Note: * mean significant different at 0.05 level; ** mean significant different at 0.01 level.
Correlation Analysis with Geographic Factors
Meanwhile, from the results of correlation analysis of oil content and major fatty acid fractions of A. truncatum seed kernel with geographic factors (Table 6), it can be seen that the oil content of seed kernel showed highly significant positive correlation with annual mean temperature, January mean temperature, July mean temperature and annual precipitation, and highly significant negative correlation with altitude, indicating that A. truncatum in the southern plain area of China, which is at a lower elevation, with higher temperatures and sufficient precipitation, is more a seed source of high oil content, and its climatic conditions are are more suitable for the accumulation ofA. truncatum seed oil. Among the saturated fatty acids, both palmitic acid and stearic acid showed significant positive correlation with altitude, palmitic acid showed highly significant negative correlation with January mean temperature and frost-free period, and stearic acid only showed significant negative correlation with frost-free period; among the unsaturated fatty acids, eicosapentaenoic acid showed highly significant positive correlation with altitude, oleic and linoleic acid showed significant positive correlation with altitude, and the correlation between saturated fatty acids and unsaturated fatty acids and altitude was similar, and the content increased with the increase of altitude. The correlation between saturated fatty acids and unsaturated fatty acids with altitude was similar, and the content increased with increasing altitude; α-linolenic acid showed a highly significant positive correlation with longitude, while eicosapentaenoic acid and erucic acid showed a strong negative correlation with mean annual temperature, erucic acid also had a strong negative correlation with January mean temperature, meanwhile, neuronic acid showed highly significant negative correlation with mean annual temperature, mean January temperature, annual precipitation and frost-free period, indicating that the relative content of neuronic acid was lower in the seed source with high temperature and sufficient precipitation; and there was a significant or highly significant negative correlation between the frost-free period and the main saturated fatty acid fractions, which indicated that the relative content of fatty acid fractions of A. truncatum was more in the case of lower temperature and shorter growing period.
In summary, the oil content of A. truncatum seed kernels was more affected by latitude, temperature and precipitation, and altitude, temperature and precipitation were the main reasons for the geographic variations of fatty acid fractions, and the results of the correlation analyses also reflected A. truncatum ’s habit of preferring cooler and wetter temperatures, and being more drought-tolerant.
Table 6. Correlation analysis between seed kernel oil content, main fatty acid components and geographical factors of Acer truncatum