Effects of time of day, moisture stress, and frosting on the alkaloid content of Phalaris tuberosa

Abstract

Time of day had a slight effect on the level of N,N-dimethylated indolealkylamines in leaf tissue of plants of Phalaris tuberosa L. grown under controlled environmental conditions, and a somewhat larger effect on plants grown under field conditions. The alkaloid content was not affected significantly by moderate increases in moisture stress, but severe wilting caused an increase in the alkaloid content. The immediate regrowth from plants previously stressed had a higher alkaloid content than regrowth from unstressed plants. Severe moisture stress also caused an increase in certain related compounds, as yet unidentified. Frosting increased the alkaloid content more in plants receiving adequate nitrogen, and even more in plants grown at 21/16°C compared with plants grown at 15/10°.

Changes in alkaloid content are discussed in relation to field observations and previous experimental results on the toxicity of P. tuberosa pastures to sheep.