Role of triacylglycerols in leaves

Triacylglycerol (TAG) levels of up to 5 mg (g fresh weight)−1 were identified in leaves of 13 plants. The fatty acid composition of the leaf TAG was distinct from the total leaf fatty acids that predominately arose from galactolipids in the thylakoid membranes and was very similar to the TAG found in the seeds. The exception was in senescent crabapple leaves where the TAG composition was more similar to that of the total leaf suggesting that this TAG might arise from fatty acids released from membrane lipids. In crabapple leaves the TAG was metabolically active with higher levels at the end of the photoperiod than the beginning. 14C-acetate was also incorporated into leaf TAG more rapidly in the light than dark. The rate of TAG accumulation in the light was about 6% of the net photosynthetic rate. These observations suggest that TAG serves along with carbohydrates as a diurnal photosynthetic store in these plants.