Research on the Effects of Light on Basil Plants

Plant Form

• Research by Xianmin Chang et al., published in 2009 in the Journal of Horticulture and Forestry, explored the effects of supplementary ultraviolet-B light on basil plants. Extra UV-B light resulted in shorter plants with more lateral branching, compared with plants that did not receive UV-B light. The authors suggest that UV-B alters the concentration of the plant hormone IAA, the naturally occurring auxin involved in stem elongation and lateral branching.

Volatile Compounds

• Volatile compounds contribute to the aroma of basil leaves. These compounds have strong antioxidant properties that promote health. Scientists John H. Loughrin and Michael J. Kasperbauer reported in 2003 in the Journal of Agricultural and Food Chemistry that the color of light affects the concentration of volatile compounds in basil leaves. The authors grew basil plants in mulch of different colors. The mulch reflected varying ratios of far red, red and blue light. Plants grown over black, green and yellow mulch had the greatest amount of volatile compounds compared with plants grown over red, blue and white mulch. In addition, in their study, Chang et al. reported that additional UV-B light induced greater amounts of volatile compounds in basil leaves.

Phenolics

• Like volatile compounds, many phenols are also beneficial antioxidants. A major phenolic compound in basil is rosmarinic acid. In a study published in 2009 in Plant Biotechnology, Tomomi Shiga et al. concluded that rosmarinic acid increases in basil plants that receive light in the red wavelength. In a study published in 2001 in the Journal of Agricultural and Food Chemistry, Loughrin and Kasperbauer reported that basil leaves subjected to the smallest amount of blue light had the greatest amount of phenol compounds.

Leaf Characteristics

• Research studies have shown that different types of light influence the attributes of the basil leaf. For example, in the 2001 publication, Loughrin and Kasperbauer reported that basil leaves grown over red mulch had greater leaf area and moisture compared with basil planted in black mulch. They suggested that the type of light reflected from red mulch typically promotes plant growth. Results from these studies may be useful for enhancing the quality of basil leaves for culinary and medicinal purposes.