Injury to immature maize seed caused by early season frost is of great economic concern to seed producers. Surprisingly, there has been very little research investigating the adverse effects of freezing on immature seed and the resulting biochemical changes in seedlings germinated from freeze damaged seed. In this three-part study, we investigated the effects of freezing injury, first as they pertained to the overall viability of the seed, then to how exposure of immature seed to freezing induces biochemical changes in seedlings germinated from these seed. We found that the extent of freezing injury as determined by reduced viability and observed cellular damage was significantly influenced by the physiological maturity of the seed at time of exposure and by the duration of exposure. We found that several changes in gene expression occurred in seedlings germinated from freeze-damaged seed. First, three day old seedlings germinated from freeze-damaged seed had elevated rates of cellular respiration which correlated with depleted levels of maize peroxysomal catalase isozyme 1 (CAT1). Six day old seedlings also had greater rates of respiration and showed a strong induction of mitochondrial catalase isozyme 3 (CAT3) in response to freezing stress.

Seed development and germination; Phenotypic maternal effect of photoperiod on seed germination; Seed dormancy and germination; Seed vigor, stress and seed germination.

Viability and longevity, Dormancy, The release from dormancy, The control of dormancy, Perspective on dormancy, Environmental control of germination.

Seed development and germination; Seed dormancy and germination; Seed vigor, stress and seed germination.