Dionex model dx500

Nitrate concentrations were determined by ion chromatography (Dionex model DX500; Dionex Corporation, Sunnyvale, CA, United States) with a conductivity detector, using the pre-column IonPack AG14 and the column of separation IonPack AS14 (Signore et al., 2008 ). Ultrapure water at 18 MΩ/cm (Milli-Q Academic Millipore) was used in all the analysis.

Glucose and fructose content were determined by ionic chromatography (Dionex model DX500; Dionex Corp., Sunnyvale, CA, USA) using a pulsed amperometric detector (PAD) according to protocols used by Renna et al. [11 (link)]. Peak separation was performed using a Dionex CarboPac PA1 and isocratic elution with 50 mmol L⁻¹ NaOH. Results were expressed as mg g⁻¹ FW.
The sweetness index (SI) was calculated based on the content and sweetness properties of individual carbohydrates by multiplying the sweetness coefficient of each sugar (glucose = 1.00, fructose = 2.30 and sucrose = 1.35) by the concentration (g 100 g⁻¹ FW) of that sugar in fruits [37 (link)]. The following formula was used:

Inorganic ions (both from NS and plant material) were determined by ion chromatography (Dionex model DX500; Dionex Corporation, Sunnyvale, CA, USA) with a conductivity detector, using the pre-column IonPack AG14 and the column of separation IonPack AS14 for the anions, and the pre-column IonPack CG12A and the column of separation IonPack CS12A for the cations (Di Gioia et al., 2013 ). Ultrapure water at 18 MΩ/cm (Milli-Q Academic Millipore) was used in all the analysis.
Total Kjeldahl nitrogen in the plant was determined from 0.1 g of dried and ground leaf tissue by the Kjeldahl method (Kjeltec 2300 Auto Analyser; Foss-Tecator, Hillerød, Denmark) adding salicylic acid to recover the NO₃-N (15 mL 0.18 M salicylic acid in 96% H₂SO₄, selenium compounds and Zn as catalysts). Plant phosphorus content was determined by spectrophotometry.
The pH and EC of NS were measured using the portable pH-meter HI 9025 and the conductivity-meter HI-9033 (Hanna Instruments, Padova, Italy). The pH was not subjected to analysis because its correction was done only to maintain its value in the 5.5–6.5 range, in the same manner for all the treatments.
Total soluble solids were measured using a portable reflectometer (Brixstix BX 100 H; Techniquip Corporation, Livermore, CA, USA); the DM was determined after drying until constant weight in a forced-draft oven at 65°C.