Genetic and Environmental Factors that Influence Microgametophytic Variation

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A large portion of the genetic material in pollen (microgametophytes) is read off during pollen development, pollen germination and pollen tube growth. Consequently, the performance of pollen (speed of germination, pollen tube growth rate and ability to achieve fertilization) can potentially be affected by its genetic makeup, by its interactions with the material portion of the flower through which it grows, by environmental conditions such as temperature, and by the resources (e.g. nitrogen and phosphorus) provided to pollen grains by the pollen-producing parent. Drs. Stephenson and Winsor will continue their detailed investigations of the factors that affect pollen performance. They will determine if these factors result in non-random fertilization, and if non-random fertilization affects the performance of the progeny. Specifically, they will use Cucurbita texana to examine the extent to which pollen tube growth can be selected for by allowing only the fastest growing tubes to achieve fertilization. Next, they will examine the effects of variation in the amount of soil phosphorus on pollen production, pollen grain size, the quantity of stored phosphorus in pollen, and the performance of pollen (ability to sire seeds in mixtures). Finally, they will separate the effects of temperature during pollen production from the effects of temperature during pollen germination on pollen performance. These experiments, when combined with prior and ongoing studies, will result in a complete picture of the genetic and environmental factors that influence pollen performance, the non-random transmission of genes from one generation to the next, and their effects on the resulting progeny. The results of these studies will address and clarify some of the most actively debated issues in plant population biology. In addition, this research will have far-reaching implications for the applied sciences. The possibility of using pollen to select for agriculturally desirable traits in the pollen represents a considerable savings of time, money and space over both traditional breeding programs and the newer biotechnology programs. Finally, it may be possible to use pollen to monitor environmental degradation, to determine which species are susceptible to particular forms of pollution, and to develop lines of plants that are more resistant.