Adaptive strategies compared between the diploid and tetraploid forms ofOryza punctata

Abstract

In order to examine variations of characters with regard to their relationships to the conditions of habitats, 17 strains ofOryza punctata Kotschy ex Steud. were observed, with respect to 22 characters. Of them, 9 strains were diploid (2n=24) and 8 were tetraploid (2n=48). Descriptions of the original habitats were available for 14 strains. Among them, diploid strains were from open grasslands while tetraploid strains were from forests. Character differences due to the ploidy level were strongly intercorrelated. The diploid strains had a high reproductive effort, well developed awns, low regenerating abilities of excised stem segments, short anthers, and a high degree of seed dormancy, as compared with the tetraploid form. The mode of differentiation in adaptive attributes was similar to that observed in the case ofO. perennis, with the exception that genomic differentiation was involved in this species but not inO. perennis.