Short-Term Ion Uptake by Phalaenopsis as Affected by Concentration of the Solution

Abstract

Nutrient uptake over a 72 h culture period by clonal micropropagules of Phalaenopsis Tanigawa x Yukimai Dream 'KS 370' and 'KS 352' were surveyed by Ichihashi's (1997) nutrient solution at the original ion strength and its half and quarter. Uptake of major anions [nitrate (NO3-), phosphate (H2PO4-), and sulfate (SO42-)] and cations [ammonium (NH4+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+)] measured with an ion chromatograph increased as the ionic strength of the solution increased in both cultivars. The final uptake rates of nutrients were 0.8, 2.0, 2.1, 1.2, 3.0, 2.0, and 1.6 me L-1, respectively in the order of ions mentioned above. The ratios of the uptake rates between cations (mono or bivalent) were almost in proportion to the ratio of their initial ion strength. Therefore, no antagonistical absorption of cations was found in that ion strength. Leaf content of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and copper (Cu) increased as the ionic strength of the solution increased, but concentrations of iron (Fe), manganese (Mn), and zinc (Zn) were not affected significantly. Nitrogen (N) content of leaves in 'KS 370' after 72 h culture increased significantly by increasing the ionic strength of the solution. Root concentrations of P, K, Ca, Mg, and Fe increased as the ionic strength of the solution increased in both cultivars. The N concentrations of roots in either 'KS 370' or 'KS 352' had positive correlations with an increasing ionic strength of the solution, although they were constantly greater in 'KS 370' than in 'KS 352'. The greatest fresh weight was obtained when the plants were cultured in a half strength solution. Whereas dry weight decreased in all treatments as the ionic strength of the solution decreased. These findings show that increased ion absorption affected plant dry weight. The obtained findings provide fundamental information for the closed hydroponic system of phalaenopsis cultivation.