Thank You Ray!
In my gh that is almost what exactly happens. During the winter I
rarely see temps over 75, which are quite common in summer inspite of
the cold location. The gh is heated only to 70 in the winter and on
some days the temps do not reach even that. The plants, as you state,
do quite well.

On Wed, 27 Oct 2004 08:56:46 -0400, "Ray"
wrote:

Think of "on the cool side" this way: if your plant can typically be
expected to see daytime temperatures between 65°F and 85°F, for the same
light intensity, growing it at 70° will give "better" plants than if they
are grown at 80°. Let me explain the (probably oversimplified) logic.
Please keep in mind that these are generalities, and the applications to
individual plants is quite varied.

More light results in greater generation of food and energy, and their
assimilation into the plant. Higher temperatures result in faster
metabolism, hence growth, with the accompanying consumption of those
reserves.

The application of more light intensity, however, is accompanied by
increased localized heating of the plant tissues, and too much can be bad
for the plant, even if not outright damaging. By having the environment be
a bit cooler, it offsets that heating effect to a degree.

If we consider that the plant's metabolism will also be reduced by the
cooler temperatures, we can see that those conditions will give the plant an
opportunity to benefit from making and storing more reserves while expending
less on vegetative growth - hence a sturdier plant that has more energy for
blossoms.

I also am aware of (but will not claim to "know" anything about) differences
in tissue growth rates effected by light levels - cell walls thicker in
higher light, cells elongated and thinner-walled in low light - which
explain the "soft and leggy" comment I made in an earlier post, but I'm sure
there's someone else out there who can explain that better than I.