EFFECTS OF TEMPERATURE ON LEAF AND CURD INITIATION IN RELATION TO JUVENILITY OF CAULIFLOWER

Cauliflower plants (Brassica oleracea L. var. botrytis subvar. cauliflora, cultivar 'Delira') were grown at 14 or 22°C to study the effect of temperature on leaf and curd initiation. The rate of leaf initiation depended on the leaf number: the first 11 leaves were initiated at a lower rate than the following leaves. A linear relationship was found between the number of leaves > 2 cm and the total number of initiated leaves of vegetative plants. The slope of the regression line was independent of temperature and different from unity. The time between initiation of a leaf and its attaining a length of 2 cm increased linearly with leaf number. The relationship between dry matter production or leaf area and the number of leaves > 2 cm was hardly influenced by temperature. By transferring plants from weak curd-inducing conditions (22°C) to strong curd-inducing conditions (14°C) at different times, the number of leaves at which the juvenile phase ended could be estimated by assessing the effect of the number of initiated leaves at the moment of transfer on the final number of leaves. For this cultivar, the juvenile phase ended when 16-18 leaves were initiated. During the juvenile phase, the linear relationship between the number of initiated leaves and the diameter of the apical dome was independent of temperature. After the juvenile phase, the apical dome diameter of vegetative plants at 22°C increased more slowly than at 14°C. The maximum dome diameter of vegetative plants was between 0.35 and 0.40 mm at both temperatures. © 1990.