Pelc Sandra E, Linder C Randal
US Vegetable Laboratory, Agricultural Research Service, United States Department of Agriculture Charleston, South Carolina, 29414 ; Department of Integrative Biology, University of Texas at Austin Austin, Texas, 78712.
Department of Integrative Biology, University of Texas at Austin Austin, Texas, 78712.
Ecol Evol. 2015 Jan;5(1):164-71. doi: 10.1002/ece3.1265. Epub 2014 Dec 10.
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.
早期幼苗出土可以提高植物在竞争环境下的适应性。种子油成分（油中脂肪酸的类型和相对含量）可能在决定油籽的出土时间和早期生长速率方面发挥重要作用。饱和脂肪酸每个碳原子提供的能量比不饱和脂肪酸多，但熔点要高得多（当链长保持恒定时）。这一特性构成了一个适应性假说的基础，即熔点较低的种子（饱和脂肪酸比例较低）在较冷的萌发温度下应该更具优势，因为它们在光合作用之前能更早萌发且生长更快，而在较温暖的萌发温度下，能量含量较高的种子（饱和脂肪酸比例较高）应该更具优势。为了评估种子油熔点对幼苗出土时间和适应性的影响，在一个全因子实验中，将拟南芥重组自交系的高熔点和低熔点品系在温暖和寒冷温度下与两种不同密度处理进行竞争实验。在这两种温度下，这些品系之间的出土时间没有显著差异，这与温暖温度下的预测一致，但与寒冷温度下不符。在所有条件下，与高熔点品系竞争的植株相对于与低熔点品系竞争的植株适应性更低，这与出土时间无差异的预期相符。
