Fatty Acid Concentration in Portulaca oleraceae L. is Altered by Photosynthetic Photon Flux

Abstract

Purslane (Portulaca oleraceae L.) seedlings were grown under an instantaneous photosynthetic photon flux (PPF) of 299 or 455 μmol·m–2·s–1 for a daily duration of either 8, 12, 16, or 20 h. Thus plants were exposed to a daily PPF of 8.6, 12.9, 17.2, and 21.5 mol·m–2·d–1 in the low PPF treatment (299 μmol·m–2·s–1) and 13.1, 19.7, 26.2, and 32.8 mol·m–2·d–1 in the high PPF treatment (455 μmol·m–2·s–1). All treatments received a 20-h photoperiod using a PPF of ≈5 μmol·m–2·s–1. At low PPF, purslane grown under 16-h PPF duration produced the highest concentration of total fatty acid (TFA), linoleic acid (LA), and linolenic acid (LNA) per unit leaf dry mass (DM) and leaf area; but at high PPF, the concentration of these compounds was highest under 8- and 12-h PPF duration. Trend analysis indicated that maximum TFA, LA, and LNA concentrations occurred with a PPF of 14.1, 16.9 and 17.2 mol·m–2·d–1 respectively; and protein, chlorophyll, and LNA concentrations in thylakoid membranes were maximized at PPF of 21.8, 19.9, and 16.1 mol·m–2·d–1, respectively. LNA as percent of TFA was unaffected by treatment. DM increased with PPF up to the highest PPF exposure of 32.8 mol·m–2·d–1.