ON THE INHERITANCE OF FLOWERING TIME IN PHARBITIS NIL
1938 Volume 14 Issue 3 Pages 107-116
Details
1938 Volume 14 Issue 3 Pages 107-116
Regarding the flowering time, this plant is divided into early strains and late strains. The hybrid between an early strain and a late strain was intermediate in the flowering time, and segregated intermediate, early and late plants in the ratio 9:3:4 in F2. The raising of F3 plant confirmed this segregation. The correlation coefficient+0.907±0.0187 was calculated between the flowering time of F2 plants and their offspring.
From this genetic experiment, it has been concluded that the flowering time is a Mendelian character, lateness being recessive to earliness, and that the determination of the flowering time concerns with at least two pairs of quantitative genes, viz. early (ea) and late (la).
That the flowering time is made early by restricting the length of days, seems to be due to the condition of the manifestation of the genes for the flowering time, and not to the modification of the genes itself. And the differentiation of flower-buds may be determined by the genes for the flowering time.
Besides these causes of the genetical modification of the flowering time, the germination period is responsible for the determination of the flowering time. Late germination gives rise to the late flowering. As a cause of late germination, the hardness of seed-coat which is assumed as a dominant character, is considered. The white seed strain germinates earlier than the black seed one, and the flowers of the former bloom somewhat earlier than those of the latter.
Moreover the position of flowers on the stem is recognized as an element influencing the flowering time. A strain which has a recessive gene precocious, blooms early and a strain which has a recessive gene tardy blooms late. The former gene makes the flowers on lower nods of stem, bloom early. The latter gene make the flowers on the nods of upper branches, bloom very late, because the flower-buds of the lower stem shrink before growth. The gene precocious links to cordata, tardy to maple, the recombination percent of the latter being by far larger than the former. The gene late links to pear with 20.1 percent recombination.
