Water activity‐moisture content relations of primed, film‐coated and/or pelleted vegetable seeds

Seed moisture is a crucial aspect of seed quality which reflects the physiological status of the seed tissues. The International Seed Testing Association (ISTA) currently requires seed moisture to be reported as the percentage ‐ by weight ‐ of the sample that is water, most often determined using the constant temperature oven method. The introduction of water activity ( a w ) as an alternative method is being evaluated, hence in this study, we determined the moisture relations of film‐coated or pelleted vegetable seeds to see whether a w measurement is a reliable method to assess seed moisture status. The film coating used on these seeds did not significantly change the relationship between seed moisture content (MC; % fresh weight) and a w for carrot and endive seeds. There were some differences in the relationship between control (non-coated) and film‐coated lettuce seeds. The sowing unit of pelleted seeds of lettuce (primed seeds) and chicory showed very much lower moisture contents, suggesting that the pellet material had very different moisture relations compared with the seeds themselves. Moisture history, including priming, is an important consideration when reporting a w results.