Morphology and growth of ornamental seedlings grown under supplemental light-emitting diode lighting and chemical plant-growth regulators

摘要

The use of supplemental light emitting diode (LED) lighting to promote plant compactness can be an alternative to chemical plant-growth regulators (PGRs). The objective of this experiment was to compare plant growth and morphology under different supplemental lighting (SL) treatments in combination with a PGR application. Petunia, dianthus, and geranium were grown in a greenhouse until the plug stage under 3.2 mol m 2 d 1 solar daily light integral (DLI), 23.2+2.0°C, and 41.5±16% relative humidity.Seven growing treatments were used. Two treatments consisted of LED SL with different percentages of blue (B), green (G), and red (R) photon flux (PF): B19:R81 and B6:G5:R89. There were two SL controls: high-pressure sodium (HPS) and no SL (No-SL). Three light treatments included a PGR application: No-SL+PGR, HPS+PGR, and B6:G5:R89+PGR. SL treatments received 5.76 mol nr2 d1 additional DLI (100 umol m 2 s 1 PF for 16 h). Morphological and growth parameters indicated the benefits of SL. Petunia seedlings under B6:G5:R89 had 23-32% greater plant compactness than plants under supplemental HPS and B19:R81. dianthus and geranium showed no significant differences in plant compactness among SL treatments. Petunia and geranium seedlings grown under B6:G5:R89had 49 and 21%, respectively, greater plant compactness than those under HPS+PGR. SL by itself promoted plant compactness in all plant species compared to plants grown with no SL and with an application of chemical PGR. In addition, for petunia, using SLwith B6:G5:R89 yielded plants with greater compactness than plants under HPS+PGR. For dianthus, SL by itself yielded the same plant compactness as seen in plants under HPS+PGR. For geranium plants, HPS yielded plants with similar compactness as HPS+PGR.