Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 28, 2000
Publication Date: N/A
Interpretive Summary: Basil is a high value specialty crop that is used fresh as an herb or dried as a spice to add a distinct aroma and flavor to food. It is grown commercially and by many home gardeners. This herb can be grown outdoors in full sunlight over plastic mulches that conserve water, control weeds and keep soil from splashing onto the leaves. By using colors other than the standard black for these soil covers, scientists at the Coastal Plains Soil, Water and Plant Research Center near Florence, South Carolina, were able to keep the benefits attributed to black plastic mulch and alter the amounts of blue, red and far-red light reflected to the developing leaves. The color of light reflected to the developing leaves acted through the natural growth regulating system within the plants and affected their size, aroma and concentration of soluble phenolics, some of which are important antioxidants.
Technical Abstract: Basil (Ocimum basilicum L.) is an herb whose leaves are used to add a distinct aroma and flavor to food. We hypothesized that size and chemical composition of sungrown basil leaves could be influenced by color of light reflected from the soil surface, and by action of the reflected light through the natural growth regulatory system within the growing plants. Leaf morphology, aroma compounds and soluble phenolics were compared in basil that had been grown over six colors of polyethylene row covers. Altering the ratios of blue, red and far-red light reflected to growing plants influenced both leaf morphology and chemistry. Leaves developing over red surfaces had greater area, moisture percentage (succulence) and fresh weight than those developing over black surfaces. Basil grown over yellow and green surfaces produced significantly higher concentrations of aroma compounds than did basil grown over white and blue covers. Leaves grown over yellow and green mulches also contained significantly higher concentrations of phenolics than those grown over the other colors. Clearly, the wavelengths (color) of light reflected to growing basil plants affected leaf size, aroma and concentrations of soluble phenolics, some of which are antioxidants.