Date of Award
Doctor of Philosophy
J. S. Burris
A preconditioning process (treatment at 35°C prior to high-temperature drying) that precludes high-temperature (>45°C) drying injury without major moisture loss was used to study the nature of the desiccation damage in high-moisture seed corn (Zea mays L.). 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. The roles of soluble sugar, membrane phospholipid composition and thermal properties, ABA content, and protein synthesis in the induction of high-temperature desiccation tolerance and membrane stabilization were studied;The percentage composition of sucrose and a larger oligosaccharide, raffinose, increased significantly during preconditioning. The high correlations between the ratio of raffinose to sucrose and warm germination, conductivity, and sugar leakage (r = 0.829, -0.801, and -0.707 for A632, and 0.887, -0.782 and -0.787 for B73, respectively) indicate the added effect of raffinose on the induced protection. These results suggest that soluble sugar compositional relationship rather than absolute content may play an important role in protecting maturing seed from high-temperature drying damage;Among membrane lipids, phosphatidylcholine (PC) accumulated, resulting in an increase in the PC/phosphatidylethanolamine (PE) ratio from 3.6 to 8 within 48 h of preconditioning. The increase in PC/PE ratio coincided with a decrease in both phase transition temperature and enthalpy of transition, which indicate more stable membranes. An increase in fatty acid saturation may result in membranes which more easily cope with high-temperature desiccation;The ABA levels and appearance of desiccation induced proteins indicate that preconditioning and the newly induced proteins may be related to the transfer from desiccation intolerance to desiccation tolerance during post-harvest drying. The relationship of ABA and protein accumulation with high-temperature desiccation tolerance and membrane stabilization will be discussed.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Chen, Yuguang, "Membrane stabilization and desiccation tolerance during seed corn (Zea mays L.) drying " (1990). Retrospective Theses and Dissertations. 9426.