In article ,
"David E. Ross" wrote:

On 1/3/2010 5:13 PM, Wildbilly wrote:
In article
,
Frank wrote:

On Dec 29 2009, 11:56 am, "David E. Ross"
wrote:
On 12/22/2009 11:03 AM, Frank wrote:

Sunleaves are the large leaves at the base of and associated
with secondary branches.

I assume their role is to feed the secondaries with products
of photosynthesis and release of stored mobile nutrients such
as N, P, K.

That being understood, what is the effect of pruning out
one or the other, as when making a plant into a bonsai?
If we're trying to arrest stem elongation by pinching back,
does it leave the plant stronger to remove just the tip in
question without removing the sunleaves?

I don't think "sunleaves" are any different from other leaves. They are
larger primarily because they are on branches that are sufficiently
mature to sprout side branches. When the side branches mature, they too
will have larger leaves. All leaves participate in photosynthesis once
they have opened up from their buds.

Leaves -- even the larger leaves on mature stems -- do not usually store
or release N, P, and K. Leaves use those nutrients to produce sugars.
Only fleshy leaves (e.g., on succulents) might store any nutrients other
than sugar.

What accounts for the various spots and blanching on older
leaves specific to a given deficiency? I would have thought
nutrient translocation to be the cause.

Plants will, of necessity, use what energy and nutrients they have for
their meristems (growing tips). As the plants get larger, and they have
more meristems, more resources are diverted from the earlier leaves, to
their detriment, to the benefit of the new growth.

Quite correct. Nutrients are diverted to the meristems, but they are
not depleted from the older leaves. It's just that the older leaves
fail to receive as much nutrients as they received while still growing.

In the meantime, the older leaves still receive enough nutrients to
engage in photosynthesis, producing sugars that are transported by sap
to the meristems and elsewhere within the plant. Other plant tissues
convert the sugars into starches, cellulose, and other carbohydrates.
And still other plant tissues combine the sugars with other nutrients to
produce proteins and oils. It does not take large basal leaves to
produce sugars; any leaf containing chlorophyll can do this. Even stems
containing chlorophyll can do this.

Still, new growth up above, means shadows below, at least for plants
that I have grown.
--
³When you give food to the poor, they call you a saint. When you ask why the poor have no food, they call you a communist.²
-Archbishop Helder Camara

http://www.jpost.com/servlet/Satelli...cle%2FShowFull
http://countercurrents.org/roberts020709.htm