On the Life History of Porphyra tenera

Abstract

Porphyra tenera is edible red alga cultivated in Japan. In late September many twigs of bamboos are set in the sea. “Autumn spores” appear and fix themselves on the twigs and begin to develop. In winter plants grow thick, When spring comes, they decrease and the twigs are taken away. In late spring, some poor plantlets, less than several milimetre so called “summer plantlets” are found here and there, in late summer they are lost in sight.
Carpospores are formed sexually on the winter plants, while monospores are formed asexually on some of the young plants in autumn especially in November and also on summer plantlets.
It remains in doubt, where the autumn spores come from, i.e. whether they are monospores from survived summer plantlets or carpospores rested during spring and summer. To make clear the nature of this autumn spores, diameter of spores and thickness of young sporelings on bamboo twigs were measured in whole year and compared each other. The results are as follows.
1. Monospores from summer plantlets and also from autumn plants are all 15μ in diameter (Fig. 1, C-F). Carpospores in winter are 11μ (Fig. 1, B). Autumn spores are also 11μ. (Fig. 1, A).
2. By thickness, young sporelings can be divided in two groups. Sporelings from monospores in summer and also in late autumn are belong to thicker group (Fig. 3, II & IV) and those from autumn spores in early autumn to thinner group (Fig. 3, I), i.e. the latter must be originated from smaller spores, nothing but carpospores in previous winter.
These results show that, a greater part of the carpospores in winter rest during summer and appear again in early autumn and make crigin of next winter plants. “Summer plantlets” may be in a side road of life history.