Effect Of Nitrogen, Sulfur And Water On Growth And Glucosinolates Concentration On Turnips (Brassica Rapa L.)

Turnip is an important brassica vegetable and contains abundant gluconasturtiin, which is a kind of important bioactive substance and its breakdown products are of great benefit to human health. The research was conducted to investigate effects of N, S and water supply on plant growth and concentration of GS in turnip. Main results were as follows: Total eleven individual GS were identified, including six aliphatic GS, one aromatic GS and four indolyl GS in HY turnip, The composition of GS in BY turnip was the same as HY, expect BY didn't contain progoitrin.Nitrogen was significantly difference for GS concentration. Increasing nitrogen supply decreased total GS in turnips. Increasing S supply enhanced total glucosinolates concentration at all levels of N supply in turnip roots, but no significantly difference for the total GS concentration in shoot of turnip. However difference showed that the total glucosinolates in turnip roots was declined by increasing S supply under the high nitrogen (240 kg N ha-1). Since S uptake is suppressed by high N supply. The result indicated that the balance between N and S plays a large role in the regulation of the synthesis and / or accumulation of glucosinolates in turnip roots. Therefore, N/S was an important factor to influent GS concentration in plant. Increasing nitrogen and sulfur supply increased indolyl glucosinolate concentration. Nitrogen and water supply influenced glucosinolate in plant. Nitrogen had different results for glucosinolate concentration in plant at different stages. Nitrogen was only significantly difference in turnip roots when growth times were in 39d and 46d. Increasing nitrogen supply decreased GS concentration. Water had different results for glucosinolate concentration in plant at different stages. Water was only significantly difference in turnip roots when growth times were in 39d and 52d. Increasing growth time supply decreased total GS concentration, but increased at different growth stages. In different growth stages, aliphatic GS and aromatic GS concentration didn't change significantly, but indolyl GS changes significantly. Indolyl GS decreased with increasing the growth.Concentrations of GS in shoots and roots of BY were higher than that of HY. The most abundant individual GS in roots and shoots of BY was gluconapin, which accounted about 83.07% and 66.31% of total GS in shoots and roots respectively. However, the most abundant individual GS in shoots and roots of HY were glucobrassicanapin and gluconasturtiin, which accounted about 47.15% and 33.81% of total GS in shoots and roots respectively.In general, we eat mainly root of turnip. Therefore, best nitrogen application is 160 kg/ha, and sulfur is 60 kg/ha in pot experiment. The best condition is that nitrogen application is 120kg/ha, not to irrigate, under growth for 52d.