. Also techniques such
as in situ hybridization for monitoring transcript abundance
in different tissues are not easily applied to constitutively
expressed genes since cell density and volume changes
affect the intensity of the signal. However, as more sensitive
techniques for measuring the levels of proteins and
transcript are applied to the study of purine and pyrimidine
nucleotide metabolism, the functional significance of these
housekeeping genes in plant development will become
more evident.