Abstract
Droplets of heavy metal salts (1mM) were applied to holes punctured by a glass capillary tube on the surfaces of detached rice leaves, and the accumulation of phytoalexins in tissues surrounding the holes and in droplets were quantitated with gas chromatography-mass spectrometry-selected ion monitoring (GC-MS-SIM). This analytical method was highly sensitive and accurate, minimizing material and time requirements. Copper ion treatment induced two diterpenoid phytoalexin groups of rice plants, i. e., oryzalexins A, B, C, and D, and momilactones A and B. These phytoalexins differed in diffusion rates from leaves into droplets. Among the momilactones, momilactone A showed a marked induction. Among the oryzalexins, oryzalexin B was induced to the greatest extent. The accumulation of momilactone A was first noted 12hr after application of copper ion, reaching maximum after 72hr. As these phytoalexins accumulated brown spots appeared in areas surrounding the punctured holes. Iron and mercury ions made up approximately 37% and 20% of the elicitor activity of copper ion, respectively. Manganese and cobalt ions hardly showed any elicitor activity.
