Effects of shading on growth rate, flower initiation and flower development ofBegoniaxsemperflorens-cultorum

Seedlings of Begonia x semperflorens-cultorum Hort. ‘Scarletta’ were grown under 0,45, or 57% of ambient light in a glass greenhouse. Shoot dry weight, lateral shoot leaf area, total leaf area, and node number decreased under increasing shade over time. Histological examination of shoot apices indicated that floral initiation occurred two to three weeks later in plants under 57% shade than those under ambient light or 45% shade. Plants under ambient light reached visible bud about five weeks before those under 57% shade and the time of floral development from visible bud to anthesis was also shorter for plants in ambient light compared with those grown under 45 and 57% shade. Staminate flower numbers on the first inflorescence increased under 45% shade compared with ambient light and 57% shade while pistillate flower numbers were unchanged.