Respiration during germination of diploid and triploid watermelon

The aim of this work was to determine how differences in lipids and starch content among diploid and triploid watermelon seeds affect respiration and the glyoxylate cycle during germination. In comparison to diploid watermelon seeds, the respiratory quotient (RQ) associated with CO2 release and O-2 uptake in triploids was very high initially and declined through four days of germination. The high RQs may indicate unavailability of oxygen due to the thick seed coats of triploids while the lower RQs observed later are consistent with respiration of lipids. Isocitrate lyase (ICL) activity, a marker for the glyoxylate cycle, might be affected by the fatty acid levels, especially high linoleic acids (C18:2) in triploids with low germination. Lower ICL activity in triploid seeds could be physiologically relevant to higher levels of fatty acids, a response to lipid metabolism, and thus contribute to poor germination of triploids.