Ethylene extends the vase life of Dodonaea 'Dana' cut branches: Possible mechanisms

Dodonaea 'Dana' is an Israeli hybrid of Dodonaea viscosa L. 'Purpurea' and Dodonaea lobulata (Sapindaceae), characterized by purple tinted decorative foliage and fruits. Cut Dodonaea branches showed seasonal variations in vase life longevity, wilting after one week in winter, and having a vase life of three weeks in summer. The wilting phenomenon resulted from improper water conductance, caused by temperature-induced seasonal anatomical changes. Exposure of cut branches to ethylene (0.5-10 μL L^-1, 24 h) improved their longevity in a concentration-dependent manner, expressed in the absence of leaf wilting and a significant increase in fresh weight (FW) during 12 days. Application of the ethylene inhibitor 1-methylcyclopropene (1-MCP) (0.05-0.2 μL L^-1, 4 h) resulted in opposite effects. Ethylene improved water uptake of cut branches but did not affect the transpiration rate or the leaf relative water content (RWC), suggesting that the increased FW might have resulted from new growth. Indeed, a significant ethylene-enhanced increase in both elongation and widening dimensions was observed only in immature leaves (3-to 5.5-cm-long), but not in mature leaves (7.5-to 11-cm-long). The aquaporin inhibitor, phloretin, which reduced the branch FW and leaf size, completely abolished the ethylene-induced increase in branch FW and leaf size, suggesting that the positive response of the cut branches and young leaves to ethylene might involve phloretinsensitive aquaporins. The data suggest that the ethylene-induced increase in FW of cut Dodonaea branches is related to young leaf growth and water flow, which seem to be mediated by the activity of aquaporins.