DISTRIBUTION OF NORDITERPENE ALKALOIDS IN TALL LARKSPUR PLANT PARTS THROUGH THE GROWING SEASON

Authors: Ralphs, Michael; Gardner, Dale

Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2003
Publication Date: 9/9/2003
Citation: Ralphs, M.H., Gardner, D.R. 2003. Distribution of norditerpene alkaloids in tall larkspur plant parts through the growing season. Journal of Chemical Ecology. Vol. 29, No. 9 pp. 2013-2021

Interpretive Summary: Tall larkspur is an important poisonous plant on mountain rangelands causing acute poisoning and rapid death in cattle. Concentration of alkaloids decline as the plant matures rendering the plant relatively non-toxic towards the end of the growing season. The objective of this study was to measure the concentration and pools of toxic and total alkaloids in larkspur plant parts and evaluate the changes in these pools over the growing season as an estimate of diterpenoid alkaloid kinetics in tall larkspur. Alkaloid pools declined in the roots during early growth, while the pools in foliar parts increased, suggesting the alkaloids are synthesized in the roots and are translocated upward to the leaves and stems. During the late flower and pod stage, alkaloid pools in the leaves and stems declined rapidly while the pools in roots increased. However, we do not know if the alkaloids are translocated back to the roots or if they are catabolized in the shoots and synthesis in roots began anew. A relatively small amount of alkaloid is lost in the seeds

Technical Abstract: Previous research showed toxic and total alkaloid pools in tall larkspur (Delphinium barbeyi) increased during early growth then declined precipitously during the late flower and pod stage of growth. The objective of this study was to measure the concentration and pools of toxic and total alkaloids in tall larkspur plant parts, including roots, and to evaluate the changes in these pools over the growing season as an estimate of diterpenoid alkaloid kinetics in tall larkspur. Twenty entire plants were harvested at each phenological stage: beginning of growth in the spring, early flower, early pod, late pod and senescence. The plants were separated into the respective parts, freeze dried, extracted and analyzed for toxic and total alkaloid concentration and alkaloid pools were calculated. Concentration of toxic and total alkaloids in leaves and stems declined as the plants matured, while concentration in flowers and pods increased (P > 0.0004). Concentration of alkaloids in the root declined in the early growth, then increased at the end of the season (P = 0.002). Alkaloid pools in the root decreased during early growth, with a corresponding increase of pools in foliar parts, which suggests the alkaloids are translocated from the roots upward to the leaves and stems. In the late flower and pod stage alkaloid pools in the leaves and stems declined rapidly while the pool in the crown and roots tended to increase. It is still not known whether the alkaloids are translocated back to the roots or if they are catabolized in the shoots then synthesis resumes in the root in late summer and fall.