Distribution of indole-acetic acid, gibberellin and cytokinins in apoplast and symplast of parthenocarpic tomato fruits

Abstract

The levels of indole-acetic acid (IAA), gibberellic acid1 (GA1), trans-zeatin (Z) and trans-zeatin riboside (ZR) in seedless fruits of parthenocarpic tomato (Lycopersicon esculentum Mill. cv. Rarkuna First) were analysed using 13C6-IAA, 2H2-GA1, 2H5-Z and 2H5-ZR, as internal standards by liquid chromatography–mass spectrometry. Fruits were sampled at 6 cm in diameter (referred to as 6-cm-fruit) and 8 cm (8-cm-fruit, mature green stage) and separated into pericarps, partitions and locule tissues. The pericarps and partitions were centrifuged for the collection of apoplast (AP) solution (sap outside a cell) and symplast (SP) solution (sap within a cell). IAA concentrations of the pericarps and partitions were higher in 8-cm-fruit than in 6-cm-fruit. In the partitions, IAA concentrations of SP solution were higher than those of AP solution in both 6- and 8-cm-fruit. The SP solution of the partitions in 6-cm-fruit had the highest concentration of Z (4.6 pmol/g fresh weight) and was 2.7 times than the AP solution, while in the pericarps Z concentrations were the same level in AP and SP solution. The ZR concentration in locule tissues in 6-cm-fruit (55 pmol/g fresh weight ) was the highest of all parts. The results suggest that the sites of synthesis may be the SP of partitions for IAA and Z, and locules for ZR.