Effects of Growing Conditions and Fertility Levels On Health-Promoting Phytochemicals In Tomato and Pac-Choi

A field experiment was conducted at the Kansas State Horticulture Research and Extension Center, Olathe, Kansas during 2009 and 2010 to determine the effects of growing conditions (high tunnel and open field), fertility levels and management practices (conventional and organic) on the accumulation of health promoting phytochemicals in pac-choi (Brassica rapa L. cv. Mei Qing Choi) and tomato (Solanum lycopersicum L. cv. Bush Celebrity). Tomato was grown as a summer crop while pac choi was grown both as spring and fall crops in 2009. Tomato grown in open field had higher levels of antioxidant capacity, total phenolic content and individual phenolic compounds including rutin, p-coumaric acid and chlorogenic acid than that grown in high tunnels. The rutin content of field-grown tomatoes was approximately four times higher than those grown in high tunnels. The ruitn accumulation increased with fruit ripening while other phenolic compounds including ferulic acid decreased during the ripening process. However, some phenolic compounds such as caffeic acid and p-coumaric acid were found only in the ripening fruits but not in green fruits suggesting that ripening stage may have a significant impact on the accumulation of phenolic compounds.    In pac choi the dominant phytochemical was sinapic acid followed by querecitin-3-O-glucoside, chlorogenic acid, p-coumaric acid and ferulic acid.  Levels of many of these  phenolic compounds were significantly higher in field- grown pac-choi than when grown in high tunnels for both spring and fall crops. Typically, the spring pac-choi crop was richer in phytochemicals compared to the fall crop.   In both tomato and pac-choi, low fertility tended to improve their phytochemical accumulation and antioxidant capacity.  The consistent observation that open field improves the phytochemical accumulation in these crops may suggest a favorable impact of higher light intensity and its quality on the crop quality. However, crops grown in high tunnel produced significantly higher yield than those grown in open field, but with lower health-promoting qualities. Thus, consideration of open field and high tunnel production in these crops may involve a trade-off between the yield and  health-promoting qualities.