Abstract
The experiment was performed to study the effects of pH, calcium concentrations and sources of nitrogen on the growth and inorganic compositions of natsudaidai (Citrus natsudaidai HAYATA) seedlings in solution culture under glass. Nitrogen was supplied with NaNO3 or NH4NO3 in the concentration of 112ppm, pH of solution was adjusted at 4, 5.5 and 7, and calcium concentrations supplied were low, medium and high, totalling 18 combination treatments.
The appearance of leaves of the seedlings at pH 5.5 in NaNO3 series was normal, however, it was rather dark green in NH4NO3 series. At pH 4, leaves became somewhat dull green, and at pH 7 they tended to become chlorotic in both forms of nitrogen. Chlorosis was more remarkable in NaNO3 series. Roots were white in pH 5.5, however, at pH 4 or pH 7 they turned light brown in NaNO3 series. The elongation of roots at pH 4 was inferior to those at other pHs, and tips of laterals became stubby. In NH4NO3 series, roots generally became brown, and their elongation was less than that in NaNO3 series. At pH 4, tips of laterals became stubby, and in advanced stage the cortex disintegrated and sloughed off. These symptoms were more remarkable in the treatment supplied with low Ca.
In general, seedlings supplied with NaNO3 made better growth than those supplied with NH4NO3. In both forms of nitrogen, growth of seedlings was the minimum at pH 4. In NaNO3 series, growth of seedlings was the maximum at pH 5.5, and intermediate at pH 7. However, there was no clear difference of growth between pH 5.5 and pH 7 in NH4NO3 series except Ca low treatment. As for calcium concentration, seedlings supplied with medium Ca showed better growth at every pH in NaNO3 series. On the other hand, no consistent difference of growth due to calcium concentration was observed in NH4NO3 series.
NaNO3 plants had generally higher concentrations of K and Ca, and lower concentrations of N, P, and Mg as compared with NH4NO3 plants in their leaves. While, in their roots, NaNO3 plants showed higher concentrations of P, Ca, and Mg, and lower concentrations of K than those of NH4NO3 plants. With the rise of pH level in the solution, concentrations of N, Ca, and Mg increased and K decreased in the leaves irrespective of nitrogen forms. In their roots also, concentrations of Ca, Mg, and P increased, and K decreased with the rise of pH. When Ca level in the solution was raised, only Ca concentration in the seedlings increased.
