Color of light reflected to leaves modifies nutrient content of carrot roots

Improved yield and nutrient content of food crops are important to both growers and consumers. We hypothesized that color of light reflected from the soil surface to developing leaves of field grown plants could result in modified concentrations of nutrients in edible roots. Carrot (Daucus carota L.) was used as the test plant. The plants were grown in trickle-irrigated field plots that were covered with panels that reflected various combinations of far-red (FR), red (R), and blue light (BL) to the growing leaves. The highest FR to R photon ratio reflected to developing leaves resulted in greatest shoot weight and the lowest root-to-shoot weight ratio. However, an increased quantity of photosynthetic light resulted in greater total weight per plant. Roots from yellow- and white-covered plots had highest concentrations of beta-carotene and ascorbic acid. Those from yellow- and black-covered plots had highest concentration of phenolics. In general, concentrations were higher in cortex than in xylem tissues. We conclude that color of light reflected from the soil surface to developing leaves can influence yield and chemical composition of edible roots. This discovery suggests that color of light reflected to growing shoots may also influence chemical composition of plant species used as phytonutraceuticals.