Survival characteristics of corn seed during storage: I. Normal distribution of seed survival

Understanding the survival characteristics of hybrid corn (Zea mays L.) see d during storage is necessary to predict seed deterioration This investigat ion tested one key assumption of the Ellis and Roberts viability equation, namely, that seed survival is normally distributed. Eleven corn seed lots ( six hybrids) with little mechanical injury and a wide range in initial vigo r were stored in various combinations of constant temperatures (20, 30, 40, and 50 degrees C) and seed moisture contents (100, 120, 140, and 160 g kg( -1), fresh weight basis). Seed-survival curves were constructed by conducti ng successive germination tests at frequent intervals during storage. The c hi(2) goodness-of-fit test was used to evaluate the normality of survival c urves constructed ham either full or truncated (germination between 95 and 5%) data sets. When the data were truncated, the majority (79%) of the 187 survival curves analyzed were classified as normal (P > 0.05) or near-norma l [P < 0.05 but relatively small chi(2) heterogeneity factor (H = chi(2)/df ) < 10], Only 57% of the curves from the full data set followed a normal or near-normal distribution. Seed moisture and storage temperature had no con sistent effect an the shape of the survival curves. Survival of low-vigor s eed lots was more likely to be normally or near-normally distributed than w as survival of high vigor seed lots, The assumption that seed survival is n ormally distributed was generally valid for truncated data sets of hybrid c orn seed in constant storage environments.