Chemical Composition of Turnip Roots Stored or Intermittently Grown at Low Temperature

Abstract

Field and greenhouse studies were conducted to investigate the effects of low temperature on the starch, sugar, ascorbic acid, and glucosinolate (GS) concentration in turnip [Brassica rapa ssp. rapifera (Metzg.) Sinsk] roots. Field-harvested roots were stored at 0C for 2 and 4 weeks. In the greenhouse, plants were grown at 0 to 12C for parts of 11 days before harvest. Cold-stored roots decreased in both starch and total sugar concentration (sucrose, fructose, and glucose) when compared to freshly harvested roots. Greenhouse-grown plants subjected to low temperatures had roots with a similar starch content but with a higher concentration of total sugars than the control. In both experiments, the cold treatments induced a slight but significant increase in root sucrose concentration. The ascorbic acid concentration of roots was not affected by low temperature. In both the field and greenhouse studies, low temperature did not change the total concentration of the eight major GSs identified in peeled root “and peel tissues, but did alter the concentration of specific GSs.