senescence processes, and is linked to alterations in carbohydrate metabolism, amino acid,
protein, nucleotide synthesis, the tricarboxylic acid (TCA) cycle and mitochondrial electron
transport chain [20–22]. The TCA-cycle intermediates, citrate, isocitrate and malate were all
significantly reduced in induced plants as was the TCA cycle inhibitor malonate. In addition,
glutamate, stearate, palmitate and β-sitosterol all increased in concentration in induced plants.
Together, these observations suggest increased flux through the TCA cycle, with intermediates
being drawn off for synthesis of lipids and glutamate (Fig 11).