Date of Award
Doctor of Philosophy
This study investigated the impacts of shrunken-2 (sh2) endosperm mutation on sweet corn embryogenesis and germination acquisition during seed development and maturation. Comparison between three pairs of sh2 and sugary (su) isogenic inbred lines and two dent corn inbreds showed that sh2 not only reduced the endosperm reserve accumulation, but also significantly retarded embryo development, especially during early seed development, resulting in a smaller embryo after maturation. Developing seed of sh2 lines acquired the same germinability at least 10 days later than su and dent corn seeds. During the late maturation stage, the germinability of sh2 seeds tended to decline but su and field corn inbred seeds remained unchanged. Microscopic observations indicate that sh2 seed exhibits impaired starch grain deposition in scutellar and axis tissue. Because the sh2 gene is only expressed in endosperm, the adverse effects of sh2 on embryo development may be attributed to the complex interactions between endosperm and embryo during seed development. In addition, sh2 seeds tended to accumulate substantial amounts of toxic carbohydrate byproducts, i.e., ethanol and lactate, which might be detrimental to embryo growth when germinating under cold and wet conditions. Research efforts also included film coating technology and chemical application to the parent plants in an attempt to improve sh2 seed and seedling vigor. This study revealed that film coating may be used as the delivery system for "growth additives" to improve seed germination and seedling growth under cold germination conditions. Incorporation of 0.1 PPM growth regulator 24-epibrassinolide or 500 PPM ZnSO4.7H2O into a film coating significantly increased cold test seed germination and seedling growth of sh2 inbreds WH9261 and WH2. The results of field trials over three years revealed that the response of seed germination and subsequent seedling growth to specific chemical application to sh2 parent plants is complex and could be effected by genotype, the formulation (with/without fungicide), application timing, and dose. Application of certain growth retardants, including flurprimidol, SS3307, or a combination of NAA and B9, to parent plants during seed maturation showed potential in improving seed and seedling vigor for sh2 inbred WH2.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Duan, Xianming, "Seed development of shrunken-2 sweet corn (Zea mays L.) and the use of film coating and field chemical applications to improve seed quality " (1997). Retrospective Theses and Dissertations. 11791.