Effects of different levels of calcium and sources of nitrogen on the growth and composition of citrus seedlings in solution culture

Abstract

The investigation was undertaken to study the effect of different Ca levels and sources of nitrogen supplied on the growth and the inorganic composition of natsudaidai (Citrus natsudaidai HAYATA) seedlings in solution culture.On the Ca deficient seedlings in both NaNO3 and NH4NO3 series, the growth was reduced, and their upper leaves turned to dull yellow green from the margin, finally left normal green only in the areas of the inverted V shape around the midrib. The interveinal parts outside the areas of the inverted V shape were dotted with many, small, light brown specks. In severe case, affected leaves dropped, and shoot apex exhibited the appearance of die back. Roots turned to brown, and rotted. Especially, in NH4NO3 series, deficiency symptoms were severer, and appeared even in the higher Ca level than in NaNO3 series.In NH4NO3 series, the higher Ca level was necessary for their maximum growth than in NaNO3, but the growth of seedlings in NH4NO3 series was inferior to that of NaNO3 in every Ca level.In the leaves of NaNO3 series, N, P and Ca contents increased, while K and Mg decreased with increment of Ca concentration in the medium. In NH4NO3 series, only Ca content increased, while K, Mg and N (beyond Ca 2ppm) decreased with the increasing concentration of Ca in the medium. In the roots of both sources of N, the contents of P, Ca and K increased, while Mg decreased, with increasing Ca supply.In both leaves and roots of seedlings supplied with NH4NO3, N content was generally higher, but contents of cations were lower than those of NaNO3 series.