Photosynthetic Daily Light Integral Influences Flowering Time and Crop Characteristics of Cyclamen persicum

This study was carried out to examine the effect of photosynthetic daily light integral (DLI) on the growth and flowering of cyclamen (Cyclamen persicum Mill. 'Metis Scarlet Red'). Plants with six fully unfolded leaves were grown at 24/16 degrees C (12 h/12 h) under an 8- or 16-h photoperiod at a photosynthetic photon flux of 50, 100, 150, 200, and 300 mu mol.m(-2).s(-1), which provided seven DLIs: 1.4, 2.9, 4.3, 5.8, 8.6, 11.5, and 17.3 mol.m(-2).d(-1). Days to first flower decreased from 133 to 75 as DLI increased from 1.4 to 17.3 mol.m(-2).d(-1), although the acceleration of flowering was less pronounced when the DLI was greater than 5.8 mol.m(-2).d(-1). Mean leaf and flower number increased from 8.7 to 28.0 and from 0 to 14.7, respectively, as DLI increased from 1.4 to 11.5 mol.m(-2)-d(-1), but there was no further increase under a DLI of 17.3 mol.m(-2).d(-1). Total dry weight and net photosynthetic rate showed a similar trend as leaf and flower number. We conclude that supplemental lighting can accelerate greenhouse production of potted cyclamen under a low ambient DLI (i.e., less than 12 mol.m(-2)-d(-1)).