Lateral Root Anlage Development in Excised Roots of Vicia faba L., Pisum sativum L., Zea mays L. and Phaseolus vulgaris L.

The development of lateral root primordia has been investigatedin excised roots of Vicia faba, Pisum sativum, Zea mays andPhaseolus vulgaris cultured in White's medium supplemented with2 per cent sucrose and compared with previously published dataon such development in primaries of the corresponding intactplants (control roots). Primordia were produced in each batchof excised roots over the 6 day culture period but at a lowerrate (number day^–1) than in the controls. Such primordia in cultured roots of Zea and Phaseolus completedtheir development and grew out as lateral roots over a periodsimilar in length to that found in the controls, but with acell number of only about 33 per cent of that attained at thetime of secondary emergence in the primaries of the latter roots.These lower cell numbers were at least partly a reflection ofincreases in mean cell doubling time over the period of anlagedevelopment investigated in the excised roots relative to thecorresponding values found in the controls. Primordia initiated in excised roots of Pisum and Vicia didnot complete their development in culture, i.e. no lateral rootsemerged and arrest took place with cell numbers of only 37 (Pisum)and 17 (Vicia) per cent of the numbers determined at the timeof secondary root emergence in the controls. Such arrested primordiahad few nuclei in S and none in mitosis. Moreover, at leastin Pisum, the frequency distribution of the relative DNA contentof the nuclei in the latter primordia approximated that foundin the apical meristem of primary roots following the establishmentof the stationary phase under conditions of carbohydrate starvation. It has also been demonstrated in the course of these investigationsthat lateral root primordium development in all four speciesis at least biphasic and possibly triphasic. Vicia faba L., broad bean, Pisum sativum L., garden pea, Zea mays L., maize, Phaseolus vulgaris L., dwarf bean, root primordia, anlage, cell doubling time, lateral root emergence