MORPHOGENESIS OF ROOT-NODULES IN WHITE CLOVER - III - THE EFFECT OF MUTATION IN NOD IJ GENES OF THE MICROSYMBIONT UPON THE DNA LEVEL IN THEHOST TISSUE

On the basis of cytophotometric measurements a slightly increased DNA level in the nuclei of curled root hairs containing infection threads was observed in white clover inoculated with wild and mutant strains o f Rhizobium leguminosarum biovar. trifolii, as compared to normal root hairs of te same plants. Cells of the root nodule primordia in 72 h a fter the inoculation, as compared to the root primary cortex, demonstr ated an increased level of the nuclear DNA. No differences were observ ed in the nuclear DNA contents in individual layers of the cortex of t he 28 day-old nodules. Generally it was low, varying from 2c to 4c. Th e meristematic and bacteroidal tissues in the effective nodules were c haracterized by a higher DNA level, as compared to the respective zone s in ineffective nodules induced with the strains ANU261 (nod I-) and ANU262 (nod J(-)). The DNA level in the effective bacteroidal tissue v aried from 4c to 32c, while in the tissue containing the strain ANU261 only the 2c-8c nuclei could be found and in the tissue with the strai n ANU262 - the 4c-16c nuclei.