Margaret
While a cellular approach may work well
for understanding some aspects of plant growth in other cases a
different angle may be more helpful.
Cold can cause major problems to living things,
as should their cells freeze the ice crystals which form will usually
cause lethal damage. Many organisms simply avoid freezing
temperatures by such means as living naturally in frost free
areas, entering into protective hibernation/dormancy or in the case of
annual plants spending the cold time in the form of dry seeds, but
some animals and plants have adapted to freezing cold by
developing more specifc survival strategies
Where actual resistance to freezing
temperatures occurs in the living world it follows one of two pathways.
The one used by mammals and birds is a form of central heating
reinforced in most cases by an insulating outer body covering, but living
things which cannot regulate their body heat instead may develop a natural
antifreeze in their cells. This second method may be found
in various cold blooded animals which lack the ability to control
theri body temperature and also in many cold resistant
plants.
While deciduous trees can gain considerable
cold protection from dropping their easily-damaged foliage for the
winter, evergreen trees do not have this facilty (though a few normally leaf
retaining plants I have grown can if
pushed adopt a sort of pesudo dormancy and become leafless
in my garden with its slight frosts. Plants which I have come
across which show this trend include quite a few varieties of fuchsia and
also lantana).
Any evergreen shrubs and trees which can live
with frost and come through winter regularly with little or no cold
damage I think we may presume are among those which can produce
antifreeze and this will I am sure be the case with the stock used to graft
your winter-tender species.Once the graft is fully established substances
produced in the roots and stem of the stock will be shared with the scion at
least to some extent, thus conferring a degree of winter hardiness in the
normally tender C.ficifolia..
Moira
