عنوان مقاله [English]
Medicinal plant are very importnat in health care for today societies and the need for it is increasing. Greenhouse production of transplants face different limitations including light. LED lights are introduced for solving the problem. An LED lamp or LED light bulb is an electric light for use in light fixtures that produces light using one or more light-emitting diodes (LEDs). LED lamps have a lifespan many times longer than equivalent incandescent lamps, and are significantly more efficient than most fluorescent lamps. Experiments revealed surprising performance and production of vegetables and ornamental plants under LED light sources. Many plant species have been assessed in greenhouse trials to make sure that the quality of biomass and biochemical ingredients of such plants is at least comparable with those grown in field conditions. Plant performance of mint, basil, lentil, lettuce, cabbage, parsley and carrot was measured by assessing both the health and vigor of the plants and the success of the LEDs in promoting growth. Also noticed was profuse flowering of select ornamentals including primula, marigold and stock.
Materials and Methods In order to investigate the effect of supplementary LED light on the growth parameters and the amount of active ingredient in Hypericum perforatum L. “Topaz” cultivar, a research was conducted in two independent experiments. The research was set up in a completely randomized design with three replications. The first experiment experienced the extended of day length with 4 hours at the end of the day (started from sunrise to sunset). LED treatments were started at 10 cm height of the transplants. The second experiment examined the light types. In this order the considered treatments consisted of four levels of red light (L1), blue light (L2), combination of 67% red light and 33% blue light (L3), white (L4), 100% natural light(L5), with an intensity equal to (200 fc). Measurement of traits in the first experiment was carried out at flowering stage. Aerial part fresh and dry weights, number of black nodes, days to flowering, leaf area, total chlorophyll, antioxidant activity, total phenol, plant height and hypericine percentage were determined within both experiments.
Results and Discussion The results showed that the simple effect of supplementary combination red and blue light (started from sunrise to sunset) on growth, morphological, physiological and biochemical traits was significant at 1% probability level. The highest plant dry weight was detected in L3 in the first and second harvests respectively (8.63 g, 66.29 g). Also, the highest percentage of Hypericine in the first harvest was obtained for L3 (0.17%). Measurement of the traits in the second experiment was carried out at the seedling stage. Results showed that the simple effect of supplementary combination light (sun exposure and day length increased for 4 hours) had a significant effect (p≤0.01) on growth rate, physiological, morphological and biochemical properties. So that the lowest number of days to flowering (early flowering) was obtained from L3 treatment (101 day), and the highest percentage of Hypericin was related to L3 treatment (0.156%). Black node numbers and total phenol content were increased by 27 and 53 % with supplementary light treatments respectively. Antioxidant activity was also raised and enhanced from 33 % to 75 % with LED light application. Plant height and total chlorophyll content were enhanced from 13 to 23 cm and 12 to 22 mg/g FW as well. Regarding studied traits and the obtained results of the both experiments, the positive effect of applying LED light, red and blue on the growth and biochemical properties, especially the Hypericine percentage and yield of St. John’s wort is quite evident.
Different reactions were observed in response to supplementary light treatments for St. John’s wort. Most of the enhancements observed were mainly due to optimized photosynthesis activities and more metabolic production processes.
Conclusions Regarding studied traits and the obtained results of the both experiments, the positive effect of applying LED light, red and blue on the growth and biochemical properties, especially the Hypericine percentage and yield of St. John’s wort is quite evident. It seems that a combination of red and blue light could be suggested for solving the light limitations and increasing the medicinal plant production for future.
Keywords: Supplementry light, light quality, Hypericum perforatum, Hypericine