305 Omega-3 Fatty Acid Concentration of Purslane (Portulaca oleraceae L.) Is Influenced by the Stage of Harvest and the Variety

Abstract

Omega-3 fatty acids (O3FA) are essential for normal human growth, development, and disease prevention. Purslane (Portulaca oleraceae L.) is an excellent source of alpha-linolenic acid (LNA, an O3FA) and the anti-oxidant alpha-tochopherol. Twenty-one-day-old seedlings of cultivated purslane seedlings were transplanted into greenhouse (≈18-20 °C) and arranged in a randomized complete-blocks design with six replications. Plants were fertilized with nitrogen at 25 mg·mL-1 for the first week, 50 mg·mL-1 for the next week, and 100 mg·mL-1 until harvest using a 20N-4.4P-16.6K water-soluble fertilizer in the irrigation water. The terminal three nodes of shoots were harvested at 6, 10, and 14 trueleaf stage. At each harvest the dry mass (DM), fresh mass (FM), and leaf area were determined. The leaf and stem LNA concentration were determined using gas chromatography. The leaf fatty acid concentrations were 30% to 52% higher at the 6- and 14-leaf stages than at 10-leaf stage. The fatty acid concentrations at the 6- and 14-leaf stages did not differ significantly from each other. FM, DM, and leaf area were the highest at the 14-leaf stage. These data indicate that fatty acid levels do vary with the stage of development in purslane. A more detailed study is necessary to follow the change in LNA concentration in purslane throughout its ontogeny beyond 14 leaves. In another study to determine if the LNA concentration of the upright cultivated type of purslane differed from that of the prostrate wild type, we observed that at 14 to 16 true-leaf stage. the leaves from the cultivated type had 52.5% and 35.2% greater linoleic acid and LNA, respectively, than the wild purslane. In both varieties, leaves were richer in LNA than were the stems. Though the varieties did not differ significantly in the DM yield, the FM and leaf area were higher in the cultivated type than the wild type.