re: any theories about quality of light and growth?

A new baby!?  Ain't you got fun??  Don't know how anyone grows pumpkins with 
a new baby in the house.  The year our second was born I grew NOTHING.  
Nada.  Zip.  Buncha weeds out there.  Right, Brock??

>>I've noticed that on bright, sunny days my pumkins don't really >>grow at 
>>all during the day (maybe 1/4") and that virtually ALL of >>the growth 
>>comes at night.

Yes, the fruit gains more size at night.  This is normal and natural and 
good.  In the daytime it takes in energy through photosynthesis; at night it 
puts that energy to work to expand the fruit.  All living things have a 
natural ebb and flow - wake/sleep cycles, respiration, etc.  We would do 
well to enhance the AG's natural flow.  And for gosh sakes, don't WORRY 
about it.  You've made a good observation, but it isn't something that needs 
to be changed.

Here's yet another clip from the archives, authored by Rick Noffke (it's 
from December 97 in case anyone wants to go back and find the thread):

"It is true that on most all occasions where someone was able to take 
measurements frequently, the fruit puts on most of its weight at night. 
There is a physiological reason for this and Brock just about put his finger 
on it. There are two factors that allow the individual cells inside a fruit 
to expand. One is turgor pressure and the other is the elasticity of the 
cell membrane. There is a plant growth regulator (hormone) that when present 
in the right concentration makes the cell wall fluid and flexible thus able 
to expand. Then turgor pressue is what actually pushes the cell wall outward 
and thus it grows. Turgor pressure changes with water relations in the 
plant....just as brock said. If you pick a head of leaf lettuce during the 
middle of a hot August day it is fairly limp as compared to a head that you 
cut early in the morning right at dawn. I'm sure all of us have seen the 
rigidity of most plants in the early morning hours.

"Brock is right that the reason for this is that the plants water uptake is 
able to get ahead of the evapotranspiration that is going on during the day. 
Its all a function of how much water the plant is able to take up verses how 
much is being evaporated. At night the plant is not actively 
photosynthesizing so the stomates are mostly closed, thus reducing 
evapotranspiration. Also the relative humidity is lower so the potential 
difference is lower. You can think of a growing cell like a balloon. The 
turgor pressure is the air you blow in it to blow it up and the hormone is 
present to make the rubber flexible enough to expand.....and so they grow 
mostly at night. "


Have fun,
Beth


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