Golden Plants

Jeremy Harbinson "Jeremy Harbinson" at users.tbpt.wau.nl
Thu Apr 25 08:53:43 EST 2002


The term variegation covers a multitude of sins; some variegated plants have
golden rather than white sectors, or zones, in the leaf; extend this to the
whole leaf and you have a completely golden leaf. An increase the amount of
flavones is not really necessary (though it might occur); these are present in
the most long-lived leaves in any case and they represent at least some of the
non-photosynthetic blue-light absorbing pigments that reduce the quantum yield
of blue-light for photosynthesis. The increase in  carotenoids is an interesting
one. Chloroplasts can degenerate to chromoplasts that are pigmented by
carotenoid pigments. If a yellow colour develops with time then the formation of
chromoplasts is certainly a plausible explanation; notably the chloroplasts of
many leaves of plants with greening mutations have a disorganised membrane
structure. It would be interesting to examine such chloroplasts for
chromoplast-like features.  So, reducing the amount of chlorophyll in a leaf, by
whatever means, will often be aasociated with in a relative increase in blue
light absorption, ie yellowing. This may occur over the whole leaf or over just
part of the leaf.

Cereoid* wrote:

> The feature to which you allude is called variegation. There are many
> possible causes of variegation one of which is chlorosis. However, that does
> not appear to be what Zillah is alluding to.
>
> A yellow leaf color can also be attributed to an increased amount of
> carotinoid plastid pigments or flavone cell pigments.
>
> Jeremy Harbinson <"Jeremy Harbinson"@users.tbpt.wau.nl> wrote in message
> news:3CC6DC3B.AACE6526 at users.tbpt.wau.nl...
> > There are many possible explanations for this feature. Virus infections
> can
> > cause chlorosis, and some ornamental variegated forms of plants owe their
> colour
> > to a virus. Nutrient deficiencies are also a cause, iron and manganese
> > deficiency will cause chlorosis in plants like Rhododendron that require
> an acid
> > soil but which have been planted on a soil whose pH is too high; other
> nutrient
> > deficiencies can also provoke chlorosis though I doubt that you would see
> these
> > deficencies on a normal garden soil. Other physiological stresses such as
> high
> > light in combination with low temperatures can cause loss of chlorophyll,
> and
> > thus chlorosis. Most commonly, though, the golden colour you refer to is
> the
> > result of a mutation that causes a low chlorophyll concentration in the
> leaf;
> > sometimes this requires bright light to fully manifest itself, and
> sometimes it
> > is has clear developmental path (eg young leaves green, older leaves
> yellow).
> > The causes of this chlorosis are not often understood in terms of the what
> the
> > missing gene product does, though is some cases this is known. For example
> in
> > some cases the golden colour is associated with severely reduced amounts
> of
> > chlorophyll b.
> > all the best,
> > Jeremy Harbinson
> >
> > Zillah wrote:
> >
> > > Does anyone know what makes plants go gold?  I have a Fatsia which was
> green
> > > when small, but is now very golden-green -  and makes a very bright
> accent
> > > in the garden.  I know there are many other golden cultivars of other
> plants
> > > such as Pelargoniums (e.g. Mrs. Quilter) and the Choisya called I think
> > > Sundance.  Just wondered how they come about initially.
> > > Thanks for reading this -
> >




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