Effects of Light upon the Germination of Spores of Ferns II.

Abstract

Experiments were performed to make clear the effect of light and darkness, on germination of the spores of Dryopteris crassirhizoma which have a typical character of “Long Day Seeds”. 1) A high germination rate was obtained by a single illumination so long as its duration is fairly long, for exmple, 18 or 24hours. However, the illumination on the 4th day in the presoking time had rather weak effect on the germination, as the light-sensitivity changed with the lapse of presoaking time, as observed in the case of tabacco seeds (Fig. 3). 2) One long light period mentioned above was divided into two short light periods, L1 and L2 with insertion of one dark period D1. With varying dark periods, it was revealed that the dark period optimum for germination was 12-18 hours, regardless of the lengths of both light periods. 3) The germination rates secured by insertion of a dark period were higher than the rates obtained with one continuous exposure to light whose length was Table 1. Effects of two light periods of different duration at optimum dark period of 15hours Table II. Effects to two light periods of different duration at optimum dark period of 15hours. equal to the total period of L1+D1+L2. Therefore, it might be concluded that the dark period inserted between two light periods promoted the germination of the spores positively. 4) With various combination of L1 and L2 and an optimum dark period of 15 hours, it was recognized that the germination rates were generally increased in proportion to the total length of both the light periods, and had no direct relation to each length of them. In this photo-germinating character, the spore of Dryopteris crassirhizoma is obviously different from the seed of Epilobium cephalostigma.