Nutrient concentrations of phloem sap of aromatic coconut grown under various nutrient conditions

Abstract

To clarify the phloem transport of nutrients, the nutrient concentration of phloem sap of aromatic coconut palm was studied at Petchaburi Horticultural Research Center in Thailand. An experiment in randomised complete block design with three replications for aromatic coconut (Cocos nucifera) cultivation was carried out in Gray Podzolic soil (Ustoxic Dystropept) with the application of N-P-K: 0-0-0, 0-0.26-0.83, 0.4-0.26-0.83, 0.6-0.26-0.83, 0.8-0.26-0.83, 0.6-0-0.83, 0.6-0.18-0.83, 0.6-0.35-0.83, 0.6-0.26-0, 0.6-0.26-0.66, 0.6-0.26-1, 0.8-0.35-1 kg plant⁻¹ year⁻¹. In the second year of production, phloem sap was collected from the cut tips of fruit-bearing stems of coconut palms. The nutrient concentration of phloem sap was analysed by means of atomic absorption spectrometry.

The phloem sap contained higher concentrations of potassium (13.87–42.33 mM) relative to nitrogen (3.36–14.43 mM) and phosphorus (5.10–8.00 mM). The concentrations of Ca, Mg, Cu, Zn, Mn, and Fe were about 102, 378, 4,14, 75 and 24μM, respectively. No significant differences among the treatments concerning nutrient concentrations in phloem sap were detected except for Mg.