Growth of various ecotypes ofLemna paucicostata in Japan under various temperature conditions, and their wintering forms

Abstract

Lemna paucicostata in Japan is classified into 4 types, N-1, N-2, K and S types. S type strains which are distributed in southern Japan grew more rapidly than other strains at the temperatures of both 27 and 17C. With the extension of the culture period at 17 C to which the plants had been transferred from 25C, the growth rate increased greatly in S type strains, while it decreased in N-1 type strains which are distributed widely from Hokkaido to Kyushu, and particularly in those distributed in the northern area. S type strains survived winter mostly in the form of normal fronds under natural conditions at Kyoto (minimum temperature is lower than OC), while most of the fronds of N-1 type strains died after producing seed before winter. Thus S type strains are considered to have adapted to the climate of southern Japan so as to survive winter in the form of fronds, while N-1 type strains overwinter in the form of seed. N-2 type strains which are distributed in the northern part of the area adjacent to the Japan Sea produced turion-like fronds during winter under natural conditions, while none of the other strains did. The K type strain which was found only at the campus of Kyoto University overwintered only in the form of fronds which produce no seed.