Effects of varied irradiance on flowering time of facultative Long-Day ornamental annuals

Seeds of five facultative long day plants (fldps) i.e. moss rose cv. sundance,pansy cv. baby bingo,snapdragon cv. coronette,petunia cv. dreams and annual verbena cv. obsession were sown into module trays containing homogeneous leaf mould compost. after germination,saplings of each cultivar were shifted into four light intensity chambers (42,45,92 and 119μmol.m-2.s-1) for a duration of 8h (from 08:00 to 16:00h). the findings of this study showed that facultative ldps grown under high irradiance (92 and 119 μmol.m-2.s-1) flowered earlier. however,there was a non-significant difference between 42/45μmol.m-2.s-1 and 92/119μmol.m-2.s-1 irradiance levels. although fldps under 119μmol.m-2.s-1 flowered few days earlier than those received 92μmol.m-2.s-1 irradiance but the quality of plants (plant height and leaf size/appearance) was inferior. it is therefore concluded that for better plant quality and early flowering fldps should be grown under 92μmol.m-2.s-1 irradiance.