Data from: Emergence timing and fitness consequences of variation in seed oil composition in Arabidopsis thaliana

Early seedling emergence can increase plant fitness under competition. Seed oil composition (the types and relative amounts of fatty acids in the oils) may play an important role in determining emergence timing and early growth rate in oilseeds. Saturated fatty acids provide more energy per carbon atom than unsaturated fatty acids but have substantially higher melting points (when chain length is held constant). This characteristic forms the basis of an adaptive hypothesis that lower melting point seeds (lower proportion of saturated fatty acids) should be favored under colder germination temperatures due to earlier germination and faster growth before photosynthesis, while at warmer germination temperatures, seeds with a higher amount of energy (higher proportion of saturated fatty acids) should be favored. To assess the effects of seed oil melting point on timing of seedling emergence and fitness, high- and low-melting point lines from a recombinant inbred cross of Arabidopsis thaliana were competed in a fully factorial experiment at warm and cold temperatures with two different density treatments. Emergence timing between these lines was not significantly different at either temperature, which aligned with warm temperature predictions, but not cold temperature predictions. Under all conditions, plants competing against high-melting point lines had lower fitness relative to those against low-melting point lines, which matched expectations for undifferentiated emergence times.幼苗早期出土可提升竞争环境下植物的适合度（fitness）。种子油组分，即油脂中脂肪酸的种类与相对含量，可能在油料作物的出苗时间与早期生长速率调控中发挥关键作用。饱和脂肪酸（saturated fatty acids）相较于不饱和脂肪酸（unsaturated fatty acids），在每个碳原子上可提供更多能量，但在碳链长度固定时，其熔点（melting point）显著更高。这一特性构成了一项适应性假说的核心依据：在低温萌发条件下，低熔点种子（饱和脂肪酸比例更低）应更具竞争优势，因其可更早完成萌发，并在光合作用启动前实现更快生长；而在高温萌发条件下，高能量密度（饱和脂肪酸比例更高）的种子应更受青睐。为评估种子油熔点对幼苗出苗时间与适合度的影响，本研究以拟南芥（Arabidopsis thaliana）重组自交杂交组合构建的高、低熔点品系为实验材料，在温、冷两种萌发温度与两种不同密度处理下开展完全析因竞争实验。结果显示，两种品系的出苗时间在任一温度条件下均无显著差异，这一结果与高温条件下的预测相符，但与低温条件下的预测相悖。在所有实验处理中，与高熔点品系竞争的植株，其适合度均低于与低熔点品系竞争的植株，该结果与出苗时间无分化的预期完全一致。