## 4 Discussion  
The present studies have evaluated potential effects of six laser radiation from the visible spectrum upon chemical composition and biological activity (cytotoxicity, in vitro) of aqueous extract from _Plantago lanccolata_, dried plant. The selection of particular laser wavelengths under study (488, 514, 532, 552, 660, and 785 nm) is based on several scientific reports, both on vegetal and animal test matter, from which the interest for identical, or close wavelengths was found. Based on the observation that if the wavelength is short and the exposure time is long, burning (oxidation), or increase in thermal energy of the sample may be due [71; 72], there were selected lower powers at higher frequencies (shorter wavelengths) and, inverse, higher powers at lower frequencies (longer wavelengths): 488 nm/40 mW, 514 nm/15 mW, 532 nm/20 mW, 552 nm/15 mW, 660 nm/75 mW, and at 785 nm/70 mW. Furthermore, laser experiments have proved that powers higher than 5 mW have an effect on the intensity of the aromatic bands [73]. This observation is clearly demonstrated in some laser studies at 532 nm, by Raman measurements of the lignin polymer in spruce trees, which proved punctual modifications at the main aromatic band at 1600/1600 cm\({}^{-1}\) related to C=C extent of the phenol ring, finally reflected on coniferyl alcohol monomer [6]; studies also reported that wavelengths at 514 nm, 633 nm, and 785 nm have not produced subsequent changes in the Raman spectrum up to 220 mW and 200 s total irradiation time, even if the power used was sufficient to produce the activation of the coniferyl alcohol [6]. This way, in the case of living matter, in vitro studies on animal, murine lung epithelial line (MLE-12), cells irradiated with wavelengths of 488 and 514 nm (at power laser of mW) indicated clear harmful effects, while wavelength of 785 nm (115 mW for 40 min) indicated positive effects on the exposed cells [74]; similarly, laser irradiation at the wavelength 514.5 nm, but not at 660 nm (20 mW), indicated a clear spectral degradation (by Raman measurements) of the single human lymphocytes and chromosomes in the test [75]. In the specific case of living vegetal matter, the effects of the interaction of visible light (the wavelengths from 400-700 nm) with the green plants represents one of the essential conditions of life, and the final effects basically depend on its color (Figure 7) [76]. For example, radiation from 440-500 nm (blue light) was proved to play a major role in plant quality and plant development, by increasing chlorophyll absorption, therefore blue light has major beneficial effects on the leaf part; radiation from 510-610 nm (green light) results in photosynthesis stimulation, therefore the major benefits are on plant size, plant weight and synthesis of growth factors; radiation from 610-700 nm (yellow-red light) was related with stimulation of chlorophyll function, with germination and flower, and bud development; radiation from 700-800 nm (far red light) have revealed stimulatory effects on the plant growth by extension and general benefits [77]. Regarding the particular effects of light in visible on the secondary metabolites in plants, polyphenol compounds have been proved to be highly responsive to particular wavelengths in the spectrum. Thus, it was proved that blue and red light generally induces the accumulation of the bioactive compounds in medicinal plants [78]. Specifically, blue light increased the efficacy of accumulation of total phenols and total flavonoids in _Prunella vulgaris_ calli [79]; blue and red light significantly increased coumarins accumulation in _Sarcandra glabra_ seedlings [80], and callus culture of _Eclipta alba_ L. [81], as well as dry mass, rosmarinic and caffeic acid contents of seedlings in cultured _Ocimum bsilicum_ [82], and biomass, anthocyanins, and 20-hydroxyechisone in _Pfaffia glomerata_[83].