Effects of LED Light on Seed Emergence and Seedling Quality of Four Bedding Flowers

Recently much attention has been paid by horticulturists to lightemitting diodes 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 this study we examined their potential in promoting seed germination and producing quality flower seedlings for which we designed four growth chambers each equipped with a different light quality sources, namely red, blue, combination of 25% blue and 75% red and fluorescent lamps. Seeds of four annual bedding flowers including impatiens (Impatiens balsamina), zinnia (Zinnia elegans), petunia (Petunia × hybrida) and verbena (Verbena aubletia) were sown and grown to produce seedlings. Plants were illuminated 12 hours per day in the growth chambers. According to the results, seedlings under 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 in leaf number. The stem diameter of impatiens increased under red light. By contrast, in petunia stem diameter increased under blue light significantly. Inclusion of 25% blue light to red light reduced hypocotyl and shoot height and increased root fresh weight and root length of most plant types. Light quality did not affect the time of emergence (T50), true leaf stage, four-leaf stage and shoot fresh weight. Our study demonstrated that light-emitting diodes could be an effective and reliable source of lighting under controlled environment for production of quality flower seedlings. Generally, the pure red light enhanced seedling emergence and during growth period, high quality seedlings could be produced when 25% blue light was added to red light.