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Trillium Enthusiast Discussion List (and other Woodland pl= Trillium Enthusiast Discussion List (and other Woodland pl=
Mon Oct 11 06:37:06 CEST 2010


ants)"  <TRILLIUM-L at NIC.SURFNET.NL> <TRILLIUM-L at NIC.SURFNET.NL>
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From: Fern Hill <fernhill at VOICENET.COM>
Subject: Re: growth status - report/request
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Russ,

I have seen (and have somewhere in my reference piles) an article that
showed; measurements of photosynthetic ativity of trillium leaves. The
activity was maximum about the time the leaves were just reaching full
expansion and then declined with time by what looked like a power-law
relationship.  Although the plants can remain green under good conditions
for some time, the rate of photosynthesis has probably decreased to a low
level.

Senescence of the leaves is related to the availability (or lack of
availability) of cytokinins.  Plants with seed production remain green mu=ch
longer than plants that are vegetative because the ovary is a site of
cytokinin production.

Root tips are another site for cytokinin production.  Plants with large r=oot
systems growing in well aerated, but moist substrates without disease
pressure from root rots (pythium, phytopthera, fusarium mainly) may be ab=le
to translocate enough hormone to maintain green foliage into early fall. =It
is likely that SOME mycorrhizal organisms can inhibit the root rots so th=at
roots with those organisms in their mycorhizza will be more likely than m=ost
to remain green into the fall.

Leaf senescence in some cases is related to damage to the stem's vascular
system.  This can be due to the above rots or to strangulation from the
growth of new rhizome tissue and/or the apical bud.  Personal opinion at =the
moment is that vascular damage in the stem is the most likely cause of le=af
senescence when growing conditions are good.  When conditions are poor -
soil too hot and dry - then senescence will be due to lack of cytokinin
production because the root tips have stopped active growth.

John Gyer  Clarksboro  NJ  USA

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