ABSTRACT

Maize (Zea mays L.) is an important agronomic crop throughout the world. Maize seed production and trait introgression is performed in both field and greenhouse settings (which allow for continual production seasons). The winter months within the greenhouses produce maize tassels with increased barren tassel branches (suppressed anther production) and the hypothesis is that the most limiting factor is daily light integral (DLI). Growing maize year-round in temperate regions, such as the northern part of the United States, requires the use-of greenhouse production. The low light intensities of these regions in the winter months creates a need for supplemental lighting for crops such as maize, that are high-light species. Utilizing a controlled environment, such as a greenhouse, also allows for control over the environmental factors such as temperature, light, moisture, gases and nutrients. Temperature, moisture, and nutrients can be supplied as needed, and maize does not require CO2 regulation because it is a C4 plant. The last factor, light, is most limited on cloudy or winter days, therefore plants require supplemental lighting to provide the additional light needed to produce a high-quality maize tassel. Our objectives were to investigate how the maize plant grows and develops in response to lower DLI levels. After determining the impact that DLI has on maize quality we aimed to quantify the threshold of low DLI needed before tassel barrenness increases, and to explore opportunities to prevent the low DLI stress from occurring. This thesis describes research that was carried out to achieve these objectives and provides a discussion on the implications of these results.