Role of Carbohydrates in Desiccation Tolerance and Membrane Behavior in Maturing Maize Seed
Seed corn (Zea mays L.) ears harvested at seed moisture contents greater than 400 g H2O kg−1 fresh wt. (fw) are sensitive to rapid, high-temperature (45–50 °C) drying, but tolerant to low-temperature drying. A preconditioning process that precludes this injury without major moisture loss was used to study the nature of the drying damage and the role of soluble sugars in membrane stabilization during drying of two seed corn hybrids. Ears were harvested at moisture contents of 550, 450, and 400 g H2O kg−1 fw, and preconditioned at 35 °C for 6 to 48 h before drying at 50 °C. Seed germination was correlated with leachate conductivity (r = −0.79) and sugar leakage (r = −0.80) after different times of preconditioning indicating the involvement of membrane function in the damage caused by high temperature drying. Total soluble-sugar concentration decreased during preconditioning with no significant change individual monosaccharide content. The percentage composition of sucrose and a larger oligosaccharide, raffinose, increased significantly during preconditioning. The high correlations between raffinose/sucrose and warm germination, conductivity, and sugar leakage (r = 0.83, −0.80, and −0.71 for A632, and 0.89, −0.78, and −0.79 for B73, respectively) indicates the added effect of raffinose on induced protection. These results suggest that soluble-sugar compositional relationships rather than absolute content may play an important role in membrane stabilization. The presence of raffinose at certain levels also may be a key factor in protecting maturing seeds from high temperature drying damage. The results also indicate that the transition from desiccation intolerance to tolerance is metabolic and not necessarily related to moisture loss.
Copyright © 1990.