Purslane (Portulaca oleracea) is a member of the portulacaceae family and is an annual that produces hundreds of seeds that remain dormant until conditions are favorable for germination. Over the last 10 years, purslane has gained added attention as a result of the discovery that it possessed the highest content of omega-3 fatty acid among several green leafy and succulent vegetables such as spinach, red leaf lettuce, buttercrunch lettuce, or mustard greens (Alamazan and Adeyeye, 1998; Liu et al., 2000; Palaniswamy et al., 1997, 1998, 2001; Simopoulos, 2002). Guil-Guerrero and Rodriquez-Garcia (1999) showed that leaves of purslane yielded a greater amount of lipids/100 g dry weight compared with other edible species.
There is a fair amount of variation in the lipid content of purslane based on time of harvest. For example, Omara-Alwala et al. (1991) reported that lipid content of purslane leaves and stems varied depending on harvest time [30, 49, or 59 d after planting (DAP)]. Palaniswamy et al. (2001) reported that the concentration of polyunsaturated essential fatty acids in the leaves of purslane harvested at six-, 10- and 14-true-leaf developmental stages (corresponding to 35, 49, and 60 DAP) varied significantly. They found a lower concentration of lipids at the 10-true-leaves stage vs. at six- or 14-true-leaf stages. They also reported differences with respect to the ratio of omega-3 to omega-6 regardless of stages of development.
Liu et al. (2000) also showed that leaves, stems, and seeds of Australian purslane were an excellent source of alpha linolenic acid compared with American varieties harvested at different stages of growth (45, 60, or 70 DAP) regardless of whether plants were grown in the field or a greenhouse. Total fatty acids and alpha linolenic acid were greater in the seeds, whereas longer-chain fatty acids were not detected in any of the samples. These reports suggest that the amount of omega-3 fatty acids in purslane depends largely on the developmental stage at which the plants are harvested as well as the plant parts analyzed.
There are several sources of omega-3 fatty acids that are available commercially, including from fish and flax seed oils. However, these are relatively expensive to obtain and adequately consumed in proper dosages. Growing and consuming purslane would be a relatively inexpensive source of this essential fatty acid. There is limited information available concerning the content and form of omega-3 and omega-6 fatty acids present in purslane at intermediate harvest intervals.
Our objective was to evaluate the influence of sequential intermediate harvest intervals on growth responses and omega-3 fatty acid content of purslane.
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