Blue-light-induced shift of the phototropic fluence-response curve in Pilobolus sporangiophores

• Published in: Planta 1989-10, Vol.179 (3), p.288-292
• Main Authors: Kubo, Hiroyoshi, Mihara, Hitoshi
• Format: Article
• Language: English
• Subjects: Arm; Coleoptiles; Curvature; Data lines; Fluence; Irradiation; Phototropism; Phycomyces; Scotophase
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/BF00391073

The effects of preirradiation with blue light on the shift of the fluence-response curve for the first and the second positive curvatures were examined in Pilobolus crystallinus (Wiggers) Tode sporangiophores. A 1-min preirradiation with blue light at 47 or 960 nmol·m-2 lowered the fluence-response curve for the first positive curvature and shifted the peak to a higher fluence. The fluence-response curve was shifted back to a lower fluence when a dark period was inserted between the preirradiation and the curvature-inducing light. This shift back to lower fluence was biphasic when the fluence was high (960 nmol·m-2), indicating the participation of two components in the phototropic reaction for the first positive curvature. The fluence-response curve for the second positive curvature did not seem to be shifted to a higher fluence region when fluence was varied by varying exposure time. However, the fluence-response curve obtained by varying the fluence rate of a 20-min irradiation period indicated that the second positive curvature was also shifted to a higher-fluence region by preirradiation with blue light. A small shoulder appeared on the fluence-response curve when preirradiation at a high fluence rate was given.