ACCUMULATION AND PARTITIONING OF MINERAL NUTRIENTS IN WHEAT AS INFLUENCED BY NITROGEN FORM

The form of nitrogen (N) [e.g., nitrate (NO3-) and ammonium (NH4+)] av ailable to plants affects many growth processes, including mineral nut rient acquisition. The objective of this study was to assess the effec ts of N form on the accumulation and partitioning of mineral nutrients in wheat. Two species of spring wheat (Triticum aestivum L. cv. Len a nd Triticum durum Desf. cv. Inbar) were grown hydroponically in the gr eenhouse with N supplied as either all NO3- or all NH3+, or an equal m ixture of the two forms (mixed N). Plants were harvested after 21 days of growth, divided into shoots and roots and each part analyzed for n ine mineral elements [phosphorus (P), potassium (K), calcium (Ca), mag nesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), and bo ron (B)]. The accumulation and partitioning of the mineral nutrients w as dependent on the wheat species, the N form, and the nature of the i on. Inbar plants always accumulated more of each element than did Len. Compared with all NO3- nutrition, mixed N increased the whole plant a nd/or shoot accumulation of P, K, Cu, and B, but not Ca, Mg, Fe, Mn, a nd Zn; while all NH4+ decreased these values for most elements. With f ew exceptions, N form did not affect either the accumulation or partit ioning of Mg and Fe. Plants grown with all NO3- accumulated more Mn an d Zn than those receiving mixed N or all NH4+, while the partitioning of both ions was not affected by N form. When grown with mixed N or al l NH4+, less P, K, Cu, and B was partitioned to the roots compared to plants receiving all NO3-. These results demonstrate the differential effects of N form on mineral nutrient acquisition and nutrient use by wheat, which may be related to N-form induced differences in plant gro wth.