Changes of the contents of nitrate, oxalic acid and polyamines in tea plants (Camellia sinensis L.) grown with different nitrogen forms and concentrations.

摘要

Four-year-old tea plants were transferred from a field to hydroponics for 16-week culturing. The nitrogen in the culture solution was varied (in mg N/litre); no N (N0), 50 (ammonium nitrate, AN-50), 100 (AN-100), 500 (AN-500), 500 (ammonium sulfate,A-500) and 100 (nitric acid, N-100). At harvest, samples from new shoots, mature leaves, white roots and brown roots were obtained, freeze dried and ground. The weight increase of tea plants after nitrogen treatment was largest in AN-50, AN-100 and AN-500, followed by N-100. The content of nitrate was also highest in AN-100 and AN-500. Significant nitrate in AN-50 and N-100 treatments was only observed in white roots, while there was an obvious increase of nitrate in the young shoots and mature leavesof plants that received AN-100, and a more pronounced increase in the AN-500 treated plants. The oxalic acid concentration was highest in mature leaves, and increased with increasing nitrate in the culture solution. Presuming that nitrate reduction is related with oxalic acid synthesis, the major site of nitrate reduction was concluded to be roots when the administration of nitrate is small, and mature leaves when nitrate addition is large. Polyamines (putrescine, cadaverine, spermine, and spermidine) were present in tea organs. Putrescine content was large in roots and increased with increasing ammonium concentrations. Spermidine concentrations were high in young shoots, and also increased with ammonium nitrate concentrations.