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Dear All, Sept 6, 2012
Have been to the North Alton woodlot 55 times since Mar 20, to cut,
split or pile wood, maintain roads, etc. and have seen ticks only twice; one
in late April or early May (no record) and one Sept 4.
The ample rain of Sept 5 (90 mm on my unofficial raingauge) lowered the
branch tips on the Norway Maple by up to 5'. I have seen this (or
equivalent) many times but it suddenly clicked that water content of leaves
must have increased substantially.
My 1st year Botany text (Holman & Robbins, 1939) tied the large
intercellular spaces of spongy parenchyma to CO2 movement; Where stomata are
sparse or absent on the upper epidermis of leaves "...the supply of carbon
dioxide to the palisade cells during periods of active photosynthesis would
be insufficient were it not for the loose nature of the spongy parenchyma."
One must wonder why a very porous layer would be needed for gas transfer
within the leaf if a few widely spaced slits on the lower eperdermis
suffice.
On the other and, the open structure of the spongy parenchyma of leaves
would be well suited to capture of rain, mist or fog water and or storage of
water during periods of low moisture stress without tissue rupture or
distortion. Closely packed or closely spaced cells would not be able to
change much in size without causing tissue distortion as in split Tomato
fruit or curled Corn leaves (there is a Plant Morphology term for
distribution of cell enlargement that avoids tissue distortion but it
escapes me).
A small patch of Psythyrella condolleana sprouted on the lawn today,
probably primed by the earlier rains and given a final push by yesterday's
rains.
Yt, Dave Webster, Kentville
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