The most important harvested organs of crop plants,
such as seeds, tubers and fruits, are often described as
assimilate sinks. They play little or no part in the
fixation of carbon through the production of sugars
through photosynthesis, or in the uptake of nitrogen
and sulphur, but import these assimilated resources to
support metabolism and to store them in the form of
starch, oils and proteins. Wild plants store resources
in seeds and tubers to later support an emergent
young plant. Cultivated crops are effectively storing
resources to provide us with food and many have
been bred to accumulate much more than would be
required otherwise. For example, approximately 80%
of a cultivated potato plant's dry weight is contained
in its tubers, ten times the proportion in the tubers of
its wild relatives (Inoue & Tanaka 1978). Cultivation
and breeding has brought about a shift in the
partitioning of carbon and nitrogen assimilate between
the organs of the plant.
