Meiosis in Diploid and Tetraploid Plants of <i>Linum angustifolium</i> Huds

Abstract

1) The diploid and tetraploid forms of Linum angustifolium HUDS. were cytologically analysed. The somatic number was 30 in 2x and 60 in 4x.2) The diploid plant contained 15 bivalents in meiotic metaphase, while the tetraploid plant had some multivalents and univalents. According to the analysis of chromosomal pairing, the mean frequency of quadrivalent was 7.1 per cell, of trivalents 0.4, of bivalents 14.9 and of univalents 1 per cell. It was characterised as forming fairly many trivalents and univalents, and it was discussed from the mechanical points of view that such a pairing type might be due to the higher number of chromosomes which prevents their pairing by mechanical interference.3) The behaviour of univalents was studied in each meiotic stage. They migrated as the dyad or monad in the first division and the monad in the second division. It was suggested that univalents might Wcome one of the origins of numerical unbalance when they were not too infrequently formed.4) The failure of spindle mechanism, such as the big spindle with scattering of chromosomes, or the multipolar or supernumeral spindle, was found in the course of meiosis in tetraploid plants.5) Meiosis of hypotetraploid plant having 50 chromosomes in somatic cells was observed. This plant grew lively showing slight dwarf feature.6) The approximate value of true breed of tetraploid progenies was found in 80% of all the observed cases, but this was estimated as maximum for the chromosome number was flexible to count.7) Fertility of tetraploid plants examined showed rather low value of 10-28% while the diploid had about 95% in fertility. Aneuploid plants found in the tetraploid strain showed a slight reduced fertility.