Floral transition in lisianthus (Eustoma grandiflorum)

Floral transition was studied in lisianthus [Eustoma grandiflorum (Raf.) Shinn.] plants grown in a greenhouse at two planting times (winter and summer) under two photoperiod regimes: long day (LD) and short day (SD), 16 h/8 h and 8 h/16 h (light/dark), respectively. Morphological analyses of the flower meristem of the lisianthus cultivar 'Heidi Deep Blue' revealed three distinct stages of development: (1) sepal primordia, (2) petal and stamen primordia (almost simultaneously), and (3) carpel primordia. The appearance of sepal primordia was taken to mark the floral transition stage. Floral transition was hastened in summer-grown plants and under LD treatment, as expressed by a reduction in both the number of nodes and the time from planting. Stem length from base of plant to floral meristem, as measured at floral transition, was similar in all treatments, regardless of the number of nodes produced. At both planting dates, SD induced a higher number of flowers per inflorescence than LD. This report thus describes the direct effect of environmental factors on floral transition in lisianthus.