Spatial variation of steryl glucosides in Cycas micronesica plants: Within- and among-plant sampling procedures

Abstract

Amyotrophic lateral sclerosis-parkinsonism dementia complex (ALS-PDC) of the Western Pacific has been linked to the consumption of washed Cycas micronesica seed tissue. The search for a causal toxin in the seed tissue has generated decades of research, yet none of the published reports include an adequate description of sampling methods. We set out to design and conduct a study to serve as a model for future research. We used three populations of plants with similar recent plant life history, size, shade, seed load, and co-occurring species to determine intra- and interplant variation of four steryl glucoside variants. Variation was greatest among tissue types within seeds, intermediate among plants, and least among locations within plants. Results demonstrate the need of adhering to appropriate sampling protocols in cycad biochemistry research. Uses of appropriate sampling scheme and sample size are clearly required to avoid artifacts as this important area of research progresses.