ABSTRACT
The biosynthesis of ecdysteroids in plants and their distribution within the plant is well understood. The function of this review is to bring together the limited information available on these processes, and to attempt a synthesis and an integration of our knowledge of plant biosynthetic capabilities with the assumed function of these phytoecdysteroids as defense compounds against insect herbivory. The distribution of phytoecdysteroids within an individual plant is related to the organ type and position of organ on the plant as well as the state of development of the organ. The presence of phytoecdysteroids within a specific organ may fluctuate over the time course of growth, depending upon cycles of biosynthesis and transport. Few analyses of the fluctuation of ecdysteroids between plant parts were reported in the early period of phytoecdysteroid discovery, since the major emphasis was on isolation and structural characterization.
