Light emitting diodes (LEDs) affect morphological, physiological and phytochemical characteristics of pomegranate seedlings

The impact of light-emitting diodes (LED) on developmental, physiological, and phytochemical characteristics of pomegranate (Punica granatum L.) seedlings was investigated. Five LED lights [L20AP67 (moderate blue and red, high green), AP673L (moderate blue, high red and red:far-red), G2 (low blue, high red and far-red), AP67 (moderate blue, high red), and NS1 (high blue and green, low red, high red:far-red, 1% UV) with wide and continuous radiation spectra were used. Fluorescent [FL (high blue and green, low red)] tubes constituted the control treatment. Among treatments, seedlings grown under L20AP67 exhibited the best morphological and growth characteristics (rapid height increase, longer roots, greater fresh and dry weight, greater leaf area). Root activity was comparable among the various treatments, with FL exhibiting the lowest arithmetic value. A variant effect on pigments and secondary metabolites was recorded with the highest chlorophyll and carotenoid content detected under FL, flavonoid under G2 and AP67, and anthocyanin under G2, AP67 and NS1. In addition, NS1 produced the highest total phenolic compound content. Root growth capacity (RGC) was monitored in specialized chambers, then assessed to evaluate the transplanting capacity. Transplanted seedlings of AP67 had the longest, of L20AP67 the heaviest newly formed roots, thus securing a successful transplantation. The herein undertaken study demonstrates that certain LEDs promoted developmental characteristics in pomegranate more efficiently than conventional FL. In particular, the use of L20AP67 was proven a promising tool for producing robust pomegranate seedlings, while some of the other LEDs tested apparently imposed a stressful situation on plants.