THE ANALYSIS OF PHYTOECDYSTEROIDS IN SINGLE (PREFLOWERING STAGE) SPECIMENS OF FAT HEN, CHENOPODIUM-ALBUM

A simple microextraction procedure together with an ecdysteroid-specific radioimmunoassay (RIA) have been used to quantify the levels of phytoecdysteroid in small (< 50 mg dry wt.) samples of plant tissues during the development of Chenopodium album. The existence of a distinct concentration gradient of phytoecdysteroids within the aerial portions has been confirmed by the detailed analysis of ecdysteroid titres throughout single plants. Ecdysteroid concentration increased steadily up the main stem of the plant. This pattern was reflected in the main leaves and in the petioles associated with the main leaves. The ecdysteroid concentration in the growing tip was higher than those at the top of the stem or in the uppermost leaves. High concentrations were also present in the roots. The distinct concentration gradient characteristic of the main stem, associated leaves and growing tip recurred in each of the side-shoots on a mature plant. The identity of the RIA-positive material is essentially identical in most parts of the plant, being mainly 20-hydroxyecdysone (20OHE) and polypodine B (PolB; 5-beta,20-dihydroxyecdysone) with much smaller amounts of more polar and less polar unidentified compounds. In the oldest leaves. the contribution of 20OHE and PolB is reduced and new polar and apolar compounds are found, indicating that catabolism of phytoecdysteroids occurs as leaves begin to senesce.