Cannabinoids Accumulation in Hemp ( Cannabis sativa L.) Plants under LED Light Spectra and Their Discrete Role as a Stress Marker

Hemp adaptability through physiological and biochemical changes was studied under 10 LED light spectra and natural light in a controlled aeroponic system. Light treatments were imposed on 25 days aged seedlings for 16 h daily (300 µmol m^-2 s^-1) for 20 days. Plant accumulated highest Cannabidiol (CBD) in R₇:B₂:G₁ light treatment, with relatively higher photosynthetic rate and lower reactive oxygen species, total phenol content, total flavonoid content, DPPH radical scavenging capacity, and antioxidant enzymatic activities. Tetrahydrocannabinol (THC) also accumulated at a higher level in white, R₈:B₂, and R₇:B₂:G₁ light with less evidence of stress-modulated substances. These results indicated that CBD and THC have no or little relation with light-mediated abiotic stress in hemp plants. On the contrary, Tetrahydrocannabinolic acid (THCA) was accumulated higher in R₆:B₂:G₁:FR₁ and R₅:B₂:W₂:FR₁ light treatment along with lower photosynthetic rate and higher reactive oxygen species, total phenol content, total flavonoid content, DPPH radical scavenging capacity, and antioxidant enzymatic activities. However, Cannabidiolic acid (CBDA) was accumulated higher in R₆:B₂:G₁:FR₁ light treatment with higher stress-modulated substances and lower physiological traits. CBDA was also accumulated higher in R₈:B₂ and R₇:B₂:G₁ light treatments with less evidence of stress-modulated substances. Besides, Greenlight influenced CBD and CBDA synthesis where FR and UV-A (along with green) play a positive and negative role in this process. Overall, the results indicated that the treatment R₇:B₂:G₁ enhanced the medicinal cannabinoids most, and the role of THCA as a stress marker is more decisive in the hemp plant than in other cannabinoids under attributed light-mediated stress.