effects of led light on seed emergence and seedling quality of four bedding flowers

Recently much attention has been paid by horticulturists to lightemittingdiodes as a new source of economical and spectral-selective light.the reason is mainly coming from their versatility in handling and mounting,long working time, wattage use efficiency and lower heat production. in thisstudy we examined their potential in promoting seed germination andproducing quality flower seedlings for which we designed four growthchambers each equipped with a different light quality sources, namely red,blue, combination of 25% blue and 75% red and fluorescent lamps. seeds offour annual bedding flowers including impatiens (impatiens balsamina),zinnia (zinnia elegans), petunia (petunia × hybrida) and verbena (verbenaaubletia) were sown and grown to produce seedlings. plants were illuminated12 hours per day in the growth chambers. according to the results, seedlingsunder red light showed the highest emergence percentage, rate and value.light quality variably affected growth characteristics among plant species.impatiens and zinnia plants under blue light showed a significant increase inleaf number. the stem diameter of impatiens increased under red light. bycontrast, in petunia stem diameter increased under blue light significantly. inclusionof 25% blue light to red light reduced hypocotyl and shoot height andincreased root fresh weight and root length of most plant types. light qualitydid not affect the time of emergence (t50), true leaf stage, four-leaf stage andshoot fresh weight. our study demonstrated that light-emitting diodes couldbe an effective and reliable source of lighting under controlled environmentfor production of quality flower seedlings. generally, the pure red lightenhanced seedling emergence and during growth period, high quality seedlingscould be produced when 25% blue light was added to red light.