http://www.geocities.com/davd.geo/index.html#top
http://davd.tripod.com/GrAPR-011228.html#top
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