Effects of Plant Stages on bolting of the Breeding Line 'Leafy Green Parental Line No.2' (Brassica rapa L. pekinensis group)

Bolting characteristics of a late bolting breeding line 'Leafy Green Parental line No.2' (PL-No.2, previously known as Ano No.3 or FNC31·63) of Brassica rapa L. pekinensis group, syn. B. campestris L. pekinensis group, or Chinese cabbage, were examined with regard to its plant stages. Seedling sensitivity to low temperatures was very low, irrespective of plant stages ; differentiation of flower buds occurred very late. Bolting and flowering were induced by a 16-hr photoperiod. However, a long-day with supplementary lighting was ineffective in initiating bolting and subsequent flowering. Seedlings grown under 16-hr photoperiod required nearly 70 days to anthesis. As the plants grew, the time from the onset of the long-day treatment to flowering became less than 50 days. The long-day sensitivity of 'PL-No.2' increased as the plants grew.