The variability of cottonseed yield under different potassium levels is associated with the changed oil metabolism in embryo

Although the effects of potassium (K) fertilizer on cottonseed yield have been explored, reports on cottonseed yield components and related oil metabolism in genotypes differing in sensitivity to low K are limited. To this end, the cultivars Simian 3 (low K-tolerant) and Siza 3 (low K-sensitive) were grown in 2012 and 2013 under three K2O rates (0, 150 and 300 kg ha−1). Results indicated that K application treatments (150 and 300 kg K2O ha−1) increased seedcotton yield, oil yield, protein yield, seed weight boll‐1 and individual seed weight. Higher individual seed weight as the most basic cottonseed yield component was attributed to the enhanced oil weight seed−1 rather than protein weight seed−1 at higher K application rates. Higher oil weight seed−1 in the K application treatments than the 0 kg K2O ha−1 treatment was a consequence of differences in oil accumulation dynamics. Additionally, higher rates of oil accumulation in the K application treatments were closely associated with phosphatidic acid phosphatase and glucose-6-phosphate dehydrogenase activities. Fatty acid composition was also altered by K treatment, where the percentage of palmitic and tetradecanoic acids decreased and linoleic acid percentage increased with K application, leading to a higher ratio of total unsaturated fatty acids to total saturated fatty acids. Furthermore, the magnitudes of increases in seedcotton yield and individual seed weight with K application were greater in the low-K sensitive cultivar than the low-K tolerant one. K application influenced oil accumulation dynamics and fatty acid saturation levels to a greater extent in the low-K sensitive cultivar than the low-K tolerant cultivar. In conclusion, K application could positively influence cottonseed yield by increasing oil accumulation in individual seed and positively improve the unsaturated fatty acid percentage of cottonseed oil.