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Isoetes
Robert Hudson had asked about the issue of how much CO2 plants can obtain
from the soil/substrate vs the water column. Well plants like the soft water
Isoetes group gets 60-100% from their roots. One of it's terrestrial genera
has no stomata at all(Stylites andicola)! It gets all of it's CO2 from the
ground only. That's weird......
But back to the rest of the plants....... wetland plants in the few studies
done it seems that about .25% of the CO2 seems to come from the soil in
nature. Not much. A few. A few get their CO2 from the substrate but only
after it leaves the substrate as CO2 being dissolved into the water
column(water soldier, Stratioles).
I'll look into it further but it seems to be the case thus far from my
readings.
The Isoetes are soft water plants and most soft water plants would have to
pursue this avenue since there's no HCO3 source nor does the air provide
much/enough so they go down into the ground for Carbon. Another weird thing
about these already weird plants is that some have CAM metabolism like some
succulents and cacti.
A water plant that has the same metabolism as a cactus? What's up with that
one? Well just like a cactus which doesn't want to lose any water so it
stores CO2 it gets at night when water losses are at their lowest and doles
it out during the light phase to make sugars, the Isoetes waits till
darkness when the CO2 rises back up from respiration/decomposition/diffusion
and stores it for when the other plants/algae start taking in CO2 during the
day when CO2 becomes extremely low in the water column. And then there are
the schematics and evolution of this group.....
Regards,
Tom Barr