Independent mode of action of cyanide and light on lettuce seed germination

Gaseous hydrogen cyanide stimulated subsequent lettuce seed ( Lactuca sativa L. cv. Grand Rapids) germination in darkness when applied for 1 or 22 h. Optimum concentrations were 5 × 10-5 M and 10-6 M, respectively. However, seeds did not germinate in the presence of HCN even at 10-8 M. The effects of unsaturating red light (R) and HCN (1 μM) showed a slight synergism. On the other hand, there was no difference between the effects of the sequences HCN – R and R – HCN. Stimulation of lettuce germination by an HCN pulse was practically not affected by far-red illumination, independently of the sequence of treatments. It was concluded that the primary stimulatory effect of HCN is of a regulatory character. Cyanide controls a regulatory point different from that affected by activated phytochrome.