Relationship between Germination and PFR Level in Spores of the Fern Lygodium japonicum

The relationship between germination and P_FR level in sporesof the fern Lygodium japonicum was investigated. Percent P_FRestimated from direct spectrophotometric measurement of sporesincreased with the logarithm of total fluence of 660 nm-light.The transformation from P_R to P_FR was saturated by giving ca.200 Jm^–2 of 660 nm-light and half-saturated by ca. 55J^–2 of 660 nm-light. Clear positive correlation was observedbetween % P_FR levels and germination rates in spores irradiatedwith 660 nm and/or 730 nm-light, or with 686 or 700 nm-light.The P_FR percentage in spores was raised to 16–34% by blue(415 nm) light irradiation. This P_FR level was enough to causesome germination when produced by monochromatic light of redto far-red region, but blue light did not cause any germination. After 660 nm-light irradiation, the P_FR level decreased graduallyin darkness (25±1°C) and P_FR completely disappearedin 8 h, but 730 nm-light given even 16 h after 660 nm-lightirradiation inhibited germination. ⁴Present address: Tropical Botanic Garden and Research Institute,Navaranga Road, Trivandrum 695 011, India. (Received March 15, 1983; Accepted June 4, 1983)