Alignment of Lipid Bodies along the Plasma Membrane during the Acquisition of Desiccation Tolerance in Maize Seed
2002
Cordova-Tellez, Leobigildo | Burris, Joseph S.
The impairment of lipid body alignment along the plasma membrane during artificial drying of maize (Zea mays L.) seed has been associated with decreases in germination and vigor. In this study, we question further its potential functions as well as the alignment mechanisms. Ears of hybrid maize [B73 × (H99 × H95)] were harvested at about. 550, 500, 400, and 320 g H₂O kg⁻¹ fresh weight (fw) and subjected to preconditioning (PC) (ear drying at 35°C and 0.47 m s⁻¹ airflow rate) for 0, 12, 24, 36, and 48 h before fast drying (shelled seed, 35°C and 5.10 m s⁻¹ airflow rate) treatments to decrease seed moisture content (MC) to about 130 g H₂O kg⁻¹ fw. In a cross section of the embryo radicle, alignment of lipid bodies (LB) occurred first in the root cap, followed by outer quiescent center (QC) cells and inner QC cells. This alignment pattern was observed during PC and under field drying conditions. Cell plasmolysis and aberrations of the LB were evident in seed harvested at MC > 400 g H₂O kg⁻¹ fw and subjected to fast drying without PC. Lipid body aberrations decreased in severity with PC, seed development, and field drying. The alignment of LB coincided with changes in embryo-drying rates. Decreases in lipid body aberrations coincided with decreases in cell solute leakage and shoot/root ratio and increases in germination percentage. We conclude that alignment of LB along the plasma membrane is a progressive process that occurs from the periphery to the inner QC cells of the embryo radicle. Alignment of LB along the plasma membrane may change cell water relations leading to a more organized dehydration during seed drying. High embryo drying rates may prevent alignment of LB along the plasma membrane and are associated with low germination and vigor.
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