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.

在竞争环境下，幼苗早期出苗可提升植物适合度。种子油组分（即油脂中脂肪酸的种类与相对含量）可能对油料籽实的出苗时间与早期生长速率具有重要调控作用。饱和脂肪酸的单位碳原子供能水平高于不饱和脂肪酸，但在碳链长度固定时，其熔点显著更高。这一特性构成了一项适应性假说的基础：在较低的萌发温度下，熔点更低（饱和脂肪酸占比更低）的种子因能更早萌发、且在进行光合作用前生长更快，更具选择优势；而在较高的萌发温度下，供能更高（饱和脂肪酸占比更高）的种子更受青睐。为评估种子油熔点对出苗时间与植物适合度的影响，本研究以拟南芥（Arabidopsis thaliana）重组自交系杂交获得的高、低熔点品系为材料，在温、冷两种萌发温度与两种不同密度处理下开展全因子竞争实验。结果显示，两类品系在任一温度下的出苗时间均无显著差异，这一结果符合高温环境下的预测，但与低温环境下的预测不符。在所有实验条件下，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，这与出苗时间无差异的预期结果一致。