Imbibitional injury in maize seed independent of chilling temperature

Low and high moisture kernels and embryos were imbibed by soaking in distilled water at 5°C and 25°C. Leaching of seeds and embryos was measured by ion conductivity of imbibition water after fixed time intervals. Imbibed kernels were placed on moist filter paper after 1 h imbibition and embryos on a solid culture medium after 15 min imbibition and germinated at 25°C. Primary root length was measured 3 days after germination. The leakage from seeds or embryos was correlated with the velocity of water uptake but did not show its highest values when low moisture seeds or embryos were imbibed at chilling temperature. Furthermore germination was apparently not affected by imbibitional chilling of either low moisture content seeds or embryos. In one of the three genotypes tested (B73) seedlings from low moisture content seeds imbibed at 5°C showed a reduction of the primary root growth. However, this reduction was also seen in seedlings from low moisture B73 seeds imbided at 25°C and resulting in higher level of leaching. Thus, injury by imbibition of low moisture seeds appears independent of chilling temperature and not due to loss of semipermeability of membrane lipids. Our results suggest that, in the case of embryos, water inrush into the cells reaches levels injurious for membrane integrity independently of the two moisture contents and temperature considered.