Changes in embryo drying rates, the alignment of lipid bodies along the plasma membrane, and dehydrin-like proteins during the acquisition of desiccation tolerance in maize seed

摘要

Preservation of maize seed quality during artificial drying is an important concern in the maize seed industry. In this study, we investigated embryo drying rates, the alignment of lipid bodies, and changes in dehydrin-like proteins during the acquisition of desiccation tolerance in maize seed. Ears of hybrid corn [B73 x (H99 x H95)] were harvested in 1998, 1999, and 2000 at ca. 55, 50, 40 and 32% mc and subjected to preconditioning (PC) (ear drying at 35°C and 0.47 m/s airflow rate) for 0, 12, 24, 36, and 48h prior to fast drying (shelled seed, 35°C and 5.10 m/s airflow rate) treatments to decrease moisture to ca. 13%. With increases in PC time or maturity, embryo-drying rates increased while intact seed drying rates decreased. Under fast drying conditions, embryo mc declined at very rapid rates down to ca. 40%. These drying rates slightly decreased with increases in maturation and PC time. Alignment of lipid bodies (LB) along the plasma membrane occurred first in root cap, followed by outer and inner core cells. However, cell plasmolysis and aberrations or coalescence of LB were evident in seed harvested at mc \u3e40% and subjected to fast drying without PC. These aberrations decreased in severity with PC or field maturation and appeared to be associated with incomplete alignment of LB prior to fast drying. Embryo axes of seed harvested at 55 and 50% mc subjected to fast drying conditions, exhibited a detectable increase in dehydrin-like proteins with increases in PC time. These proteins were located interspersed on surfaces of the plasma membrane, lipid bodies, and throughout the cytoplasm. Changes in embryo drying rates, better alignment of LB along the plasma membrane, and higher accumulation of dehydrin-like proteins are associated with lower cell solute leakage and higher performance in germination and vigor tests. We conclude that slow embryo drying rates, alignment of LB along the plasma membrane and accumulation of dehydrin-like proteins may act synergistically to decrease the potential cell dehydration damage leading to higher seed quality following artificial drying.