Mirov (The genus Pinus, 1967) mentions (pp. 402-403): "It has been known for a
long time that pines have the capacity to photosynthesize in winter, although
opinions differ on this subject. According to some investigators,
photosynthesis continues in pines throughout the winter (Zacharowa, 1929);
others have found that in the northern climates, it practically ceases with the
advent of cold weather and is resumed in the spring (Ivanov & Orlova, 1931). In
winter, the slowdown is caused by inactivation of the chloroplasts. Their
appearance and their position in the cell are changed by the low temperatures.
With increasing temperatures, the normal shape and distribution of the
chloroplasts are restored. . . . More recent studies of seasonal conditions
of chloroplasts were made by Parker & Philpott (1961). In winter, a network of
reticulum occurred in all living cells, aparently enmeshing mitochondria as well
as chloroplasts, and in sieve cells extending through the plates."
I don't have access to the cited papers, but they might be worth following up.
The network of reticulum I guess could be connected with the prevention of ice
crystal formation at low temperatures, which would othewise damage the cells.
Removal of some of the chloroplast contents would also render them less liable
to damage when water in them expands on freezing.
It is not just pines which show this phenomenon; compare e.g. the winter foliage
bronzing of two cypress family species, Microbiota decussata and Cryptomeria
japonica (particularly its cv. 'Elegans').
Mike the Tree Doctor wrote:
>> No, your are correct - I refer to the seasonal yellowing phenomenon that
> usually reverses itself come Spring.
>> Any thoughts on why the trees cannibalize chlorophyll? Is there hard
> experimental evidence on the nature of the 'benefit' vis a vis winter that
> the tree obtains via this process? Is it a mere shunting to the roots of N
> and Mg rich solutes resulting from the lysis of chlorophyll? Is there a
> concomitant reduction in the efficiency of photosynthesis at the yellow and
> red ends of the absorption spectrum??
>> Thanks for your input!
>> Mike the Tree Doctor
>> michael frankis <michael.frankis at which.net> wrote in message
> news:382C7A69.3686CBC6 at which.net...> > Is this something new, that has only recently started happening, or are
> you just
> > noticing for the first time something that has always happened?
> > Reason I ask, is that many conifers turn yellowish in winter, a character
> > usually cited as reducing the amount of chlorophyll so as to be able to
> > with extreme winter cold more successfully. What I don't know is whether
> > observations refer to this, or to something else new and potentially more
> > serious. Please let me know.
> > In Scots Pine (Pinus sylvestris), this yellowing is variable with origin -
> > Siberian origins go the yellowest (to a drab mossy green), while Turkish
> > (var. hamata) hardly turn yellow at all (which is why they are preferred
> > christmas trees in the USA). One selected clone of Scots Pine (named as
> > 'Aurea') turns such a bright yellow in winter, it makes a good selling
> point for
> > garden use.
> > I'll try and dig out some references to it over the next few days.
> > Michael Frankis
> > Newcastle, England
> > Mike the Tree Doctor wrote:
> > > Folks:
> > >
> > > I have to pose a general question to any with experience in the matter
> > > seasonal chloroses in conifers - principally hard pines.
> > >
> > > I have a situation in southern New England (Zone 4) where for multiple
> > > now I have observed gradual yellowing of pitch pines (Pinus rigida),
> > > mtn. pine (Pinus pungens), and to a lesser degree 'Waxman' eastern white
> > > pines as each winter approached.
> > >
> > > The trees in question are from multiple provenances, in multiple soils,
> > > obtained in multiple years. Not each individual of a species for lot is
> > > affected. I have done the usual battery of soil and paired soil/foliage
> > > nutrient assays - all are inconclusive. Soil pH, iron, manganese,
> > > Ca:Mg ratios are all in the ball park, but micronutrient concentrations
> > > foliage are off in some tests. All trees have been treated with NPK,
> > > sea-kelp extracts, humates, etc. at various times.
> > >
> > > Generally speaking, the condition goes away or attenuates greatly with
> > > onset of Spring - any ideas or similar experiences.
> > >
> > > Thanks!
> > > --
> > > Mike the Tree Doctor
> > > www.treedoctors.com
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