DEVELOPMENT OF LATERAL ROOT PRIMORDIA IN VICIA-FABA, PISUM-SATIVUM, ZEA-MAYS AND PHASEOLUS-VULGARIS - RATES OF PRIMORDIUM FORMATION AND CELL DOUBLING TIMES

Lateral root primordium development has been examined in primary roots of Vicia faba L., Pisum sativum L., Zea mays L. and Phaseolus vulgaris L. Following their initiation from an estimated minimum number of 77-162, 20-57, 17 and 12 cells respectively in Vicia, Phaseolus, Pisum and Zea, the primordia rapidly increased in cell number to emerge as secondary roots about 2.8-3.6 days later depending on the species being examined. Cell doubling times were estimated directly from cell numbers at different times following primordium inception and were found to increase with increase in primordium size in each of the species investigated.The number of primordia formed per cm of root growth per day was greatest in Zea and least in Pisum. A comparison of the data obtained for Vicia with that in the literature led to the conclusion that although the number of primordia produced per cm of root growth was independent of the rate of primary elongation, the number produced per day increased in a linear fashion with increase in the rate at which the primary lengthened. © 1979, Annals of Botany Company.