Adaptation of Seed Oil to Germination Temperature in Helianthus annuus

对于许多种类的植物，种子油在光合作用开始之前为发芽的种子提供能量和碳的基本功能。 由于发芽的时间和速度已被证明强烈影响许多物种的植物的适合度，种子油的组成可以在强选择的范围内，因为它们影响这些特征。 种子油成分中一个非常显著和一致的模式是，生长在高纬度的植物种子中饱和油的比例低于生长在低纬度的植物。 无论是在物种之间还是在具有广泛纬度范围的物种内部，这种模式都是成立的。 基于生物化学、生理学、能量和生态学的证据，假设发芽温度是种子中饱和油比例的主要选择剂。 预测在较冷温度下发芽的具有较低比例的饱和油的种子比具有较高饱和油的种子具有更好的发芽性能。 这种性能优势应导致提高竞争力和更高的健身。 在温暖的发芽温度，相对适合的种子与高，低比例的饱和油应该扭转。 由于发芽温度在高纬度地区降低，这一假设可以解释种子中饱和油比例的纬度梯度。 本试验将测试不同饱和油比例的种子的性能、竞争力和适合度是否如预测的那样受到发芽温度的影响。 特别培育的高和低饱和油线的野生向日葵，向日葵，将被用来测试的预测。 实验的结果将帮助我们理解一种几乎无处不在的种子油成分模式的进化意义，它将更普遍地帮助我们理解为什么种子油成分变化如此之大。 这些结果也可能对农业产生影响，因为它们将建议具有所需比例的饱和和不饱和种子油的植物出现在哪里，以及如何培育更好地适应它们种植区域的种子。 最后，这里提出的工作将是未来工作的基础，测试向日葵籽油的模式和过程是否更普遍，以及饱和油比例的遗传基础是否一致。

For many species of plants, seed oils perform the essential function of providing energy and carbon to germinating seeds before photosynthesis begins. Since the timing and rate of germination have been shown to strongly affect the fitness of many species of plants, the composition of seed oils could be under strong selection insofar as they affect these characters. One very striking and consistent pattern in seed oil composition is that plants growing at higher latitudes have lower proportions of saturated oil in their seeds than plants growing at lower latitudes. The pattern holds whether one looks among species or within species that have broad latitudinal ranges. Based on biochemical, physiological, energetic, and ecological lines of evidence, it is hypothesized that germination temperature is the primary selective agent on the proportion of saturated oil in seeds. Seeds with a lower proportion of saturated oil that germinate at cooler temperatures are predicted to have better germination performance than seeds higher in saturated oils. This performance advantage should lead to improved competitiveness and higher fitness. At warmer germination temperatures, relative fitnesses of seeds with high and low proportions of saturated oil should reverse. Since germination temperature decreases at higher latitudes, this hypothesis could account for the latitudinal gradient in the proportion of saturated oil in seeds. The experiments in this proposal will test whether the performance, competitiveness and fitness of seeds with different proportions of saturated oils are affected by germination temperature as predicted. Specially bred high and low saturated-oil lines of a wild sunflower, Helianthus annuus, will be used to test the predictions. The results of the experiments will help us understand the evolutionary significance of a nearly ubiquitous pattern in seed oil composition, and it will more generally help us understand why seed-oil compositions vary to such a great extent. The results may also have agricultural implications because they will suggest where plants with desired proportions of saturated and unsaturated seed oils occur and possibly how to breed seeds that are better adapted to the zones where they are planted. Finally, the work proposed here will be the foundation for future work testing whether the patterns and processes in Helianthus seed oils hold more generally and whether the genetic bases of saturated oil proportions are consistent.