Induction of Morph-Physiological and Biochemical Alternation of Salvia Officinalis L. by Manipulating Light Spectrum

Light spectrum of growing environment is a determinant factor for plant growth and photosynthesis. Photoregulation is an effective strategy to improve productivity of plants. Light sources such as metal-halide, fluorescent, high-pressure sodium, neon lamps and light-emiting diode (LED) can be used for production of plants in closed environments instead of sunlight. Nowadays, by using the LED (Light Emitting Diode) technology, it is possible to study the physiological effect of different light spectra for optimization of growth conditions and for increase the production of plants in controlled environments. Due to high marketability, producers continually investigate to maximize yield and productivity of sage.The main purpose of this study was to examine and compare different combinations of LED light spectra on morpho-physiological and biochemical response of sage plant. In this study, the effects of different light spectra were implemented and performed as a pot experiment soilless media in the plant growth chamber based on a completely randomized design with 6 lighting spectra including white, blue, red, red30: blue70, red50: blue50 and red70: blue30 with tree replication. The light intensity in all growth chambers was adjusted to photosynthetic photon flux density (PPFD) of 250 ±10 μmol m-2s-1 PPFD intensity and light spectrum were monitored using a sekonic light meter. Growth condition was set at 14/10 h day/night cycles, 25/20oC day/night temperatures and 40% relative humidity. In this study, different morphological traits (plant height, root length, root volume, stem diameter, number of leaves, Leaf length, Leaf width, Leaf area, specific leaf area, Number of nodes, Internode length, Number of branches), vegetative parameters, photosynthetic pigment concentrations and biochemical characteristics were measured analyzed. Data analysis of variance (ANOVA) was performed using IBM SAS software (Version 9.1), and the differences between means were assessed using Duncan’s multiple range tests at p ≤ 0.01. The results showed that the morphological, growth and content of photosynthetic pigments of sage plant were affected by different light spectra. R:B combinational lights caused a better growth in comparison with monochromatic R and B lights. The plants grown under red light had the tallest stem in comparison with the stem lengths of plants grown under other light spectra. The highest shoot and root fresh weight were measured in 70:30 red: blue light. Highest root dry weight and root volume were detected under R70B30 and lowest values of them were observed under R light. In the present study, increasing the ratio of blue light led to the generation of short and small plants, while increasing the ratio of red light led to the improvement of growth characteristics. Concentrations of all photosynthetic pigments in the sage leaves were significantly influenced by the light spectra. The highest Chl a and Chl b concentration was observed under R50B50 and R70B30 lights. Highest total Chl content was detected under R70B30. Highest amount of total phenolic content and antiradical activity was observed in leaves of plants grown under 70:30 red: blue light. Growth and morphology and content of photosynthetic pigments of plants were considerably influenced by light spectra in this study. In conclusion, combined red and blue lights (red70: blue30) by inducing of production of more photosynthetic pigments improved growth and improving growth of sage plant. Therefore, it can be expressed that the presence of both wavelengths (blue and red) is necessary for a better and more complete growth of the plant. In general, it can be suggested that the use of LEDs can result in better economic production-controlled environment systems.