An overview of plant macromolecular systematics during the period 1950-2000
is presented. The general Vend during this period has been from secondary
compounds (not included in this review) to proteins and then to DNA. Amino
acid sequencing of proteins from the 1960s through the 1970s, while having
very little lasting impact on plant phylogeny, raised a number of issues th
at continue to be discussed. Enzyme electrophoresis has provided data at th
e population and lowest taxonomic levels, and has stimulated discussions an
d studies on the tempo and mode of speciation. DNA data, initially from res
triction sites and subsequently from sequencing, have been employed extensi
vely in generating phylogenies for groups ranging from species and genera u
p to plants as a whole. Despite the potential, molecular data have been use
d infrequently to study evolutionary processes and speciation. Phylogenies
generated from molecular data provide the necessary framework for such inve
stigations. The incorporation of molecular data has had a positive stimulat
ory effect on plant systematics during the past five decades, but the resul
ts of molecular studies are of greatest value when they are part of more br
oadly-based investigations that include more "traditional" approaches such
as field and chromosomal studies. However, one of the side effects of incre
ased emphasis on molecular systematics has been less emphasis on "tradition
al" systematic studies. Hopefully, the next five decades will witness a mel
ding of the old and new to continue the "unending synthesis" that makes sys
tematics such a vital discipline in plant biology.