was from a Millipore apparatus, Sep-Pak-C18 Cartridges from
Waters Associates; pH-values were measured with a WTW Sentix
21 electrode and a WTW pH535 digital pH meter.
2.1.2. Plant material
A peace lily (Sp. wallisii) (see Supplementary material (Supp-
Mat), Fig. S1) grew inside under normal day light, and developed
naturally senescent leaves sporadically (see Fig. 2). Yellow senescent
Sp. wallisii leaves were freshly cut and frozen with liquid
nitrogen and either stored at 80 C, or they were extracted directly
(see below).
2.2. Chromatographic methods
HPLC: Hewlett Packard HPLC-system, P1100 pump, online degasser,
Agilent1100 diode detector and fluorescence detector. Injection
loop 1 ml (Rheodyne valve), Hypersil ODS 5 lm 250 4.6 mm