Changes in macroelement content of rhizomes of Nuphar lutea [L.] Sibith. and Sm. during the annual cycle

This study presents the results of studies on the chemical composition of rhizomes of Nuphar lutea which were carried out from July 2006 to November 2007 (the samples were collected at two-week intervals from March to November 2007). The first indication of the start of the growing season was the growth of leaves in the apical part of the rhizomes. Clearly visible signs that marked the beginning of the growing season were unfolding of leaves, which became arrow-shaped. The leaves had already unfolded and were arrow-shaped (saggitate) on April 10th when the temperature of the bottom water layer was 7oC. It may be assumed, therefore, that the growing season began between the 28th March and 10th April 2007. The phosphates, nitrates, sodium, calcium, total iron and sulphates levels in the rhizomes declined just after the growing season had started. The total nitrogen content remained at a constant level whereas the amount of dissolved silica increased. Considerable changes in the macroelement contents were noted when Nuphar lutea was in full bloom (10th-24th June). The macroelement contents presented in the tables and diagrams were expressed on a dry matter basis. An additional table illustrates the macroelement contents expressed on a fresh matter basis. The problem of collecting rhizomes of polycormic plants is discussed.