Root tip mitosis in different plants. a Metaphase spread showing 12 standard (A) chromosomes of Plantago lagopus. NOR bearing chromosomes have been marked b Metaphase spread showing 12 A and one B chromosome. Note the B chromosome is indistinguishable c Mapping of 5S rDNA sequences in 0B plant using FISH. Note the presence of 5S rDNA signals on two A chromosomes d Painting of B chromosome with 5S rDNA probe, besides signals of 5S rDNA on two A chromosomes e A metaphase spread containing one B chromosome probed with 45S rDNA, showing two additional NOR sites (arrow heads) f 5S rDNA probed metaphase spread showing 12 A and two B chromosomes gFISH of a metaphase spread of 23-chromosome plant revealing the presence of 5 B chromosomes h Metaphase spread showing 28 chromosomes. Scale bars: 10μm.