B-Chromosomes in Gymnosperms

B-chromosomes show a non-random distribution in different taxa of gymnosperms. They are generally smaller and show similar centromeric position as the normal complement and are heterochromatic in nature and may show DAPI or CMA banding. They are generally devoid of any gene content, do not pair at meiosis and show accumulation through female line. They show incremental effect on genome size and some adaptive value in particular ecological conditions.