Influence of Light Intensity on Flower Initiation and Differentiation in Hybrid Geranium

Abstract

Actively expanding apical meristems of geranium ( Pelargonium × hortorum Bailey) growing in ambient light or in 60% shade were viewed with a scanning electron microscope at weekly intervals. Floral initiation was 37 days earlier in plants receiving ambient light and differentiation time was reduced by 7 days compared with shadegrown plants. Leaves of shade-grown plants emerged more slowly and were smaller when plants were young compared with ambient light-grown plants. Flowers of shadegrown plants were smaller and fewer in number compared with ambient-grown plants, both during differentiation and at anthesis. Shade-grown plants had 22–24 nodes at flower initiation compared with 16–18 nodes in ambient-grown plants.