Physiological and isozyme alterations in lettuce seeds under different conditions and storage periods

The objective of the study was to determine the physiological and isozyme alterations in lettuce seeds submitted to different conditions and storage periods. We used a completely randomized design with four replications in a factorial arrangement with six lettuce cultivars (Everglades, Baba de Verao, Elisa, Grand Rapids, Hortencia and Salinas 88) and four storage periods (30, 60, 90 and 120 days), on three storage rooms (15, 25 and 35 degrees C). The physiological quality was evaluated by first and final germination count, emergence, and germination and emergence speed indexes. The isoenzyme expression of catalase (CAT), esterase (EST), alcohol dehydrogenase (ADH) and malate dehydrogenase (MDH) were determined. The physiological quality of lettuce seeds was preserved when stored at 15 degrees C room temperature. The high room temperatures associated with higher storage periods cause a reduction in physiological quality and alterations in enzymatic patterns of CAT, EST, ADH and MDH. For seeds stored at 15 degrees C, there were no physiological changes. The lettuce cultivars, especially Everglades, have different levels of tolerance to storage and isoenzyme expressions.