The Improvement in the Growth and Biosynthesis of Polyphenols in <i>Ocimum basilicum</i> L. Plants Through Simultaneous Modulation of Light Conditions and Soil Supplementation

The sweet basil <i>Ocimum basilicum</i> L. is the subject of numerous studies and is cultivated as a food and ornamental plant. Moreover, <i>O. basilicum</i> could be useful in the prevention of stroke ischemia, and its anticancer properties were recently shown. Caffeic acid derivatives, such as rosmarinic acid (RA), chicoric acid, salvianolic acids, and anthocyanins, provide the medicinal properties of basil. Therefore, investigations of the optimal growth conditions that can provide cost-effective cultivation of highly productive basil plants are relevant and important. The aim of the present work was to study the effects of a combination of soil composition and light conditions on the morphological and biochemical characteristics of <i>O. basilicum</i>. In totally artificial (indoor) environments, light-emitting diodes (LEDs) may provide a broad range of narrowband wavelengths with different intensities. This technology can lower operating costs. In addition to the spectral composition, light intensity (PPFD, µmol m⁻²s⁻¹) is an important parameter for the optimal growth of plants. In the experiment, we used different spectra of LED lamps with intensities of 300 µmol m⁻²s⁻¹: warm white, monochromatic (green and red), and a combination of blue and red. Plants were grown under various lighting conditions in soil supplemented with fertilizer, Z-ion, and Crystallon. The results showed that supplementation of soil with Crystallon had a greater effect on the growth of both above- and below-ground parts of <i>O. basilicum</i> plants. Interestingly, growing <i>O. basilicum</i> plants under R and RB light led to a 2-fold increase in the biosynthesis of both the key caffeic acid derivative RA and anthocyanin. However, given that under RB light, there is no positive effect of Crystallon on growth, the productivity of RA and anthocyanin reached a maximum when <i>O. basilicum</i> plants were grown under R light and Crystallon. Under these conditions, the productivity of anthocyanins and caffeic acid derivatives in <i>O. basilicum</i> was more than eight times greater than that in untreated <i>O. basilicum</i> plants.