Chromosome Numbers in Root Nodules and Root Tips of Certain Leguminosae

Abstract

Infected cells of root nodules of 31 diploid spp. belonging to Lathyrus, Medicago, Meli-lotus, Pisum, Trifolium, and Vicia contain in each case the tetraploid number of chromosomes. Uninfected cells in the nodular cortex possess the diploid number characteristic of the particular species. The chromosome number in infected nodular cells from diploid and autotetraploid strains of Melilotus alba, from diploid, triploid, tetraploid, and octoploid forms of Medicago, and from a natural poly-ploid series in Trifolium is twice that found in normal somatic cells of the respective plants. There is definitely and consistently a 21 chromosome ratio between infected and uninfected cells of the root nodules on the leguminous plants examined. Factors inhibiting the fixation of free N do not affect this 2:1 chromosome ratio in the nodular cells. Chromosome numbers herein reported for the first time are: Melilotus altissima 2n = 16, M. caspia 2n = 16, M. gracilis 2n=16, Trifolium agrarium 2n = 14, T. dubium 2n = 28, and T. involucratum 2n = 28.