Phytochrome and Seed Germination. I. Temperature Dependence and Relative PFR Levels in the Germination of Dark-germinating Tomato Seeds

Abstract

Germination of the dark-germinating seeds of 3 varieties of tomato is controlled by the phytochrome system. Germination is inhibited by far red(FR) radiation and repromoted by red(R) applied after FR. At low temperatures 17-20[degree] C, a single, low energy FR irradia-tion is sufficient to inhibit germination in all 3 varieties. At higher temperatures FR is less effective in the inhibition of germination of the tomato seeds and prolonged irradiations are necessary. The phytochrome fraction present as Pfr in the dark-germinating seeds of the "Ace" variety of tomato seeds is about 40% of the total phytochrome present.