Characterization of the loss of seedling vigor in pea (Pisum sativum L.)

The physiological age of pea (Pisum sativum L.) seeds was accelerated using high temperature and relative humidity (RH), resulting in a range of vigor classes within one seed lot. This differentially aged seed was then used to determine the impact of seed vigor on plant growth and yield. For seeds incubated at 38°C for 2, 4, or 6 d at 100% RH prior to germination (accelerated aging), the percentage germination and rate of seedling emergence decreased with increasing time of aging. Aging at 38°C decreased seed vigor as indicated by reduced seedling root and shoot growth relative to higher-vigor seeds aged at 20°C. The respiration rate of seeds aged at 38°C was significantly higher than that of seeds aged at 20°C throughout the 6-d aging interval. However, no differences in respiration were evident during subsequent germination among the seeds aged at 38°C for 0, 2, 4, or 6 d. The higher-vigor seeds aged at 20°C had a higher respiration rate than those aged at 38°C during subsequent germination. Seeds that expressed high and low vigor in controlled-environment conditions showed similar trends in the field; however, seed vigor had no significant effect on total seed yield over two growing seasons. These data indicate that under certain conditions, the loss in seed vigor can be substantial without affecting overall yield, due to the plasticity of vegetative and reproductive growth in pea. Key words: Germination, pea, Pisum sativum, seeds, seedling vigor, respiration